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Can altered body position alleviate post-exercise pulmonary diffusing capacity impairment?

University of British Columbia

Pulmonary diffusing capacity for carbon monoxide (Dlco), alveolar-capillary membrane diffusing capacity (Dm), and pulmonary capillary blood volume (Vc) are all significandy reduced following exercise. It is unknown if measurement position affects this impaired gas transfer postexercise. Prior to (baseline) and 15 minutes, 1, 2, and 4 hours following an incremental cycle to fatigue Dlco, Dm, and Vc were recorded in 10 healthy male subjects in both a supine and upright seated position. It was expected that the supine post-exercise measurement position would significantly reduce the decrement in Vc and thus Dlco, by facilitating a return of blood to the thoracic cavity. With removal of the 15 minute data, due to the lack of achievement of a resting cardiovascular state (heart rate, systolic and diastolic blood pressure all significantly different from baseline), a significant reduction in Dlco, Dm, and Vc was observed 1, 2, and 4 hours postexercise, as indicated in Table 1. [TABLE 1] There was a significant difference between positions for Dlco (4.66+0.98 vs. 5.22±0.89, seated vs. supine, p=0.022) and Dm (6.28±1.36 vs. 7.00+1.32, seated vs. supine, p=0.016), but there was no position effect for Vc. Nor was there any significant interaction between the positions over time for Dlco, Dm, or Vc. The change in Dlco appears to be primarily due to a decrease in Vc. The limited decrease in Dm in the supine position was likely due to a redistribution of blood within the lung, due to gravity, enhancing the surface area available for diffusion. Although the mechanism for the reduction in Vc cannot be determined from this data, a passive relocation of blood into the periphery due to gravity can be discounted, indicating that active vasoconstriction of the pulmonary vasculature and/or peripheral vasodilatation maybe occurring post-exercise. This is the first data to indicate that the maintained diffusion impairment is independent of measurement position.

Thesis/Dissertation

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2009-04-28

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http://hdl.handle.net/2429/7659

Human Kinetics

University of British Columbia

UBCV

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