Apnea-induced hemoglobin desaturation during one-lung vs two-lung ventilation

Purpose: To compare the rate of apnea-induced hemoglobin desaturation during one-lung ventilation (OLV) vs two-lung ventilation (TLV) in patients undergoing thoracic surgery. Methods: Six patients undergoing thoracotomy or thoracoscopywere included. Each patient served as his/her own control. The lungs were ventilated with oxygen 100% using TLV, followed after 20-30 min by OLV and the resultant PaO2 was measured. Apnea was then induced following the two techniques of ventilation, and the times for every 1% decrease in hemoglobin saturation from 100% to 95%, as monitored by pulse oximetry, were recorded. The times for every 1% decrease in the saturation were compared in the two groups. Results: The mean PaO2 Value following TLV(445 +/- 99 mmHg) was higher than the mean PaO2 following OLV (1 56 +/- 18 mmHg). Also, the mean time for subsequent apnea induced hemoglobin desaturation from SpO(2) 100% to 95% following TLV was twice the time of desaturation following OLV (6.3 +/- 1.2 min vs 3.2 +/- 0.5. min, P < 0.05). Conclusion: Hemoglobin desaturation occurs more rapidly during apnea following OLV than TLV: The rapid desaturation may be attributed to the decrease of FRC, associated with an increased transpulmonary shunting. The results suggest that two-lung ventilation with oxygen 100% provides a greater safety margin than one-lung ventilation with oxygen 100% whenever ventilation is interrupted.