Lactate and ammonia measurements during cardiopulmonary exercise testing and its recovery phase-Consideration of age and sex in its interpretation.

Background: Cardiopulmonary exercise testing with lactate and ammonia samples is used in the diagnostics of metabolic myopathies. As the effect of age and sex on the exercise lactate and ammonia levels are incompletely characterized for clinical associations, our aim was to assess the effects of these factors on healthy subjects to improve the test's interpretation.

Methods: Seventy-three subjects (34 men and 39 women; age < 35 years, n = 26, 35-50 years, n = 23 and >50 years, n = 24) performed cardiopulmonary exercise tests with venous blood gases, plasma lactate and ammonia analyses at rest, during exercise, and 2, 4, 6, 10, 20 and 30 min into recovery.

Results: The lactate (p = 0.021-0.044) and ammonia values (p = 0.002-0.038) differed between men and women measured during recovery and between three age groups point-by-point in maximal exercise and the recovery phase and also longitudinally, most notably between <35- and >50-year-groups (lactate p = <0.001-0.040, ammonia p = 0.002-0.03). In the linear model, the yearly reduction of lactate was maximally -0.119 mmol/L and that of ammonia -1.514 µmol/L. The yearly reduction of lactate was greater in women than in men (-0.131 vs.-0.099 2 min into recovery), but for ammonia, the results were not as clear.

Conclusions: Plasma lactate and ammonia concentrations measured during cardiopulmonary exercise were lower in older age groups, and their yearly reduction was also influenced by sex. These data give new information on lactate and ammonia levels and the effect of aging on them during exercise and recovery and may help assess cardiopulmonary exercise testing results.