Capillary blood gas test usefulness to evaluate gas exchange with 21% and 100% of oxygen inspired fractions in subjects with stable cardiopulmonary disease at 2,240 meters above sea level

Capillary blood gas test has had ample use in the infantile population. In the adult population, the information is limited and controversial. The agreement between capillary-arterial gases seems to parallel the pH and the carbon dioxide pressure in different studied populations. In order to know the degree of agreement between these gases, we evaluate them at breathing room air and at 100% of oxygen fractions at 2,240 meters above sea level. We obtained capillary-arterial blood gases simultaneously from subjects with stable cardiopulmonary disease in both conditions of inspired oxygen. Demographic, hemodynamic, diagnostic, and laboratory variables were gathered. agreement was analyzed with the intraclass correlation coefficient and the Bland-Altman procedure. We studied 101 subjects, 48 men and 53 women, whose respective ages were 55 +/- 16 and 56 +/- 16. Mean systemic arterial pressure was 94.96 +/- 10.57 mmHg. Hemoglobin was 15.94 +/- 2.48 g/dl. The agreement between the variables with the inspired oxygen fractions, 21%, 100%, and the mean difference in parenthesis was respectively: potential hydrogen, 0.94 (0.0091), 0.94 (0.0039); oxygen pressure, 0.90 (2.94), 0.84 (74.99); carbon dioxide pressure, 0.97 (0.079), 0.97 (0.179); bicarbonate, 0.93 (-0.067), 0,96 (0.262); total dissolved carbon dioxide, 0.94 (-0.142), 0.93 (0.161); base excess: 0.94, (-0.125), 0.92 (0.235); oxygen saturation, 0.98 (0.764), 0.97(0.202). Capillary blood gas test could be a useful alternative to the arterial one, nevertheless, it is limited by its low agreement with the oxygen pressure in both oxygen inspired fractions.