Mismatch HFpEF dead space exercise intolerance gas exchange inefficiency.Ĭopyright © 2022 American College of Chest Physicians. These data suggest that the increase in V˙/Q˙ mismatch may be explained by increases in VD alveolar and that increases in VD alveolar worsens ventilatory efficiency, which seems to be a key contributor to exercise intolerance in patients with HFpEF. If underlying pathophysiology causes a problem with ventilation and/or perfusion in the form of a shunt or dead space, the resultant VQ mismatch will cause hypoxemia. 01), which was correlated with peak V˙o 2peak (r = 0.46 P <. Moreover, the increase in VD alveolar correlated with the V˙ E/V˙co 2 slope (r = 0.69 P <. VD alveolar was greater in patients with HFpEF compared with control participants at rest, 20W, and peak exercise (main effect for group, P <. 01 vs 20W) and control participants (0.19 ± 0.17 L/breath P =. Thereafter, VD alveolar increased from 20W to peak exercise in patients with HFpEF (0.37 ± 0.16 L/breath P <. Thus VA is equal to the minute volume of gas expired from alveolar structures only when all these structures have a mean PaCO2 value equal to PaCO2. 01), whereas VD alveolar did not change from rest (0.01 ± 0.06 L/breath) to 20W (0.06 ± 0.13 L/breath) in control participants (P =. Physiologic dead-space fraction (ratio of dead space to tidal volume V D /V T) is the portion of tidal volume that does not participate in gas exchange and therefore consists of expired gas without carbon dioxide. Anatomic, airway, or tracheal, dead space is the part of the tidal volume that does not participate in gas exchange. VD alveolar increased from rest (0.12 ± 0.07 L/breath) to 20W (0.22 ± 0.08 L/breath) in patients with HFpEF (P <. 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. VD alveolar was calculated as: (VD / VT × VT) - anatomic dead space. The physiologic dead space (VD physiologic) to tidal volume (VT) ratio (VD/VT) was calculated using the Enghoff modification of the Bohr equation. Ventilatory efficiency (evaluated as the V˙ E/V˙co 2 slope) also was measured from rest to 20W in patients with HFpEF. Gas exchange (ventilation, oxygen uptake, and CO 2 elimination ) and arterial blood gases were analyzed at rest, twenty watts (20W), and peak exercise. Twenty-three patients with HFpEF and 12 control participants were studied. Therefore, we tested the hypothesis that VD alveolar would increase during exercise to a greater extent in patients with HFpEF compared with control participants.ĭo patients with HFpEF develop VD alveolar during exercise? Conceptually, alveolar units with ventilation-perfusion ratios of greater than one, but not infinity, can be described as if the units were functionally equivalent to areas of. Patients with heart failure with preserved ejection fraction (HFpEF) exhibit many cardiopulmonary abnormalities that could result in V˙/Q˙ mismatch, manifesting as an increase in alveolar dead space (VD alveolar) during exercise. Physiologic dead space occurs when the pulmonary capillary of an alveolar-pulmonary structure has little or no perfusion, resulting in high ventilation-perfusion ratios.
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