In controls, VD/VT VDM remained stable such that no change was observed (P > 0.05) from rest (0.17 ± 0.06) to submaximal exercise (0.14 ± 0.06), or thereafter to peak exercise (0.14 ± 0.05). In HFpEF, VD/VT VDM did not change (P = 0.58) from rest (0.29 ± 0.07) to submaximal exercise (0.29 ± 0.06), but increased (P = 0.02) thereafter to peak exercise (0.33 ± 0.06). VD/VT VDM was calculated as Pa CO 2 – PE CO2 /Pa CO 2 –VDM/VT. VD/VT was calculated as Pa CO 2 – PE CO2 /Pa CO 2. Pulmonary gas exchange and arterial blood gases were analyzed at rest, submaximal (20 W for HFpEF and 40 W for controls), and peak exercise. We evaluated whether calculating physiological dead space with (VD/VT VDM) and without (VD/VT) correcting for VDM impacts the interpretation of gas exchange efficiency during exercise in HFpEF. However, studies have not corrected VD/VT for apparatus mechanical dead space (VDM), which may confound the accurate calculation of VD/VT. Heart failure with preserved ejection fraction (HFpEF) is associated with cardiopulmonary abnormalities that may increase physiological dead space to tidal volume (VD/VT) during exercise.
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