METHODS: A total of 49 patients were considered for CPET based on their standard of care as well as 4 controls. Patients were categorized into PH, ILD, PH+ILD or control group. CPET was conducted on an electronically braked cycle ergometer (Ergoline 800s; SensorMedics, Yorba Linda, CA) using a SensorMedics Vmax229d system. Patients were asked to exercise until they no longer could due to dyspnea or muscle fatigue. Results were analyzed in accordance with ATS/ACCP Guidelines on Cardiopulmonary Exercise Testing. Two way analysis of variance (ANOVA), where PH (yes, no) and ILD (yes, no) were the factors that were used to examine the effect of those factors on each outcome. The interaction between PH and ILD was included in all models.