Chronic heart failure modifies the response to positive end-expiratory pressure in patients with chronic obstructive pulmonary disease

IntroductionPotentially beneficial effects of positive end-expiratory pressure (PEEP) in patients with chronic obstructive pulmonary disease (COPD) must be balanced against further overinflation and increased alveolar dead space. Concurrent chronic heart failure (CHF) is common and can lead to changes in lung that can reduce the detrimental effects of PEEP.ObjectiveThe aim of this study was to compare the effect of PEEP on volumetric capnography, blood gases, pulmonary mechanics, and vital signs in subjects with either COPD (n = 13) or COPD + CHF (n = 7) during pressure support ventilation.MethodsPositive end-expiratory pressure was administered at 0, 5, 10, 15, and 0 cm H2O for 15 minutes with pressure support maintained at 10 cm H2O. Data are expressed as mean ± SD, and the effect of PEEP and differences between COPD alone and COPD + CHF were tested with repeated-measures analysis of variance.ResultsSubjects were elderly (72.5 ± 13.3 years) with severe COPD (force expired volume in 1 second, 1.3 ± 0.6L; force expired volume in 1 second/force vital capacity, 40% ± 15%). With increasing PEEP in COPD subjects, dead space ratio increased (P < .001), minute alveolar ventilation decreased (P = .001), and Paco2 increased (P = .013), with no change in COPD + CHF subjects. Subjects with COPD + CHF had improvement in Pao2 and lower mean arterial pressure, whereas both were unchanged in subjects with COPD alone.ConclusionIn subjects with severe COPD alone, caution must be used when administering PEEP 10 cm H2O or greater. Subjects with COPD + CHF may benefit from higher levels of PEEP.