Giáo trình Auto-PEEP
Auto-positive end-expiratory pressure (auto-PEEP) is a
common problem in patients receiving full or partial
ventilatory support, as well as in those ready to be
weaned from the ventilator. Physicians should be alert for
it and take measures to reduce it, as it can have serious
consequences.
REVIEW
MAJID M. MUGHAL, MD DANIEL A. CULVER, DO
Assistant Professor of Medicine, University of South Alabama Department of Pulmonary, Allergy, and Critical Care Medicine,
Medical Center, Mobile The Cleveland Clinic Foundation
OMAR A. MINAI, MD ALEJANDRO C. ARROLIGA, MD
Department of Pulmonary, Allergy, and Critical Care Medicine, Professor of Medicine, Cleveland Clinic Lerner College of
The Cleveland Clinic Foundation Medicine of Case Western University; Head, Section of Critical
Care Medicine, Department of Pulmonary, Allergy, and Critical
Care Medicine, The Cleveland Clinic Foundation
Auto-positive end-expiratory pressure:
Mechanisms and treatment
■ A B S T R AC T - UTO POSITIVE END-EXPIRATORY PRESSURE
A (auto-PEEP), a common problem in
Auto-positive end-expiratory pressure (auto-PEEP) is a patients receiving mechanical ventilation,
common problem in patients receiving full or partial can have serious consequences. The clinician
ventilatory support, as well as in those ready to be needs to fully understand the physiology of
weaned from the ventilator. Physicians should be alert for auto-PEEP so as to choose appropriate venti-
it and take measures to reduce it, as it can have serious lator settings.
consequences. Why should generalists think about
mechanical ventilation? A recent study
■ KEY POINTS showed that intensivists care for only 36.8%
of critically ill patients in the United States,
Auto-PEEP occurs much more frequently than was while general internists, surgeons, and anes-
previously thought. thesiologists manage the rest.1 The incidence
of acute respiratory failure requiring mechani-
Auto-PEEP and dynamic hyperinflation may cause cal ventilation increases nearly 10-fold
significant discomfort and precipitate patient-ventilator between the ages of 55 and 85 years.2 With
the aging of the population, even more gener-
asynchrony through several mechanisms. alists will likely care for these patients in the
future, and it is necessary for them to under-
Auto-PEEP increases the work of breathing and can stand the important elements of managing
worsen gas exchange and decrease cardiac output. patients on mechanical ventilation.
This review, part of a series of articles cov-
In some patients with auto-PEEP due to airflow ering topics in mechanical ventilation pub-
obstruction and dynamic hyperinflation, external PEEP lished in this journal,3–5 provides an overview
may be used to decrease the work of breathing and of auto-PEEP.
relieve dyspnea.
■ WHAT IS AUTO-PEEP?
Positive end-expiratory pressure (PEEP) is
defined as pressure in the alveoli at the end of
exhalation that is greater than the atmospher-
ic pressure.
