Oxygen cost of breathing and its association with dyspnea in older patients with heart failure with preserved ejection fraction and obesity

Introduction: Obesity is associated with an increased oxygen (O 2 ) cost of breathing, which could contribute to dyspnea on exertion (DOE) and exercise intolerance. Many patients with heart failure with preserved ejection fraction (HFpEF) also have obesity, but whether an elevated O 2 cost of breathing contributes to DOE and exercise intolerance in these patients is unclear. Therefore, the purpose of this study was to examine the O 2 cost of breathing and its association with DOE and exercise intolerance in patients with HFpEF and obesity. Methods: We evaluated 14 patients with HFpEF and obesity (HFpEF-Ob, BMI: 40.4±5.4 kg/m 2 ), 11 older control adults with obesity (CTL-Ob, BMI: 36.1±5.7 kg/m 2 ), and 20 older control adults without obesity (CTL-nonOb, BMI: 25.5±2.9 kg/m 2 ). All participants performed an eucapnic voluntary hyperpnea task at 30-40L/min (EVH LOW ) and 50-60L/min (EVH HIGH ), a 6-minute submaximal constant-load cycling test, and a maximal incremental cycling test. Results: The O2 cost of breathing was higher in HFpEF-Ob compared with CTL-nonOb (2.95±0.66 vs. 2.11±0.43mL/L, P=0.001) but was not different compared with CTL-Ob (2.48±0.73mL/L, P=0.130 vs. HFpEF-Ob). The rating of perceived breathlessness (RPB) was ≥1-unit higher in HFpEF-Ob, which is considered clinically significant. The O 2 cost of breathing was associated with BMI (r 2 =0.457, P<0.001), RPB (r2=0.280, P<0.001), and V̇O 2peak in mL/min/kg (r 2 =0.161, P=0.006). Conclusion: These findings suggest that the magnitude of obesity could increase the O 2 cost of breathing, which could subsequently contribute to greater sensations of DOE and exercise intolerance in patients with HFpEF and obesity.