• Kyuho Lee, Young Jun Oh, Yong Seon Choi, and Shin Hyung Kim.
• Department of Anesthesiology and Pain Medicine, Anesthesia and Pain Research Institute, Yonsei University College of Medicine, Seoul, Republic of Korea.
• J Clin Anesth. 2015 Sep 1; 27 (6): 445-50.

Study ObjectiveTo investigate the effects of a 1:1 inspiratory-to-expiratory (I:E) ventilation ratio on oxygenation and respiratory mechanics during one-lung ventilation (OLV) in patients with low diffusion capacity of lung for carbon monoxide (DLCO).DesignProspective, randomized, crossover study.SettingOperating room, university hospital.PatientsTwenty-six patients with a preoperative DLCO less than 80% who were scheduled for lung lobectomy requiring OLV under general anesthesia.InterventionsIn the first group (n = 13), OLV was begun with a 1:1 I:E ratio, which was switched to a 1:2 I:E ratio after 30 minutes. In the second group (n = 13), the modes of ventilation were performed in the opposite order. Pressure-controlled ventilation with 5 cm H2O of positive end-expiratory pressure and a tidal volume of 5 to 8 mL/kg was applied during OLV.MeasurementsArterial and central venous blood gas analyses were recorded and used to calculate intrapulmonary shunt fraction and physiologic dead space. These measurements were taken at 4 time points: 10 minutes after two-lung ventilation in the lateral decubitus position, 30 minutes after initiation of OLV, 30 minutes after switching the I:E ratio, and 10 minutes after two-lung ventilation was resumed.Main ResultsThere was no difference in arterial oxygen tension during OLV between the 2 groups (P = .429). Arterial carbon dioxide tension and peak airway pressure were lower in the 1:1 group than in the 1:2 group (P = .003; P = .008). Physiologic dead space was also decreased in the 1:1 I:E ratio group (P = .003). Mean airway pressure and dynamic compliance were higher in the 1:1 group (P = .003; P = .007).ConclusionsPressure-controlled ventilation with a 1:1 I:E ventilation ratio did not improve oxygenation in patients with low DLCO during OLV compared with a 1:2 I:E ventilation ratio. However, it did provide benefits in terms of respiratory mechanics and increased the efficiency of alveolar ventilation during OLV.Copyright © 2015 Elsevier Inc. All rights reserved.

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