Physiological and sensory consequences of exercise oscillatory ventilation in heart failure-COPD

Abstract

Background: Exercise oscillatory ventilation (EOV) is associatedwith poor ventilatory efficiency and higher operating lung volumes in heart failure. These abnormalitiesmay be particularly deleterious to dyspnea and exercise tolerance in mechanically-limited patients, e.g. those with coexistent COPD. Methods: Ventilatory, gas exchange and sensory responses to incremental exercise were contrasted in 68 heart failure-COPD patients (12 EOV+). EOV was established by standard criteria. Results: Compared to EOV-, EOV+ had lower exercise capacity, worse ventilatory inefficiency and higher peak dyspnea scores (p < 0.05). Peak capillary PCO2 (PcCO2) was higher and end-tidal CO2 (PETCO2) was lower in EOV+. Thus, greater (i.e., more positive) P(c-ET) CO2 and dead space/tidal volume values were found in these patients compared to EOV- (p < 0.05). Ventilatory inefficiency was related to increased dead space/tidal volumein EOV+ (r = 0.74

p < 0.01). Owing to higher operating lung volumes, inspiratory reserve volume (IRV) decreased to a greater extent in EOV+. Tidal volume oscillations consistently ceased when a "critical" IRV was reached (similar to 0.3-0.5 L)

thereafter, PcCO2 stabilized or increased and dyspnea scores rose sharply. Exercise capacity was closely related to IRV decrements and peak dyspnea in EOV+ (r = -0.78 and 0.84, respectively

p < 0.01). Conclusions: Dyspnea and exercise tolerance are negatively influenced by EOV in heart failure patients presenting with COPD as co-morbidity. Pharmacological and non-pharmacological interventions known to decrease EOV might prove particularly valuable to mitigate symptomburden and exercise intolerance in this specific heart failure group. (C) 2016 Elsevier Ireland Ltd. All rights reserved.