Abstract
Incremental exercise tests on a bicycle ergometer were performed by twenty pneumoconiosis patients working in foundries in order to determine the anaerobic threshold (AT) by abrupt increase in arterial blood lactate.
The validity of their AT in the evaluation of their physical working capacity was studied in comparison with their maximum oxygen uptake (VO2·max) and also in consideration of pulmonary gas exchange function during exercise.
1. The mean values of their AT and VO2·max were 0.771±0.279L/min (13.1±4.4ml/kg/min) and 1.600±0.417L/min (27.4±7.0ml/kg/min) respectively, which were lower than those in healthy male subjects, reported by other workers. This suggested that the physical working capacity of these patients was generally low.
2. The AT of each individual patient (VO2·AT) correlated well with their VO2·max. The regression equation was
VO2·max=1.3948 VO2·AT+0.5252 (L/min)r=0.9336, p<0.01
or, VO2·max=1.4142 VO2·AT+8.8387 (ml/kg/min) r=0.9028, p<0.01.
Accordingly, their physical working capacity can be evaluated by their AT without determining their VO2·max.
3. PaO2 and AaDO2 in each individual patient at AT significantly correlated with those at maximum work load (r=0.6591 & 0.7684, p<0.01), suggesting that the pulmonary gas exchange disturbances at AT reflected those at maximum work load.
4. The decrease of physical working capacity for these patients was related to some extent to the reduction of MVV, %MVV or %DLCO and the severity of chest X ray findings (profusion of small opacities).
Consequently, we concluded that AT can be regarded as a useful index in the evaluation of physical working capacity for pneumoconiosis patients.
