Journal international de médecine physique et de réadaptation
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Verification of Blood Lactate during Incremental Exercise Testing

Kazuyuki Kominami*, Masatoshi Akino

Background:The increase in Blood Lactate (BLa) level during incremental exercise testing (Inc-Ex) leads to bicarbonate ion buffering and excretion of carbon dioxide (CO₂). The relationship between the excretion of excess CO₂ and BLa during Inc-Ex is unclear. This study aimed to verify whether BLa could be estimated from excess CO₂ excretion during Inc-Ex.

Methods: We recruited 11 patients (group P, age: 72.6 ± 8.5 years; male: 9) who were prescribed medication for cardiovascular risk factors or diseases. Twenty-two healthy participants (group H, age: 69.3 ± 6.7 years; male: 9) were also recruited for comparison. All participants performed the symptomatic limited cardiopulmonary exercise test, and their BLa levels were measured. Excess CO₂ (the difference between oxygen uptake and CO₂ excretion) was determined from breath-by-breath gas analysis data. BLa level was measured from arterialized fingertips every minute during Inc-Ex (10 W/min ramp exercise). Plots of per-minute excess CO₂ and BLa were linearly regressed, and regression equations and coefficients were calculated along with 95% confidence intervals and prediction intervals.

Results: BLa levels were measured 9.2 ± 2.4 times per participant during Inc-Ex. BLa was significantly correlated with excess CO₂ in both groups H and P (all participants: r=0.862, p<0.001, y=0.0139x+1.7364; group H: r=0.872, p<0.001, y=0.0108x+1.617; and group P: r=0.878, p<0.001, y=0.0139x+1.7364).

Conclusion: Excess CO₂ aided in verifying BLa levels within a certain range. Excess CO₂ during the cardiopulmonary exercise test is useful for estimating BLa levels.