Expiratory flow was determined with a heated linear pneumotachograph, shock-mounted variable pressure transducer (± 2-0 cm HaO) and a carrier demodulator while the patient breathed through a high flow, low-resistance, low-dead-space valve (Hans-Rudolph No. 3800). The concentration of COa and Os in expired air was determined by a rapid responding infrared absorption analyzer and zirconia fuel cell sensor, respectively (Cad/Net System 2001, Medical Graphics Corp, St. Paul, MN). All gas and flow measurements were corrected for ambient temperature, barometric pressure and water vapor.
From the expired gas Po„ Pco„ and Ve, Oa consumption, and CO production were derived. The Vd/Vt was estimated from the mean and end-tidal expired COa concentrations. Oxygen pulse was calculated by dividing the Oa consumption by the heart rate. The arterial oxygen saturation during rest and exercise was measured by pulse oximetry (Nellcor, model N-100, Hayward, CA). Maximal oxygen uptake was defined as the highest Oa consumption obtained during the symptom-limited exercise test. buy ortho tri-cyclen
All data are expressed as mean ± SD. Students t test for unpaired data was used to compare differences between patients with and without pulmonary hypertension and between those with and without active disease. We accepted p<0.05 to indicate statistical significance.