Cardiopulmonary exercise test and PaO2 in evaluation of pulmonary hypertension in COPD

Ingunn Skjørten,1,2 Janne Mykland Hilde,3 Morten Nissen Melsom,1 Jonny Hisdal,4 Viggo Hansteen,5 Kjetil Steine,2,3 Sjur Humerfelt6 1Department of Pulmonary Medicine, LHL Glittre Clinic, Hakadal, 2Faculty of Medicine, University of Oslo, Oslo, 3Department of Cardiology, Akershus University Hospital, Lørenskog, 4Section of Vascular Investigations, 5Department of Cardiology, Oslo University Hospital-Aker, 6Clinic of Allergology and Respiratory Medicine, Oslo, Norway Background: Exercise tolerance decreases as COPD progresses. Pulmonary hypertension (PH) is common in COPD and may reduce performance further. COPD patients with and without PH could potentially be identified by cardiopulmonary exercise test (CPET). However, results from previous studies are diverging, and a unified conclusion is missing. We hypothesized that CPET combined with arterial blood gases is useful to discriminate between COPD outpatients with and without PH. Methods: In total, 93 COPD patients were prospectively included. Pulmonary function tests, right heart catheterization, and CPET with blood gases were performed. The patients were divided, by mean pulmonary artery pressure, into COPD-noPH (<25 mmHg) and COPD-PH (≥25 mmHg) groups. Linear mixed models (LMMs) were fitted to estimate differences when repeated measurements during the course of exercise were considered and adjusted for gender, age, and airway obstruction. Results: Ventilatory and/or hypoxemic limitation was the dominant cause of exercise termination. In LMM analyses, significant differences between COPD-noPH and COPD-PH were observed for PaO2, SaO2, PaCO2, ventilation, respiratory frequency, and heart rate. PaO2 <61 mmHg (8.1 kPa) during unloaded pedaling, the only load level achieved by all the patients, predicted PH with a sensitivity of 86% and a specificity of 78%. Conclusion: During CPET, low exercise performance and PaO2 strongly indicated PH in COPD patients. Keywords: COPD, pulmonary hypertension, right heart catheterization, cardiopulmonary exercise test, hypoxemi

Exercise capacity in COPD patients with exercise-induced pulmonary hypertension

Ingunn Skjørten,1,2 Janne Mykland Hilde,3 Morten Nissen Melsom,1 Jonny Hisdal,4 Viggo Hansteen,5 Kjetil Steine,2,3 Sjur Humerfelt6 1Department of Pulmonary Medicine, LHL Hospital Gardermoen, Jessheim, 2Faculty of Medicine, University of Oslo, Oslo, 3Department of Cardiology, Akershus University Hospital, Lørenskog, 4Section of Vascular Investigations, Oslo University Hospital-Aker, 5Department of Cardiology, Oslo University Hospital-Aker, 6Clinic of Allergology and Respiratory Medicine, Oslo, Norway Background: Pulmonary hypertension (PH) in patients with COPD is associated with reduced exercise capacity. A subgroup of COPD patients has normal mean pulmonary artery pressure (mPAP) at rest, but develops high mPAP relative to cardiac output (CO) during exercise, a condition we refer to as exercise-induced pulmonary hypertension (EIPH). We hypothesized that COPD patients with EIPH could be identified by cardiopulmonary exercise test (CPET) and that these patients have lower exercise capacity and more abnormal CPET parameters compared to COPD patients with normal hemodynamic exercise response.Methods: Ninety-three stable outpatients with COPD underwent right heart catheterization with the measurement of mPAP, CO, and capillary wedge pressure at rest and during supine exercise. Resting mPAP <25 mmHg with ΔmPAP/ΔCO slope above or below 3 mmHg/L/min were defined as COPD-EIPH and COPD-normal, respectively. Pulmonary function tests and CPET with arterial blood gases were performed. Linear mixed models were fitted to estimate differences between the groups with adjustment for gender, age, and airflow obstruction.Results: EIPH was observed in 45% of the study population. Maximal workload was lower in COPD-EIPH compared to COPD-normal, whereas other CPET measurements at peak exercise in % predicted values were similar between the two groups. After adjustment for gender, age, and airflow obstruction, patients with COPD-EIPH showed significantly greater increase in oxygen uptake, ventilation, respiratory frequency, heart rate, and lactate with increasing work load, as well as more reduction in pH compared to those with normal hemodynamic responses.Conclusion: COPD-EIPH could not be discriminated from COPD-normal by CPET. However, COPD-EIPH experienced a higher cost of exercise in terms of higher oxygen uptake, ventilation, respiratory frequency, heart rate, and lactate for a given increase in workload compared to COPD-normal. Keywords: COPD, pulmonary hypertension, right heart catheterization, cardiopulmonary exercise tes