Download Respiratory failure Type A Q4

Acute respiratory failure
Clinical problems
LEARNING OBJECTIVES
After studying this module on Respiratory failure, you should be able to:
1.
2.
3.
4.
Identify patients suffering from acute respiratory failure (ARF)
Understand strategies for providing ventilatory support
Become familiar with the associated supportive measures
Recognise and know how to manage the complications of ventilatory support
FACULTY DISCLOSURES
The authors of this module have not reported any disclosures.
DURATION
7 hours
Copyright©2009. European Society of Intensive Care Medicine. All rights reserved.
ISBN 978-92-95051-62-1 - Legal deposit D/2005/10.772/9
INTRODUCTION
Acute respiratory failure (ARF) is a common and important indication
for admission into critical care units and is associated with a
substantial mortality. For the purpose of this module, ARF is defined
as any acute lung condition (with the exception of obstructive lung
disease) that requires active ventilatory therapy.
The reader should also be aware that there are a variety of clinical
conditions that can precipitate ARF, such as acute cardiogenic
pulmonary oedema, fluid overload, massive pulmonary embolism and
coma. ARF is not a disease in itself but a reaction to an underlying
condition, e.g. trauma, sepsis or pneumonia. Because definitions
differ, the incidence and mortality rates for ARF vary across studies.
In addition, the underlying condition strongly influences prognosis.
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Acute respiratory failure is
always caused by an
underlying condition that will
need urgent treatment
Most ARF discussed in this
module is due to lung failure
The reported incidence of ARF, including acute lung injury (ALI) and acute
respiratory distress syndrome (ARDS) varies between around 78–149 per 100
000 people >15 years of age per year.
Ninety-day mortality is close to 40% for ARF and 31–60% for ALI / ARDS.
Whether mortality rates have decreased over time is still a matter of debate.
The majority of patients have ARF of pulmonary origin with pneumonia as the
predominant diagnosis.
1/ HOW TO IDENTIFY/CATEGORISE/MONITOR THE PATIENT SUFFERING FROM
ARF
This Task will provide you with definitions, outline aetiology, risk factors, clinical
manifestations and symptoms. The Task concludes with a section on how to monitor the
course of acute respiratory failure.
Definitions
For the purpose of this module, we will focus on ALI and ARDS. The ALI/ARDS is a pulmonary
definition of ARDS is under discussion but the definition proposed by inflammatory process
a Joint North American–European consensus committee (NAECC) in
1994 is still accepted. ARDS is defined as an inflammatory process in
the lungs with:
 An acute onset of respiratory failure
 New bilateral pulmonary infiltrates on frontal chest
radiograph or computed tomography (CT)
 Absence of left ventricular failure (clinically diagnosed or a
pulmonary artery occlusion pressure <18 mmHg)
 Hypoxaemia with a ratio between the partial pressure of
oxygen in the arterial blood and the fraction of inspired
oxygen (PaO2/FiO2) ≤27 kPa (201 mmHg) independent of
the level of positive end-expiratory pressure (PEEP)
ALI is defined by the same criteria except that the PaO2/FiO2 ratio is
between 27 kPa (201 mmHg) and 40 kPa (300 mmHg).
However, there are problems with this definition:
 The definitions of left ventricular cardiac failure are vague,
and the interpretation of a chest radiograph may be
difficult.
 Lung recruitment manoeuvres and PEEP influence both
the degree of hypoxaemia and the appearance of the
chest radiograph.
 The PaO2/FiO2 ratio is dependent on the FiO2 used.
It has been suggested, therefore, that the definition should be
modified, for example by defining 'acute' and by specifying the PEEP
level and the FiO2 at which PaO2 should be obtained (see references
below).
Another commonly used, but more complicated definition was
suggested by Murray; the Lung Injury Severity Score (LISS). In this
score, the PaO2/FiO2 ratio, the chest radiograph, compliance of the
respiratory system and the level of PEEP are scored on a scale 0-4.
If compliance is not measured this variable can be omitted and if the
patient is not receiving mechanical respiratory support PEEP can
also be excluded. The sum of the scores is then divided by the
number of components. A total score greater than 2.5 defines ARDS.
Heart failure can exist
concomitantly with a
pulmonary inflammatory
process similar to ALI/ARDS
N OTE
Neither LISS nor the initial degree of arterial hypoxaemia (if PaO2 is not severely
low) are related to outcome.
In the next five patients who are admitted to your ICU with ARF check whether
they fulfil the ARDS definition by LISS, the NEACC criteria or both. Please check
the level of PEEP. For more information about the different definitions of
ALI/ARDS see the following references.
Aetiology and risk factors
ALI/ARDS is an acute inflammatory condition in the lungs and not a disease in itself, and is
therefore always due to an underlying disease process.
The pulmonary inflammation may be caused by:


A direct (primary or pulmonary) injury to the lungs or
An indirect (secondary or extra-pulmonary) injury
ALI/ARDS due to a direct injury comprises 50-60% of all cases, with pneumonia as the most
important single cause (40-50% of all cases). Other common direct causes are aspiration of
gastric contents, pulmonary contusion, inhalation of toxic gases and near drowning.
