ASPIRATION PNEUMONIA - BENEFICIAL AND HARMFUL EFFECTS OF POSITIVE END-EXPIRATORY PRESSURE

Abstract

With an ex vivo, isolated, ventilated, perfused canine pulmonary lobe, the effects of various levels of positive end-expiratory pressure (PEEP) were evaluated following acid injury. Following intrabronchial instillation of HCl, 8 lobes were ventilated with 5 cm of H2O of PEEP, 12 lobes with 10 cm of PEEP and 8 lobes with 15 cm of PEEP during a 4 h perfusion period. Blood flow was kept constant in all preparations. Lobes with 5 cm of PEEP developed a 39% intrapulmonary shunt and increased their weight by 220%. When PEEP was increased to 10 cm, wt gain was similar (184%), but shunting decreased markedly to 7%. When PEEP was increased further to 15 cm, shunting remained low (13%), but wt gain increased markedly, to 411% of the initial lobe wt. This study demonstrates the beneficial effects of PEEP in aspiration pneumonia, but it also points out that increasing levels of PEEP can magnify acid-pulmonary injury by causing a further increase in interstitial and intralveolar edema.