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Critical Care Nursing Theory
Mechanical ventilation
Mechanical Ventilation
Mechanical Ventilation is ventilation of the lungs by artificial means usually
by a ventilator. Once a patient’s PaO2 cannot be maintained by the basic
methods of oxygen delivery systems, i.e. masks, cannula; endotracheal
intubation and mechanical ventilation are instituted.
A
ventilator
delivers gas to the lungs with either negative or positive pressure.
It must be understood that no mode of mechanical ventilation can or will
cure a disease process but merely supports the patient until resolution of his/
her symptoms is accomplished.
Purposes:
Mechanical ventilation is instituted to:
1- Maintain or improve ventilation, i.e. for adequate tissue oxygenation.
2- Decrease the work of breathing and improve patient’s comfort.
Indications:
Acute respiratory failure due to:
 Mechanical failure, includes neuromuscular diseases as Myasthenia
Gravis, Guillain-Barré Syndrome, and Poliomyelitis (failure of the
normal respiratory neuromuscular system)
 Musculoskeletal abnormalities, such as chest wall trauma (flail chest)
 Infectious diseases of the lung such as pneumonia, tuberculosis.
Abnormalities of pulmonary gas exchange as in:
 Obstructive lung disease in the form of asthma, chronic bronchitis or
emphysema.
 Conditions such as pulmonary edema, atelectasis, pulmonary fibrosis.
Dr. Abdul-Monim Batiha-
Assistant Professor Of Critical Care Nursing
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Critical Care Nursing Theory
Mechanical ventilation
**Patients who has received general anesthesia as well as post cardiac
arrest patients often require ventilatory support until they have
recovered from the effects of the anesthesia or the insult of an arrest.
Criteria for institution of ventilatory support:
Parameters
Ventilation
indicated
Normal range
Pulmonary function studies:




> 35
Respiratory rate (breaths/min).
Tidal volume (ml/kg body wt)
<5
Vital capacity (ml/kg body wt)
Maximum Inspiratory Force (cm
< 15
HO2)
10-20
5-7
65-75
<-20
75-100
< 7.25
7.35-7.45
< 60
75-100
> 50
35-45
Arterial blood Gases
 PH
 Pa2 (mmHg)
 PaCO2 (mmHg)
NB. These parameters are used in making judgments about the adequacy of
respiratory function.
Types of Mechanical ventilators:
1- Negative-pressure ventilators
2- Positive-pressure ventilators.
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Assistant Professor Of Critical Care Nursing
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Critical Care Nursing Theory
Mechanical ventilation
Negative-Pressure Ventilators
- Early negative-pressure ventilators were known as “iron lungs.” The
patient’s body was encased in an iron cylinder and negative pressure was
generated by a large piston to enlarge the thoracic cage. This caused
alveolar pressures to fall, and a pressure gradient was formed so that air
flowed into the lungs. The iron lung are still occasionally used today.
- Intermittent short-term negative-pressure ventilation is sometimes used in
patients with chronic diseases. Rarely, this method of support is chosen for
patients who are not candidates for aggressive mechanical ventilation as
provided through an artificial airway. These patients suffer from a wide
variety of conditions such as
- COPD,
- Diseases of the chest wall (kyphoscoliosis),
- Neuromuscular diseases (Duchenne’s muscular
dystrophy, amyotrophic lateral sclerosis [ALS]).
- The iron lung is cumbersome to use and very large. Most negative-pressure
ventilators in use today are more portable. To improve mobility and
comfort, there is a device that fits like a tortoise shell, forming a seal over
the chest. A hose connects the shell to a negative-pressure generator. The
thoracic cage is literally pulled outward to initiate inspiration.
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Assistant Professor Of Critical Care Nursing
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Critical Care Nursing Theory
Mechanical ventilation
- The use of negative-pressure ventilators is restricted in clinical practice,
however, because they limit positioning and movement and they lack
adaptability to large or small body torsos.
- Our focus will be on the positive-pressure ventilators.
Positive-pressure ventilators
- Positive-pressure ventilators deliver gas to the patient under positivepressure, during the inspiratory phase.
Positive-Pressure Ventilators
Volume Ventilators.
- The volume ventilator is commonly used in critical care settings. The basic
principle of this ventilator is that a designated volume of air is delivered
with each breath.
- The amount of pressure required to deliver the set volume depends on :- Patient’s lung compliance
- Patient–ventilator resistance factors.
- Therefore, PIP must be monitored in volume modes because it varies from
breath to breath.
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Assistant Professor Of Critical Care Nursing
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Critical Care Nursing Theory
Mechanical ventilation
- With this mode of ventilation, a respiratory rate, inspiratory time, and tidal
volume are selected for the mechanical breaths.
Pressure Ventilators.
- The use of pressure ventilators is increasing in critical care units. A typical
pressure mode delivers a selected gas pressure to the patient early in
inspiration, and sustains the pressure throughout the inspiratory phase. By
meeting the patient’s inspiratory flow demand throughout inspiration,
patient effort is reduced and comfort increased.
- Although pressure is consistent with these modes, volume is not. With
changes in resistance or compliance, volume will change.
- Therefore, exhaled tidal volume is the variable to monitor closely.
- With pressure modes, the pressure level to be delivered is selected, and
with some mode options (i.e., pressure controlled [PC], described later),
rate and inspiratory time are preset as well.
High-Frequency Ventilators.
- The high-frequency ventilator accomplishes oxygenation by the diffusion
of oxygen and carbon dioxide from high to low gradients of concentration.
This diffusion movement is increased if the kinetic energy of the gas
molecules is increased.
- High-frequency ventilators use small tidal volumes (1 to 3 mL/kg) at
frequencies greater than 100 breaths/minute. The breathing pattern of a
person on a high-frequency ventilator is somewhat analogous to the
breathing pattern of a panting dog; panting entails moving small volumes
of air at a very fast rate.
- A high-frequency ventilator would be used to achieve lower peak
ventilatory pressures, thereby
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Assistant Professor Of Critical Care Nursing
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Critical Care Nursing Theory
Mechanical ventilation
- Lowering the risk of barotrauma
- Improving ventilation– perfusion matching because .
- Potential adverse effects associated with high-frequency ventilators
include:
- Gas trapping
- Necrotizing tracheobronchitis, when used in the absence of adequate
humidification.
Classification of positive-pressure ventilators:
- Ventilators are classified by their method of cycling from the inspiratory
phase to the expiratory phase (changeover from inspiratory to expiratory
phase), that is to say according to how the inspiratory phase ends. The
factor which terminates the inspiratory cycle reflects the machine type.
- They are classified as: pressure, volume or time cycled machines.
 Volume-cycled ventilator,
- In which inspiration is terminated after a preset volume has been delivered
by the ventilator. i.e. the ventilator delivers a preset tidal volume (V T), and
inspiration stops when the preset tidal volume is achieved.
 Pressure-cycled ventilator,
- In which inspiration is terminated when a specific airway pressure has been
reached. i.e. the ventilator delivers a preset pressure; once this pressure is
achieved, end inspiration occurs.
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Assistant Professor Of Critical Care Nursing
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Critical Care Nursing Theory
Mechanical ventilation
 Time-cycled ventilator,
- In which inspiration is terminated when a preset inspiratory time, has
elapsed. Time cycled machines are not used in adult critical care settings.
They are used in pediatric intensive care areas.
Ventilator Modes
- Several different modes of ventilatory control are available on ventilators.
- There is no one best mode for managing patients in respiratory failure,
although each mode has its advantages and disadvantages.
Modes of mechanical ventilation
- The term “ventilator mode” refers to the way the machine ventilates the
patient .i.e. how much the patient will participate in his own ventilatory
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Assistant Professor Of Critical Care Nursing
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Critical Care Nursing Theory
Mechanical ventilation
pattern. Each mode is different in determining how much work of
breathing the patient has to do.
A- Volume Modes
1- Assist-control (A/C) mode
2- Synchronized intermittent mandatory ventilation (SIMV) mode.
1- Assist Control Mode A/C
- The ventilator provides the patient with a pre-set tidal volume at a pre-set
rate and the patient may initiate a breath on his own, but the ventilator
assists by delivering a specified tidal volume to the patient.
- Client can initiate breaths that are delivered at the preset tidal volume.
- Client can breathe at a higher rate than the minimum number of
breaths/minute that has been set.
- The total respiratory rate is determined by the number of spontaneous
inspiration initiated by the patient plus the number of breaths set on the
ventilator.
- In A/C mode, a mandatory (or “control”) rate is selected.
- If the patient wishes to breathe faster, he or she can trigger the ventilator
and receive a full-volume breath.
- Often used as initial mode of ventilation
-This mode of ventilation is often used fully to support a patient, such as
- When the patient is first intubated
- When the patient is too weak to perform the work of breathing
(e.g., when emerging from anesthesia).