Indirect ALI/ARDS is caused by systemic inflammation with generalised activation of
mediators, inflammatory cells and endothelium due to infection (sepsis, peritonitis), tissue
ischaemia or tissue damage (trauma, cardio-pulmonary bypass, pancreatitis, major surgery
and some intoxications and overdoses).
Experimental and recent clinical studies have shown that ALI/ARDS might also be due to, or
be accentuated by mechanical ventilation using high tidal volumes and low levels of PEEP.
The independent risk factors for ARF are old age, infection, neurological disease, alcohol
abuse and multiple transfusions.
Because ALI/ARDS is always caused by an underlying disease process, treatment of
precipitating factors, together with the patient's comorbidities and genetic predisposition are
major determinants for the progression of the lung condition and its outcome.
T HINK
Why are old age, neurological disease, infection, multiple transfusions and genetic
diversity important risk factors for the development of ARF? See the references below
for further information.
Clinical manifestations and symptoms
Clinical manifestations and symptoms may be divided into:
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Pulmonary, caused by ALI/ARDS and
Extra-pulmonary, caused by the underlying disease
Ascertain the diagnosis: laboratory tests and imaging
According to the definitions, the diagnosis of ALI/ARDS is first established by:
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The medical history: acute onset of respiratory failure in combination with an
underlying condition which has the potential to initiate pulmonary inflammation.
A recent frontal chest radiograph or thorax CT showing bilateral infiltrates.
A clinical examination (and medical history), echocardiography or pulmonary
artery catheterisation (PCWP <18 mmHg) to exclude significant left ventricular
failure.
An arterial blood sample together with measurement of FiO2, showing a
PaO2/FiO2 ratio ≤27 kPa for the diagnosis of ARDS and <40 kPa for the
diagnosis of ALI.
Early in ALI/ARDS, the blood gas analysis might, in addition to hypoxaemia, show a degree
of hypocapnia due to an increased ventilatory drive induced by increased stiffness of the
lungs. In addition, the patient is usually apprehensive. Respiratory acidosis develops rather
late in the process and signals imminent respiratory decompensation. Metabolic acidosis
may be seen, but usually this is a consequence of the underlying process (sepsis or tissue
hypoperfusion) rather than ALI/ARDS.
The results of other laboratory tests are usually non-specific and
dependent on the underlying disease. It is common to find evidence
of inflammation and coagulopathy.
Clinical examination and
obtaining a medical history
are extremely important in the
management of ALI/ARDS
In ventilated patients, lung mechanics show a low respiratory system
compliance and functional residual capacity is reduced.
How can you determine whether a low compliance (high elastance) is due to a pulmonary
condition or to a stiff chest wall, e.g. caused by intra-abdominal distension?
See the PACT module on Respiratory monitoring for more information
The chest radiograph typically shows bilateral interstitial infiltrates that later become diffuse
and fluffy. In addition bilateral basal atelectasis is common. Therapeutic intervention, i.e.
recruitment manoeuvres and application of PEEP, might modify the findings and sometimes
even normalise the appearance of the chest radiograph.
N OTE
A chest radiograph obtained during expiration, compared with one taken during
inspiration will show more pronounced changes.
Computed tomography (CT) examinations are useful for evaluation of the lung pathology.
CT can more accurately define infiltrates, pleural effusions and small pneumothoraces
especially those lying anteriorly or posteriorly. In extrapulmonary ARDS, bilateral
symmetrical dorsal and caudal densities, indicating lung collapse and alveolar oedema, are
common when the patient is supine. Bilateral pleural effusions are also typical findings. In
pulmonary ARDS the more dense lung regions tend to be asymmetrical and localised to the
areas most affected by the primary process. However, these differences in apprearance
between pulmonary and extra-pulmonary ARDS are not always conclusive. Furthermore the
findings change with time as the process evolves.
T HINK
Consider the benefits of obtaining a CT versus the costs and risk of moving the patient
from the ICU.
How to monitor the course of ARF
See also the PACT modules on Mechanical ventilation
Haemodynamic monitoring
, Respiratory monitoring
ALI/ARDS is frequently part of the multiple organ dysfunction
syndrome. Therefore, it is important to monitor and detect early signs
of additional organ involvement, e.g. renal dysfunction, and to rapidly
institute measures to prevent further deterioration. Maintaining
adequate tissue perfusion is of paramount importance, especially
when arterial oxygenation is compromised.
N OTE
Monitoring is useless without
correct interpretation of the
data and appropriate decision
making
Before initiating monitoring, particularly with invasive devices, always consider
whether such monitoring has the potential to usefully influence patient
management.
In all types of ARF, continuous monitoring should include:
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and
Depth of sedation
Respiratory frequency
FiO2
Peripheral oxygen saturation by pulse oximetry
In addition:
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If the patient is mechanically ventilated, all relevant
ventilatory variables are automatically and continuously
obtained. It is important to check that alarm limits for tidal
volumes and pressures are set correctly.
Ventilatory variables (mode, PEEP, auto-PEEP, peak and
plateau pressures, tidal volume, inspiratory:expiratory (I:E)
ratio, ventilator rate) should be noted at prescribed regular
intervals.
Arterial blood gases should be sampled at regular
intervals and when deterioration in the patient's condition
is clinically evident.
A chest X-ray should be performed at least twice weekly if
the course is benign and more often in those with severe
lung injury.