Normally, during passive exhalation, the
lungs empty by elastic recoil, and at the end of
exhalation the alveolar pressure is the same as
the atmospheric pressure. However, for sever-
al reasons, the lungs may not deflate fully
before the next breath starts, and the pressure
remains elevated. PEEP can be applied inten-
CLEVELAND CLINIC JOURNAL OF MEDICINE VOLUME 72 • NUMBER 9 SEPTEMBER 2005 801
AUTO-PEEP MUGHAL AND COLLEAGUES
TA B L E 1 limitation on expiratory flow,10 and auto-
PEEP is not uncommon in ventilated patients
Physiologic mechanisms of auto-positive with sepsis, respiratory muscle weakness,8 or
end-expiratory pressure the adult respiratory distress syndrome.11
Dynamic hyperinflation
plus intrinsic expiratory flow limitation ■ THREE TYPES OF AUTO-PEEP
Chronic obstructive pulmonary disease
Three types of auto-PEEP can occur in
Dynamic hyperinflation patients on mechanical ventilation, each with
without intrinsic expiratory flow limitation
Breathing pattern and ventilator settings
a different cause and consequences (TABLE 1).10
Rapid breaths
High tidal volume Dynamic hyperinflation
Inspiration greater than expiration with intrinsic expiratory flow limitation
End-inspiratory pause The main cause of auto-PEEP in patients with
Added flow resistance COPD on mechanical ventilation is closure of
Fine-bore endotracheal tube the airways, which limits expiratory flow.12
Ventilator tubing and devices In COPD, the alveolar attachments that
Without dynamic hyperinflation normally keep the smaller airways open via
Recruitment of expiratory muscles radial traction are lost. Consequently, during
exhalation, when the pleural pressure is posi-
tive, these airways can be compressed and col-
lapse. The flow of air during expiration is
tionally from the outside, but when it arises therefore limited and cannot be augmented by
inadvertently it has been called auto-PEEP, effort, resulting in auto-PEEP and dynamic
occult PEEP, or intrinsic PEEP.6,7 hyperinflation.12
Mechanical causes of auto-PEEP in a pas- This condition can be helped by applying
sive respiratory system are: external PEEP (FIGURE 1).
Auto-PEEP • Increased resistance to expiration, eg, in a
should be patient with asthma or chronic obstruc- Dynamic hyperinflation
tive pulmonary disease (COPD) without expiratory flow limitation
anticipated in • A large volume of air delivered per minute Auto-PEEP can also occur even if the airways
exacerbations by the ventilator are widely patent without intrinsic expiratory
• A short expiratory time flow limitation. This may occur if the volume of
of COPD • A combination of these factors. air delivered per minute is high (usually > 20
L/minute), if the exhaled time is too short to
■ WHO DEVELOPS AUTO-PEEP? allow exhalation to functional residual capacity,
or if exhalation is impeded by a blockage exter-
Auto-PEEP is more common than previously nal to the patient, such as a blocked endotra-
thought in critically ill, mechanically ventilat- cheal tube, exhalation valve, or PEEP valve.10
ed patients. Unexpected auto-PEEP occurs in Under such circumstances, external PEEP
up to 35% of patients even when there is no would not be beneficial because it would
significant history of wheezing or COPD.8 impose a back pressure to expiratory airflow,
Auto-PEEP should be anticipated in causing parallel increases in lung volume and
patients with respiratory failure due to airway, alveolar, and thoracic pressures.10
obstructive lung disease. Patients with an
exacerbation of COPD who require intuba- Exaggerated expiratory activity
tion and mechanical ventilation frequently without dynamic hyperinflation
develop dynamic hyperinflation from Although auto-PEEP and dynamic hyperinfla-
impaired lung-emptying due to a limitation of tion are usually thought to be synonymous,
expiratory flow, resulting in auto-PEEP.7,9 auto-PEEP does not necessarily imply dynam-
However, auto-PEEP and dynamic hyper- ic hyperinflation. Auto-PEEP may also occur
inflation may also occur without any intrinsic when strong expiratory muscle activity con-
802 CLEVELAND CLINIC JOURNAL OF MEDICINE VOLUME 72 • NUMBER 9 SEPTEMBER 2005
■ Auto-PEEP in chronic obstructive pulmonary disease
Auto-positive end-expiratory pressure (auto-PEEP) is common in patients with respiratory
failure due to obstructive lung disease who require intubation and mechanical ventilation.
Causes: obstruction (the most common cause, shown here), rapid breathing, large volumes
of air, and exaggerated expiratory effort.
Air is trapped 0 cm H2O
in auto-PEEP External PEEP
treats auto-PEEP
In auto-PEEP, alveoli
remain inflated at The positive pressure of external
end-expiration due PEEP eases the amount of work
to obstruction, so the diaphragm must do to draw
alveolar pressure air in, by allowing small negative
is greater than deflections in intrapleural pressure
atmospheric Obstructive to be sensed by the ventilator when
+ 10
pressure. In the cm H2O
airway the patient tries to trigger a breath.
absence of Alveolar pressure
inspiratory
effort,
Pleural pressure + 10
intrapleural + 10 cm H2O cm H2O
pressure
approximates
alveolar pressure.
