Occult positive end-expiratory pressure in mechanically ventilated patients with airflow obstruction: the auto-PEEP effect.
Alveolar pressure can remain positive throughout the ventilatory cycle of mechanically-ventilated patients with airflow obstruction, even when positive end-expiratory pressure (PEEP) is not applied intentionally. The increase of intrathoracic pressure associated with this "auto-PEEP" phenomenon can severely depress cardiac output as well as elevate the end-expiratory pulmonary artery wedge pressure. Such effects may be exaggerated in patients with chronic obstructive pulmonary disease because abnormally compliant lungs transmit a high fraction of alveolar pressure to intrathoracic vessels. Failure to recognize the hemodynamic consequences of auto-PEEP may lead to inappropriate fluid restriction or unnecessary vasopressor therapy. Although not apparent during normal ventilator operation, the auto-PEEP effect can be detected and quantified by a simple bedside maneuver: expiratory port occlusion at the end of the set exhalation period.
D005260:Female; D006439:Hemodynamics; D006801:Humans; D007385:Intermittent Positive-Pressure Ventilation / Q000009:adverse effects* / Q000379:methods; D008173:Lung Diseases, Obstructive / Q000503:physiopathology* / Q000628:therapy; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration / Q000009:adverse effects*; D011312:Pressure; D011650:Pulmonary Alveoli / Q000503:physiopathology*; D012121:Respiration, Artificial / Q000379:methods