Effectiveness of Ventilation of Nondependent Lung for a Brief Period in Improving Arterial Oxygenation during One-lung Ventilation: A Prospective Study

BACKGROUND: Hypoxemia is common during one-lung ventilation(OLV), predominantly due to transpulmonary shunt. None of the strategies tried showed consistent results. We evaluated the effectiveness of ventilating the operated, non-dependent lung (NDL) with small tidal volumes in improving the oxygenation during OLV. METHODS: 30 ASA 1 and 2 patients undergoing elective, open thoracotomy were studied. After standard induction of anesthesia, lung seperation was acheived with left sided DLT. The ventilatory settings for two lung ventilation (TLV) were: FiO(2) of 0.5, tidal volume of 8-10ml/kg and respiratory rate of 10-12/min. After initiating OLV, the dependent lung alone was ventilated with the above settings for 15 minutes and an arterial blood gas (ABG) analysis was done. Then the NDL was ventilated with a separate ventilator, with FiO(2) of 1, tidal volume of 70 ml, I:E ratio of 1:10 and respiratory rate of 6/min for 15 minutes. The NDL ventilation was started early if the patients desaturated to <95%. ABG was done at 5 and 15 mins of NDL ventilation. We compared the PaO(2) values. RESULTS: The mean PaO(2) decreased from 232.2 ± 67.2 mm of Hg (TLV-ABG1) to 91.2 ± 31.7 mm of Hg on OLV (OLV-ABG1). The ABG after 5 minutes and 15 minutes after institution of NDL ventilation during OLV showed a PaO2 of 145.7 ± 50.2 mm of Hg and 170.6 ± 50.4 mm of Hg which were significantly higher compared to the one lung ventilation values.