– 1 cm H2O
Auto-PEEP increases
the work of breathing
To overcome the positive
pressure in the alveoli
during inspiration,
the diaphragm must +9
generate enough cm H2O
negative pressure to +8
exceed the auto-PEEP – 3 cm cm H2O
and transmit negative H2O
pressure to the central
airways, generating
airflow.
+ 6 cm H2O
– 13 cm H2O
CCF
©2005
FIGURE 1
CLEVELAND CLINIC JOURNAL OF MEDICINE VOLUME 72 • NUMBER 9 SEPTEMBER 2005 803
AUTO-PEEP MUGHAL AND COLLEAGUES
Estimating auto-positive end-expiratory pressure (auto-PEEP)
Valve closed
pressure
Airway
+
0
- in Valve open
Valve closed
Flow
0
out
Valve open
increasing
Volume
0 Valve closed
Auto-PEEP 0 2 4 6 8 10 12 14 16
is measured Valve open
by occluding
FIGURE 2. Expiratory hold techniques to estimate auto-PEEP. The exhalation valve is
the airway at closed during an expiratory hold at the end of the set expiratory time. When the
end-expiration flow equals zero, airway pressure rises to the auto-PEEP level. With the valve open,
flow continues, and the additional exhaled volume equals the volume of trapped gas.
for several MACINTYRE NR. INTRINSIC PEEP. PROB RESPIR CARE 1991; 4:45, WITH PERMISSION.
seconds
tributes to alveolar pressure, often with nor- ■ CONSEQUENCES OF AUTO-PEEP
mal or even low lung volumes. If the flow per-
sists to the end of the expiratory cycle, there Increases the work of breathing
will be an end-expiratory gradient of alveolar Auto-PEEP causes a considerable increase in
to central airway pressure—an auto-PEEP the resistive and elastic work of breath-
effect without lung distention.13,14 This auto- ing,16,17which may interfere with attempts at
PEEP phenomenon is due to dynamic airway weaning from mechanical ventilation.18 This
collapse with exaggerated expiratory activity. can cause significant discomfort and precipi-
Zakynthinos et al15 demonstrated that in tate patient-ventilator asynchrony.
intubated patients who are spontaneously
breathing and actively exhaling, auto-PEEP Worsens gas exchange
due to expiratory muscle contraction can be Brandolese et al compared the impact of auto-
estimated by subtracting the average expirato- PEEP and external PEEP on pulmonary gas
ry rise in gastric pressure from the end-expira- exchange in mechanically ventilated patients.19
tory airway pressure during airway occlusion. Arterial oxygen tension was lower in patients
804 CLEVELAND CLINIC JOURNAL OF MEDICINE VOLUME 72 • NUMBER 9 SEPTEMBER 2005
with auto-PEEP than in patients with a compa- increase in intrathoracic pressure may
rable level of external PEEP, an effect the falsely increase the pulmonary capillary
authors attributed to a less homogenous distrib- wedge pressure and right atrial pressure,
ution of auto-PEEP among lung units. which can lead to mistakes in hemody-
namic management.
Can cause hemodynamic compromise • Erroneous calculations of static respirato-
Auto-PEEP also has hemodynamic conse- ry compliance: the true value of static
quences. Elevated intrathoracic pressure compliance will be underestimated in the
reduces the preload of the right and left ven- presence of auto-PEEP.19
tricles, decreases left ventricular compliance, • Inappropriate fluid administration or
and can increase right ventricular afterload by unnecessary vasopressor therapy.
