Higher Respiratory Muscle Oxygen Cost of Breathing During Exercise in Heart Failure With Preserved Ejection Fraction

Background Patients with heart failure with preserved ejection fraction (HFpEF) have pulmonary system abnormalities resulting in impaired ventilatory reserve and heightened respiratory muscle work during submaximal exercise. Research Question Do patients with HFpEF have higher respiratory muscle oxygen uptake ( V ˙ o 2 ) during submaximal exercise than control patients? Study Design and Methods Patients with HFpEF (n = 13) and control patients (n = 16) completed 2 visits. The first visit included pulmonary function tests and an incremental exercise test. On the second visit, participants mimicked their exercise breathing patterns across a range of work rates (voluntary hyperpnea) in the absence of exercise to quantify respiratory muscle V ˙ o 2 . Respiratory muscle V ˙ o 2 was reported during exercise at 40 W and approximately 65% peak work rates. Results During exercise at 40 W, patients with HFpEF had higher respiratory muscle V ˙ o 2 expressed as % of whole-body V ˙ o 2 (control patients, 4.6% of whole-body V ˙ o 2 ; interquartile range [IQR], 2.0-5.7 vs HFpEF, 8.3% of whole-body V ˙ o 2 ; IQR, 6.1-9.2; P < .01) and mL/kg/min (control patients, 0.53 mL/kg/min; IQR, 0.24-0.68 vs HFpEF, 0.79 mL/kg/min; IQR, 0.69-1.10; P < .01). During exercise at 40 W, respiratory muscle V ˙ o 2 was related to FVC % predicted ( r = –0.64; P = .02) and breathing frequency during exercise ( r = 0.70; P = .01) for patients with HFpEF, but not control patients (both r > 0.19; P > .40). During exercise at approximately 65% peak work rates, patients with HFpEF had higher respiratory muscle V ˙ o 2 expressed as % of whole-body V ˙ o 2 (control patients, 4.6% of whole-body V ˙ o 2 ; IQR, 2.8-6.3 vs HFpEF, 7.2% of whole-body V ˙ o 2 ; IQR, 6.0-8.8; P < .01). When accounting for ventilation, patients with HFpEF had higher respiratory muscle V ˙ o 2 during exercise at 40 W and approximately 65% peak work rates (all P < .03). Interpretation Our results show that respiratory muscle V ˙ o 2 is significantly elevated in patients with HFpEF compared with control patients during submaximal exercise.