Factors which alter the relationship between ventilation and carbon dioxide production during exercise in normal subjects期刊界 All Journals 搜尽天下杂志传播学术成果专业期刊搜索期刊信息化学术搜索

Factors which alter the relationship between ventilation and carbon dioxide production during exercise in normal subjects

Authors:	Andrew L. Clark Maurizio Volterrani M. Piepoli Andrew J.S. Coats

Affiliation:	(1) Department of Cardiac Medicine, National Heart and Lung Institute, Dovehouse Street, SW3 6LY London, England;(2) Medical Unit C, Southern General Hospital, 1345 Govan Road, G51 4TF Glasgow, Scotland

Abstract:	The slope of the linear relationship between ventilation $left( {dot V_{text{E}} } right)$ and carbon dioxide production $left( {dot V{text{CO}}_{text{2}} } right)$ has been thought to indicate that $dot V{text{CO}}_{text{2}}$ is one of the major stimuli to $left( {dot V_{text{E}} } right)$ . A group of 15 normal subjects undertook different incremental treadmill exercise protocols to explore the relationship between $left( {dot V_{text{E}} } right)$ and $dot V{text{CO}}_{text{2}}$ . An incremental protocol using 1 instead of 3-min stages of exercise resulted in an increase in the $dot V_{text{E}}$ to $dot V{text{CO}}_{text{2}}$ ratio [26.84 (SEM 1.23) vs 31.08 (SEM 1.36) (P < 0.008) for the first stage, 25.24 (SEM 0.86) vs 27.83 (SEM 0.91) (P < 0.005) for the second stage and 23.90 (SEM 0.86) vs 26.34 (SEM 0.81) (P = 0.001) for the third stage]. Voluntary hyperventilation to double the control level of $dot V_{text{E}}$ during exercise resulted in an increase in the $dot V_{text{E}}$ to $dot V{text{CO}}_{text{2}}$ slope [from 21.3 (SEM 0.71) for the control run to 35.1 (SEM 1.2) for the hyperventilation run (P < 0.001)]. Prolonged hyperventilation (5 min) during exercise at stage 2 of the Bruce protocol resulted in a continuted elevation of $dot V{text{CO}}_{text{2}}$ and the ${{dot V_{text{E}} } mathord{left/ {vphantom {{dot V_{text{E}} } {dot V{text{CO}}_{text{2}} }}} right. kern-nulldelimiterspace} {dot V{text{CO}}_{text{2}} }}$ slope. A steady state of $dot V_{text{E}}$ and metabolic gas exchange can only be said to have been present after at least 3 min of exercise. Voluntary hyperventilation increased the slope of the relationship between $dot V_{text{E}}$ and $dot V{text{CO}}_{text{2}}$ . End-tidal carbon dioxide fell, but remained within the normal range. These results would suggest that a non-carbon dioxide factor may have been responsible for the increase we found in $dot V_{text{E}}$ during exercise, and that factors other than increased dead space ventilation can cause an increased ventilation to $dot V{text{CO}}_{text{2}}$ slope, such as that seen in some pathophysiological conditions, such as chronic heart failure.

Keywords:	Ventilation Carbon dioxide production Exercise
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