Decreasing TcPO2  (1 ATA) O2  Breathing
The negative differences are not simply random outcomes from a generally increasing trend, but constitute a different pattern of response.
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A DECREASE in TcPO2 with sea level oxygen breathing is a very sensitive test for arterial disease. It may only be present in 10% of patients, but if present indicates the need for revascularization.
Dr. Otto feels that since the slope of the red line (the “droppers”) is so different, that this represents some different physiological process than the others.