Pulmonary evaluation included posteroanterior and lateral chest radiographs with subjects erect and complete PFTs. All chest radiographs were reviewed by two authors (C.H., G.K.). Pulmonary hypertension was diagnosed by chest radiograph when the hilar to thoracic ratio exceeded 0.36.® Pulmonary function tests performed included spirometry, and the measurement of lung volumes and Dsb. The FVC, FEV1? FEV,/FVC, and MW were determined with a pneumotachograph spirometer (Medical Graphics Corp, St. Paul, MN). Functional residual capacity was determined by open-circuit nitrogen washout technique, and TLC, KV, and RWTLC ratio were calculated. The Deo was determined and corrected for carboxyhemoglobinemia. Maximum inspiratory and expiratory pressures were measured at TLC and KY£ respectively, using a water-filled manometer. All values obtained were also expressed as percent predicted using standard prediction formulas.
Exercise capacity was determined during a multistage incremental exercise test with instantaneous breath-by-breath measurements and analysis of gas exchange. The exercise protocol consisted of 2-min stages with 10-W increments performed on a cycle ergometer (Mijnhardt, model KEM-3, Bunsich, Holland) until the patient readied a symptom-limited Vo, max. Heart rate was monitored on a cardiotachometer (Rigel Cardiac Monitor, model 302, Morden, Surrey, England).