increasing pulmonary vascular resistance. This
can lead to hemodynamic compromise.12,20 ■ RECOGNIZING AUTO-PEEP
In a dog model described by Marini et al,21
selective hyperinflation of the lower lobes Four practical clues may suggest the diagnosis
(particularly the right lower lobe) or any dis- of auto-PEEP:
tention of lung tissue adjacent to the right side • Exhalation that continues until the next
of the heart was associated with decreased breath starts, as determined on physical exam-
stroke volume. The decrease in stroke volume ination23 or on graphic display of expiratory
was more closely related to an increase in right flow vs time in a patient on a ventilator that
atrial pressure than in left atrial pressure, is set to deliver a certain number of breaths
implying that impaired venous return was the per minute
dominant cause of reduced cardiac output. • A delay between the start of inspiratory
This mechanism is likely the cause of hypoten- effort and the drop in airway pressure or the
sion in patients with inadvertent PEEP. start of machine-delivered flow in a patient on
Hemodynamic effects of auto-PEEP a ventilator that is set to deliver breaths on
should be considered as a possible reversible demand
cause of pulseless electrical activity. In one • Failure of peak airway pressure to change Suspect
report,22 auto-PEEP may have played a part in when external PEEP is applied auto-PEEP
up to 13 (38%) of 34 patients with electro- • In paralyzed or heavily sedated patients,
mechanical dissociation. reduction of plateau pressure after prolonged if exhalation
During cardiopulmonary resuscitation, exhalation. continues
dynamic hyperinflation can develop in
patients with obstructive airway disease, ■ HOW TO MEASURE AUTO-PEEP until the next
owing to rapid manual ventilation with inad- breath starts
equate time for exhalation. This elevated Static auto-PEEP. Auto-PEEP can be
end-expiratory pressure (auto-PEEP) decreas- accurately measured only in patients without
es venous return and may depress cardiac out- active respiratory effort. It is routinely deter-
put even after a cardiac rhythm has been mined under static conditions by occluding
established. Transient withdrawal of ventila- the airway at end-exhalation. During con-
tion allows the dynamic hyperinflation to trolled mechanical ventilation, reliable quan-
diminish, reducing intrathoracic pressure and tification of auto-PEEP requires an end-expi-
permitting the return of spontaneous circula- ratory hold maneuver, terminating expiratory
tion. flow and allowing equilibration of alveolar
pressure and the airway pressure (FIGURE 2). The
Can lead to inappropriate treatment resulting airway pressure represents the aver-
Failure to recognize auto-PEEP and adjust for age total PEEP present within a nonhomoge-
it can lead to inappropriate treatment in sev- neous lung, and auto-PEEP is calculated by
eral ways: subtracting external PEEP from total PEEP.
• Misinterpretation of central venous and Dynamic auto-PEEP. There is no accept-
pulmonary artery catheter pressure mea- ed, reliable method to measure auto-PEEP in
surements12: the auto-PEEP-induced spontaneously breathing patients. However,
CLEVELAND CLINIC JOURNAL OF MEDICINE VOLUME 72 • NUMBER 9 SEPTEMBER 2005 805
AUTO-PEEP MUGHAL AND COLLEAGUES
TA B L E 2
Auto-positive end-expiratory
pressure: measured value can Treatment of auto-positive
underestimate true value end-expiratory pressure
Change ventilator settings
End-expiratory airway occlusion pressure Increase expiratory time
(cm H2O) Decrease respiratory rate
Decrease tidal volume
5 Reduce ventilatory demand
Reduce anxiety, pain, fever, shivering
Reduce dead space
13 Give sedatives and paralytics
Reduce flow resistance
Use large-bore endotracheal tube
5 (measured Suction frequently
value) Give bronchodilators
Counterbalance expiratory flow limitation
15 External positive end-expiratory pressure
20
PEEP reflects the lowest regional auto-PEEP
and therefore underestimates static auto-PEEP
FIGURE 3. Hypothetical model showing in the presence of heterogenous mechanical
low measured auto-positive end- properties,20 ie, if some airways are blocked
expiratory pressure despite high average and some not, or some parts of the lung are
end-expiratory alveolar pressure as a stiff and others are compliant. Maltias et
consequence of widespread airway al24demonstrated that dynamic auto-PEEP
closure.
considerably underestimates static auto-PEEP
FROM LEATHERMAN JW, RAVENSCRAFT SA: LOW MEASURED INTRINSIC
POSITIVE END-EXPIRATORY PRESSURE IN MECHANICALLY VENTILATED in patients with significant airway obstruction.