Advantages:
- Ensures ventilator support during every breath
- Each breath has the same tidal volume
Disadvantages:
- Hyperventilation,
- Air trapping
- Work of breathing may be increased if sensitivity or flow rate is too low.
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Assistant Professor Of Critical Care Nursing
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Critical Care Nursing Theory
Mechanical ventilation
2- Synchronized Intermittent Mandatory Ventilation SIMV
- The ventilator provides the patient with a pre-set number of breaths/minute
at a specified tidal volume and fio2. In between the ventilator-delivered
breaths, the patient is able to breathe spontaneously. The ventilator does
not assist the spontaneous breaths i.e. the patient determines the respiratory
rate and tidal volume.
- Between machine breaths, the client can breathe spontaneously at his own
tidal volume and rate with no assistance from the ventilator.
- In SIMV mode, the rate and tidal volume are preset.
- If the patient wants to breathe above this rate, he or she may.
- However, unlike the A/C mode, any breaths taken above the set rate are
spontaneous breaths taken through the ventilator circuit.
- The tidal volume of these breaths can vary drastically from the tidal
volume set on the ventilator, because the tidal volume is determined solely
by the patient’s spontaneous effort.
- Adding pressure support during spontaneous breaths can minimize the risk
of increased work of breathing. In the past, SIMV has been used as a
popular weaning mode.
- Same as intermittent mandatory ventilation except stacking is avoided i.e.
ventilators breaths are synchronized with the patient spontaneous breathe.
- Used to wean the patient from the mechanical ventilator.
- To wean the patient, the mandatory breaths were gradually decreased,
thereby allowing the patient to assume more and more of the work of
breathing.
- Often used as initial mode of ventilation and for weaning
Advantages:
- Allows spontaneous breaths (tidal volume determined by patient) between
ventilator breaths;
- Weaning is accomplished by gradually lowering the set rate and allowing
the patient to assume more work
Disadvantages:
Patient–ventilator asynchrony possible
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Assistant Professor Of Critical Care Nursing
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Critical Care Nursing Theory
Mechanical ventilation
B- Pressure Modes
- Pressure modes include :1- Pressure-controlled ventilation (PCV) mode,
2- Pressure-support ventilation (PSV) mode,
3- Continuous positive airway pressure (CPAP)/PEEP mode,
5- Noninvasive bilevel positive airway pressure ventilation (BiPAP) mode.
1- Control Mode CM
Continuous Mandatory Ventilation( CMV)
- Ventilation is completely provided by the mechanical ventilator with a
preset tidal volume, respiratory rate and oxygen concentration prescribed
by the physician.
-Ventilator totally controls the patient’s ventilation i.e. the ventilator initiates
and controls both the volume delivered and the frequency of breath.
- Client does not breathe spontaneously.
- Client can not initiate breathe
1- Pressure-Controlled Ventilation Mode( PCV)
The PCV mode is used
- to control plateau pressures in conditions such as ARDS where
compliance is decreased and the risk of barotrauma is high.
- It is used when the patient has persistent oxygenation problems
despite a high FIO2 and high levels of PEEP.
- The inspiratory pressure level, respiratory rate, and inspiratory–expiratory
(I:E) ratio must be selected.
- Tidal volume varies with compliance and airway resistance and must be
closely monitored.
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Critical Care Nursing Theory
Mechanical ventilation
- Sedation and the use of neuromuscular blocking agents are frequently
indicated, because any patient–ventilator asynchrony usually results in
profound drops in the SaO2.
- This is especially true when inverse ratios are used. The “unnatural”
feeling of this mode often requires muscle relaxants to ensure patient–
ventilator synchrony.
- Most ventilators operate with a short inspiratory time and a long expiratory
time (1:2 or 1:3 ratio). This promotes venous return and allows time for air
to exit the lungs passively.
- Inverse ratio ventilation (IRV) mode reverses this ratio so that inspiratory
time is equal to, or longer than, expiratory time (1:1 to 4:1).
- Inverse I:E ratios are used in conjunction with pressure control
to improve oxygenation in patients with ARDS by expanding stiff
alveoli by using longer distending times,
thereby providing more opportunity for gas exchange and
preventing alveolar collapse.
- As expiratory time is decreased, one must monitor for the development of
hyperinflation or auto-PEEP. Regional alveolar overdistension and
barotrauma may occur owing to excessive total PEEP.
- When the PCV mode is used, the mean airway and intrathoracic pressures
rise, potentially resulting in a decrease in cardiac output and oxygen
delivery. Therefore, the patient’s hemodynamic status must be monitored
closely.
- Used to limit plateau pressures that can cause barotrauma
Severe ARDS
Disadvantages:
Patient–ventilator asynchrony possible, necessitating sedation/paralysis
Monitor
a- Tidal volume at least hourly.
b- Barotraumas
c- Hemodynamic instability
Inverse ratio ventilation (IRV)
Usually used in conjunction with PCV
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Critical Care Nursing Theory
Mechanical ventilation
Increases ratio I:E to
a- Allow for recruitment of alveoli
b- Improve oxygenation
Disadvantages:
- Almost always requires paralysis
Monitor for
a- Auto-PEEP,
b- Barotrauma,
c- Hemodynamic instability.
2- Pressure Support Ventilation ( PSV)
- The patient breathes spontaneously while the ventialtor applies a predetermined amount of positive pressure to the airways upon inspiration.
- Pressure support ventilation augments patient’s spontaneous breaths with
positive pressure boost during inspiration i.e. assisting each spontaneous
inspiration.
- Helps to overcome airway resistance and reducing the work of breathing.
- Patient must initiate all pressure support breaths.
- Pressure support ventilation may be combined with other modes such as
SIMV or used alone for a spontaneously breathing patient.
- Indicated for patients with small spontaneous tidal volume and difficult to
wean patients.
- It is a mode used primarily for weaning from mechanical ventilation.
- PSV mode augments or assists spontaneous breathing efforts by delivering
a high flow of air to a selected pressure level early in inspiration, and
maintaining that level throughout the inspiratory phase.
- The patient’s effort determines the rate, inspiratory flow, and tidal volume.
- When PSV mode is used as a stand-alone mode of ventilation, the pressure
support level is adjusted to achieve the approximate targeted tidal volume
and respiratory rate.
- At high pressure levels, PSV mode provides nearly total ventilatory
support.
- Specific uses of PSV are
- To promote patient comfort
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Assistant Professor Of Critical Care Nursing
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Critical Care Nursing Theory
Mechanical ventilation
- To promote synchrony with the ventilator,
- To decrease the work of breathing necessary to
overcome the resistance of the endotracheal tube,
- For weaning. As a weaning tool,
- PSV is thought to increase the endurance of the respiratory muscles by
- Decreasing the physical work
- Decreasing oxygen demands during spontaneous breathing.
- Because the level of pressure support can be gradually decreased,
endurance conditioning is enhanced.
- In PSV mode, the inspired tidal volume and respiratory rate must be
monitored closely to detect changes in lung compliance.
- In general, if compliance decreases or resistance increases, tidal volume
decreases and respiratory rate increases.
- PSV mode should be used with caution in patients with
- Bronchospasm
- other reactive airway conditions.
Intact respiratory drive in patient necessary
Used as a weaning mode, and in some cases of dyssynchrony
2- Continuous Positive Airway Pressure CPAP (a variation of PEEP)
- Positive pressure applied at the end of expiration during spontaneous
breaths i.e. for patients breathing spontaneously.
- No mandatory breaths (ventilator-initiated are delivered in this mode)
- All ventilation is spontaneously initiated by the patient.
- PEEP & CPAP are used in patients with hypoxemia refractory to oxygen
therapy. They improve oxygenation by opening collapsed alveoli &
preventing them from collapsing at the end of expiration.
- CPAP allows the nurse to observe the ability of the patient to breathe
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Critical Care Nursing Theory
Mechanical ventilation
spontaneously while still on the ventilator.
- CPAP is supplied during spontaneous breathing. PEEP is the term used to
describe positive end-expiratory pressure with positive-pressure (machine)
breaths. CPAP assists spontaneously breathing patients to improve their
oxygenation by elevating the end-expiratory pressure in the lungs
throughout the respiratory cycle.
- CPAP can be used for intubated and nonintubated patients.
- It may be used as a weaning mode and for nocturnal ventilation (nasal or
mask CPAP) to splint open the upper airway, preventing upper airway
obstruction in patients with obstructive sleep apnea.
- Constant positive airway pressure for patients who breathe spontaneously
Advantages:
- Used in intubated or nonintubated patients
Disadvantages:
- On some systems, no alarm if respiratory rate falls
- Monitor for increased work of breathing.
4- Noninvasive Bilateral Positive Airway Pressure Ventilation (BiPAP)
- BiPAP is a noninvasive form of mechanical ventilation provided by means
of a nasal mask or nasal prongs, or a full-face mask.