Continuous measurement of systemic blood pressure.
Fluid balance and urine output should be updated hourly.
Do not forget to examine the
patient frequently!
Additional monitoring (airway pressure-lung volume relationships, lung volume
measurements, mixed venous or central venous oxygen saturation, cardiac output
measurement, echocardiography, pulmonary artery catheterisation, or arterial
transpulmonary indicator dilution catheter) should be instituted according to the severity of
respiratory failure and the level of support required, as well as the degree of additional
organ dysfunction and support. Nutritional therapy should be monitored biochemically. The
clinical utility of a promising new monitoring method, electrical impedance tomography, is
not clear.
In the next five patients with ARF in your ICU observe the monitoring techniques
employed. Do you agree with these monitoring protocols? Give arguments (pros
and cons). Discuss the issues with your supervisor or a colleague.
2/ STRATEGIES FOR VENTILATORY SUPPORT (LUNG PROTECTIVE
VENTILATION)
See also the PACT module on Mechanical ventilation
The goal for ventilatory therapy in ARF is to achieve adequate gas exchange (usually
PaO2 >8 kPa, oxygen saturation of haemoglobin in arterial blood (SaO2) >90% and pH 7.27.4) without causing additional iatrogenic damage to the lungs and other organs, i.e. a lung
protective ventilatory strategy. In this context it is important to recognise that a ventilator can
only replace the work performed by the respiratory muscles and not the gas exchange
function of the lungs. However, by using lung recruitment manoeuvres, positive end-
expiratory pressure and by changing the inspired oxygen concentration, gas exchange can
be improved and supported.
In the reference below you will find more information about ventilatory support of patients
with ARDS.
When to initiate ventilatory support?
As a general rule,
 All patients with ALI/ARDS should immediately receive
oxygen via a mask.
 If hypoxaemia persists and the clinical condition does not
improve rapidly more active measures are urgently
required.
 If the patient has concomitant conditions that compromise
cardiopulmonary function, more active measures should
be considered early.
The mean inspired oxygen
concentration via a standard
face mask is only 40-50% at
flow rates of 10-15 l O2 /min
The patient's clinical condition is more important than the values obtained by blood gas
analysis in deciding when to start ventilator support.
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If the patient is fully awake, haemodynamically stable and
is not fatigued there is no immediate need for ventilatory
support even if blood gases indicate hypoxaemia. On the
other hand, because almost all patients with ALI/ARDS
require some form of ventilatory support, mechanical
ventilation should always be considered early in the
disease process.
If the patient is exhausted, has a respiratory rate above
30-35/min, blood gases indicate significant hypoxaemia
(PaO2 <7-8 kPa) on oxygen via mask, an increasing
carbon dioxide pressure in the arterial blood (PaCO2) or
pH is below 7.3 (showing that the patient cannot maintain
a normal pH by spontaneous breathing) mechanical
ventilation should be instituted expeditiously.
If the patient is haemodynamically unstable but can
maintain PaO2 above 8 kPa on oxygen via mask,
haemodynamic support is indicated under careful
ventilatory monitoring before invasive ventilatory support
Oxygen consumption and
CO2production increase by 610% per °C. This increased
demand can exacerbate
respiratory distress
(intubation) is initiated.
Why does a low PaO2 not necessarily indicate tissue hypoxia? How can you improve tissue
oxygenation without increasing PaO2?
See PACT module on Respiratory monitoring for further information
Sedation and initiation of positive pressure ventilation may cause severe
cardiovascular collapse in hypovolaemic patients.
In the last five patients with ARF in your department what were the PaO 2, PaCO2,
arterial pH and respiratory rate before initiating ventilator therapy.
Should we start a trial with non-invasive ventilation (NIV)?
Non-invasive support with continuous positive airway pressure (CPAP) may be considered
in otherwise stable patients with hypoxaemia in the absence of CO 2 retention. Non-invasive
positive pressure ventilation is otherwise the preferred method in patients with ARF. NIV
can only be considered if the staff members are experienced with the method and if the
patient is:
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Fully conscious
Cooperative
Haemodynamically stable
Tolerant of short periods without ventilatory support
Able to take adequate tidal volumes
Not fatigued
The trial of NIV should be terminated if the patient does not markedly
improve clinically within an hour.
NIV should always be considered in patients who are
immunosuppressed because of the importance of preventing
nosocomial infections in such patients (tracheal intubation is
associated with nosocomial pneumonia and sinusitis). This approach
has been associated with improved outcomes.
A NECDOTE
Never delay initiating invasive
ventilation by applying NIV to
a patient who is exhausted.
A patient infected with human immunodeficiency virus (HIV) with bilateral pulmonary
interstitial infiltrates on the chest radiograph was transferred to the ICU at 2.00 a.m. He
was at that time fully awake, his respiratory rate was 40/min and his PaO2 was 7 kPa
on face mask O2 at 15 l /min. Pneumocystis jiroveci pneumonia was suspected and
trimethoprim-sulfmethoxazole was started. Because the patient was cooperative NIV
was started with pressure support ventilation (see PACT module on Mechanical
ventilation) of 15 cm H2O above 5 cm H2O PEEP and FiO2 of 1.0. The patient
improved initially. After two hours the patient became more tired with increasing
PaCO2 and decreasing pH. However, since it was early morning (5.00 a.m.) the nurse
decided to wait a further hour before informing the intensivist on call. When the
intensivist arrived just after 6.00 a.m. he found the patient severely lethargic and
exhausted with an arterial oxygen saturation of 77% on pulse oximetry. An emergency
oral tracheal intubation was performed but unfortunately the patient developed cardiac
arrest, which could not be reversed. This case illustrates the need for continuous close
attention by experienced staff and that invasive ventilation should be instituted
promptly if NIV is not successful.