PATIENTS WITH SEVERE ASTHMA: HIDDEN AUTO-PEEP.
CRIT CARE MED 1996; 24:541–546, WITH PERMISSION.
In such patients two major problems must be
solved, therefore, to obtain a correct measure
of auto-PEEP: airway occlusion must be syn-
chronized to the end of the expiratory cycle,
an esophageal balloon catheter can be used to and respiratory muscle activity must be sup-
measure the auto-PEEP during unoccluded pressed. On the other hand, tensing of abdom-
breathing in such patients, as the esophageal inal expiratory muscles at end-expiration may
pressure is assumed to be about the same as the cause the measured auto-PEEP to greatly over-
pleural pressure. This is achieved by calculat- estimate the end-expiratory elastic recoil pres-
ing the negative deflection in esophageal pres- sure.14
sure from the start of inspiratory effort to the It is also crucial that the airway occlusion
onset of inspiratory flow. be maintained for several seconds to avoid
This method is based on the assumption gross underestimation of average end-expira-
that the change in esophageal pressure reflects tory alveolar pressure. Some lung units may
the inspiratory muscle pressure required to not communicate with the proximal airway, as
counterbalance the end-expiratory elastic the peripheral airways may be blocked by
recoil of the respiratory system (ie, auto- mucous hypersecretion or increased wall
PEEP). To obtain valid measurements, the thickness, and the alveolar pressure in these
inspiratory and expiratory muscles need to be noncommunicating lung units will not direct-
relaxed at end-expiration.13,14 ly contribute to the pressure measured during
It has been suggested that dynamic auto- airway occlusion (FIGURE 3).25
806 CLEVELAND CLINIC JOURNAL OF MEDICINE VOLUME 72 • NUMBER 9 SEPTEMBER 2005
■ REDUCING AUTO-PEEP
External PEEP to treat auto-PEEP:
Reducing dynamic hyperinflation and auto- The analogy of the waterfall
PEEP can have a major impact on the care
of mechanically ventilated patients, espe- Alveolus Upstream Downstream
cially those with exacerbations of COPD segment segment
and asthma.
If auto-PEEP is suspected, it should be Alveolar
measured and its causative factors should be pressure Airway
delineated. Efforts to minimize auto-PEEP pressure
should be directed at the contributing factors.
The following methods can be used to Critical
avoid or reduce auto-PEEP (TABLE 2): pressure
• Change the ventilator setting to provide
the longest expiratory phase compatible
with the patient’s comfort and adequate
gas exchange Alveolar
• Reduce patient ventilatory demand and pressure Critical
minute ventilation pressure
• Minimize airflow resistance. Airway
A discussion of these methods is beyond pressure
the scope of this manuscript but can be found
in several recent reviews.9,10,12 We will discuss FIGURE 4. Top, expiratory flow limitation within a
the role of external PEEP in the management lung. The alveolar pressure at the end of passive
of patients with auto-PEEP. expiration (auto-PEEP) in a dynamically hyperinflated
patient exceeds the critical pressure at which
How much external PEEP to apply, and why? dynamic airway compression occurs. External PEEP,
In patients with airflow obstruction, external applied at the airway opening, will not worsen auto-
PEEP is employed to decrease the work of PEEP if it does not exceed the critical pressure.
