Published: 23 June 2022

Authors: Bryce N. Balmain, PhD Andrew R. Tomlinson, MD James P. MacNamara, MD Linda S. Hynan, PhD Benjamin D. Levine, MD Satyam Sarma, MD Tony G. Babb, PhD

Source: This abstract has been sourced from NZ Respiratory Research Review Issue 207


    Patients with heart failure with preserved ejection fraction (HFpEF) exhibit many cardiopulmonary abnormalities that could result in V˙V˙/Q˙Q˙ mismatch, manifesting as an increase in alveolar dead space (VDalveolar) during exercise. Therefore, we tested the hypothesis that VDalveolar would increase during exercise to a greater extent in patients with HFpEF compared with control participants.

    Research Question

    Do patients with HFpEF develop VDalveolar during exercise?

    Study Design and Methods

    Twenty-three patients with HFpEF and 12 control participants were studied. Gas exchange (ventilation [V˙V˙E], oxygen uptake [V˙V˙o2], and CO2 elimination [V˙V˙co2]) and arterial blood gases were analyzed at rest, twenty watts (20W), and peak exercise. Ventilatory efficiency (evaluated as the V˙V˙E/V˙V˙co2 slope) also was measured from rest to 20W in patients with HFpEF. The physiologic dead space (VDphysiologic) to tidal volume (VT) ratio (VD/VT) was calculated using the Enghoff modification of the Bohr equation. VDalveolar was calculated as: (VD / VT × VT) – anatomic dead space. Data were analyzed between groups (patients with HFpEF vs control participants) across conditions (rest, 20W, and peak exercise) using a two-way repeated measures analysis of variance and relationships were analyzed using Pearson correlation coefficient.


    VDalveolar increased from rest (0.12 ± 0.07 L/breath) to 20W (0.22 ± 0.08 L/breath) in patients with HFpEF (P < .01), whereas VDalveolar did not change from rest (0.01 ± 0.06 L/breath) to 20W (0.06 ± 0.13 L/breath) in control participants (P = .19). Thereafter, VDalveolar increased from 20W to peak exercise in patients with HFpEF (0.37 ± 0.16 L/breath; P < .01 vs 20W) and control participants (0.19 ± 0.17 L/breath; P = .03 vs 20W). VDalveolar was greater in patients with HFpEF compared with control participants at rest, 20W, and peak exercise (main effect for group, P < .01). Moreover, the increase in VDalveolar correlated with the V˙V˙E/V˙V˙co2 slope (r = 0.69; P < .01), which was correlated with peak V˙V˙o2peak (r = 0.46; P < .01) in patients with HFpEF.


    These data suggest that the increase in V˙V˙/Q˙Q˙ mismatch may be explained by increases in VDalveolar and that increases in VDalveolar worsens ventilatory efficiency, which seems to be a key contributor to exercise intolerance in patients with HFpEF.

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