title: Comparison of gas exchange, lactate, and lactic acidosis thresholds in patients with chronic obstructive pulmonary disease.
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 VCO2 kinetics are slower than VO2 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.
authors.affiliation: Division of Pulmonary Disease, Clinica del Lavoro Foundation, Veruno, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Patessio
authors.forename: R
authors.initials: R
authors.lastname: Casaburi
authors.forename: M
authors.initials: M
authors.lastname: Carone
authors.forename: L
authors.initials: L
authors.lastname: Appendini
authors.forename: C F
authors.initials: CF
authors.lastname: Donner
authors.forename: K
authors.initials: K
authors.lastname: Wasserman
mesh_terms: D000140:Acidosis, Lactic / Q000097:blood / Q000503:physiopathology* / Q000534:rehabilitation; D015308:Anaerobic Threshold; D001639:Bicarbonates / Q000097:blood; D002245:Carbon Dioxide / Q000502:physiology; D005080:Exercise Test; D006801:Humans; D007773:Lactates / Q000097:blood*; D019344:Lactic Acid; D008173:Lung Diseases, Obstructive / Q000097:blood / Q000503:physiopathology* / Q000534:rehabilitation; D008297:Male; D008875:Middle Aged; D011659:Pulmonary Gas Exchange; D013147:Spirometry; D013997:Time Factors
chemical_list: D001639:Bicarbonates; D007773:Lactates; D002245:Carbon Dioxide; D019344:Lactic Acid