Ventilatory Limitation in Patients with HFpEF and Obesity: The Balance Between Increased Ventilatory Demand vs. Reduced Ventilatory Capacity
Authors: Babb T. , Balmain B. , Tomlinson A. , Hearon C. , Wakeham D. , Hynan L. , Levine B. , MacNamara J. , Sarma S. 
Published: May 2023

Study Objective: Patients with heart failure with preserved ejection fraction (HFpEF) have an increased ventilatory demand during exertion. Whether ventilatory capacity can meet this increased demand is unknown, especially in those with obesity. Hypothesis: We hypothesized that ventilatory capacity would be reduced in patients with HFpEF due to age- and obesity-related mechanical ventilatory constraints. Methodology: Body composition (DEXA) and pulmonary function were measured in 20 patients with invasively confirmed HFpEF (69±6yr; 9M/11W). Cardiorespiratory responses, breathing mechanics, and arterial blood gases were measured at rest, during exercise at 20 W, and at peak exercise. Based upon inspection of resting forced vital capacity (FVC, L) values, the patients were grouped into those with an FVC<3L (n=12; 2M/10W) and those with an FVC>3.8L (n=8; 7M/1W). Differences between the two groups were compared using independent t-tests. Comparisons were not made between conditions (rest, 20W, & peak exercise). Results: Percent body fat was greater in the FVC<3L group (51% vs. 38%, p<0.01). Ventilatory demand (V̇E/V̇CO2) was equally elevated in both groups at rest and during exercise. FVC was 2 L less in the FVC<3L group (79±14 vs. 100±13 %predicted) and maximal voluntary ventilation was approximately 50 L/min less (p<0.01). All lung volume subdivisions (L) were significantly lower in the FVC<3L group at rest and during exercise (p<0.05). End expiratory lung volume (L) was higher during exercise in both groups as many of the patients had expiratory flow limitation at rest and during exercise (>50% VT at peak exercise). End inspiratory lung volume (L) approached 90% of total lung capacity in both groups, thus VT (%FVC) expansion was limited in both groups. The FVC<3L group was not able to increase V̇E (L/min) enough to lower arterial CO2 at peak exercise as much as the FVC>3.8L group (40±4 vs 35±3; p<0.05). Peak V̇O2 (%predicted) was approximately 22% less (p<0.05) in the FVC<3L group. Ratings of perceived breathlessness and unpleasantness were higher in the FVC<3L group at 20 W (p<0.05). Conclusion: Ventilatory capacity is limited in patients with HFpEF and obesity; this is particularly true for patients who have a small or reduced FVC. We propose that quantifying ventilatory limitations in patients with HFpEF is critical to establishing whether they can meet the challenges of an elevated ventilatory demand and whether these limitations may play a role in provoking exertional dyspnea and exercise intolerance. This research was supported by the National Institutes of Health (1P01HL137630), King Foundation, Cain Foundation, and Texas Health Presbyterian Hospital Dallas. B.N. Balmain is supported by an American Heart Association Fellowship (grant number: 826064). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.