Transcutaneous monitoring of oxygen tension during one-lung anesthesia

Twenty adult patients were monitored with a transcutaneous oxygen tension sensor during one-lung ventilation. Anesthesia was maintained with enflurane-oxygen or isoflurane-oxygen. The transcutaneous oxygen tension values accurately followed the trend of arterial oxygen tension (r = 0.94, n = 96, transcutaneous oxygen tension = 4.8 + 0.78 X arterial oxygen tension). The transcutaneous oxygen tension values averaged 80% of the arterial oxygen tension values (transcutaneous oxygen tension index = transcutaneous oxygen tension/arterial oxygen tension = 0.80 +/- 0.18) (mean +/- standard deviation). When one-lung ventilation was initiated, there was a progressive drop in transcutaneous oxygen tension which reached a minimum of 19 +/- 10 minutes. The mean of the minimum transcutaneous oxygen tension and arterial oxygen tension values was 66 +/- 44 torr and 83 +/- 43 respectively. This resulted in a mean alveolar-arterial oxygen gradient of 515 +/- 152 torr during one-lung ventilation. In eight patients, the arterial oxygen tension fell below 60 torr, 45 +/- 9 torr. When two-lung ventilation was resumed, the transcutaneous oxygen tension and arterial oxygen tension values promptly rose to mean values of 342 +/- 121 torr and 411 +/- 103 torr, respectively in 9 +/- 3 minutes. The transcutaneous oxygen tension monitor provided a continuous assessment of the patient's oxygenation, gave early warning of potentially hazardous hypoxia, and permitted nearly real-time assessment of the efficacy of corrective therapies.