Pulmonary Function Measures: Spirometry and lung volume measurements were performed with a body plethysmograph (MedGraphics model 1085; Medical Graphics Corp; Minneapolis, MN). Spirometry and lung volume measurements were made using the guidelines of the America Thoracic Society.
Graded Exercise Test: During all graded exercise tests (GXTs), spirometry and respiratory gas analysis were performed with a cardiopulmonary exercise system (CPX/d; Medical Graphics Corp). During the exercise test, oxygen saturation of hemoglobin (Spo2) was monitored using a pulse oximeter (Armstrong Medi-cal/BCI International; Waukesha, WI) and was defined as the lowest value that occurred during the test. Peak oxygen consumption (Vo2peak) was recorded in mL/kg/min and was defined as the highest Vo2 that was attained during the GXT. Minute ventilation (Ve) was measured in L/min and was defined as the Ve at the point that a Vo2peak was attained. All GXTs were conducted on a treadmill using a modified Naughton treadmill protocol and the American College of Sports Medicine termination criteria. Most tests were terminated because of shortness of breath or general fatigue. natural asthma inhaler
Six-minute Walk Test: Participants were asked to walk a measured course for 6 min, attempting to cover as much distance as possible in the given time. Participants walked at a selfselected pace and were advised to decrease their pace or to stop if perceived symptoms became excessive. Just prior to the end of the 6 min, an exercise technician approached the subject and placed a finger probe from the pulse oximeter on the subject.
Spo2 was assessed immediately after the participants stopped walking. No feedback was given during the test.
Depression: Research has indicated that depression may influence performance on a cognitive functioning test. For this reason, the Center for Epidemiological Studies Depression Scale (CESD) was used as a self-administered questionnaire. The CESD has been found to be reasonably good at screening to identify the nondepressed. Reliability as a measure of internal consistency of the CESD is 0.85.