We determined the effect of alterations in coronary arterial PCO2 on coronary vascular resistance (CVR) at a constant coronary sinus (CS) PO2 and the effect of coronary arterial PO2 variation on CVR at a constant CS PCO2. A linear but opposing effect on CVR was found for both gases. The sensitivity of CVR to O2 change, represented as CVR/CS PO2, was approximately twice that of the ratio CVR/CS PCO2. (0.0852 +/- 0.006 vs. -0.0362 +/- 0.005). The entire range of CVR variation obtainable through CO2 variation was as great as that resulting from O2 variation. During randomized variation of O2 and CO2, CVR can be mathematically related in a multiple linear expression to CS PO2 and CS PCO2.

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Further study is indicated, but this technology is a promising adjunct to clinical skin cancer screening. Additionally, if the physiologic prediction models can be validated, OTD may facilitate the noninvasive study of some aspects of cutaneous physiology.

SUMMARYWe have investigated the rate of rise of myocardial Pco» (Pmco») after coronary artery occlusion using a new method for this measurement. Previous studies of Pmcch have been limited by the slow response of the only available method, and no increase in Pmcoi prior to 3 minutes after occlusion has been found. We have implanted a miniature PcOj electrode, with a 63% response time of 14 seconds, into the left ventricle of 14 open-chest dogs. After abrupt coronary occlusion, Pmcoi began to rise in 13.6 ± 1.1 seconds in heparinized dogs and in 7.5 ± 0.7 seconds in unheparinized dogs. The subsequent magnitude of the increase in Pmcoi was 24, 88, 171, and 222 mm Hg at 2, 5, 10, and 15 minutes after occlusion. The rate of rise of Pmcoi was essentially linear from 1 minute to 10 minutes at a rate of 18.3 mm Hg/min. The rate of rise was slower during the first 30 seconds after occlusion (6.1 mm Hg/min) and also from 30 seconds to 1 minute (9.7 mm Hg/min). This rate of rise is much greater than that previously observed and reflects the severe myocardial acidosis developing during ischemia. A rise in Pmco, is one of the earliest metabolic changes that has been observed during myocardial ischemia. Ore Res 45:324-330, 1979

This technology continues to be a promising adjunct to clinical skin cancer screening.