Bottom, analogous circumstances governing
breathing and relieve dyspnea, and not as a hydrostatic pressure above and below a waterfall.
treatment for the underlying condition. The amount of flow over the waterfall remains
The seeming paradox of why applying constant until the level of water in the stream below
external PEEP does not make auto-PEEP (the airway pressure) reaches the height of waterfall
worse has been explained by analogy to a (the critical pressure) but not the stream above (the
stream with a waterfall (FIGURE 4).26,27 In this alveolar pressure).
analogy, the upstream part of the stream is like FROM GOTTFRIED SB: THE ROLE OF PEEP IN MECHANICALLY VENTILATED COPD PATIENT. IN
MARINI JJ, ROUSSOS C (EDITORS): VENTILATORY FAILURE. NEW YORK, SPRINGER-VERLAG,
the distal airways, the downstream part of the 1991:392–418: WITH PERMISSION.
stream is like the proximal airways, and the
waterfall is like a site of critical airway closure.
Pressure in the airway is like the hydrostatic
pressure in the stream. auto-PEEP level, worsening hyperinflation or
Now suppose the tide comes in (external circulatory depression are unlikely to occur.
PEEP is applied), raising the height of the But why does external PEEP help? In a
stream below the waterfall. This has no effect patient with auto-PEEP, if the ventilator is set
on either the flow or the pressure upstream of to deliver patient-initiated breaths, the inspira-
the waterfall unless the water level rises above tory muscles have to produce an initial effort to
the level of the waterfall (if the level of exter- overcome the opposing recoil pressure before
nal PEEP exceeds the critical closing pres- the ventilator can be triggered and inspiratory
sure). Above this level, external PEEP flow can begin. In that respect, auto-PEEP acts
increases the pressure upstream and exacer- as an inspiratory threshold and represents an
bates hyperinflation. However, if external additional impedance that the respiratory mus-
PEEP is kept below 75%28 to 85%,9,29 of the cles have to face. Under these circumstances,
CLEVELAND CLINIC JOURNAL OF MEDICINE VOLUME 72 • NUMBER 9 SEPTEMBER 2005 807
AUTO-PEEP MUGHAL AND COLLEAGUES
applying external PEEP (during mechanical
Will the patient benefit from extrinsic ventilation) or continuous positive airway pres-
positive end-expiratory pressure (PEEP)? sure (during spontaneous breathing) may
reduce the work of breathing.
Secondly, by stenting collapsible airways,
60
external PEEP increases expiratory flow, much
as pursed-lip breathing does for nonintubated
patients with COPD.30
50 A practical method of determining
Pressure at airway opening (cm H2O)
whether an actively breathing patient may
benefit from external PEEP may be to observe
40 the response of ventilator cycling pressures to
small increments of external PEEP (FIGURE 5). If
the peak dynamic and static cycling pressures
change very little when external PEEP is
30 applied or increased, then external PEEP may
be helpful. On the other hand, cycling pres-
sures that rise more or less in direct relation-
20 ship to the level of external PEEP imply addi-
tional hyperinflation, and application of
external PEEP in these instances may be detri-
10
mental to the patient.
In other words, external PEEP should not
Total PEEP
be applied to all patients with airflow obstruc-
tion who are mechanically ventilated—only
0 those with auto-PEEP with flow limitation
0 5 10 15 20 25 30
and dynamic airway compression.
Time (s) Ranieri et al9 suggested that external
PEEP less than 85% of the auto-PEEP value
measured on zero end-expiratory pressure does
FIGURE 5. Pressure at the airway opening vs time not significantly affect lung volume or hemo-
during controlled ventilation in a patient with an
dynamics in patients with COPD.
acute exacerbation of chronic obstructive
pulmonary disease.
Auto-PEEP was measured by end-expiratory airway ■ REFERENCES
1. Angus DC, Kelley MA, Schmitz RJ, White A, Popovich J Jr.
occlusion. From the first mechanical inflation, Caring for the critically ill patient. Current and projected
extrinsic PEEP was set by the ventilator at 5 cm H2O workforce requirements for care of the critically ill and
(second inflation) and at 10 cm H2O (third patients with pulmonary disease: can we meet the require-
inflation). Then the total PEEP (extrinsic PEEP + ments of an aging population? JAMA 2000; 284:2762–2770.