- It is used in the treatment of :a- Patients with chronic respiratory insufficiency to manage acute or
chronic respiratory failure without intubations and conventional
mechanical ventilation.
b- Used as a bridge to weaning patients from mechanical ventilation,
c- As an alternative to conventional mechanical ventilation in patients
who are ventilated in their homes.
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Assistant Professor Of Critical Care Nursing
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Critical Care Nursing Theory
Mechanical ventilation
- The system allows the clinician to select two levels of positive-pressure
support:
a- An inspiratory pressure support level (referred to as IPAP)
b- An expiratory pressure called EPAP (PEEP/CPAP level).
- BiPAP is beneficial in worsening nocturnal hypoventilation in patients
with
- Neuromuscular disease,
- Chest wall deformity,
- Obstructive sleep apnea,
- COPD;
- To avoid intubation in patients with respiratory failure & hypercarbia
- To avoid reintubation after extubation in borderline cases.
- Ventilation with a full-face mask should be used cautiously because it may
increase the risk of aspiration and of rebreathing carbon dioxide;
- Thick or copious secretions and poor cough may be relative
contraindications to BiPAP.
Advantages:
a- Decreased cost when patients can be cared for at home;
b- No need for artificial airway
Disadvantages:
- Patient discomfort or claustrophobia
- The patient should be monitored for :a- Gastric distension,
b- Air leaks from mouth
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Assistant Professor Of Critical Care Nursing
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Critical Care Nursing Theory
Mechanical ventilation
Common Ventilator Settings
● Fraction of inspired oxygen (FIO2)
- The percent of oxygen concentration that the patient is receiving from the
ventilator. (Between 21% & 100%) (room air has 21% oxygen content).
- Most ventilators allow for easy adjustment of oxygen percentage (FIO2) by
means of a dial. Oxygen analyzers, either in-circuit or external, allow the
nurse to ascertain the FIO2 that is being delivered.
- Initially a patient is placed on a high level of FIO2 (60% or higher).
Subsequent changes in FIO2 are based on ABGs and the SaO2.
- In adult patients who can tolerate higher levels of oxygen for a period of
time, the initial FiO2 may be set at 100% until arterial blood gases can
document adequate oxygenation.
- An FiO2 of 100% for an extended period of time can be dangerous
( oxygen toxicity) but it can protect against hypoxemia from
unexpected intubation problems.
- For infants, and especially in premature infants, high levels of FiO2
(>60%) should be avoided.
-Usually the FIO2 is adjusted to maintain an SaO2 of greater than 90%
(roughly equivalent to a PaO2 >60 mm Hg). Oxygen toxicity is a concern
when an FIO2 of greater than 60% is required for more than 25 hours;
therefore, most clinicians attempt to use strategies to allow for
maintenance of an FIO2 of 60% or less.
 Signs and symptoms of oxygen toxicity :1- Flushed face
2- Dry cough
3- Dyspnea
4- Chest pain
5- Tightness of chest
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Critical Care Nursing Theory
Mechanical ventilation
6- Sore throat
 Tidal Volume (VT)
- The volume of air delivered to a patient during a ventilator breath.
- The amount of air inspired and expired with each breath.
(Usual volume selected is between 5 to 15 ml/ kg body weight)
- In the volume ventilator, Tidal volumes of 10 to 15 mL/kg of body weight
were traditionally used.
- Research has identified a phenomenon of iatrogenic lung injury
(volutrauma) in which forces produced in the lungs by the large tidal
volumes may aggravate the damage inflicted on the lungs by the
pathological process that necessitated mechanical ventilation.
- For this reason, lower tidal volume targets (6 to 8 mL/kg) are now
recommended.
Peak Flow/ Flow Rate
- Peak flow is the velocity/ spead of air flow (delivering air) per unit of time,
and is expressed in liters per minute. On many volume ventilators, this is a
separate dial.
- If auto-PEEP (due to inadequate expiratory time) is present, peak flow is
increased to shorten inspiratory time so that the patient may exhale
completely.
- However, increasing peak flow increases turbulence, which is reflected in
increasing airway pressures.
- In the pressure ventilator, the inspiratory time determines the duration of
inspiration by regulating the air flow rate.
- The higher the flow rate, the faster peak airway pressure is
reached and the shorter the inspiration;
- The lower the flow rate, the longer the inspiration.
- A very high flow rate may produce turbulence, shallow inspirations, and
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Assistant Professor Of Critical Care Nursing
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Critical Care Nursing Theory
Mechanical ventilation
uneven distribution of volume.
Respiratory Rate/ Breath Rate / Frequency ( F)
- The number of breaths the ventilator will deliver/minute (10-16 b/m).
- Total respiratory rate equals patient rate plus ventilator rate.
- The nurse double-checks the functioning of the ventilator by observing the
patient’s respiratory rate.
 For adult patients and older children:- Without existing lung disease --- a tidal volume of 12 mL per kg
body weight is set to be delivered at a rate of 12 times a minute
- With COPD ---A reduced tidal volume of 10 ml/kg is to delivered
10 times a minute to prevent overinflation and hyperventilation.
- With chronic pulmonary disease, however, should be ventilated to
stay relatively close to their normal ABG values. This usually means
accepting relatively high carbon dioxide levels, lower-than average
oxygenation, or both.
- With ARDS --- a more reduced tidal volume of 6-8 mL/kg is used with a
rate of 10-12/minute. This reduced tidal volume allows for minimal
volutrauma but may result in an elevated PCO2 (due to the relative
decreased oxygen delivered) but this elevation does not need to be
corrected (termed permissive hypercapnia)
 For infants and younger children:- Without existing lung disease -- a tidal volume of 4-10 ml/kg to be
delivered at a rate of 30-35 breaths per minute.
- With ARDS -- decrease tidal volume and increase respiratory rate
sufficient to maintain PCO2 between 45-55. Allowing higher PCO2 ,
may help prevent ventilator induced lung injury
 Minute Volume (VE)
- The volume of expired air in one minute .
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Critical Care Nursing Theory
Mechanical ventilation
- Respiratory rate times tidal volume equals minute ventilation
- VE = (VT x F)
- Minute volume determines alveolar ventilation.
- Increasing the minute volume decreases the PaCO2. Conversely, decreasing
the minute volume increases the PaCO2.
- In special cases, hypoventilation or hyperventilation is desired.
 In a patient with head injury,
Respiratory alkalosis may be required to promote cerebral
vasoconstriction, with a resultant decrease in ICP.
In this case, the tidal volume and respiratory rate are increased to
achieve the desired alkalotic pH by manipulating the PaCO2.
 In a patient with COPD
Baseline ABGs reflect an elevated PaCO2 should not hyperventilated.
Instead, the goal should be restoration of the baseline PaCO2.
These patients usually have a large carbonic acid load, and lowering
their carbon dioxide levels rapidly may result in seizures.
Rate adjustments may also be necessary to enhance patient comfort or
when rapid rates cause air trapping that result in auto-PEEP.
 I:E Ratio (Inspiration to Expiration Ratio):- The ratio of inspiratory time to expiratory time during a breath
(Usually = 1:2)
 Sigh:- A deep breath.
- A breath that has a greater volume than the tidal volume.
- It provides hyperinflation and prevents atelectasis.
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Critical Care Nursing Theory
Mechanical ventilation
Sigh volume :------------------Usual volume is 1.5 –2 times tidal volume.
Sigh rate/ frequency :---------Usual rate is 4 to 8 times an hour.
 Peak Airway Pressure:- In adults if the peak airway pressure is persistently above 45 cmH2O, the
risk of barotrauma is increased and efforts should be made to try to reduce
the peak airway pressure.
- In infants and children it is unclear what level of peak pressure may cause
damage. In general, keeping peak pressures below 30 is desirable.
 Pressure Limit
- On volume-cycled ventilators, the pressure limit dial limits the highest
pressure allowed in the ventilator circuit.
- Once the high pressure limit is reached, inspiration is terminated.
- Therefore, if the pressure limit is being constantly reached, the designated
tidal volume is not being delivered to the patient.
- The cause of this can be :- Coughing,
- Accumulation of secretions,
- kinked ventilator tubing,
- Pneumothorax,
- Decreasing compliance
- A pressure limit set too low.
 Positive End-Expiratory Pressure (PEEP)
- Positive pressure applied at the end of expiration during ventilator breaths.
- The PEEP control adjusts the pressure that is maintained in the lungs at the
end of expiration.
- PEEP can be visualized on the respiratory pressure gauge or display.
Instead of returning to zero (atmospheric pressure) at the end of
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Critical Care Nursing Theory
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expiration, the pressure value drops to the PEEP level.
- Reduction of PEEP is considered if
- PaO2 is 80 to 100 mm Hg on an FIO2 of 50% or less,
- Hemodynamic stablility,
- Stabilization or improvement of the underlying illness.
