On Smoothing Gas Exchange Data and Estimation of the Ventilatory Threshold

  • Duane L. Sherrill
  • George D. Swanson


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)).


Functional Residual Capacity Anaerobic Threshold Ventilatory Threshold Lactate Threshold Respiratory Compensation 
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Copyright information

© Plenum Press, New York 1989

Authors and Affiliations

  • Duane L. Sherrill
    • 1
  • George D. Swanson
    • 2
  1. 1.University of Arizona Health Sciences CenterUSA
  2. 2.University of Colorado Health Sciences CenterUSA

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