Download 2nd Quarter – CPAP Packet - For Medical Professionals

EMS Continuing Education
2nd Quarter 2013 Packet
Continuous Positive Airway Pressure
(CPAP)
It’s 3 a.m. on an unusually slow night. Your partner is dozing on the couch, and you’re
watching your fifth consecutive Emergency rerun when your tones sound with an EMS
call of “Difficulty breathing, cardiac history, 84-year-old female” at a local senior citizen
complex. You know you’ve been to this apartment before and cared for a patient with
congestive heart failure. On the way, you discuss with your partner how you’re surprised
she survived her last trip to the hospital as she needed to be intubated in the emergency
department. You’re both prepared for a priority patient.
An excited neighbor in a nightgown meets you at the elevator and guides you to the
apartment. You hear the familiar gurgling sounds of pulmonary edema from the hallway,
and inside find Mrs. Miller seated upright on her bed. She is pale, diaphoretic and
struggling for every breath. “I....need...the...mask...!” she tells you between gasps. A
quick assessment reveals that she woke up short of breath, just as she has before when
her “lungs filled up.” She denies chest pain but has some chest discomfort and has a long
list of medications that includes nitroglycerin and Lasix.
Your partner immediately places her on a NRB mask and obtains a set of vitals, while
you assemble a continuous positive airway pressure (CPAP) circuit. Her heart rate is 140,
sinus tachycardia on the monitor, pulse ox 82%, respiratory rate 36 with coarse crackles
in all lung fields, and BP 210/150. You connect the CPAP tubing to your portable oxygen
tank, administer a spray of nitroglycerin under her tongue, and place the tight-fitting
mask on her face, while your partner obtains IV access. A few minutes after the mask is
applied, she becomes less anxious and nods her head when you ask if it is easier to
breathe. You have also called ALS to assist with the patient and they have arrived. They
apply an inch of nitroglycerin paste to her chest, and help you package her onto the
stretcher. You reassess her vitals en route to the hospital; she now has a heart rate of 128,
pulse ox 100%, respiratory rate 24, BP 178/94, and you obtain a 12-lead ECG that shows
1 mm of ST depression in leads I, aVL, V5 and V6. You call the hospital to advise that
your patient is on CPAP. They give you a room assignment and assure that a respiratory
therapist will be standing by.
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At the hospital, Mrs. Miller is transferred to a BiPAP machine, given Lasix and started on
a nitroglycerin infusion. Her skin color is almost back to normal now, and she is not
nearly as diaphoretic. As you say goodbye to her, she thanks you several times, now able
to speak much easier.
Because respiratory distress is one of the most common causes for calling 9-1-1, EMS
providers have several tools to treat and improve discomfort before arriving at the
hospital. Once a differential diagnosis can be made for the cause of the breathing
difficulty, high-flow oxygen and appropriate medications usually help alleviate it.
However, some patients are in such profound distress that their breathing must be assisted
with a bag-valve mask, followed by intubation. While often necessary for survival,
endotracheal intubation is an invasive procedure that carries a host of drawbacks and
complications. Noninvasive ventilatory support in the prehospital setting is an effective
treatment option for patients who need some support for breathing but can still maintain
an airway. In cases of acute pulmonary edema from congestive heart failure, COPD and
asthma exacerbations, it has been shown to decrease the need for endotracheal intubation
and relieve symptoms. Noninvasive ventilatory support is delivered by continuous
positive airway pressure (CPAP) and bi-level positive airway pressure (BiPAP) devices.
Airway Management Options
Historically, endotracheal intubation has been the standard method used to assist
ventilation in the patient who is in danger of respiratory arrest or remains hypoxic after
other interventions have failed. It provides definitive airway control and a method of
precisely titrating respiratory rate and tidal volume. It can also adjust the positive end
expiratory pressure (PEEP), which is pressure in the lungs at the end of expiration that
keeps collapsing airways open.
Intubation can be difficult to accomplish in the field, however, with a patient who is still
breathing and has a gag reflex. If medications are not available to facilitate intubation,
you must wait until the patient becomes so fatigued and hypoxic that he loses his gag
reflex before attempting an oral intubation. If medications are used and intubation
attempts are unsuccessful, the results can be deadly. Another option for the breathing
patient is nasal intubation, which can cause bleeding that compromises the airway.
Hypoxia, lethal dysrhythmias, tracheal trauma and aspiration are potential complications
of either method. Even when intubation is successful, intubated patients lose the warming
and humidifying functions of the upper airway until they can be placed on a ventilator.
