Comparison of gas exchange after lung resection with a Boussignac CPAP or Venturi mask

Abstract

Background Postoperative continuous positive airway pressure (CPAP) can improve lung function. The aim of our study was to assess the efficacy of prophylactic CPAP on the $P{\hbox{a}-\rm O2}}}\hbox{/}F{\small{\rm I}}\rm O}-2}}\!$ ratio measured the day after surgery in patients undergoing lung resection surgery (LRS). Methods The study population comprised 110 patients undergoing LRS. On arrival in the postanaesthesia care unit (PACU), patients were randomized to receive CPAP at 5-7 cm H2O during the first 6 h after surgery (CPAP group) or supplemental oxygen through a Venturi mask (Venturi group). The $Phbox{a-rm O}-2\hbox/F\small\rm I-\rm O}-2}}\!$ ratio was measured on arrival in the PACU, 7 h after admission, and the day after surgery. The $P\hbox{a}-\rm O-2}}}\hboxF\small\rm I-{{{\rm O}-2}}$ ratio is the primary endpoint of our study. We also analysed the chest radiograph and assessed the postoperative course. We then analysed the impact of ventilatory management in the PACU depending on the respiratory risk of the patient. Results Baseline characteristics were similar in both groups. Patients who received CPAP had significantly higher $Phbox{a}-\rm O-2}}}\hbox{/}F{\small{\rm I}}-{{{\rm O}-2}}\!$ at 24 h after surgery compared with patients managed conventionally (Venturi group) (48.6±14 vs 42.3±12, P=0.031), but there were no differences at 7 h. On subgroup analysis, we found that the benefits of CPAP were greater in higher risk patients. The incidence of postoperative pulmonary complications and stay in the PACU and hospital were similar in both groups. Conclusions In patients undergoing LRS, prophylactic CPAP during the first 6 h after surgery with a pressure of 5-7 cm H2O improved the $P\hbox{a}-\rm O}-2}}}\hbox{/}F{\small{\rm I}}-{{{\rm O}-2}}\!$ ratio at 24 h. This effect was more evident in patients with increased risk of postoperative pulmonary complications. © 2014 The Author. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved.