Estimating exercise PaCO2 in patients with heart failure with preserved ejection fraction

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Abstract

Patients with heart failure with preserved ejection fraction (HFpEF) exhibit cardiopulmonary abnormalities that could affect the predictability of exercise PaCO2 from the Jones corrected partial pressure of end-tidal CO2 (PJCO2) equation (PJCO2 = 5.5 0.9 × PETCO2 - 2.1 ×VT). Since the dead space to tidal volume (VD/VT) calculation also includes PaCO2 measurements, estimates of VD/VT from PJCO2 may also be affected. Because using noninvasive estimates of PaCO2 and VD/VT could save patient discomfort, time, and cost, we examined whether partial pressure of end-tidal CO2 (PETCO2 ) and PJCO2 can be used to estimate PaCO2 and VD/VT in 13 patients with HFpEF. PETCO2 was measured from expired gases measured simultaneously with radial arterial blood gases at rest, constant-load (20 W), and peak exercise. VD/VT[art] was calculated using the Enghoff modification of the Bohr equation, and estimates of VD/VT were calculated using PETCO2 (VD/VT[ET]) and PJCO2 (VD/VT[J]) in place of PaCO2. PETCO2 was similar to PaCO2 at rest (-1.46 ± 2.63, P = 0.112) and peak exercise (0.66 ± 2.56, P = 0.392), but overestimated PaCO2 at 20 W (-2.09 ± 2.55, P = 0.020). PJCO2 was similar to PaCO2 at rest (-1.29 ± 2.57, P = 0.119) and 20 W (-1.06 ± 2.29, P = 0.154), but underestimated PaCO2 at peak exercise (1.90 ± 2.13, P = 0.009). VD/VT[ET] was similar to VD/VT[art] at rest (-0.01 ± 0.03, P = 0.127) and peak exercise (0.01 ± 0.04, P = 0.210), but overestimated VD/VT[art] at 20 W (-0.02 ± 0.03, P = 0.025). Although VD/VT[J] was similar to VD/ VT[art] at rest (-0.01 ± 0.03, P = 0.156) and 20 W (-0.01 ± 0.03, P = 0.133), VD/VT[J] underestimated VD/VT[art] at peak exercise (0.03 ± 0.04, P = 0.013). Exercise PETCO2 and VD/VT[ET] provides better estimates of PaCO2 and VD/VT[art] than PJCO2 and VD/VT[J] does at peak exercise. Thus, estimates of PaCO2 and VD/VT should only be used if sampling arterial blood during CPET is not feasible.

Original languageEnglish (US)
Pages (from-to)36-45
Number of pages10
JournalJournal of applied physiology
Volume132
Issue number1
DOIs
StatePublished - Jan 2022

Keywords

  • Arterial end-tidal carbon dioxide difference
  • Blood gases
  • HFpEF
  • Physiological dead space
  • Pulmonary capillary wedge pressure

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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