While intubated and on a ventilator, patients are unable to talk, must remain sedated until
they are weaned off, and are at an increased risk of pneumonia. Even though intubation
will provide adequate ventilation and is often lifesaving, it is advantageous to avoid it if
less-invasive options are available.
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CPAP is a noninvasive option for EMS providers to provide respiratory support through a
mask rather than an ET tube. It can get patients through their crisis without their having
to be intubated, or at least buy some time until intubation is needed. CPAP is the most
common form of noninvasive ventilatory support utilized in the pre-hospital environment
because of the small size of the equipment needed and oxygen-powered generator. For
our providers at the EMT-Basic or EMT-Intermediate Technician level, it delivers
continuous positive air pressure at 5 cm H2O throughout the respiratory cycle. For our
providers at the paramedic level, it uses 5 cm, 7.5 cm or 10 cm pressure. CPAP is also
used in the home to treat obstructive sleep apnea, where it works by preventing the upper
airway structures from collapsing and stops subsequent hypoxic episodes that disrupt the
sleep cycle. It has more recently been studied for emergent treatment of respiratory
distress as a means of decreasing the patient’s work of breathing. This is different from
BiPAP, which delivers two levels of positive pressure during the different phases of the
respiratory cycle. If CPAP is set for 5 cm H2O throughout the respiratory cycle, BiPAP
might deliver 10 cm H2O during inspiration and 5 cm H2O during expiration. While
BiPAP units, which are used most often in hospitals, can provide more relief, they are
less practical for field use because they are larger, more expensive and require more
energy.
Prehospital Research of CPAP
While endotracheal intubation is generally viewed as a last resort for respiratory distress,
emergency department studies of CPAP show that it seems to have the most benefit when
initiated early. Logically, this would carry over to the field and even be useful in systems
with short transport times. A few clinical trials have studied pre-hospital use of CPAP,
and all show a decrease in intubations and symptom improvement with no major
complications.
Benefits of CPAP
Prior to the advent of CPAP and alternative or rescue airways, EMS providers
administered ventilatory support in the field with bag-valve masks (BVMs) or the
invasive intervention of intubation. CPAP helps prevent the need for mechanical
ventilation and intubation by delivering positive end-expiratory pressure (PEEP) while
decreasing the incidence of barotrauma. It also helps EMS providers avoid complications
from intubation-related sedation or paralysis, in addition to such unexpected difficulties
as hypoxia, lethal dysrhythmia, tissue trauma, aspiration and undetected esophageal
intubation.
Provider use of CPAP helps reduce patients’ admission to an intensive care unit (ICU),
reducing the increased morbidity and mortality associated with ventilator-acquired
pneumonia (VAP) and such nosocomial infections as Methicillin-resistant
Staphylococcus aureus (MRSA) and Klebsiella.
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Every EMS provider should understand the physiology of breathing and how CPAP
works, so they can properly use this therapy to treat patients in respiratory distress.
Physiology of Ventilation
To understand how CPAP works, providers should begin with an understanding of the
physiology of the pulmonary system. The lower airways resemble an inverted tree
extending from the trachea through the bronchi to the alveolar sacs.
Alveoli form the primary constituent of lung tissue. An average adult has 300–600
million alveoli, each of which measures about 1/3 mm in diameter. Alveolar walls consist
of a single layer of cells and elastin fibers that permit stretching and contracting during
ventilation.
The internal surface of each alveolus is covered by a thin film of fluid containing
surfactant that decreases surface tension and keeps alveolar walls from collapsing and
sticking together on expiration. This reduces the work of reopening them with each
breath.
Surfactant production diminishes when lungs are hypoperfused and hypoxic. Without
adequate surfactant, alveoli collapse and atelectasis develops. The lungs become stiff, and
alveoli ultimately fill with fluid.
The alveolar-capillary surface area available for gas exchange is about 1 sq. meter/kg of
body weight in the average adult. Normally, the blood-gas barrier is one cell thick. Every
red blood cell circulating through the lungs spends about one second in the pulmonary
capillary network. During that time, it goes through two to three alveoli and picks up its
full complement of oxygen (O2) in one-fifth of a second.
The brief time each red blood cell spends in the pulmonary capillary network is normally
sufficient for adequate gas exchange. However, this isn’t the case in states of disease,
such as emphysema and lung cancer, when the gas exchange surface area is reduced by
more than two-thirds and the membranes are thicker or interstitial or alveolar fluid is
present. In this situation, O2 diffusion will be inadequate to meet the body’s demands at
rest, and carbon dioxide (CO2) won’t be adequately eliminated.
