Cardiorespiratory responses to incremental exercise in patients with asbestos-related pleural thickening and normal or slightly abnormal lung function.

An increasing number of patients with asbestos exposure are being identified with pleural thickening (PT) alone, with little or no impairment in standard tests of lung function despite their frequent complaint of dyspnea. We have employed incremental cardiorespiratory exercise testing to evaluate the types and mechanisms of impairment in 23 such patients. All had normal lung fields on radiographic examinations and normal (group 1, n = 12) or minimally reduced (group 2A slight restriction, n = 5, group 2B, slight obstruction, n = 6), lung function. Excessive ventilation was common in all groups, but especially in group 2B. Abnormal dead space ventilation (VD/VT) was more frequent in groups 2A (4/5) and 2B (4/6) than in group 1 (3/12). It was associated with O2 desaturation in three patients in groups 2A and B. Cardiovascular abnormalities were rare (1/23). Excessive ventilation and dead space provide a basis for the symptom of dyspnea in these patients.