2. Behrendt CE. Acute respiratory failure in the United States:
auto-PEEP) was measured again by end-expiratory incidence and 31-day survival. Chest 2000; 118:1100–1105.
airway occlusion. 3. Frutos-Vivar F, Esteban A. When to wean from a ventilator:
Since PEEP partly replaced auto-PEEP, without an evidence-based strategy. Cleve Clin J Med 2003;
adding it to it, because of flow limitation, the peak 70:389–397.
4. Wiedemann HP, Arroliga AC. Acute respiratory distress syn-
cycling pressure did not change despite increasing
drome: low-stretch ventilation improves survival. Cleve Clin
PEEP set by the ventilator. J Med 2000; 67:435–440.
This figure illustrates a similar way to assess the 5. Arroliga AC. Noninvasive positive pressure ventilation in
effect of extrinsic PEEP set by the ventilator in acute respiratory failure: does it improve outcomes? Cleve
patients with auto-PEEP, at least during controlled Clin J Med 2001; 68:677–680.
6. Marini JJ. Pressure-targeted mechanical ventilation of acute
ventilation. lung injury. Semin Respir Med 1993; 14:262–269.
7. Kimball WR, Leith DE, Robins AG. Dynamic hyperinflation
FROM ROSSI A, POLESE G, BRANDI G, CONTI G. INTRINSIC POSITIVE END-EXPIRATORY PRESSURE
(PEEPi). INTENSIVE CARE MED 1995; 21:522–536,
and ventilator dependence in chronic obstructive pul-
COPYRIGHT SPRINGER-VERLAG; REPRINTED WITH PERMISSION. monary disease. Am Rev Respir Dis 1982; 126:991–995.
8. Bernasconi M, Ploysongsang Y, Gottfried SB, Milic-Emili J,
Rossi A. Respiratory compliance and resistance in mechani-
cally ventilated patients with acute respiratory failure.
808 CLEVELAND CLINIC JOURNAL OF MEDICINE VOLUME 72 • NUMBER 9 SEPTEMBER 2005
Intensive Care Med 1998; 14:547–553. failure during mechanical ventilation. The effect of intrinsic positive
9. Ranieri VM, Giuliani R, Cinnella G, et al. Physiologic effects of positive end-expiratory pressure. Am Rev Respir Dis 1985; 131:672–677.
end-expiratory pressure in patients with chronic obstructive pulmonary 21. Marini JJ, Culver BH, Butler J. Mechanical effect of lung distention
disease during acute ventilatory failure and controlled mechanical ven- with positive pressure on cardiac function. Am Rev Respir Dis 1981;
tilation. Am Rev Respir Dis 1993; 147:5–13. 124:382–386.
10. Marini JJ. Should PEEP be used in airflow obstruction? Am Rev Respir 22. Lapinsky SE, Leung RS. Auto-PEEP and electromechanical dissociation
Dis 1989; 140:1–3. [letter]. N Engl J Med 1996; 335:674.
11. Koutsoukou A, Bekos B, Sotiropoulou C, Koulouris NG, Roussos C, 23. Kress JP, O’Connor MF, Schmidt GA. Clinical examination reliably
Milic-Emili J. Effects of positive end-expiratory pressure on gas detects intrinsic positive end-expiratory pressure in critically ill,
exchange and expiratory flow limitation in adult respiratory distress mechanically ventilated patients. Am J Respir Crit Care Med 1999;
syndrome. Crit Care Med 2002; 30:1941–1949. 159:290–294.
12. Pepe PE, Marini JJ. Occult positive end-expiratory pressure in mechani- 24. Maltais F, Reissmann H, Navalesi P, et al. Comparison of static and
cally ventilated patients with airflow obstruction: the auto-PEEP effect. dynamic measurements of intrinsic PEEP in mechanically ventilated
Am Rev Respir Dis 1982; 126:166–170. patients. Am J Respir Crit Care Med 1994; 150:1318–1324.
