Invasive Cardiopulmonary Exercise Testing in Chronic Thromboembolic Pulmonary Disease; Obesity and the V/VCO Relationship.

: Invasive cardiopulmonary exercise testing (iCPET) provides valuable insight into dyspnea in patients with chronic thromboembolic pulmonary disease, in part through an increased relationship of minute ventilation to CO production (V/VCO). Obesity lowers the V/VCO in patients without cardiopulmonary disease; however, whether this holds true in obese subjects with chronic thromboembolic pulmonary hypertension (CTEPH) and chronic thromboembolic pulmonary disease (CTEPD) is unknown. : Report on the iCPET findings of patients with CTEPH and CTEPD and investigate the relationship between obesity and gas exchange parameters, especially V/VCO in these patients. : Retrospective analysis of CTEPH and CTEPD patients undergoing iCPET. : We studied 60 patients; 34 (56.7%) had CTEPH and 26 (43.3%) had CTEPD. The mean age was 61.2 ± 14 years and the mean BMI was 31.8 ± 8.3 mg/kg. A higher V/VCO (41.9 ± 10.2 vs. 36.8 ± 8.9; = 0.045) was observed in CTEPH vs. CTEPD. There was an inverse relationship between the V/VCO slope and BMI. For an increase of 1 point in BMI, the V/VCO slope fell by 0.6 in CTEPD and 0.35 in CTEPH ( < 0.001). The mean V/VCO slope in CTEPH and CTEPD groups was 48.6 ± 10.4 in BMI < 25 and 31.3 ± 6.5 in BMI > 35 ( < 0.001). The lower V/VCO slope in obesity relates to an increased VCO/work rate relationship; there was no difference in the V/work relationship. : The V/VCO slope is markedly reduced by obesity, independent of the level of pulmonary vascular obstruction in CTEPH or CTEPD. Thus, obesity masks key physiologic evidence of pulmonary vascular obstruction on the gas exchange assessment of obese individuals.