Intraoperative compliance profiles and regional lung ventilation improve with increasing positive end‐expiratory pressure. Issue 9 (12th July 2016) - Wirth, S.
Abstract : Background: Anaesthesia and mechanical ventilation can lead to impaired lung. Intraoperative positive end‐expiratory pressure (PEEP) should prevent intratidal recruitment/derecruitment without causing overdistension. The intratidal compliance profile indicates both unwanted phenomena. We hypothesized that a higher than usual PEEP improves the intratidal compliance and the regional lung ventilation of patients with healthy lungs. Methods: After ethics approval, 30 adult patients scheduled for limb surgery were investigated at PEEP 5, 7 and 9 cm H2 O during mechanical ventilation. We calculated the dynamic compliance of the respiratory system (CRS ) and the intratidal volume‐dependent CRS curve. The CRS curve indicated intratidal recruitment/derecruitment and/or overdistension. Regional ventilation was measured using electrical impedance tomography. Results: At PEEP 5, 7 and 9 cm H2 O, intratidal recruitment/derecruitment was observed in 92%, 84% and 46% ( P < 0.05) of the patients respectively. Increasing PEEP was associated with recruitment in the dorsal regions of the lungs ( P < 0.001). At PEEP 9 cm H2 O, lung overdistension was indicated in two patients. With PEEP levels up to 9 cm H2 O, no significant effects on haemodynamic variables were found. Conclusion: We conclude that in most patients, the often applied PEEP of 5 cm H2 O is insufficient to prevent intratidal recruitment/derecruitment and that few patients show overdistension at high PEEP levels. To establish optimal pressure–volume relationships in the respiratory system, the analysis of the individual intratidal compliance profiles could be a means for individualized perioperative PEEP titration.