- Monitor the effects of PEEP before and after changes in PEEP by
evaluating :- ABGs,
- SaO2,
- Compliance,
- Hemodynamic pressures (cardiac output & blood pressure)
- PEEP is usually USED IN low levels increased in increments of 2 to 5 cm
H2O in the intubated patient.
- Monitor the patient for adverse effects, such as :-
- Hypotension
- Dysrhythmias.
- If these occur, the PEEP is reduced. If higher PEEP is tolerated, the patient
is stabilized on the new PEEP settings for approximately 15 minutes. The
monitored parameters are then repeated.
- Hemodynamic measurements are taken at end-expiration with the patient
on PEEP.
- Cardiac output [ CO ],
- Pulmonary artery pressure [PAP],
- Central venous pressure [CVP],
- Pulmonary artery wedge pressure [PAWP]
- Accuracy in selecting the point of end-expiration on the waveform tracing
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Critical Care Nursing Theory
Mechanical ventilation
is facilitated by using continuous airway monitoring ( PEEP does not need
to be discontinued before obtaining hemodynamic measurements.
- Hemodynamic measurements can be inaccurate (as an indicator of volume
status) if a patient is on high PEEP or the position of the transducer is not
leveled at the phlebostatic axis.
- Attempts are made to minimize removing the patient from the ventilator
when using high levels of PEEP. Oxygenation can deteriorate and be slow
to rebound because it takes a significant amount of time for the effects of
PEEP to be reestablished. Therefore, if the patient is being oxygenated
using an MRB, it must be equipped with a valve that allows levels of
PEEP to be dialed in. An inline suction apparatus may be helpful to
prevent breaking the PEEP circuit to suction the patient.
- PEEP is increased in 2- to 5-cm H2O increments when FIO2 levels are
greater than 50% to attain an acceptable SaO2 (<90%) or PaO2 (>60 to 70
mm Hg).
- PEEP is most often necessary in patients with refractory hypoxemia (e.g.,
those with ARDS), where the PaO2 deteriorates rapidly despite greater
concentrations of oxygen administration.
- PEEP is used to keep alveoli stented open and it may recruit alveolar units
that are totally or partially collapsed.
- This end-expiratory pressure increases the functional residual capacity
(FRC) by reinflating collapsed alveoli, maintains the alveoli in an open
position, and improves lung compliance. This decreases shunt and
improves oxygenation enhances surfactant regeneration by keeping the
alveoli open.
- High levels of PEEP should rarely be interrupted because it may take
several hours to recruit alveoli again and restore the FRC; until this occurs,
oxygenation may suffer.
- The patient who does not have adequate circulating blood volume,
institution of PEEP decreases venous return to the heart, decreases cardiac
output, and decreases oxygen delivery to the tissues.
- If hypotension or decreased cardiac output results from PEEP application,
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restoring circulating intravascular volume with administration of
intravenous fluids may correct the hypotension.
- Another serious complication of PEEP is barotrauma. It can occur in any
mechanically ventilated patient but is most common when high levels of
PEEP are used (≥10 to 20 cm H2O) in lungs with high ventilating pressures
and low compliance, and in patients with obstructive airway disease.
- The development of barotrauma is an emergency and usually requires
placement of a chest tube.
 Sensitivity
- The sensitivity function controls the amount of patient effort needed to
initiate an inspiration, as measured by negative inspiratory effort.
- Increasing the sensitivity (requiring less negative force) decreases the
amount of work the patient must do to initiate a ventilator breath.
- Decreasing the sensitivity increases the amount of negative pressure that
the patient needs to initiate inspiration and increases the work of breathing.
Ensuring humidification and thermoregulation
- All air delivered by the ventilator passes through the water in the
humidifier, where it is warmed and saturated. Because of this, insensible
water loss is decreased.
- Humidifier temperatures should be kept close to body temperature 35 ºC37ºC.
- In some rare instances (severe hypothermia), the air temperatures can be
increased. Caution is advised because prolonged inhalation of air at high
temperatures can cause tracheal burns.
- The humidifier should be checked for adequate water levels
- An empty humidifier contributes to drying the airway, often with resultant
dried secretions, mucus plugging and less ability to suction out secretions.
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- Humidifier should not be overfilled as this may increase circuit resistance
and interfere with spontaneous breathing.
- As air passes through the ventilator to the patient, water condenses in the
corrugated tubing. This moisture is considered contaminated and must be
drained into a receptacle and not back into the sterile humidifier.
- If the water is allowed to build up, resistance is developed in the circuit and
- PEEP is generated. In addition, if moisture accumulates near the
endotracheal tube, the patient can aspirate the water.
- The nurse and respiratory therapist jointly are responsible for preventing
this condensation buildup. The humidifier is an ideal medium for bacterial
growth. Institutional policies should describe the frequency of ventilator
circuit changes.
Ventilator alarms:- Mechanical ventilators comprise audible and visual alarm systems, which
act as immediate warning signals to altered ventilation.
- Mechanical ventilators are used to support life. Alarm systems are
necessary to warn the nurse of developing problems. Alarm systems can be
categorized according to volume and pressure (high and low).
- High-pressure alarms warn of rising pressures. Electrical failure alarms are
necessary for all ventilators.
- Low-pressure alarms warn of disconnection of the patient from the
ventilator or circuit leaks.
- Complications of Mechanical Ventilation:I- Airway Complications,
I- Mechanical complications,
III- Physiological Complications,
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IV- Artificial Airway Complications.
I- Airway Complications
1- Aspiration
2- Decreased clearance of secretions
3- Nosocomial or ventilator-acquired pneumonia
II- Mechanical complications
1- Hypoventilation with atelectasis with respiratory acidosis or hypoxemia.
2- Hyperventilation with hypocapnia and respiratory alkalosis
3- Barotrauma
a- Closed pneumothorax,
b- Tension pneumothorax,
c- Pneumomediastinum,
d- Subcutaneous emphysema.
4- Alarm “turned off”
5- Failure of alarms or ventilator
6- Inadequate nebulization or humidification
7- Overheated inspired air, resulting in hyperthermia
III- Physiological Complications
1- Fluid overload with humidified air and sodium chloride (NaCl) retention
2- Depressed cardiac function and hypotension
3- Stress ulcers
4- Paralytic ileus
5- Gastric distension
6- Starvation
7- Dyssynchronous breathing pattern
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IV- Artificial Airway Complications
A- Complications related to Endotracheal Tube:-
1- Tube kinked or plugged
2- Rupture of piriform sinus
3- Tracheal stenosis or tracheomalacia
4- Mainstem intubation with contralateral lung atelectasis
5- Cuff failure
6- Sinusitis
7- Otitis media
8- Laryngeal edema
B- Complications related to Tracheostomy tube:-
1- Acute hemorrhage at the site
2- Air embolism
3- Aspiration
4- Tracheal stenosis
5- Erosion into the innominate artery with exsanguination
6- Failure of the tracheostomy cuff
7- Laryngeal nerve damage
8- Obstruction of tracheostomy tube
9- Pneumothorax
10- Subcutaneous and mediastinal emphysema
11- Swallowing dysfunction
12- Tracheoesophageal fistula
13- Infection
14- Accidental decannulation with loss of airway
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Nursing care of patients on mechanical ventilation
Assessment:
- Assess the patient
- Assess the artificial airway (tracheostomy or endotracheal tube)
- Assess the ventilator
Assessment of the mechanically ventilated patient
1- Assess the patient at least hourly for the following:
● Vital signs.
- Regularly monitor the vital signs (according to policy)
● Respiratory status
- Respiratory rate for a full minute & compared with the set ventilatory rate.
(To identify whether they are machine-controlled breaths or combined
machine-controlled and spontaneous breaths.)
- Symmetry of chest movement during machine breath
- Synchronization of chest movement with the ventilator during machine
breath
- Breath sounds q2–4h and PRN. (lack of breaths sounds may indicate that
the ETT is displaced)
- Pulse oximetry and end-tidal CO2.
- ABGs as indicated by changes in noninvasive parameters, patient status, or
weaning protocol. ( to evaluate oxygenation status & acid-base status)
- Need for suctioning. (As secretions heard during respiration, a
rise in ventilator peak inspiratory pressures, assess color, amount,
consistency & odor of sputum.)
- Perform systematic assessment of the oral mucosa daily, and with
each cleaning.
● Cardiovascular status
- Heart rate
- Blood pressure,
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- Cardiac output
- Continuous cardiac monitoring should be initiated. (dysrhythmia may
occur due to:- Hypoxia,
- Acidosis,
- Alkalosis,
- Electrolyte imbalance.
- Central venous pressure measurement (reflect right heart function)
- Pulmonary artery pressure
- Hemodynamic effects of initiating positive-pressure ventilation (e.g.,
potential for decreased venous return and cardiac output).
- Electrocardiogram (ECG) for dysrhythmias related to hypoxemia.
