Radiographic (ILO) reading predicts desaturation during exercise but notvtfcmax in subjects with asbestosis

Cardiopulmonary exercise testing is useful in evaluating disability in subjects with asbestosis but is often limited by co-morbidities and motivation. Submaximal exercise ventilation and static pulmonary function testing had limited value in predicting exercise performance (VOjmax), rz=0.44 (Cotes et al 1988). The profusion score of the International Labour Office (ILO) classification of chest radiographs correlates with resting pulmonary function but its value in predicting exercise performance has not been explored. AIMS: To determine if ILO scores (1) correlate with static lung function tests and exercise performance in subjects with asbestosis and (2) add value to static lung function tests in predicting exercise performance. METHODS: 52 male patients with asbestosis (asbestos exposure, crackles and interstitial fibrosis on high resolution CT scan) were included. Chest radiographs were read according to the ILO classification by 3 observers. Progressive exercise performance was measured on a cycle ergometer. RESULTS: Mean age was 67 (55-78). 41 subjects were smokers. ILO scoring of profusion, opacities and number of affected zones showed significant correlation with the % predicted values of DLCO, FVC, TLC, A-a gradient and VdNt. Desaturation during exercise was related to profusion score, number of affected zones and DLCO (r2=0.31). VCfcmax was significantly related only to DLCO (r2=0.35) and was not predicted by the ILO score. DLCO showed the highest correlation with ILO score for parenchymal disease. CONCLUSION: Radiological abnormalities correlate with oxygen desaturation on exercise but do not predict VChmax. Maximum exercise performance depends on the integrity of multiple organ systems. Exercise test remains important in disability assessment as a direct measurement of performance which cannot be accurately predicted from ILO score or static lung function test results.