The relationship between pressure inside the pulmonary system and atmospheric pressure
determines the direction of airflow, and the amount of air moved into the lungs depends
on airway resistance and lung compliance.
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Airway Resistance
Several factors determine airway resistance. These include airway diameter, motor nerve
impulses, the length of the airway, lung volume, tissue resistance, compliance and work
of breathing.
Airway diameter: If the airway radius is narrowed by half, the resistance through it
increases by 16. There’s a reduction in airflow to the fourth power. Airway diameter is
affected by receptors in the trachea and large bronchi that are activated by irritants or
immune system responses.
Motor nerve impulses: Resistance may greatly increase due to airway secretions or
bronchial constriction. The vagus nerve constricts bronchioles and sympathetic
stimulation dilates bronchioles. Release of histamine causes constriction of smooth
muscle resulting in bronchoconstriction.
Length of the airways: If length doubles, resistance doubles.
Lung volume: Diminished lung volume results in increased airway resistance. Small
airways may close completely. Patients with increased airway resistance often breathe at
high volumes to help decrease airway resistance.
Tissue resistance: Tissue resistance accounts for about 20% of the total airway resistance
in young patients, although it may be increased with some diseases.
Compliance: This is the ability of the lungs and thorax to expand easily with inhalation.
Good compliance means easy expansion. A normal breath of 500 mL requires a
distending pressure of less than 3 cm of water (H2O). A child’s balloon may need a
pressure of 300 cm of water for the same change in volume.
Work of breathing: In healthy persons, the energy required for normal quiet breathing is
small (only 3% of the total body expenditure). Loss of surfactant, increased airway
resistance, decreased compliance, airflow obstruction and lung hyperinflation increase
the work of breathing. As lungs become “stiffer,” respiratory muscles become fatigued,
resulting in ventilatory failure. Anything that increases functional reserve capacity (FRC)
will improve lung mechanics and enable more work to be generated for the same effort.
Although work of breathing is difficult to measure at the bedside, it’s easy to appreciate
clinically. EMS providers can do this by observing the patient for tripoding, use of
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accessory muscles and retractions. O2 consumption increases as ventilatory reserves
decrease. As the amount of O2 needed becomes excessive, the body becomes hypoxic.
How CPAP Works
CPAP has been most studied as a treatment option for patients with pulmonary edema
from congestive heart failure, where distress is caused by increased vascular pressure
from the failing left ventricle that forces interstitial fluid into the alveoli. This fluid not
only impedes oxygen exchange, but it washes out the surfactant that holds alveolar sacs
open, allowing them to collapse. CPAP increases pressure in the lungs and holds open
collapsed alveoli, pushes more oxygen across the alveolar membrane, and forces
interstitial fluid back into the pulmonary vasculature. This improves oxygenation,
ventilation and ease of breathing. In addition, the increased intrathoracic pressure
decreases venous return to the heart and reduces the overwhelming preload (pressure in
the ventricles at the end of diastole). It also lowers the pressure that the heart must pump
against (afterload), both of which improve left ventricular function.
The mechanism by which CPAP can be useful in treating COPD and asthma is less
understood. In these patients, respiratory distress is caused by constriction of the lower
airways from an irritant (bronchoconstriction), collapse of the alveolar walls from disease
and plugged airways from excess mucus secretion. Patients with COPD are often unable
to completely empty their lungs during expiration, which leaves positive pressure in the
airways at the end of expiration. This is known as intrinsic positive end expiratory
pressure (PEEP) that is usually about 5 cm H2O. It must be overcome before negative
pressure can be generated to inhale more air. These patients will exhale through pursed
lips to keep the airways open. With CPAP applied, this pressure is overcome
mechanically and the workload is taken off of the patient. If one exhales against
resistance, smaller, dependent airways are “splinted” open at the end of expiration, and
small bronchi and alveoli don’t collapse. Keeping these structures open on exhalation
allows the muscles that were working to keep them open (the ones exerting auto-PEEP)
to be recruited into inspiration. When alveoli stay open, inspiratory effort doesn’t have to
be expended to reinflate them. This reduces inspiratory work, relieves respiratory muscle
fatigue and decreases work of breathing. In addition to reinflating collapsed alveoli,
CPAP delivers more oxygen, can pop the obstructing mucus secretions, and delivers
nebulized medications more effectively.