- Assess effects of ventilator setting changes (inspiratory pressures, tidal
volume, positive end-expiratory pressure[PEEP], and fraction of inspired
oxygen [FIO2]) on hemodynamic and oxygenation parameters.
● Neurological status
- Level of consciousness;
- Changes in arousability
- Changes in behavior,
- Ability to follow commands,
● Renal status
- Fluid balance
- Intake and output
- Fluid balance
- Hydration status in relation to clinical examination,
- Daily weight
- Urine specific gravity, or serum osmolality
- Electrolyte values
● Gastro-intestinal status
- Gastric secretions for bleeding.
- Bowel sound
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- Nutritional assessment
- PH of gastric secretion
- urea, creatinine, albumin and total protein
blood glucose levels
● Integumentary system/ skin
- Assess skin integrity at least every shift.
- Assess bony prominences for evidence of pressure injury.
● Signs & symptoms of complications
- Signs of decreased cardiac output
- Decrease in pulse &B.P
- Signs of pneumothorax (barotrauma):
- Asymmetrical chest movements;
- Diminished / absent breath sounds on
affected side;
- Cyanosis;
- Tachycardia with weak pulse;
- Hypotension.
- Signs of infection:- Increase temperature above 38ºC,
- Heart rate above 100 b/m
- Erythema of tracheostomy
- Change in secretions characteristics
- Blood work
- Chest X-ray
2- Assess the tracheostomy or endotracheal tube:
- Soiled or loosened tape
- Presence of ulcer in tissue around the endotracheal tube
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- Endotracheal tube position through marking the point at which
the tube exits the mouth or nose. (to know whether it is moved in or out.)
- Cuff inflation pressure. (Inadequate cuff pressure can lead to loss of
delivered tidal volume.)
3- Assess the ventilator parameters/ settings at least hourly :- Mode of ventilation
- Ventilator setting
- Fio2
- Tidal volume VT
- Minute ventilation VE
- Respiratory rate (number of breaths / minute delivered
by the ventilator)
- PEEP level if in use or CPAP
- I:E ratio
- Sigh (frequency / rate & volume)
- Airway pressures q1–2h.
- Airway pressures after suctioning
- Alarm settings, that alarms are turned on.
- Alarm checks q4h (minimum) or per hospital protocol
- Level of water in the humidifying unit
- Temperature of the humidifier
- Tubing and connections to ensure circuit leaks do not occur
- Tubing to ensure that it is well drained and free from water build-up
NB:- Ventilator settings must be frequently evaluated against patient
response.
Nursing Diagnosis:
- Ineffective, airway clearance
- Ineffective Breathing Pattern
- Comfort, Altered pain
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- Fluid volume excess
- Impaired Tissue Perfusion
- Impaired Acid–Base Status
- Nutrition, Altered: less than body requirements
- Altered oral mucous membrane
- Bowel Elimination, Altered: constipation
- Anxiety / Fear
- Communication, Impaired verbal
- Ineffective Coping
- Alteration in Body Image (related to intubation or tracheostomy)
- Impaired Thought Processes—Agitation or Anxiety
- High Risk for Impaired Gas Exchange
- High risk for infection
- High risk for impaired skin integrity
- High Risk for Complications Associated with Mechanical Ventilation
- High Risk for Complications Associated with Tracheostomy
Nursing Interventions:
1-Maintain airway patency& oxygenation
2- Promote comfort
3- Maintain fluid & electrolytes balance
4- Maintain nutritional state
5- Maintain urinary & bowel elimination
6- Maintain eye , mouth and cleanliness and integrity:7- Maintain mobility/ musculoskeletal function:8- Maintain safety:9- Provide psychological support
10- Facilitate communication
11- Provide psychological support & information to family
12- Responding to ventilator alarms /Troublshooting ventilator alarms
13- Prevent nosocomial infection
14- Documentation
Nursing Interventions
1- Maintain patent airway & Oxygenation
- Provide adequate humidification and warming
- Perform measures to mobilize secretions through chest physiotherapy
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and proper suctioning technique to clear the airway (guideline for
proper suctioning technique to be revised.)
- Suction as needed for rhonchi, coughing, or oxygen desaturation.
- Hyperoxygenate and hyperventilate before and after each suction pass.
- Provide tube care through:
- Anchoring ETT securely to prevent tube movement
- Placing an oral bite block to prevent the patient from biting on tube
- Anchoring a large loop of the tube to the bed to facilitate patient
movement without tube movement.
- Checking the tube cuff pressures.
- Administer bronchodilators and mucolytics as ordered.
- Perform chest physiotherapy if indicated by clinical examination
or chest x-ray.
- Turn side to side q2h.
- Consider kinetic therapy or prone positioning as indicated by clinical
scenario.
- Get patient out of bed to chair or standing position when stable.
2- Promote comfort:- Perform arterial punctures by skilled personnel
- Suction tracheal secretions skillfully and gently
- Provide meticulous oral care q1–4h.
- Change position frequently
- Perform range of motion exercises
- Assist the patient to a chair as often as possible when he is stable.
- Prevent pulling and jarring of the ventilator tubing and endotracheal or
tracheostomy tube.
- Document pain assessment, using numerical pain rating or similar scale
when possible.
- Provide analgesia as appropriate, document efficacy after each dose.
- Administer sedation as indicated.
3- Maintain fluid and electrolytes balance:- Administer intravascular volume as ordered to maintain preload
- Administer electrolyte replacements (IV or enteral) per physician’s order.
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4- Maintain nutritional state
- Administer the prescribed medication (cimetidine, ranitidine, and
antacid prophylactically)
- Provide the correct proportions of fats, CHO, and proteins as well as
water through enteral or parenteral routes.
- Establish regular bowel elimination pattern.
- Consult dietitian for metabolic needs &recommendations.
- Provide early nutritional support by enteral or parenteral feeding, start
within 48 hours of intubation.
- Administer bowel regimen medications as ordered, along with adequate
hydration.
- Respiratory muscles, like all other body muscles, need energy to work. If
energy needs are not met, muscle fatigue occurs, leading to discoordination
of respiratory muscles and a decrease in tidal volume.
- Hypomagnesemia and hypophosphatemia have been implicated in muscle
fatigue caused by depleted levels of adenosine triphosphate (ATP). In
prolonged starvation, the body cannibalizes the intercostals and
diaphragmatic muscles for energy.
- Metabolic needs in critically ill patients are much higher than in normal
subjects. Basic caloric requirements are usually increased by 25% for
hospital activity and stress associated with treatment.
. If the gastrointestinal tract is intact, enteral nutrition is preferred and can be
provided through a feeding tube.
- Many chronically ill patients, such as those with COPD, have longstanding protein and calorie malnutrition. Initial tube feeding is started
slowly,
. The nurse observes the patient for signs of intolerance, such as diarrhea
and hyperosmolar dehydration. If the patient tolerates feedings, the rate is
gradually increased until the desired rate is achieved.
- If tube feedings cannot be tolerated, parenteral hyperalimentation should be
considered.
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- Patients who require long-term mechanical ventilation typically need 2,000
to 2,500 calories per day.
- Overly large caloric loads increase carbon dioxide production and can
precipitate respiratory failure in a compromised patient.
5- Maintain urinary and bowel elimination:- Nursing care for urinary catheter
- Maintain urinary output at 30-60 ml/hour
- Nursing measures to prevent constipation and diarrhea
- Avoid constipation by use of :


Mild cathartic
Suppositories
Enemas
6-Maintain eye , mouth and cleanliness and integrity: Eye care
- Use of artificial tears
- Instill lubricating drops or ointment,
- Apply antibiotic drops or ointments as ordered
- Close the eyelids with tape to prevent corneal ulceration
- Apply eye shields, or applying a moisture chamber
- Raise the head of the bed may reduce scleral edema. (Scleral edema is
common in the ventilated patient).
 Oral care
- Perform regular oral hygiene (every 2 hours) to prevent infection
- Establishe a scheduled, regular oral care regimen, using products that
remove plaque and cleanse the mouth without causing pain or irritation.
- Use a non–alcohol-based mouthwash , and brush the teeth a minimum of
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every 8 hours.
- Use toothbrushes which have soft bristles with toothpaste
- Use foam brush instead of toothbrush in patients with bleeding disorders or
a low platelet count
- Perform oral suctioning and care to remove subglottic secretions every 1
to 2 hours. Alternatively, Each oral care should include suctioning of
the subglottic secretions to prevent aspiration.
- Use of a chlorhexidine-based mouthwash, hydrogen peroxide or other
antibacterial or antifungal mouthwashes that is compatible with the
patient’s condition, and should not cause pain due to additives for flavor,
alcohol, or strength.)
- Use half-strength solutions diluted with water may help the patient tolerate
more frequent oral care.
- Place the tube in a central position to avoid contact with the corners of the
mouth and the lips. or it can be rotated from side to side.)
