Pressure-controlled ventilation and intrabronchial pressure during one-lung ventilation

Abstract

BackgroundPressure-controlled ventilation (PCV) has been suggested to reduce peak airway pressure (Ppeak) and intrapulmonary shunt during one-lung ventilation (OLV) when compared with volume-controlled ventilation (VCV). At the same tidal volume (VT), the apparent difference in Ppeak is mainly related to the presence of a double-lumen tracheal tube. We tested the hypothesis that the decrease in Ppeak observed in the breathing circuit is not necessarily associated with a decrease in the bronchus of the dependent lung. MethodsThis observational study included 15 consecutive subjects who were ventilated with VCV followed by PCV at constant VT. Airway pressure was measured simultaneously in the breathing circuit and main bronchus of the dependent lung after 20 min of ventilation. ResultsPCV induced a significant decrease in Ppeak [mean (sd)] measured in the breathing circuit [36 (4) to 26 (3) cm H20, P<0.0001] and in the bronchus [23 (4) to 22 (3) cm H2O, P=0.01]. However, the interaction (ventilatory mode × site of measurement) revealed that the decrease in Ppeak was significantly higher in the circuit (P<0.0001). Although the mean percentage decrease in Ppeak was significant at both sites, the decrease was significantly lower in the bronchus [5 (6)% vs 29 (3)%, P<0.0001]. ConclusionsDuring PCV for OLV, the decrease in Ppeak is observed mainly in the respiratory circuit and is probably not clinically relevant in the bronchus of the dependent lung. This challenges the common clinical perception that PCV offers an advantage over VCV during OLV by reducing bronchial Ppeak.