• D Georgopoulos, E Giannouli, and D Patakas.
• Respiratory Failure Unit, General Hospital G. Papanicolaou, Aristotelian University of Thessaloniki, Greece.
• Intensive Care Med. 1993 Jan 1;19(4):197-203.

ObjectiveTo examine the circulatory and respiratory effects of extrinsic positive end-expiratory pressure (PEEPe) in patients with chronic obstructive pulmonary disease (COPD) and dynamic hyperinflation during controlled mechanical ventilation.DesignDifferent levels of PEEPe were applied randomly in mechanically ventilated patients with COPD and dynamic hyperinflation.SettingRespiratory Intensive Care Unit of a University Hospital.Patients9 patients with acute respiratory failure and dynamic hyperinflation due to acute exacerbation of COPD.InterventionsPEEPe 35%, 58% and 86% of intrinsic PEEP (PEEPi) were applied.Measurements And ResultsUsing flow-directed pulmonary artery catheters hemodynamic measurements were obtained, while simultaneously lung volumes, airflows and airway pressures were recorded. In order to estimate alveolar pressures (Palv), rapid airway occlusions during passive expiration were also performed. At no level of PEEPe were significant changes in cardiac output, gas exchange variables, dead space, airways inflation resistances and respiratory system static end-inspiratory compliance observed. At high level of PEEPe central venous, mean pulmonary arterial and pulmonary capillary wedge pressures were increased significantly. All but one patient were flow-limited during passive expiration. PEEPe 86% of PEEPi caused a significant increase in end-expiratory lung volume and total PEEP. Iso-volume pressure-flow curves showed volume-dependence expiratory flow limitation in 2 patients, while in 8 patients volume-dependence of critical driving pressure (Palv-mouth pressure) that decreased flows was also observed.ConclusionsThe effects of PEEPe on iso-volume flow and hence on lung mechanics and hemodynamics, depend on many factors, such as airways resistances, lung volumes and airway characteristics, making the patient response to PEEPe unpredictable.

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