 Skin care:
- Turn the patient every 2 hours
- Provide pressure relief to sitting surfaces at least q1h when patient is out of
bed to chair,.
- Use special mattresses
- Perform complete bed bath for the patient daily and whenever necessary
- Keep the patient’s clothes clean and dry
- Keep the linen clean, dry and unwrinkled
- Massage & lubricate the back and over the bony prominences
7- Maintain mobility/ musculoskeletal function:- Collaborate with physical/occupational therapy staff to encourage patient
effort/participation to increase mobility.
- Progress activity to sitting up in chair, standing at bedside, ambulating with
assistance as soon as possible.
- Assist patient with active or passive range-of-motion exercises to all
extremities at least every shift.
- Keep extremities in physiologically neutral position using pillows or
appropriate splint/support devices as indicated.
8- Maintain Safety:-
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- Keep endotracheal tube in proper position.
- Stabilize endotracheal tube in positio securely
- Note and record the “cm” line on endotracheal tube position at lip or teeth.
- Use patient self-protective devices or sedation per hospital protocol.
- Evaluate endotracheal tube position on chest x-ray (by viewing film or by
report).
- Keep emergency airway equipment and manual resuscitation bag readily
available, and check each shift.
- Inflate cuff using minimal leak technique, or pressure less than 25 mm Hg
by manometer.
- Monitor cuff inflation/leak every shift and PRN.
- Maintain proper inflated endotracheal tube cuff.
- Protect pilot balloon from damage.
- Keep ventilator alarm system activated.
9- Provide Psychological support
- Provide adequate information and explanation of all procedures before
they are initiated.
- Answer alarms promptly.
- Describe the alarm system and explain that it will alert staff in the event
of an accidental disconnection.
- Oxygenate the patient before and after suctioning and remain with the
patient until his respiratory pattern and vital signs return to normal.
- Keep noise levels to a minimum especially during rest periods
- Diminish lights during the night to stimulate night and day cycles
- Place clocks & calendars within the patient’s view & verbally confirm
time & date with the patient.
- Provide a T.V or radio for the patient.
- Communicate a caring and unhurried attitude to the patient.
- Patient participates in self-care and decision making related to own
activities of daily living (ADLs) (e.g., turning, bathing).
- Patient communicates with health care providers and visitors.
- Encourage patient to move in bed and attempt to meet own basic
comfort/hygiene needs independently.
- Establish a daily schedule for bathing, out of bed, treatments, and so forth
with patient input.
- Provide a means for patient to write notes and use visual tools to facilitate
communication.
- Encourage visitor conversations with patient in normal tone of voice and
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subject matter.
- Teach visitors to assist with range-of-motion and other simple care delivery
tasks, to facilitate normal patterns of interaction.
10- Facilitate Communication:- Use alternative methods of communication such as:
- Touch or hand gesturing
- Provide paper and pencil
- Use word or letter boards / picture boards
- Use erasable marker board.
- A number of interventions can facilitate communication with the patient
who has an endotracheal or tracheostomy tube.
-, provide the patient with his or her eyeglasses or hearing aid (if applicable)
Before assessing the patient’s ability to communicate.
- Complete explanations from staff members regarding any procedures to
help decrease the patient’s stress.
- The caregiver can use verbal and nonverbal communication skills.
- Nonverbal communication may include sign language, gestures, or lip
reading.
- If the patient is unable to use these forms of nonverbal communication,
helpful devices include pencil and paper, “grease” boards, and picture or
alphabet boards.
- Once he or she is off the ventilator and tolerating the tracheostomy collar,
the tracheostomy patient can communicate by using “buttons” that occlude
the tracheostomy tube.
- The buttons allow for the passage of air around the tracheostomy to the
vocal chords. The Kirshner button mentioned later in this chapter in
weaning section is one type of button.
- Two other buttons are the Passy-Muir valve and the Shiley speaking valve.
- The Passy-Muir valve is a oneway valve that allows air to enter during
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inspiration, then closes to allow the air to flow over the vocal chords with
exhalation.
- The Shiley speaking valve works in the same way as the Passy-Muir valve,
but has a side port for oxygen tubing to be attached, providing oxygen
support without using a tracheostomy collar.
- Patients with copious secretions are at risk for obstruction of these valves.
- They must be monitored very closely. In addition, patients at high risk for
aspiration, and especially patients with laryngeal or pharyngeal
dysfunction, should be carefully assessed before one of these devices is
used.
- The nurse should store these valves in a container clearly identified with
the patient’s name for safekeeping because each type of valve is relatively
costly.
- The patient should be taught to remove the valve with excessive sputum
during cough and call for assistance to clean the valve before reuse.
- The tracheostomy patient with a speaking valve is at increased risk for
aspiration because the cuff must be deflated for the patient to communicate.
11- Provide psychological support & information to family:- Consider the needs of the patient’s family,
- Establishes open communication with the patient and family,
- Familiarize the family with the physical surroundings of ICU,
- Informing the family of the visiting hours & visitation policies,
- Provide frequent progress reports about their patient’s condition.
- Encourag family participation & involvement in patient care whenever the
patient’s condition allows through guiding and observing the family while
participating in hygienic care, feeding
- Arranges for visits proactively & encourage open visitation policies,,
12- Responding To Alarms
- If an alarm sounds, respond immediately because the problem could be
serious.
- Assess the patient first, while you silence the alarm. If you can not
quickly identify the problem, take the patient off the ventilator and
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ventilate him with a resuscitation bag connected to oxygen source until the
physician arrives.
- A nurse or respiratory therapist must respond to every ventilator alarm.
- Alarms must never be ignored or disarmed.
- Ventilator malfunction is a potentially serious problem. Nursing or
respiratory therapists perform ventilator checks every 2 to 4 hours, and
recurrent alarms may alert the clinician to the possibility of an equipmentrelated issue.
- When device malfunction is suspected, a second person manually
ventilates the patient while the nurse or therapist looks for the cause. If a
problem cannot be promptly corrected by ventilator adjustment, a different
machine is procured so the ventilator in question can be taken out of
service for analysis and repair by technical staff.
Troubleshooting Ventilator Alarms
Alarm type
Possible Causes
High pressure
- Increased secretions
- Kinked ventilator tubing or
endotracheal tube (ETT)
- Patient biting the ETT
Nursing Interventions
- Suction the patient
- Unkink tubing
- Check for adequate lung sounds
bilaterally
- Place an oral airway in patient’s mouth
-Water in the ventilator tubing.
-ETT advanced into right
mainstem bronchus.
- Disconnected tubing
- A cuff leak
- Empty water from tubing
- Notify the doctor, who will order a chest
X-ray to evaluate ETT position
Low pressure
- Secure all connections
- Deflate, then reinflate the cuff
- Recheck cuff pressure (normal pressure
is about 18 mm Hg)
- A hole in the tubing (ETT or - Change the tube.
ventilator tubing)
- A leak in the humidifier
- Tighten the humidifier
Oxygen
- The oxygen supply is
- Notify staff to correct the malfunction
Insufficient or is not properly
and manually ventilate the Patient with
connected.
O2 source - Monitor oxygen saturation
High respiratory - Episodes of tachypnea, anxiety,
rate
pain, hypoxia, fever.
Apnea
- During weaning, indicates that - Assess respirations, V.S ABGs, Sao2 &
the patient has a slow
report
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- Respiratory rate and a period
of apnea.
Temperature
Alarm
- Overheating due to too low or
no gas flow.
- Improper water levels
- A rapid or slow respiratory rate denotes
patient’s intolerance to weaning and a
need for ventilator setting changes.
- Check gas flow
- Check water levels
13- Preventing nosocomial infections:- Wash hands frequently.
- Use meticulous sterile technique when:
- Suctioning and suction on “as needed basis"
- Suction the tracheobronchial tree before suctioning the oropharynx to
avoid introducing oral pathogens into tracheobronchial tree.
- Changing tracheostomy dressings; skin around tracheostomy stoma should
be kept free of secretions, dry and clear at all times.
- Perform stoma care at least every 8 hours using aseptic technique until
stoma is completely healed.
- Perform mouth care every 2 to 4 hours, to reduce the potential of the
oropharynx as a focus of infection.
- Change ventilator equipment and tubing regularly and sterilize it before
using it again.
- Maintain asepsis of ventilator connector when disconnected by placing
them on opened sterile gauze pads and avoid unnecessary disconnection.
- Change the ventilator circuit every 24 to 72 hours.
- Use only sterile water in the humidifier and nebulizer
- Drain & discard condensation in the ventilator tubing regularly
- Keep the connectors on manual resuscitator bags clean and free of
secretions between uses.
- Avoid using resuscitator bag between patients without sterilization.
