Comparison between fluctuating PEEP and conventional PEEP in dogs with lung injury induced by blood aspiration.

It has been documented that in some patients with acute hypoxic respiratory failure the application of positive end-expiratory pressure (PEEP) may produce no improvement or even a deterioration of pulmonary oxygenation due to an increase in ventilation-perfusion mismatching. Fluctuating PEEP (F-PEEP) is a newly developed PEEP in which end-expiratory pressure (EEP) is periodically changed within a certain range. In a dog model with localized lung injury induced by the aspiration of non-heparinized blood (2 ml.kg body weight-1), F-PEEP in which the EEP was periodically changed from 0.5 to 1.5 kPa at frequencies of 10 min, and conventional PEEP with 3 different fixed EEPs, 0.5, 1.0 and 1.5 kPa (C-PEEP0.5, C-PEEP1.0 and C-PEEP1.5) were each applied for 60 min. F-PEEP produced a periodical change in PaO2 and hemodynamic variables including cardiac output, and in comparison with C-PEEP0.5, C-PEEP1.0 and C-PEEP1.5, a significantly greater improvement of A-aDO2 and dynamic compliance with relatively large cardiac output in the low EEP phase. These results suggest that F-PEEP is a useful mode of artificial ventilation for treating some kinds of acute hypoxic respiratory failure due to increased ventilation-perfusion mismatching.