What are the advantages and disadvantages of NIV in patients with hypoxaemic respiratory
failure?
See PACT module on Mechanical ventilation
Be aware that the administration of 100% oxygen for a prolonged period can
exacerbate atelectasis.
Intubation /tracheostomy
The indications for intubation in ARF are:
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Inadequate gas exchange with non-invasive respiratory support (oxygen via
mask, CPAP or NIV) or
When NIV is contraindicated or believed to be insufficient, e.g.
o Severe hypoxaemia (PaO2 <6-7 kPa)
o Severe respiratory acidosis (pH <7.2, PCO2 > 9-10 kPa)
o Semi-or unconscious/ unable to maintain and protect the airway
o Concomitant central nervous system compromise (head injury, brain
oedema due to meningitis, intracerebral bleeding, spinal injury)
o Recent surgery
In patients with ARF there is a significant risk of complications during tracheal intubation:
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Pronounced hypoxaemia
Aspiration of gastric contents
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Misplacement of the endotracheal tube
Haemodynamic compromise
Intubation, therefore, should be performed with great caution.
Because the indications are hypoxaemia or respiratory fatigue,
immediate successful tracheal intubation is essential. All means to
rapidly secure a safe airway should therefore be available; a variety
of laryngoscopes, different designs and sizes of endotracheal tubes,
stylets, bougies, forceps, a fibre optic bronchoscope or laryngoscope,
airways and devices for cricothyroidotomy. It must be possible to
suction and to administer 100% oxygen. It is important to avoid
worsening of hypoxaemia during the procedure by administering
100% oxygen or maintaining NIV as long as possible before
intubation.
Always use capnography to
confirm that the tube is
correctly positioned in the
trachea
There are three different approaches for intubation:
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Oral intubation
Fibre optic awake intubation
Blind nasal intubation
Oral intubation
If the patient is obtunded, oral intubation is the technique of choice. Oral intubation is easier,
quicker and safer to perform than nasal intubation and in addition is associated with a lower
incidence of sinusitis. Before intubation, the equipment and the tube should be checked,
and a decision made about the amount and type of drugs to be used to facilitate intubation.
A skilled assistant should be available. These patients usually have slow gastric emptying
and are at risk of regurgitation of stomach contents followed by pulmonary aspiration.
Therefore a rapid sequence intubation with cricoid pressure should be performed.
T HINK
What do you do if you cannot intubate at the first attempt in a patient with ARF? What
are your department's guidelines?
See PACT module on Airway management for more information
Fibre optic intubation
Fibre optic intubation is a good and safe choice in an awake patient, particularly if the upper
airways are compromised.
Fibre optic intubation should replace blind nasal intubation in patients with ARF.
Nasal intubation may induce serious nasal bleeding in patients with
thrombocytopenia or coagulation disorders.
How do you confirm correct positioning of an endotracheal tube?
Tracheostomy
Tracheostomy is
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Seldom a first-line measure except when the patient has a compromised upper
airway.
Performed when it is anticipated that the patient needs lengthy ventilatory
support or to facilitate the weaning process, as in severe head trauma.
Relatively contraindicated during the critical phase when the patient requires high
inspired oxygen and difficult to ventilate.
Relatively contraindicated in patients with bleeding tendency or coagulation
disorders.
It is not clear whether tracheostomy, even when performed early can decrease morbidity or
mortality compared with prolonged tracheal intubation. In clinical practice, however,
tracheostomy is more comfortable for the patient, facilitates suctioning and oral hygiene as
well as the weaning process.
N OTE
In patients with ARF, tracheostomy should be performed by a skilled and
experienced member of staff. The procedure can be performed surgically or
percutaneously. The approach adopted is mainly determined by local practices.
Assist at five tracheostomies (percutaneous or surgical). Discuss with the
operator and your supervisor / colleagues, what the arguments are for surgical,
percutaneous or both procedures being used.
What are the targets of ventilatory support?
The objective is to achieve adequate gas exchange without injuring the lungs and other
organs. The gas exchange targets are not clearly defined. It is common practice to aim for a
PaO2 and SaO2 above 8 kPa and 90%, respectively, but lower values may be acceptable as
long as there are no signs of tissue hypoxia. In fact, no studies have shown that increasing
PaO2 improves outcome. PCO2 in itself is seldom important, but pH should usually be
maintained between 7.2 and 7.4.
See the PACT modules on Mechanical ventilation
and Respiratory monitoring.
Hypocapnia constricts
coronary and cerebral
arteries and hampers oxygen
unloading
What are the benefits or drawbacks of hypercapnia? See reference below for more information.