- Remove and clean oral airway if present every 8 to 12 hours
14- Documentation:The nurse should record all:
- Patient’s measurements
- Ventilator settings
- Nursing care provided
Dr. Abdul-Monim Batiha-
Assistant Professor Of Critical Care Nursing
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Weaning from mechanical ventilator
- Weaning is the gradual process whereby a patient is transferred from
mechanical ventilation support to spontaneous breathing.
Weaning From Mechanical Ventilation
- As soon as the patient is placed on mechanical ventilation, plans begin for
weaning the patient from mechanical support.
- The process to achieve this goal includes:1- Correcting the cause of respiratory failure,
2- Preventing complications,
3- Restoring or maintaining physiological and
psychological functional status.
- Each patient should be evaluated daily for readiness to wean before
initiating weaning trials.
- Comprehensive assessment of the patient’s needs and progress toward
weaning, monitoring of the weaning parameters, and following established
goals promote successful weaning.
- Multidisciplinary and comprehensive approaches to weaning based on a
health care professional (nurse) monitoring and promoting a weaning plan
with continuity have demonstrated positive outcomes.
Methods of Weaning:1- T-piece trial,
2- Continuous Positive Airway Pressure (CPAP) weaning,
3- Synchronized Intermittent Mandatory Ventilation (SIMV) weaning,
4- Pressure Support Ventilation (PSV) weaning.
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1- T-Piece trial
- It consists of removing the patient from the ventilator and having him / her
breathe spontaneously on a T-tube connected to oxygen source.
- The T-piece is connected to the patient at the desired FIO2 (usually slightly
higher than the previous ventilator setting). The patient’s response to and
tolerance of the trial are continuously observed.
- During T-piece weaning, periods of ventilator support are alternated with
spontaneous breathing.
- The goal is to progressively increase the time spent off the ventilator.
- The duration of T-piece trials is not standardized,
- Some clinicians extubate if an initial trial of 30 minutes ends with
acceptable ABGs and patient response.
- Some clinician use trials of increasing frequency and duration to
evaluate and build the patient’s endurance with periods of rest on
the ventilator between trials. When the latter method is used, the
patient is usually deemed ready to be extubated after 25 successive
hours on a T-piece.
2-Synchronized Intermittent Mandatory Ventilation ( SIMV) Weaning
- SIMV is the most common method of weaning. allowing for some
spontaneous breathing (to prevent respiratory muscle atrophy) while
providing a backup rate.
- It consists of gradually decreasing the number of breaths delivered by the
ventilator to allow the patient to increase number of spontaneous breaths
- Weaning with the SIMV method entails a gradual reduction in the number
of delivered breaths until a low rate is reached (usually 4 breaths/minute).
The patient is then extubated if all other weaning criteria are met.
- However, low levels of SIMV (fewer than 4 breaths/ minute) may result in
a high level of work and fatigue.
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3-Continuous Positive Airway Pressure ( CPAP)Weaning
- CPAP is very similar to T-piece trial, except the patient is placed on the
CPAP mode instead of a T-tube.
- When placed on CPAP, the patient does all the work of breathing without
the aid of a back up rate or tidal volume.
- No mandatory (ventilator-initiated) breaths are delivered in this mode i.e.
all ventilation is spontaneously initiated by the patient.
- CPAP entails breathing through the ventilator circuit with a small amount
(or zero amount) of positive pressure.
4- Pressure Support Ventilation (PSV) Weaning
- The patient must initiate all pressure support breaths.
- During weaning using the PSV mode the level of pressure support is
gradually decreased based on the patient maintaining an adequate tidal
volume (8 to 12 mL/kg) and a respiratory rate of less than 25
breaths/minute.
- PSV is associated with less work of breathing than with volume modes, so
longer weaning trials may be tolerated
- Low levels of PSV decrease the work of breathing associated with
endotracheal tubes and ventilator circuits
- PSV weaning is indicated for :- Patients who are difficult to wean from the mechanical
ventilator using conventional means (T-piece, SIMV, CPAP),
- Patients with small spontaneous tidal volume.
CPAP & PSV are modes of mechanical ventilation that are completely
dependent on the spontaneous effort of the patient for initiation of
inspiration. These modes are often used for weaning purposes.
Weaning readiness Criteria
- Awake and alert
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Assistant Professor Of Critical Care Nursing
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Critical Care Nursing Theory
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- Hemodynamically stable, adequately resuscitated, and not requiring
vasoactive support
- Arterial blood gases (ABGs) normalized or at patient’s baseline
- PaCO2 acceptable
- PH of 7.35 – 7.45
- PaO2 > 60 mm Hg ,
- SaO2 >92%
- FIO2 ≤40%
- Positive end-expiratory pressure (PEEP) ≤5 cm H2O
-
F < 25 / minute
- Vt 5 ml / kg
- VE 5- 10 L/m (f x Vt)
- VC > 10- 15 ml / kg
- NIF > - 20 cm H2O ( indicates patient’s ability to take a deep
breath & cough),
- Chest x-ray reviewed for correctable factors; treated as indicated,
- Major electrolytes within normal range,
- Hematocrit >25%,
- Core temperature >36°C and <39°C,
- Adequate management of pain/anxiety/agitation,
- Adequate analgesia/ sedation (record scores on flow sheet),
Dr. Abdul-Monim Batiha-
Assistant Professor Of Critical Care Nursing
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Critical Care Nursing Theory
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- No residual neuromuscular blockade.
Types of Weaning Interventions:1-Short term weaning for patient requiring short-term ventilation (≤3 days)
2-Long term weaning for patient requiring long-term ventilation (>3 days).
1- Short-Term Ventilation Weaning
- The weaning process in this setting may proceed rapidly, based on
individual patient response to reducing ventilatory support.
- Weaning within a short time is desirable because physiological changes
caused by the mechanical ventilation begin within 72 hours.
- This type of weaning intervention is indicated for patients typically
intubated for a short time for :1- Surgical or other procedures,
2- Acute exacerbation of an underlying lung disease that can easily
reversed,
3 - Respiratory distress related to underlying pulmonary disease or
traumatic injury.
4- The need for airway protection because of :a- Airway swelling (e.g.,as a result of acute inhalation injury)
b- An acute neurological event (e.g., drug overdose).
c- Significant change in mental status (e.g., as with
cerebrovascular accident [CVA] or head injury).
- The goal of short term weaning should be extubation as soon as :- The procedure is completed,
- The patient is stabilized,
- The patient is able to protect the airway.
Dr. Abdul-Monim Batiha-
Assistant Professor Of Critical Care Nursing
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Critical Care Nursing Theory
Mechanical ventilation
2- Long-Term Ventilation Weaning
- The process of long term weaning often takes weeks. Usually this process
is complicated, and involves multiple delays and setbacks.
- The longer a patient requires mechanical ventilation, the greater the
potential for development of volume–pressure trauma, which consists of:- Multiple alveolar fractures
- Leaky alveolar–capillary membranes.
- During long-term weaning, the patient may fail a weaning trial and should
then be rested on the ventilator before another trial is attempted. The rest
period is to allow the recovery of the respiratory muscles.
- Patients who fail a weaning trial often exhibit rapid, shallow breathing
patterns consistent with their respiratory muscle weakness.
- Regular reevaluation of the weaning plan by the multidisciplinary team,
coupled with continuous communication with the patient and family, is
necessary .
- Patients on mechanical ventilation for longer than 72 hours or those having
failed short-term weaning often display significant deconditioning as a
result of acute or chronic complex illness, or both.
- These patients usually require a period of “exercising” respiratory muscles
to regain the strength and endurance needed for successful return to
spontaneous breathing.
- The use of fenestrated tracheostomy tube improve weaning tolerance and
patient comfort in long term weaning intervention.
- The goals of long term weaning are:
- To have the patient tolerate two to three daily weaning trials of
Dr. Abdul-Monim Batiha-
Assistant Professor Of Critical Care Nursing
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Critical Care Nursing Theory
Mechanical ventilation
reduction in ventilatory support without exercising to the point of
exhaustion.
- To rest the patient between weaning trials and overnight on
ventilator settings that provide diaphragmatic rest, with minimal or
no work of breathing for the patient.
Nursing Role in Weaning from mechanical ventilator
Role of nurse before weaning:1- Ensure that indications for the implementation of Mechanical ventilation
have improved
2- Ensure that all factors that may interfere with successful weaning are
corrected:- Acid-base abnormalities
- Fluid imbalance
- Electrolyte abnormalities
- Infection
- Fever
- Anemia
- Hyperglycemia
- Protein loss
- Sleep deprivation
3- Assess readiness for weaning
4- Ensure that the weaning criteria / parameters are met.
5- Explain the process of weaning to the patient and offer reassurance
to the patient.
6- Initiate weaning in the morning when the patient is rested.
7- Elevate the head of the bed.
8- Place the patient upright to facilitate breathing.
9- Ensure a patent airway and suction if necessary before a weaning trial,
10- Suction the tracheobronchial secretions before weaning.
