Interactions between Cigarette Smoking and the Natural History of Idiopathic Pulmonary Fibrosis: Methods (Part 1)
The study population consisted only of consecutive new patients with IPF observed between May 1977 and May 1987. Three patients who quit smoking between the onset of dyspnea and the BAL procedure were excluded from this study, in view of such an ambiguous past smoking history. In all cases no patients had known causes of pulmonary fibrosis, such as organic or inorganic dust inhalation, drug ingestion or primary granulomatous lung disorders. No patients had received glucocorticoids or any other immunosuppressive agents. Patients with extrathoracic clinical abnormalities suggesting connective tissue disorders also were excluded, with the exception of four patients with an isolated Raynaud phenomenon and two with inflammatory arthralgia. In the absence of open lung biopsy, widespread crackles, finger clubbing with peripheral and basal shadowing observed with high resolution CT scanning were mandatory criteria. Twenty-seven patients were included according to those criteria. Histologic confirmation of the diagnosis was obtained in 26 patients by open lung (n = 14), transbronchia] biopsy (n = 6) or retrospectively by necropsy (n = 6). Patients were considered as smokers if they consumed two or more cigarettes per day at the time of the onset of exertional dyspnea. Smoking habits were quantified as the number of cigarettes per day at the time of the first evaluation.
Pulmonary Function Tests
The VC and the FEV, were measured by spirometry and the TLC, by helium dilution. Results were expressed as a percentage of the predicted value. The Dsb was assessed. Arterial blood gases with subjects at rest breathing room air were measured with an automated blood gas analyzer.