DIFFERENCES BETWEEN REMAINING ABILITY AND LOSS OF CAPACITY IN MAXIMUMAEROBIC IMPAIRMENT

In the evaluation of exercise intolerance of patients with respiratory diseases the American Medical Association (AMA) and the American Thor acic Society (ATS) have proposed similar classifications for rating ae robic impairment using maximum oxygen uptake (VO(2)max) normalized for total body weight (ml min(-1) kg(-1)). However, subjects with the sam e VO(2)max weight-corrected values may have considerably different los ses of aerobic performance (VO?max expressed as % predicted). We have proposed a new, specific method for rating loss of aerobic capacity (V O(2)max, % predicted) and we have compared the two classifications in a prospective study involving 75 silicotic claimants. Logistic regress ion analysis showed that the disagreement between rating systems (high er dysfunction by the AMA/ATS classification) was associated with age >50 years (P<0.005) and overweight (P = 0.04). Interestingly, clinical (dyspnea score) and spirometric (FEV1) normality were only associated with the VO(2)max, % predicted, normal values (P<0.01); therefore, in older and obese subjects the AMA/ATS classification tended to overest imate the aerobic dysfunction. We conclude that in the evaluation of a erobic impairment in patients with respiratory diseases, the loss of a erobic capacity (VO(2)max, % predicted) should be used instead of the traditional method (remaining aerobic ability, VO(2)max, in mi min(-1) kg(-1)).