Reducing tidal volume and increasing positive end-expiratory pressure with constant plateau pressure during one-lung ventilation: effect on oxygenation

Background It is no longer safe to use large tidal volumes ( V T ) (>8 ml kg −1 ) for one-lung ventilation (OLV), and limiting plateau pressure should be a major objective. Due to the specificity of OLV, the use of positive end-expiratory pressure (PEEP) remains controversial. This study determined whether at the same low plateau pressure, reducing V T and increasing PEEP were not inferior to larger V T and lower PEEP ventilation in terms of oxygenation. Methods This prospective, randomized, non-inferiority, cross-over trial included 88 patients undergoing open thoracotomy who received two successive ventilatory strategies in random order: V T (8 ml kg −1 of ideal body weight) with low PEEP (5 cm H 2 O), or low V T (5 ml kg −1 ) with a high PEEP. Respiratory rate and PEEP were, respectively, adjusted to maintain constant ventilation and plateau pressure. The primary endpoint was the P a O 2 / F I O 2 ratio under each ventilatory strategy. Results The non-inferiority of low- V T ventilation could not be established. The mean adjusted P a O 2 / F I O 2 ratio was lower overall during low- V T ventilation, and differences between the two ventilatory modes varied significantly according to baseline (T0) P a O 2 / F I O 2 . Decreased oxygenation during low V T was smaller when baseline values were low. Systolic arterial pressure was not lower during low- V T ventilation. Conclusion During OLV, lowering V T and increasing PEEP, with the same low plateau pressure, reduced oxygenation compared with larger V T and lower PEEP. This strategy may reduce the risk of lung injury, but needs to be investigated further.