CPAP gets many patients with severe inspiratory muscle fatigue through their acute crisis
without the need for intubation. CPAP delivers a constant positive pressure to the airways
of a spontaneously breathing patient during inspiration and expiration through a
noninvasive mask. CPAP raises inspiratory pressure above atmospheric pressures and
then applies PEEP to exhalation.
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Increased pressure in the airways also allows for better distribution of gases, which leads
to an increase in alveolar pressure and re-expansion of collapsed alveoli. This reverses
micro-atelectasis. In addition, maintaining inspiratory and expiratory pressures above
normal levels results in improved functional reserve capacity, better lung compliance and
bronchodilation. This positively affects the ventilation/perfusion (V/Q) ratio.
As alveoli stay open, gas-exchange time can double. This increases oxygen levels in the
blood and decreases CO2 levels—as long as respiratory diffusion and pulmonary
perfusion dynamics work properly. This reduces hypoxia and reverses hypercarbic
ventilatory failure.
CPAP changes alveolar/hydrostatic pressure dynamics. An increase in alveolar pressures
will counterbalance interstitial or capillary hydrostatic pressures and will slow or stop
movement of fluid into the alveoli. Positive airway pressure pushes fluid out of the
alveoli in pulmonary edema and will stop further influx. It also improves cardiac output.
By reducing pulmonary edema, more fluid becomes available for circulation and preload
fluid availability increases. Increased preload equals increased cardiac output.
In cardiogenic pulmonary edema due to heart failure, CPAP increases pressures
throughout the thorax, including pressure surrounding the left ventricle (LV). This makes
it easier to eject blood out of the heart. Similarly, pressure surrounds the thoracic cavity
but not the abdominal aorta, giving the impression of reduced LV afterload outside of the
thoracic cavity. This will increase cardiac output unless PEEP levels are too high. High
intrathoracic pressures greatly reduce preload to the right heart and will reduce the blood
pressure.
CPAP produces an increase in tidal volume with a subsequent reduction in the work of
breathing. Stabilization of minute ventilation with an increase in FRC should improve
ventilation-perfusion relationships and potentially reduce oxygen requirements. This
allows for an increase in available O2 for tissue perfusion and a decrease in CO2 levels.
If CO2 elimination from the lungs decreases, CO2 levels in the blood will rise. This
condition, called hypercarbia, occurs with respiratory depression or hypoventilation,
which can be caused by airway obstruction, respiratory muscle impairment or pulmonary
obstructive diseases, among other pathologies. EMS providers should correct hypercarbia
by increasing ventilation and attempting to correct the underlying cause. Improved
ventilation and gas exchange are major benefits of CPAP.
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Who Needs CPAP?
Patients who benefit from CPAP frequently present with a chief complaint of dyspnea.
Dyspnea can be caused by cardiac, pulmonary, neuromuscular,
psychologic/social/spiritual etiologies or any combination of them. The severity varies
widely among patients. EMS providers should get a good baseline assessment to trend
improvement.
While some protocols have specific guidelines for when CPAP should be applied, it is
generally indicated for a patient in moderate to severe respiratory distress who is
completely alert and able to maintain his airway. While most patients improve shortly
after CPAP is applied, remember that it is helping alleviate symptoms more than the
underlying problem. It must be used as an adjunct to medications, and some patients will
still deteriorate after it is applied. While CPAP makes it easier for patients to breathe, it is
not a ventilator and does not breathe for them. Therefore it is contraindicated in cases of
hypoventilation, decreased mentation or any potential airway compromise, such as
vomiting. These patients are past the point where CPAP can be effective, and must have
their ventilations assisted with a bag-valve mask and be intubated. It is also not
appropriate for minor asthma and COPD exacerbations that quickly respond to
medications.
Directions for Use
While equipment varies among manufacturers, CPAP sets designed for field use are
powered by an oxygen source that can deliver 50 psi. Some generators have a fixed flow
rate, while others can be adjusted. The percentage of oxygen delivered (FiO2) usually
starts at 30% and can be increased, depending on the needs of the patient. The rest of the
equipment comes in a prepackaged kit, which includes a face mask, corrugated tubing,
bacteria filter and PEEP valve.
When applying CPAP to a patient, start by connecting the circuit to the oxygen source
according to the manufacturer’s directions. Next, apply the mask with the enclosed straps
and ensure that there is an airtight seal similar to a bag-valve mask. Once a seal is
achieved, install the PEEP valve and adjust the FiO2 as needed. Many patients have been
on CPAP before and will ask for it; for others, it can be scary and they must be coached
through the experience. Explain that it will feel like they are sticking their head out of a
car window, and encourage them to breathe in through their nose and exhale through
their mouth against the pressure. They may also hold the mask themselves to get used to
it before the straps are applied. Once applied, the mask may be removed for a few
seconds to administer sublingual nitroglycerin, and the corrugated tubing can be cut to
install a nebulizer. While this may seem cumbersome, with practice it can be
accomplished very quickly and will not significantly delay scene time.
