Right ventricular output in chronic obstructive pulmonary disease during expiration is impaired by reduced venous return

Background: High positive airway pressure impedes venous return and right ventricular (RV) output in mechanically ventilated patients. Whether this is also the case in normally breathing COPD-patients, where the expiratory intrathoracic pressure is increased due to airway obstruction, is unknown. We investigated the effects of intrathoracic pressure on venous return and how this perturbs RV output during expiration at rest and during exercise. Methods: Fourteen COPD-patients (GOLD II-IV) underwent simultaneous measurements of intrathoracic, right atrial (RA) and pulmonary artery pressures at rest and during exercise. Intrathoracic and RA pressure were used to calculate RA filling pressure. Dynamic changes in pulmonary artery pulse pressure during expiration were examined to evaluate changes in RV output. Results: Pulmonary artery pulse pressure decreased up to 40% during expiration (figure 1). This decline was associated with a low RA filling pressure (r 2 = 0.64). During exercise, a similar decline in pulmonary artery pressure was observed. Intrathoracic pressure and RA pressure increased similar, resulting in an unchanged RA filling pressure. Conclusions: We show that in COPD, pulmonary artery pulse pressure declines during expiration; most prominent in patients with a low RA filling pressure. This implies that, spontaneous breathing already impairs venous return and by that RV output in COPD.