How to adjust the ventilator settings in a patient with acute respiratory
failure
The ventilator settings should be adjusted to ensure adequate gas exchange without
causing:
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
Overdistension
Repeated opening and closing of distal units
Thus, tidal volumes and the transpulmonary pressure difference between inspiration and
expiration should be kept low.
Ventilatory mode
There are no ventilatory modes (including high frequency oscillatory
ventilation) that have been conclusively proven to be superior in ARF
as long as end-inspiratory plateau pressures and tidal volumes are
limited. However, there is some suggestion that modes which allow
for spontaneous breathing (e.g. airway pressure release ventilation,
APRV), improve oxygenation and haemodynamics, contribute to lung
recruitment and decrease the need for sedation. On the other hand,
recent studies suggest that a short initial period with heavy sedation
combined with muscle relaxation might be beneficial. See the
references below for further information about APRV and muscle
relaxation.
See PACT module on Mechanical ventilation
Use your clinical judgment at
the bedside when adjusting
the ventilator settings
If possible, use modes early
that allow spontaneous
breathing as early as possible
Tidal volume and airway pressures
 Ventilation with a tidal volume of 6 ml/kg ideal body weight has been shown to significantly
decrease mortality (by 9%) when compared with ventilation with 12 ml/kg tidal volumes.
However, the acceptable tidal volume may be more dependent on the condition of the lungs;
in small and highly inflamed lungs tidal volumes should probably be lower than 6 ml/kg but in
larger and less inflamed lungs tidal volumes somewhat larger than 6 ml/kg are probably safe.
 The end-inspiratory plateau airway pressures should be kept low (<28–30 cm H2O).
However, because the transpulmonary pressure is more important than the airway pressure,
the compliance of the chest wall should be taken into consideration. In a patient with a
compliant chest wall, e.g. a small child, an airway pressure of 30 cm H2O will translate into a
high transpulmonary pressure and is likely to injure the lungs, while in an adult, obese patient
with intraperitoneal pathology, an airway pressure of 40 cm H2O might generate a low, riskfree, transpulmonary pressure.
 Low tidal volume and low pressure ventilation may be associated with a reduction in
CO2 elimination. The rise in a PaCO2 should be tolerated (an approach termed permissive
hypercapnia).
How can you improve CO2 removal without increasing the tidal volume?
What are the drawbacks of low tidal volume ventilation?
See the PACT modules on Mechanical ventilation
and on Respiratory monitoring
Case 2
You get a request from the surgical ward for possible transfer of a 42-year-old woman, with
previously normal cardio-pulmonary health, to the ICU. She had been operated on four days previously
with a right-sided colectomy and ileo-colic anastomosis for carcinoma of the ascending colon. The
surgery and anaesthesia were uncomplicated, but afterwards she developed nausea, vomiting and
abdominal pain. Now she is complaining about difficulties with breathing and her temperature has
increased to 39.5 °C. The surgical resident suspects pneumonia and wants her transferred to the ICU.
When you arrive at the surgical ward you examine the patient. She is pale, slightly cyanotic but has
good peripheral circulation. She has a respiratory rate of 28/min and is somewhat dyspnoeic. Over
both basal lungs you can hear crepitations. The abdomen is tender and tense. The wound is not
infected. Blood pressure is 100/60 mmHg and pulse rate is 120/min. The patient has no urinary
catheter and does not remember when she voided. She has received thromboembolic prophylaxis (low
molecular weight heparin) and prophylactic antibiotics during surgery.
Which diagnosis is most probable and why?
Learning issues
Aetiology of secondary ALI/ARDS
Clinical signs of secondary ALI/ARDS
Differential diagnosis of postoperative lung disorders
What other diagnoses do you consider?
What is your first measure to improve the patient's condition? Why?
N OTE
Refresh your knowledge about treatment of severe infections.
See PACT module on Severe infection
See PACT module on Sepsis and MODS
Case 2 Screen 2
You immediately discuss your findings with the surgical consultant. He is convinced that the patient can
be handled in the surgical ward and that no further actions are necessary.
Learning issues
Definition of ALI/ARDS
Pathogenesis of secondary ALI/ARDS
Management of secondary ALI/ARDS
Give arguments to convince him this is not the best approach for this patient?
You and the surgeon decide that the patient should be transferred to the ICU for optimisation before a
surgical exploration.
What are you planning to do in the ICU? Why?
N OTE
Computed tomography examinations of the abdomen in this early period after
surgery will not be of benefit for the diagnosis and will only delay the definitive
treatment. Usually they should not be considered.
The laboratory tests show a white blood cell count of 15 10 6/l, elevated CRP, Hb 90 g/l, liver function
tests in the upper normal range, platelets 150 10 9/l, D-dimer slightly elevated, plasma creatinine
100 µmol/l and plasma sodium and potassium in the normal range. Blood gas (on 100% O 2 via a mask
with a reservoir): PaO2 12 kPa, PaCO2 4.5 kPa, BE −5, pH 7.38.
Chest radiograph: see figure below (bilateral infiltrates and pleural effusion on the left side). Urine
output in the last hour is 30 ml. Arterial blood pressure is 105/55 mmHg and pulse rate 115/min (after a
rapid i.v. infusion of 1000 ml Ringer-solution).
In the ICU a PA-catheter is introduced and shows CVP 5 mmHg, PCWP 15 mmHg and CO 8 l/min.
