Comparison of gas exchange, lactate, and lactic acidosis thresholds in patients with chronic obstructive pulmonary disease

A. Patessio, R. Casaburi, M. Carone, L. Appendini, C. F. Donner, K. Wasserman

Research output: Contribution to journalArticle

Abstract

During an incremental exercise test, three consequences of the onset of anaerobic metabolism can be observed: rise in blood lactate (lactate threshold, LT); fall in standard bicarbonate (lactic acidosis threshold, LAT); nonlinear increase in CO2 output (V-slope gas exchange threshold, GET). We compared these thresholds in 31 patients with COPD. We found that the GET and LAT overestimated the LT. A better relationship was found between LAT and GET, even though GET was significantly higher than LAT (by 124 ml/min; p <0.0001). However, since the bias is appreciably greater at lower LAT values (likely because V̇CO2 kinetics are slower than V̇O2 kinetics), we separated the studies into two groups: (A) tests where LAT occurred within the first 2 min of the increasing work rate period, and (B) tests where LAT occurred after 2 min. For Group A, there was a substantial bias between LAT and GET (323 ml/min, p <0.0001), whereas the bias was much smaller (only 5.4%, though statistically significant) for Group B (57 ml/min, p <0.01). We conclude that when lactic acidosis occurs after the first 2 min of incremental exercise, the GET closely approximates the point at which blood bicarbonate begins to fall.

Original languageEnglish
Pages (from-to)622-626
Number of pages5
JournalAmerican Review of Respiratory Disease
Volume148
Issue number3
Publication statusPublished - 1993

ASJC Scopus subject areas

  • Pulmonary and Respiratory Medicine

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