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

Abstract

BackgroundExercise oscillatory ventilation (EOV) is associated with poor ventilatory efficiency and higher operating lung volumes in heart failure. These abnormalities may be particularly deleterious to dyspnea and exercise tolerance in mechanically-limited patients, e.g. those with coexistent COPD. MethodsVentilatory, gas exchange and sensory responses to incremental exercise were contrasted in 68 heart failure-COPD patients (12 EOV+). EOV was established by standard criteria. ResultsCompared 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 volume in 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 (~0.3–0.5L); 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). ConclusionsDyspnea 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 symptom burden and exercise intolerance in this specific heart failure group.