Considering the chest radiograph, laboratory tests and the patient's clinical condition what is
your diagnosis?
Should you or should you not restrict i.v. fluids in this phase of ARDS? Why?
Learning issues
Fluid therapy in ARDS
Case 2 Screen 3
The patient is taken to surgery and found to have a generalised faecal peritonitis due to dehiscence of
the anastomosis. The peritoneum is cleaned and the bowel ends are externalised (as two stomas).
After surgery the patient is transferred back to the ICU intubated, mechanicallyventilated (volume
control) with FiO2 1.0, PEEP 10 cm H2O, tidal volume of 700 ml (12 ml/kg), rate 20/min and I:E 1:2. The
end-inspiratory plateau pressure is 45 cm H2O. The blood gas shows PaO2 7.5 kPa, PCO2 3.7 kPa, BE
−9, pH 7.45 and lactate is 5 mmol/l. Arterial blood pressure is 95/55 mmHg, pulse rate 124/min, CO 12
l/min, CVP 25 mmHg , PCWP 20 mmHg and PAP 45/25 mmHg on i.v. norepinephrine of 0.2 µg/kg/min.
During the resuscitation and surgery she had received 10 l of crystalloids, colloids and blood products.
The bleeding was negligible during surgery. Urine output has been 5, 10 and 40 ml/h during the last
three hours of surgery (i.e. with the abdomen open) despite the huge fluid intake and a 250 mg i.v.
bolus dose of furosemide. The abdominal pressure measured via the urinary catheter is 8 mmHg.
Plasma creatinine level is now 120 µmol/l.
How can you improve oxygenation in this patient?
N OTE
Refresh your knowledge about mechanical ventilation and ventilatory
monitoring.
See PACT module on Mechanical ventilation.
Would you like to change the ventilator settings? Give reasons for your answer.
Learning issues
Lung mechanics in ALI/ARDS
Ventilator therapy in ALI/ARDS
Targets for PaO2 , PCO2 and pH
Lung recruitment procedures
Prone position and adjuvant treatment
Ventilator-induced lung injury
Case 2 Screen 4
In this patient the lungs are recruited by a manoeuvre consisting of three hyperinflations of 30 sec
duration to 50 cm H2O of airway pressure after which PEEP of 16 cm H2O is found to be adequate to
maintain the improved oxygenation. The ventilatory mode is changed to pressure control with a plateau
inspiratory airway pressure of 32 cm H2O, producing a tidal volume of 350 ml (apparatus dead space is
minimised by 50 ml by removing the heat and moisture exchanger (HME) and the extension piece), the
I:E-ratio is increased to 1:1 and the ventilator rate is reduced to 20/min. FiO 2 can be decreased to 0.55.
After the change, PaO2 is 9 kPa, PCO2 6 kPa and pH 7.3.
Is there any indication for continuous renal replacement therapy (CRRT)? Explain why.
N OTE
Refresh your knowledge about treatment of acute renal failure.
See PACT module on Acute renal failure
See PACT module on Oliguria and anuria.
In this patient CRRT is initiated but is stopped after three days. Her condition including lung function
improves rapidly and after a week she is extubated. After four months she is operated uneventfully with
a reanastomosis of the bowel and is discharged home after one week in good condition.
On reflection
What are your conclusions regarding the management priorities of secondary ARDS?
Q1. Regarding ventilation in ALI/ARDS
A. All patients with ARDS should be intubated.
True
False
B. Auscultation of the chest and upper abdomen is the best method to verify a correct
position of an endotracheal tube.
True
False
C. PaCO2 should be kept high (>7 kPa) in all patients with ALI/ARDS.
True
False
D. Lung collapse after discontinuation of PEEP could occur within seconds in ARDS.
True
False
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Q1. Regarding ventilation in ALI/ARDS
Your answers
A. All patients with ARDS should be intubated.
The correct answer is : False
B. Auscultation of the chest and upper abdomen is the best method to verify a correct position
of an endotracheal tube.
The correct answer is :
False
Verification should be performed by end-tidal CO2 fraction measurement.
C. PaCO2 should be kept high (>7 kPa) in all patients with ALI/ARDS.
The correct answer is :
False
Although a high PaCO2 might be beneficial it is still regarded as a side-effect of low tidal volume ventilation.
D. Lung collapse after discontinuation of PEEP could occur within seconds in ARDS.
The correct answer is : True
Your total score is 0/4
Q2. Regarding complications in Acute Respiratory Failure
A. Air under the diaphragm on a chest radiogram is always due to other reasons (e.g. recent
abdominal surgery) than pulmonary barotrauma.
True
False
B. Ventilation with large tidal volumes (12 ml/kg) is associated with an increased mortality in
ALI/ARDS compared with small tidal volumes (6 ml/kg).
True
False
C. Nosocomial infections in ARDS patients are common.
True
False
D. VAP does not influence the length of ventilator therapy or outcome in ARDS.
True
False
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Check answ ers
Q2. Regarding complications in Acute Respiratory Failure
Your answers
A. Air under the diaphragm on a chest radiogram is always due to other reasons (e.g. recent
abdominal surgery) than pulmonary barotrauma.