13. Lessard MR, Lofaso F, Brochard L. Expiratory muscle activity increases 25. Leatherman JW, Ravenscraft SA. Low measured auto-positive end-
intrinsic positive end-expiratory pressure independently of dynamic expiratory pressure during mechanical ventilation of patients with
hyperinflation in mechanically ventilated patients. Am J Respir Crit severe asthma: hidden auto-positive end-expiratory pressure. Crit Care
Care Med 1995; 151:562–569. Med 1996; 24:541–546.
14. Ninane V, Rypens F, Yernault JC, De Troyer A. Abdominal muscle use 26. Permutt S, Bromberger-Barnea B, Bane HN. Alveolar pressure, pul-
during breathing in patients with chronic airflow obstruction. Am Rev monary venous pressure, and the vascular waterfall. Med Thorac 1962;
Respir Dis 1992; 146:16–21. 19:239–260.
15. Zakynthinos SG, Vassilakopoulos T, Zakynthinos E, Roussos C, Tzelepis 27. Pride NB, Permutt S, Riley RL, Bromberger-Barnea B. Determinants of
GE. Correcting static intrinsic positive end-expiratory pressure for expi- maximal expiratory flow from the lungs. J Appl Physiol 1967;
ratory muscle contraction. Validation of a new method. Am J Respir 23:646–662.
Crit Care Med 1999; 160:785–790. 28. Petrof BJ, Legare M, Goldberg P, Milic-Emili J, Gottfried SB. Continuous
16. MacIntyre NR, Cheng KC, McConnell R. Applied PEEP during pressure positive airway pressure reduces work of breathing and dyspnea dur-
support reduces the inspiratory threshold load of intrinsic PEEP. Chest ing weaning from mechanical ventilation in severe chronic obstructive
1997; 111:188–193. pulmonary disease. Am Rev Respir Dis 1990; 141:281–289.
17. Fessler HE, Brower RG, Permutt S. CPAP reduces inspiratory work more 29. Georgopoulos D, Giannouli E, Patakas D. Effects of extrinsic positive
than dyspnea during hyperinflation with intrinsic PEEP. Chest 1995; end-expiratory pressure on mechanically ventilated patients with
108:432–440. chronic obstructive pulmonary disease and dynamic hyperinflation.
18. Fiastro JF, Habib MP, Shon BY, Campbell SC. Comparison of standard Intensive Care Med 1993; 19:197–203.
weaning parameters and the mechanical work of breathing in 30. Tobin MJ, Perez W, Guenther SM, et al. The pattern of breathing dur-
mechanically ventilated patients. Chest 1988; 94:232–238. ing successful and unsuccessful trials of weaning from mechanical ven-
19. Brandolese R, Broseghini C, Polese G, et al. Effects of intrinsic PEEP on tilation. Am Rev Respir Dis 1986; 134:1111–1118.
pulmonary gas exchange in mechanically-ventilated patients. Eur
Respir J 1993; 6:358–363.
20. Rossi A, Gottfried SB, Zocchi L, et al. Measurement of static compli- ADDRESS: Majid Mughal, MD, University of South Alabama Medical
ance of the total respiratory system in patients with acute respiratory Center, 2451 Fillingim Street, Mobile, AL 36617-2293.
What questions do you want answered?
We want to know what questions you want addressed in ‘‘1-Minute Consult.’’
ONE All questions should be on practical, clinical topics. You may submit questions by mail, phone, fax, or e-mail.
MINUTE
CONSULT P L E A S E P R I N T C L E A R LY
BRIEF ANSWERS
TO SPECIFIC
Q:
CLINICAL QUESTIONS
NAME
ADDRESS
CITY
STATE ZIP
PHONE EMAIL
Cleveland Clinic Journal of Medicine, 9500 Euclid Ave., NA32, Cleveland, OH 44195
PHONE 216 • 444 • 2661 FAX 216 • 444 • 9385 E-MAIL [email protected]
CLEVELAND CLINIC JOURNAL OF MEDICINE VOLUME 72 • NUMBER 9 SEPTEMBER 2005 809
