Impact of normocapnic and permissive hypercapnic one-lung ventilation on arterial oxygenation

Abstract

Introduction: Physiologically, an approximately 5 to 10 mmHg difference exists between end‐tidal carbon dioxide (EtCO2) and arterial carbon dioxide (PaCO2) measured during double‐lung ventilation (DLV) that may increase during one‐lung ventilation (OLV) especially if low tidal volume is applied. There is no evidence that during OLV the EtCO2 or PaCO2 should be kept in the normal range. The aim of the present work was to test whether different ventilatory strategies to maintain EtCO2 or PaCO2 in the normal range during OLV have any impact on arterial oxygenation (PaO2). Methods: Data were obtained from 100 patients undergoing thoracic surgery necessitating OLV. Patients were randomized into two groups. In GrEtCO2 (n = 50) the OLV was guided by capnography, and the respiratory rate (RR) was adjusted to maintain EtCO2 in the normal range. In GrPaCO2 (n = 50) the OLV was guided by arterial blood gas analysis (ABG) and RR was adjusted to maintain PaCO2 in the normal range. ABG was performed in a supine position after induction and in a lateral decubitus position during DLV and every 15 minutes during OLV. During OLV 5 ml/kg tidal volume with 5 cmH2O PEEP, I:E = 1:2 ratio and FiO2 1.0 was used. Results: There were no significant differences in PaO2 values between groups during DLV and at the 15th minute of OLV. There were significant differences in PaO2 at the 30th and 45th minutes between groups. In GrPaCO2 mean airway pressure and RR was higher, and the inspiratory and expiratory time was shorter than in GrEtCO2. Conclusions: The relatively high RR impairs the emptying of alveoli and Results: in increased functional residual capacity. So the normocapnic lung‐protective OLV Results: in significantly higher PaO2 than permissive hypercapnic OLV.