The correct answer is :
False
B. Ventilation with large tidal volumes (12 ml/kg) is associated with an increased mortality in
ALI/ARDS compared with small tidal volumes (6 ml/kg).
The correct answer is :
True
C. Nosocomial infections in ARDS patients are common.
The correct answer is :
True
D. VAP does not influence the length of ventilator therapy or outcome in ARDS.
The correct answer is :
False
Ventilator associated pneumonia increases mortality and the length of stay
Your total score is 0/4
Q3. Adjuvant therapy in ARDS
A. A trial of prone positioning is mandatory in all patients with persistent hypoxia after
optimization of ventilatory settings
True
False
B. In severe ARDS e.g. with refractory air-leak, there is evidence that referral to an ECMO
centre may be beneficial
True
False
C. Steroids have no proven beneficial effects in early ARDS
True
False
D. Inhaled nitric oxide or inhaled prostacyclin are shown to improve outcome in ARDS
True
False
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Check answ ers
Q3. Adjuvant therapy in ARDS
Your answers
A. A trial of prone positioning is mandatory in all patients with persistent hypoxia after
optimization of ventilatory settings
The correct answer is :
False
Even if oxygenation increases in more than 60% of patients there might be contraindications for prone position, e.g.
intracranial hypertension, unstable fractures, facial fractures and skin lesions in areas exposed to pressure when
positioned prone.
B. In severe ARDS e.g. with refractory air-leak, there is evidence that referral to an ECMO
centre may be beneficial
The correct answer is :
True
Peek GJ, Mugford M, Tiruvoipati R, Wilson A, Allen E, Thalanany MM, et al: for the CESAR trial collaboration.
Efficacy and economic assessment of conventional ventilatory support versus extracorporeal membrane oxygenation
for severe adult respiratory failure (CESAR): a multicentre randomised controlled trial. Lancet 2009; 374(9698):
1351-1363. PMID 19762075
C. Steroids have no proven beneficial effects in early ARDS
The correct answer is :
True
D. Inhaled nitric oxide or inhaled prostacyclin are shown to improve outcome in ARDS
The correct answer is :
False
Even if both may improve gas-exchange there is no beneficial effect on outcome with inhaled nitric oxide and there is
no outcome data with inhaled prostacyclin
Your total score is 0/4
Respiratory failure Type A Q4
Regarding identification, categorising and monitoring of ARF, which of
the following is true
A.
B.
C.
D.
E.
A Improving lung function is always the highest priority when treating patients with
ARF
B
Hypoxaemia is the most important cause of death in ARF
C
ALI/ARDS is an inflammatory condition in the lungs
D The scores obtained from the lung injury severity score (LISS) are related to
outcome
E The PaO2/FiO2 ratio is only dependent on the lung pathology and is not influenced
by lung recruitment manoeuvres or PEEP
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Respiratory failure Type A Q4
Your answers
Regarding identification, categorising and monitoring of ARF, which of the following is true
A
Improving lung function is always the highest priority when treating patients with ARF
B
Hypoxaemia is the most important cause of death in ARF
C
ALI/ARDS is an inflammatory condition in the lungs
D
The scores obtained from the lung injury severity score (LISS) are related to outcome
E The PaO2/FiO2 ratio is only dependent on the lung pathology and is not influenced by lung recruitment
manoeuvres or PEEP
The correct answer is :
C.
Your total score is 0/1
Respiratory failure Type A Q5
Regarding lung recruitment manoeuvres and PEEP in ARF, which of
the following is correct?
A. Lung recruitment manoeuvres are often more effective in late than in early ARDS
B. Lung recruitment manoeuvres using airway peak pressures of 40 cm H2O or less do
usually improve PaO2 in patients with elevated intra-abdominal pressure
C. High level of PEEP should always be used in severe ARDS
D. The main pulmonary effect of PEEP is prevention of lung collapse
A.
B.
C.
D.
E.
E. Lung recruitment manoeuvres can be done safely in hypoxaemic patients in shock.
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Respiratory failure Type A Q5
Your answers
Regarding lung recruitment manoeuvres and PEEP in ARF, which of the following is correct?
A. Lung recruitment manoeuvres are often more effective in late than in early ARDS
B. Lung recruitment manoeuvres using airway peak pressures of 40 cm H2O or less do usually improve PaO2 in
patients with elevated intra-abdominal pressure
C. High level of PEEP should always be used in severe ARDS
D. The main pulmonary effect of PEEP is prevention of lung collapse
E. Lung recruitment manoeuvres can be done safely in hypoxaemic patients in shock.
The correct answer is :
D.
Your total score is 0/1
Respiratory failure Type A Q6
Regarding supportive measures in Acute Respiratory Failure, the
following are true EXCEPT
A.
B.
C.
D.
E.