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Complications and Side Effects of CPAP
While virtually all of the clinical trials evaluating CPAP show only minor complications
and side effects, there are a few things to watch for. The most common problem is
anxiety; a few patients will not tolerate it despite coaching. In these cases, it should be
removed. Because CPAP increases intrathoracic pressure, there is a theoretical risk of
hypotension and a pneumothorax. You must continually reassess for these conditions,
although neither has been demonstrated to be a problem in the current EMS research.
Another theoretical consideration is gastric distension. In the awake patient, this is
generally not a concern until positive pressure reaches 25–30 cm H2O, which is higher
than CPAP should ever be set. Other complaints include sinusitis, skin abrasions and
conjunctivitis, all of which can be minimized with a proper mask size and seal.
CPAP can rapidly deplete portable oxygen supplies, especially if the FiO2 is increased. It
is important to monitor the amount of pressure available in both portable and on-board
tanks. Once CPAP is started, it should be continued, so it may be a good idea to move the
patient to the ambulance before applying it. Give the hospital staff advance notice so they
can have their equipment ready.
Conclusion
Prior to prehospital CPAP availability, pre-hospital crews had to watch dyspneic patients
decline, requiring intubation. Patients who are still awake during intubation often
experience anxiety and discomfort and need to remain sedated. They can’t talk with the
tube passing through their vocal cords, and the aspiration risk is high with open cords.
Consideration of these complications, as well as the cost of equipment and a mandatory
ICU admission, makes avoiding intubation by administering CPAP an attractive option.
CPAP should be the first line of respiratory therapy in carefully selected patients based
on local protocols. It relieves symptoms but should be used in concert with appropriate
medications in patients with asthma, chronic obstructive pulmonary disorder (COPD) and
heart failure. This will address specific underlying pathology.
Remember, CPAP isn’t a ventilator. Patients must be monitored carefully (vital signs,
SpO2, capnography and clinical responses) after CPAP application to detect
improvement in condition or lack of improvement that may indicate the need for
intubation and assisted ventilations, as well as for signs of complications that may signal
the need to remove the CPAP mask.
When used correctly, CPAP has been shown to alleviate symptoms and decrease the need
for intubation for patients with CHF, COPD and asthma. It is safe, portable and easy to
apply. CPAP does not replace intubation, but rather is a less-invasive means of providing
respiratory support while medications work to correct the underlying cause of distress.
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Aurora Health Care – South Market | Pre-Hospital ALS/BLS Patient Care Protocols
R-7
Continuous Positive Airway Pressure (CPAP)
LEVEL
BVIP
BVIP
IP
P
BVIP
Continuous Positive Airway Pressure (CPAP) rapidly improves vital signs and
gas exchange. It decreases the work of breathing and alleviates dyspnea, CHF,
COPD, and Pneumonia.
1. Indications:
 Patient awake, cooperative having clinical signs of mild to severe
respiratory distress.
 Age over 12-years and able to fit mask.
 Able to maintain open airway.
 SBP is greater than 90 mmHg.
 At least two of the following:
o Respiratory rate is greater than 25.
o Pulse oximeter reading is less than 94% not being relieved by
other interventions.
o Retractions or accessory muscle use.
2. Contraindications:
 Respiratory arrest.
 Pneumothorax.
 Tracheostomy.
 Unresponsive patient.
3. Precautions:
 Impaired mental state (can’t cooperate).
 Vomiting.
 Excessive secretions.
 Poor respiratory drive.
 Facial deformity or problem preventing tight-fitting mask.
4. Procedure:
 Explain procedure to patient.
 Ensure adequate oxygen supply (100%).
 Place mask over mouth and nose; secure with straps.
 Use 5 cm H2O of PEEP
May Use 10 cm H2O of PEEP – titrate to effect.
o 7.5 cm H2O of PEEP if less than 16 years old.
 Check for air leaks.
 Monitor patient’s response.
 Check and record vital signs every 5 minutes.
Consider Sedation
5. Removal Procedure:
 CPAP therapy should be discontinued ONLY if patient;
o Can not tolerate it
o Patient deteriorates
AHC-SM EMS Approved 7/01/08; Revised 9/20/08, 06/01/2012
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