Mixed venous CO2 tension during exercise

Auchincloss, J. Howland; Gilbert, Robert; Kuppinger, Mitchell; Peppi, David

doi:10.1152/jappl.1980.48.6.933

Cited by 15 publications

(6 citation statements)

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“…Although there was an unexpected decrease in the P'vco2 at 600 kpm/min at 5.5 min, this decrease was within the reported range of reproducibility of the C02 rebreathing method (AUCHINCLOSS et al, 1980). Therefore, it appeared that the change in the stores and total C02 stores plotted against time following the onset of • 300, 0 450, x 600 kpm/min.…”

Section: Discussionsupporting

confidence: 69%

Immediate CO2 storage capacity at the onset of exercise.

Yano

1986

Jpn.J.Physiol

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The purpose of the present study was to obtain the immediate C02 storage capacity at the onset of exercise. The C02 stores at the onset of the exercise were calculated from the difference between the respiratory gas exchange ratio (R) and the metabolic gas exchange ratio (RQ; R obtained at 5.5 min of exercise). The C02 stores per body weight (C02 stores/w) were linearly related to the C02 pressure (P W02) determined by the C02 rebreathing method (r = 0.713, p <0.001), the slope being 0.330 ml/(mmHg . kg). The C02 stores were then corrected for change in 02 stores with exercise, that defined as total C02 stores. P'v~o2 was also corrected for the effect of lung-bag volume shrinkage and Haldane effect during C02 rebreathing, that defined as true PvC02. The total C02 stores/w were also related linearly to the true Pv~o2 (r = 0.725, p <0.001), the slope of the regression line defined as the immediate C02 storage capacity being 0.650 ml/(mmHg kg).Key words : respiratory gas exchange ratio, mixed venous C02 pressure, immediate C02 storage capacity, onset of exercise.At the steady state in light exercise, it is often assumed that metabolic C02 production is equal to the C02 output, but this assumption is invalid at the onset of exercise (YANG et al., 1984a;HUGHSON and INMAN, 1985). While metabolically produced C02 is partially exhaled from the airway, the rest is stored at the onset of exercise. The increase of body C02 storage results in the increase of mixed venous C02 pressure (CERRETELLI et al., 1966;YANO et al., 1984a). In the heavy exercise, lactate is produced and causes the excessive C02 elimination (ISSEKUTZ and RODAHL, 1961; YANG et al., 1984a), thus C02 stores are diminished. As the increases in lactate and mixed venous C02 pressure were observed in heavy exercise (YANG et al., 1984a;HUGHSON and INMAN, 1985), both effects on C02 stores should be taken into consideration. CLODS and CAMPBELL (1969) proposed a quantitative approach to distinguish the effects of lactate and mixed venous C02 pressure on C02 stores. In their model,

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Section: Discussionsupporting

confidence: 69%

Immediate CO2 storage capacity at the onset of exercise.

Yano

1986

Jpn.J.Physiol

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“…Using the indirect Fick approach, the carbon dioxide rebreathing technique is a popular technique among sports physiologists as it is totally non-invasive and more reliable at exercise than at rest 4749 50 The rebreathing manoeuvre is used to estimate mixed venous P co 2 (PV co 2 ), which, combined with end tidal P co 2 and co 2 production, gives a non-invasive Fick estimate of the cardiac output. Reproducibility is not as high as other techniques48 49and it has yet to be applied at the bedside of the sick patient.…”

Section: Non-invasive Techniquesmentioning

confidence: 99%

Cardiac output in 1998

Singer

1998

Heart

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“…P'vco2 was determined by a graphical analysis in which alveolar C02 pressure change per unit time (dPAco2/dt) plotted against PAco2 during rebreathing. The P'vco2 was the value when dPAco2/dt=0 (FARHI et al, 1976;AUCHINCLOSS et al, 1980). Since dPAco2/dt linearly related to PAco2, P'vco2 was estrapolated with the linear line.…”

Section: Methodsmentioning

confidence: 99%

“…Later, FARHI et al (1976) proposed the equation to estimate the theoretical difference between the real Pvco2 and the Pvco2 determined by the C02 rebreathing 884 T. YANG, P. NORSK, and F. BONDE-PETERSEN method (P'vco2). Nevertheless many investigators (KLAUSEN, 1965;FERGUSON et al, 1968;KNOWLTON and ADAMS, 1974;HEIGENHAUSER and FAULKNER, 1978;AUCHINCLOSS et al, 1980) have not paid attention to this effect.…”

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confidence: 99%

Cardiac output determined by the CO2 rebreathing method with correction of lung-bag volume shrinkage.

1984

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The purpose of this study was to elucidate the effect of lungbag volume shrinkage on P'vco2 estimated by the C02 rebreathing method and to correct its effect in calculation of cardiac output. The P'vco2 was extrapolated with the linear relationship between dPAco2 Jdt and PAc o 2 during rebreathing. The P'vc o 2 was higher than real mixed P002 by 0.82 mmHg at rest, by 1.35 mmHg at 50W, 1.57 mmHg at 100W, and 3.06 mmHg at 150W considering the effect of lung-bag volume shrinkage detected by argon concentration. The cardiac output obtained by the C02 rebreathing method with correction of above differences was in good agreement with that determined by the acetylene method (r=0.930, p<0.001). When the cardiac output was plotted against 02 uptake, our results and the regression line were fairly close to the reported regression lines.Key Words: cardiac output, C02 rebreathing method, lung-bag volume shrinkage, mixed venous C02 pressure. DEFARES (1956) not only introduced the rebreathing technique to estimate oxygenated mixed venous C02 pressure (Pvco2), but also was the first to discuss the effect of lung-bag volume shrinkage on the estimation of the Pvco2. The effect of lung-bag volume shrinkage which derived from 02 uptake being higher than C02 elimination during rebreathing was then judged to be negligible.The recent development of a fast responding gas analyzer makes it possible to use the C02 rebreathing method even at high exercise intensities. At the same time, since exercise requires high 02 uptake, the problem of lung-bag volume shrinkage would be revealed. In fact, LUNDIN and THOMSON (1965) proved such effect on the Pvcp2 estimation in detecting the change of nitrogen concentration. Later, FARHI et al. (1976) proposed the equation to estimate the theoretical difference between the real Pvco2 and the Pvco2 determined by the C02 rebreathing

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Mixed venous CO2 tension during exercise

Cited by 15 publications

References 0 publications

Immediate CO2 storage capacity at the onset of exercise.

Immediate CO2 storage capacity at the onset of exercise.

Cardiac output in 1998

Cardiac output determined by the CO2 rebreathing method with correction of lung-bag volume shrinkage.

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