A ARDS is associated with an increased resting energy expenditure and wasting of
proteins
B
Prone positioning improves oxygenation but not outcome in ARDS
C Although administration of high doses of corticosteroids are not mandatory,
early in the ARDS process, there are indications for this therapy in some patients
with ARDS
D Systematic reviews have shown that ketoconazole, surfactant and Nacetylcysteine increase survival in ARDS
E
Fluid restriction may improve oxygenation in ARDS
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Check answ ers
Respiratory failure Type A Q6
Your answers
Regarding supportive measures in Acute Respiratory Failure, the following are true EXCEPT
A
ARDS is associated with an increased resting energy expenditure and wasting of proteins
B
Prone positioning improves oxygenation but not outcome in ARDS
C Although administration of high doses of corticosteroids are not mandatory, early in the ARDS process, there
are indications for this therapy in some patients with ARDS
D
Systematic reviews have shown that ketoconazole, surfactant and N-acetylcysteine increase survival in ARDS
E
Fluid restriction may improve oxygenation in ARDS
The correct answer is :
D.
Your total score is 0/1
Respiratory failure Type A Q7
Regarding the aetiology and outcome in ALI/ARDS, which of the
following is true
A
A.
B.
The scores obtained from LISS (Murray) correlate well with outcome
B An increased dead space fraction in early ARDS is not associated with
increased mortality
C
An important underlying cause of ARDS is pneumonia
D
The patient may have ARDS without any inflammatory process in the lungs
E
A chest radiograph is not mandatory for the diagnosis of ARDS
Check your answers before moving to the next question
Check answ ers
C.
D.
E.
Respiratory failure Type A Q7
Your answers
Regarding the aetiology and outcome in ALI/ARDS, which of the following is true
A
The scores obtained from LISS (Murray) correlate well with outcome
B
An increased dead space fraction in early ARDS is not associated with increased mortality
C
An important underlying cause of ARDS is pneumonia
D
The patient may have ARDS without any inflammatory process in the lungs
E
A chest radiograph is not mandatory for the diagnosis of ARDS
The correct answer is :
C.
Your total score is 0/1
Respiratory failure Type A Q8
Which of the following is true of ventilatory treatment in
ALI/ARDS
A Non-invasive ventilation should always be the primary ventilatory
therapeutic measure in ARDS
B The generally accepted goals with ventilator treatment are to maintain
PaO2 10-11 kPa and PaCO2 4-5 kPa
A.
B.
C.
D.
E.
C Lung recruitment manoeuvres have been shown to improve outcome in
ARDS
D A lung recruitment manoeuvre can be performed safely in patients with
severe hypovolaemia
E
A major effect of PEEP is prevention of de- recruitment of lung regions
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Respiratory failure Type A Q8
Your answers
Which of the following is true of ventilatory treatment in ALI/ARDS
A
Non-invasive ventilation should always be the primary ventilatory therapeutic measure in ARDS
B The generally accepted goals with ventilator treatment are to maintain PaO2 10-11 kPa and PaCO2 4-5
kPa
C
Lung recruitment manoeuvres have been shown to improve outcome in ARDS
D
A lung recruitment manoeuvre can be performed safely in patients with severe hypovolaemia
E
A major effect of PEEP is prevention of de- recruitment of lung regions
The correct answer is :
E.
Your total score is 0/1
Respiratory failure Type A Q9
Regarding ventilatory treatment in ALI/ARDS, the following are
true EXCEPT
A.
B.
C.
D.
E.
A Continuous monitoring of airway pressures and tidal volumes during
ventilator treatment is mandatory in ARDS
B High end-inspiratory airway pressures (> 40 cmH2O) and large tidal
volumes (>12 ml/kg) should preferentially be used in ARDS
C Modes that allow for spontaneous breathing have been shown to be
beneficial in ARDS
D
Inverse ratio ventilation usually improves CO2-removal in ARDS
E
A method to increase CO2-removal is to decrease apparatus dead space
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Check answ ers
Respiratory failure Type A Q9
Your answers
Regarding ventilatory treatment in ALI/ARDS, the following are true EXCEPT
A Continuous monitoring of airway pressures and tidal volumes during ventilator treatment is mandatory
in ARDS
B High end-inspiratory airway pressures (> 40 cmH2O) and large tidal volumes (>12 ml/kg) should
preferentially be used in ARDS
C
Modes that allow for spontaneous breathing have been shown to be beneficial in ARDS
D
Inverse ratio ventilation usually improves CO2-removal in ARDS
E
A method to increase CO2-removal is to decrease apparatus dead space
The correct answer is :
B.
Your total score is 0/1
Respiratory failure Type A Q10
Regarding the complications in ALI/ARDS, the following are
true EXCEPT
A The impairment in cardiovascular function, sometimes found after
PEEP-application, is pronounced in hypovolaemia
B Anterior pneumothorax is easily recognised on a frontal chest
radiogram
C
Over-distension and tidal closing and opening of lung units are
A.
B.
C.
D.
E.
probable mechanisms for development of ventilator-associated lung injury
D
PEEP may prevent tidal opening and closing of lung units
E A critically important measure in ARDS management is treatment of the
underlying condition
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Check answ ers
Respiratory failure Type A Q10
Your answers
Regarding the complications in ALI/ARDS, the following are true EXCEPT
A The impairment in cardiovascular function, sometimes found after PEEP-application, is pronounced
in hypovolaemia
B
Anterior pneumothorax is easily recognised on a frontal chest radiogram
C Over-distension and tidal closing and opening of lung units are probable mechanisms for development
of ventilator-associated lung injury
D
PEEP may prevent tidal opening and closing of lung units
E
A critically important measure in ARDS management is treatment of the underlying condition
The correct answer is :
B.
Your total score is 0/1