Hemodynamics at rest and during exercise in comfortable, hot and cold environments.Measurement with a rebreathing technique

M. Küng, L. Tachmes, S. J. Birch, R. J. Fernandez, W. M. Abraham, M. A. Sackner

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Abstract

The hemodynamic effects of exercise during short-term exposure to a cold, hot and comfortable environment were studied in normal subjects. Seven untrained males (19 to 34 years) exercised on a bicycle while exposed to temperatures of 7 °C, 22 °C and 41 °C inside an environmental chamber. Values for oxygen consumption (VO2), pulmonary capillary blood flow (Qc), pulmonary capillary and tissue volume (V(t+c)) and pulmonary diffusing capacity for CO (DL) were obtained using a non-invasive rebreathing technique. These parameters and heart rate (HR) were measured after 15 min of sitting exposure and during three episodes of exercise (50, 75 and 100 W) for 5 min each. Resting VO2 at 7 °C was 31% higher than at 22 °C (p < 0.01) and 43% higher than at 41 °C (p < 0.05). During exercise, VO2 increased independently of temperature. While all measured hemodynamic parameters were similar during exercise at 7 °C and 22 °C, HR was consistently higher and stroke index lower during exercise at 41 °C. At 95% of maximum heart rate (HRmax.) at 41 °C, Qc was 13% lower than at 22 °C (p < 0.01) and 14% lower than at 7 °C (p < 0.05). V(t+c) and DL increased during exercise and were not affected by temperature. In normal man: 1) central hemodynamic changes at rest are more pronounced during short-term cold than during similar heat exposure; 2) VO2 during moderate and severe exercise is independent of ambient temperature; 3) Qc near HRmax. is decreased in hot environment; and 4) exercise induced increases in DL and V(t+c)/kg appear to be independent of ambient temperature.

Original languageEnglish (US)
Pages (from-to)429-441
Number of pages13
JournalClinical Respiratory Physiology
Volume16
Issue number4
StatePublished - Dec 1 1980

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ASJC Scopus subject areas

  • Pulmonary and Respiratory Medicine

Cite this

Küng, M., Tachmes, L., Birch, S. J., Fernandez, R. J., Abraham, W. M., & Sackner, M. A. (1980). Hemodynamics at rest and during exercise in comfortable, hot and cold environments.Measurement with a rebreathing technique. Clinical Respiratory Physiology, 16(4), 429-441.