11- Provide for rest period on ventilator for 15 – 20 minutes after suctioning.
12- Ensure patient’s comfort.,
13- Administer pharmacological agents for comfort, such as bronchodilators
or sedatives as indicated.
14- Help the patient through some of the discomfort and apprehension.
15- Support and reassurance help the patient through the discomfort and
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Assistant Professor Of Critical Care Nursing
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Critical Care Nursing Theory
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apprehension as remains with the patient after initiation of the weaning
process.
16- Evaluate and document the patient’s response to weaning.
Role of nurse during weaning:1- Wean only during the day.
2- Remain with the patient during initiation of weaning.
3- Instruct the patient to relax and breathe normally.
4- Monitor the respiratory rate, vital signs, ABGs, diaphoresis and use of
accessory muscles frequently.
5- Monitor the patient continuously for signs of weaning intolerance: Signs of Weaning Intolerance Criteria
- Diaphoresis
- Dyspnea
- Labored respiratory pattern
- Increased anxiety
- Restlessness
- Decrease in level of consciousness
- Dysrhythmias
- Increase or decrease in heart rate of > 20 beats /min.
or heart rate > 110b/m
- Sustained heart rate >20% higher or lower than baseline
- Increase or decrease in blood pressure of > 20 mm Hg
- Systolic blood pressure >180 mm Hg or <90 mm Hg
- Increase in respiratory rate of > 10 above baseline or > 30
- Sustained respiratory rate greater than 35 breaths/minute
- Tidal volume ≤5 mL/kg
- Sustained minute ventilation <200 mL/kg/minute
- SaO2 < 90%
- PaO2 < 60 mmHg
- A decrease in PH of < 7.35.
- Increase in PaCO2
6- Stop the weaning trial and return the patient to “rest” settings if the
patient displays any of the signs of weaning intolerance.
Dr. Abdul-Monim Batiha-
Assistant Professor Of Critical Care Nursing
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Critical Care Nursing Theory
Mechanical ventilation
Short Term Weaning Intervention
1- Reduce ventilator rate,
2- Convert to pressure-support ventilation (PSV) only.
3- Wean PSV as tolerated to ≤10 cm H2O.
 If patient meets tolerance criteria for at least 2 hours on this level
of support and meets extubation criteria:- Extubate the patient.
 If patient fails tolerance criteria:- Increase PSV or add ventilator rate as needed to achieve “rest” settings
(consistent respiratory rate <20 breaths/minute) and review weaning
criteria for correctable factors.
- Repeat wean attempt on PSV 10 cm after rest period (minimum 2 hours).
 If patient fails second wean trial:- Return to rest settings and use “long-term” ventilation weaning approach.
Long Term Weaning Intervention
- Transfer to pressure-support ventilation (PSV) mode,
- Adjust support level to maintain patient’s respiratory rate at less than
35 breaths /minute.
- Observe for 30 minutes for signs of early failure (intolerance criteria)
 If tolerated,
- Continue trial for 2 hours,
- Return patient to “rest” settings by adding ventilator breaths or increasing
PSV to achieve a total respiratory rate of less than 20 breaths/minute.
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Assistant Professor Of Critical Care Nursing
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Critical Care Nursing Theory
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- Repeat trial for 2 to 4 hours at same PSV level as previous trial after at
least 2 hours of rest,.
 If the patient exceeds the tolerance criteria
- Stop the trial
- Return to “rest” settings.
- Perform the next weaning trial at a higher support level than the “failed”
trial.
- Record the results of each weaning episode, including specific parameters
and the time frame if “failure” observed, on the ICU flow sheet.
- The goal is to increase the length of the trials and reduce the PSV level
needed on an incremental basis.
- With each successive trial, the PSV level may be decreased by 2 to 4 cm
H2O, the time interval may be increased by 1 to 2 hours, or both, while
keeping the patient within tolerance parameters.
- The pace of weaning is patient-specific and tolerance may vary from day to
day.
- Review readiness criteria for correctable factors daily and each time
the patient “fails” a weaning trial.
- Ensure nocturnal ventilation at “rest” settings (with a respiratory rate of
<20 breaths/minute) for at least 6 hours each night until the patient’s
weaning trials demonstrate readiness to discontinue ventilatory support.
Discontinuing Mechanical Ventilation
- Wean the patient until ventilator settings are
- FIO2 ≤40%,
- PSV ≤10 cm H2O,
- Positive end-expiratory pressure (PEEP) ≤8 cm H2O.
- Ensure that these settings are well tolerated,
- Place the patient on continuous positive airway pressure (CPAP) 5 cm
H2O or (if tracheostomy in place) on tracheostomy collar.
Dr. Abdul-Monim Batiha-
Assistant Professor Of Critical Care Nursing
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Critical Care Nursing Theory
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 If the patient meets tolerance criteria over the first 5 minutes,
- Continue the trial for 1 to 2 hours.
 If clinical observation and arterial blood gases (ABGs) indicate that
the patient is maintaining adequate ventilation and oxygenation on
this “minimal” support,
- Consider the following options
- Attempt extubation if the patient meets extubation criteria
 If the patient is on tracheostomy collar,
- Continue the trials two to three times per day with daily
increases in time on tracheostomy collar by 1 to 2 hours per
trial until total time off the ventilator reaches 18 hours
per day.
- At this point, the patient may be ready to remain on tracheostomy
collar for longer than 25 hours unless the tolerance criteria are
exceeded.
- Both of these factors are affected by physiological changes that change the
resting position of the diaphragm. With COPD, the resting length is shorter
(weakening force of contraction), and with diaphragmatic distension
ascites, or morbid obesity, the diaphragm must push down
abdominal contents as it contracts.
- Reactive airway disease increases the resistance to air flow, with increased
workload for muscles of respiration. Any of these abnormalities can lead to
significant fatigue of these muscles and respiratory distress.
- Respiratory muscle fatigue impedes weaning. It may take as long as 25
hours of complete rest (the mechanical ventilator assumes all of the work
of breathing for the patient) for recovery of fatigued respiratory muscles.
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Critical Care Nursing Theory
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Therefore, it is common practice to increase ventilatory support at night to
ensure rest. This can be accomplished with any of the “resting” modes, so
long as the patient’s respiratory rate is less than 20 breaths/minute. The
intent here is to promote and simulate the normal decrease in rate and work
of breathing that occurs during each person’s sleep/rest cycle.
 If signs of fatigue or respiratory distress develop.
- Discontinue weaning trials.
- Limit the use of sedatives and narcotics during weaning to only the level of
medication clearly needed to control pain or anxiety.
Role of nurse in extubation:1- Ensure that extubation criteria are met .
 Extubation Criteria
a- Mental status: an appropriate level of consciousness
(Alert and able to respond to commands)
b- Presence of good cough and gag reflexes,
c- Able to protect airway and clear secretions
d- Able to move air around endotracheal tube with cuff deflated
and end of tube occluded
2- Perform the “cuff leak test” before extubation in all patients,
especially in those with a history of :- Difficult intubation,
- Reactive airway disease.
3- Perform the cuff leak test by:- Suctioning of the oropharynx
- Deflating the tube cuff
- Occluding the endotracheal tube for a brief
period to demonstrate an air leak with
patient inspiration.
Dr. Abdul-Monim Batiha-
Assistant Professor Of Critical Care Nursing
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Critical Care Nursing Theory
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NB
(Absence of a leak can indicate edema, and may predict laryngeal stridor
post-extubation. )
 If the cuff leak test fails,
- Give the patient corticosteroids as prescribed to reduce edema for
25 to 48 hours,
- Re-assess for cuff leak.
- Prepare the patient for direct visualization of the trachea with a
bronchoscope as prescribed before extubation to determine if the
edema has resolved.
- Ensure that a qualified person is available to re-intubate emergently if the
patient does not tolerate extubation.
- Explain the procedure and prepare the patient
- Suctions the patient’s tube and posterior oropharynx.
- Ensure that equipment includes an manual resuscitation bag (MRB) and
mask at bedside.
- Loosen the endotracheal tube securing device or tape,
- Deflate the tracheal cuff.
- Remove the endotracheal tube quickly while having the patient cough.
- Suction the patient’s mouth
- Apply humidified oxygen immediately.
- Evaluate the patient for immediate signs of distress: stridor, dyspnea,
and decrease in SaO2.
- Administer medications for treatment of stridor as prescribed
- Administer epinephrine by inhalation
- Administer intravenous steroids (because steroids
do not work immediately, they are given before
extubation in those at risk).
- Prepare for immediate re-intubation if these interventions fail
Documentation:- Date & time of starting weaning
- Method of weaning used
- ABGs & oxygen saturation
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Assistant Professor Of Critical Care Nursing
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Critical Care Nursing Theory
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- Spontaneous respiratory rate
- Use of accessory muscle
- Time spent in the weaning process
- Patient’s response
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Assistant Professor Of Critical Care Nursing
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