Gradient of bronchial end-tidal CO2 during two-lung ventilation in lateral decubitus position is predictive of oxygenation disorder during subsequent one-lung ventilation

Purpose  Hypoxemia is one of the major problems during one-lung ventilation (OLV). During two-lung ventilation (TLV) using a double-lumen bronchial tube, bronchial endtidal carbon dioxide partial pressure () can be determined on both sides, independently. The is mainly dependent on the pulmonary perfusion to each lung. If the degree of oxygenation disorder during OLV were to be predictable before starting OLV, this could provide time to prepare for any subsequent hypoxemia. The aim of this study was to investigate whether the difference of (D-) between the dependent and the nondependent lungs during TLV in the lateral decubitus position (LP) could be a predictive factor for the severity of oxygenation disorder under subsequent OLV. Methods  Eighteen patients undergoing lung surgery were enrolled in this study. Anesthesia was induced with intravenous thiopental and fentanyl, supplemented by the inhalation of sevoflurane. A left-sided double-lumen bronchial tube was placed. The was independently determined on each side during TLV in the supine position (SP) and at 10 min after changing the position from SP to LP. / inspiratory fraction of oxygen () was taken at 15 min after switching from TLV to OLV in LP. Results  The decrease of / at 15 min during OLV in LP correlated with the reduction of the D- predetermined during TLV in LP (r = 0.698; P < 0.01). Conclusion  The D- predetermined during TLV in LP could be a predictive factor for the severity of oxygenation disorder after starting OLV in LP.