Abstract
BACKGROUND: Arterial oxygenation is often impaired during one-lung ventilation (OLV), due to both pulmonary shunt and atelectasis. Lower fraction of inspiration O(2) (FiO(2)) may reduce inflammation and complications, but may increase the risk of hypoxemia. The aim of this randomized controlled parallel trial was to analyze whether higher positive end-expiratory pressure (PEEP) could improve oxygenation and maintain lower levels of inflammation during OLV under a lower FiO(2). METHODS: One hundred and twenty patients with selective thoracotomy for esophageal cancer (EC) were classified randomly into four groups on a ratio of 1:1:1:1 using a computer-generated list, including Group A (FiO(2) =0.6, PEEP =0), Group B (FiO(2) =0.6, PEEP =5 cmH(2)O), Group C (FiO(2) =1.0, PEEP =8 cmH(2)O), and Group D (FiO(2) =1.0, PEEP =10 cmH(2)O). The oxygenation and pulmonary shunt were primary outcomes. Haemodynamics, respiratory mechanics, serum IL-6 and IL-10 levels, and complications were taken as secondary outcomes. Follow-up was terminated until discharge. RESULTS: Two patients in Group A and two in Group D were excluded due to hypoxemia and hypotension, respectively. Then the data of 116 patients (Group A =28, Group B =30 Group C =30, and Group D =28) were assessed for final analysis. Compared with Group B, the partial pressure of oxygen (PaO(2)) and dynamic compliance during OLV in Group D were significantly increased from 15 minutes to 60 minutes, while pulmonary shunt was significantly decreased (P>0.05). Patients in Group D had higher levels of central venous pressure (CVP) and airway pressure (Paw) during OLV and higher levels of IL-6 and IL-10 after OLV compared with Group B (P>0.05). No statistical differences were found in oxygen saturation (SaO(2)), PvO(2) (partial pressure of oxygen in venous blood), partial pressure of end-tidal carbon dioxide (ETCO(2)), partial pressure of carbon dioxide in artery (PaCO(2)), heart rate (HR), mean arterial pressure (MAP), and complications among the four groups (P>0.05). CONCLUSIONS: Higher PEEP increased the oxygenation under 60% O(2) during OLV. However, the haemodynamics and respiratory mechanics changed, and the levels of inflammation increased. A higher PEEP under 60% O(2) during OLV is not recommended. TRIAL REGISTRATION: Chinese Clinical Trial Registry ChiCTR1900024726.