Effects of different positive end-expiratory pressure titrating strategies on oxygenation and respiratory mechanics during one- lung ventilation: a randomized controlled trial.

Abstract

Positive end-expiratory pressure (PEEP) is widely used to reduce the risk of hypoxemia and atelectasis during one-lung ventilation (OLV); however, the optimal strategy for PEEP titrating remains unclear.The purpose of the study was to investigate the effects of different PEEP titrating strategies on oxygenation and respiratory mechanics during OLV. Patients undergoing thoracic surgery with general anesthesia were randomly allocated into five groups. In P0 group, PEEP was set to zero; in PLIP2 group, PEEP was set to 2 cmH2O plus the pressure of lower inflection point (LIP) of pressure-volume (P-V) curve; in PLIPS group, PEEP was titrated to achieve maximum static compliance from the averaged LIP pressure value; in groups PSTAT and PDYN, the incremental PEEP values were titrated to achieve maximum static compliance or maximum dynamic compliance from 4 cmH2O. Hemodynamic measurements, respiratory mechanics, and blood gas analyses were recorded at the beginning of OLV, OLV 15 min, OLV 30 min, OLV 45 min, and OLV 60 min. Also, the intrapulmonary shunt (Qs/Qt), physiological dead space to tidal volume ratio (VD/VT), and oxygenation index (OI) were calculated and compared. Seventy-five patients consented to participate in this study. Dynamic compliance, peak inspiratory pressure (PIP), and plateau inspiratory pressure (Pplat) increased after PEEP titration during OLV. PIP, Qs/ Qt, and OI showed no differences among groups. Group PDYN showed lower Pplat, lower driving pressure, and higher dynamic compliance when compared with zero PEEP group. The PEEP titrating strategy according to dynamic compliance can improve respiratory mechanics, whereas it has no significant effects on oxygenation, dead space ratio, and intrapulmonary shunt, suggesting that it is better during OLV for thoracic surgery.