On Smoothing Gas Exchange Data and Estimation of the Ventilatory Threshold
The ventilatory threshold (VT), is a non-invasive parameter of the aerobic system frequently used as an index of fitness in both patients and healthy normal subjects. Although the existence of an actual threshold may be controversial, it has proven to be a useful indicator of exercise interventions such as training. Over the last decade a variety of schemes have been proposed for estimating VT (1–5), the most recent of which involves regression analysis of the breath to breath gas exchange data (oxygen uptake (Vo2) and carbon dioxide production (Vco2)). This current procedure is intended to detect the Vo2 level where Vco2 begins to accelerate disproportionately in relation to Vo2 (6), a point which is believed to correlate with the onset of increased lactate concentrations in the blood, during progressive work tests. However, the variability in this estimate is often quite large presumedly due to the physiological variability and measurement error found in the alveolar gas exchange estimates. Thus, any technique which can reduce variability in the alveolar gas exchange estimates, should improve the precision of the VT estimates (7). Recent work in this area has attempted to reduce the physiological component of this gas exchange variability by 1) correcting for fluctuations due to breath-to-breath changes in pulmonary stores (Swanson (8)) and 2) relating breath-to-breath fluctuations in arterial CO2 to changes in alveolar CO2 production (Beaver et al. (6)).
KeywordsDioxide Lactate Helium Respiration Bicarbonate
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- 7.Sherrill, D.L. and G.D. Swanson. Application of the general linear model for smoothing gas exchange data. Computers and Biomedical Research. (In Press).Google Scholar
- 8.Swanson, G.D. Breath-to-breath considerations for gas exchange kinetics. In: Exercise Bioenergetics and Gas Exchange, edited by P. Cerretelli and B.J. Whipp. Amsterdam: Elsevier/North-Holland, 1980, p 221–222.Google Scholar
- 10.Jones, N.L. Clinical Exercise Testing, Philadelphia: W.R. Saunder Company, 1975.Google Scholar
- 11.Graybill, F.A. Theory and Application of the Linear Model. Duxbury Press, 1976.Google Scholar