Exponential analysis of the lung pressure-volume curve in patients with chronic pigeon-breeder's lung.
Pigeon-breeder's lung (PBL) is extremely common in Mexico City and often progresses to irreversible pulmonary fibrosis. The exponential analysis of the lung pressure-volume (PV) curve (V = A - Be-kp) has been suggested as a method to separate the lung restriction caused by inflammation from that caused by pulmonary fibrosis; a significantly decreased value for the exponential constant, k, suggests a change in the mechanical properties of the functioning lung parenchyma, while a normal value accompanied by restriction suggests subtraction of lung units without a change in the mechanical properties of the functioning units. We measured lung volumes and static PV curves in 29 patients who had persistent lung restriction following a biopsy-proven diagnosis of PBL. Mean values in the 29 subjects were as follows: age, 43 +/- 13 years; TLC, 61 +/- 15 percent of predicted; VC, 46 +/- 19 percent of predicted; and k, 55 +/- 17 percent of predicted. Twenty-four of the 29 patients had values for k that were below the 95 percent confidence level, and five had "normal" values. There was no difference in TLC and VC (percent of predicted) between those with or without a decreased value for k. Four of five patients with a normal value for k improved subsequent to diagnosis, while only one of 21 patients with a decreased k improved. We conclude that increased lung elasticity manifested by a low value for k is common in patients with chronic PBL. These results support the observation of frequent irreversible lung fibrosis in these patients. Measurements of k could prove a good prognostic indicator at the time of initial diagnosis.
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Departamento de Fisiologia Pulmonar, Instituto Nacional de Enfermedades Respiratorias (INER), Mexico City.
Perez-Padilla
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Paré
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Selman
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D000328:Adult; D001716:Bird Fancier's Lung / Q000503:physiopathology*; D002908:Chronic Disease; D003430:Cross-Sectional Studies; D004548:Elasticity; D006801:Humans; D008875:Middle Aged; D011312:Pressure; D012123:Pulmonary Ventilation; D014109:Total Lung Capacity; D014797:Vital Capacity