Effects of differences of oxygen affinity on circulatory response to hypoxia
Kamada, A.; Suzuki, A.; Akiyama, Y.; Inaba, S.; Dosaka, K.; Kishi, F.; Kawakami, Y.
Advances in Experimental Medicine and Biology 222: 323-329
1988
ISSN/ISBN: 0065-2598 PMID: 3129911 Document Number: 307843
It is well known that tissue hypoxia is an important prognostic predictor in patients with chronic obstructive pulmonary disease (COPD). Compensatory responses to acute hypoxia occur in various organs and the magnitude of such response may also be an important factor in prognosis. P50, (oxygen tension at which the hemoglobin is 50% saturated with oxygen) is recognized as one of the factors affecting oxygen supply to the tissue. These studies were made to determine whether differences of P50 affect the circulatory response to acute hypoxia. Studies were made on nineteen male patients with COPD. They were divided into two groups according to low (< 26.6 torr) or high (> 26.6 torr) P50. Isocapnic hypoxia was induced progressively with the patients being under right cardiac catheterization. The low P50 (25.8 .+-. SD 0.6 torr) group included ten patients, and the high P50 (27.4 .+-. 0.6 torr) group included nine patients. No differences could be detected in respect of pH, PaCO2, PaO2 or any hemodynamic parameters. Heart rate increased in both low and high P50 groups but the degree of the increase (.DELTA. HR/HR ROOM AIR .times. 100) in the high P50 group (20.7 .+-. 9.2%) was significantly greater than in the low P50 group (9.4 .+-. 10.9%). An increase in cardiac output was observed in the high P50 group (4.4 .+-. 0.8 to 5.3 .+-. 0.6 l/min), but not in the low P50 group (4.5 .+-. 1.0 to 5.0 .+-. 0.9 l/min). There was a significant positive relationship (r = 0.903) between hypoxic circulatory response and oxygen transport (TO2). These studies demonstrate that circulatory response to hypoxia is well preserved in the high P50 group but deteriorated in the low P50 group, and this suggests that patients with low P50 cannot compensate adequately for hypoxia during acute exacerbation.