Background and objective: This prospective, randomized, controlled study evaluated the effects on oxygenation by applying a selective and patient-specific value of positive end-expiratory pressure (PEEP) to the dependent lung during one-lung ventilation.
Methods: Fifty patients undergoing thoracic surgery under combined epidural/general anaesthesia were randomly allocated to receive zero PEEP (Group ZEEP, n = 22), or the preventive application of PEEP, optimized on the best thoracopulmonary compliance (Group PEEP, n = 28). Patients' lungs were mechanically ventilated with the same setting during two- and one-lung ventilation (FiO2 = 0.5; VT = 9 mL kg−1, inspiratory : expiratory time = 1 : 1, inspiratory pause = 10%).
Results: Lung-chest wall compliance decreased in both groups during one-lung ventilation, but patients of Group PEEP had 10% higher values than patients with no end-expiratory pressure (ZEEP) applied – Group ZEEP (P < 0.05). During closed chest one-lung ventilation, the PaO2 : FiO2 ratio was lower in Group PEEP (232 ± 88) than in Group ZEEP (339 ± 97) (P < 0.05); but no further differences were reported throughout the study. No differences were reported between the two groups in the need for 100% oxygen ventilation (10 patients of Group ZEEP (45%) and 14 patients of Group PEEP (50%) (P = 0.78)) or re-inflation of the operated lung during surgery (two patients of Group ZEEP (9%) and three patients of Group PEEP (10%) (P = 0.78)). Postanaesthesia care unit discharge required 48 min (25th–75th percentiles: 32–58 min) in Group PEEP and 45 min (30–57 min) in Group ZEEP (P = 0.60).
Conclusions: The selective application of PEEP to the dependent, non-operated lung increases the lung–chest wall compliance during one-lung ventilation, but does not improve patient oxygenation.