Use of 'ideal' alveolar air equations and corrected end-tidal PCO 2 to estimate arterial PCO 2 and physiological dead space during exercise in patients with heart failure.

Autor: Van Iterson EH; Department of Cardiovascular Medicine, Mayo Clinic, 200 First St SW, Rochester, MN 55905, United States. Electronic address: vaniterson.erik@mayo.edu., Olson TP; Department of Cardiovascular Medicine, Mayo Clinic, 200 First St SW, Rochester, MN 55905, United States. Electronic address: olson.thomas2@mayo.edu.
Jazyk: angličtina
Zdroj: International journal of cardiology [Int J Cardiol] 2018 Jan 01; Vol. 250, pp. 176-182. Date of Electronic Publication: 2017 Oct 07.
DOI: 10.1016/j.ijcard.2017.10.021
Abstrakt: Background: Arterial CO 2 tension (PaCO 2 ) and physiological dead space (V D ) are not routinely measured during clinical cardiopulmonary exercise testing (CPET). Abnormal changes in PaCO 2 accompanied by increased V D directly contribute to impaired exercise ventilatory function in heart failure (HF). Because arterial catheterization is not standard practice during CPET, this study tested the construct validity of PaCO 2 and V D prediction models using 'ideal' alveolar air equations and basic ventilation and gas-exchangegas exchange measurements during CPET in HF.
Methods: Forty-seven NYHA class II/III HF (LVEF=21±7%; age=55±9years; male=89%; BMI=28±5kg/m 2 ) performed step-wise cycle ergometry CPET to volitional fatigue. Breath-by-breath ventilation and gas exchange were measured continuously. Steady-state PaCO 2 was measured at rest and peak exercise via radial arterial catheterization. Criterion V D was calculated via 'ideal' alveolar equations, whereas PaCO 2 or V D models were based on end-tidal CO 2 tension (P ET CO 2 ), tidal volume (V T ), and/or weight.
Results: Criterion measurements of PaCO 2 (38±5 vs. 33±5mmHg, P<0.01) and V D (0.26±0.07 vs. 0.41±0.15L, P<0.01) differed at rest vs. peak exercise, respectively. The equation, 5.5+0.90×P ET CO 2 -0.0021×V T , was the strongest predictor of PaCO 2 at rest and peak exercise (bias±95%LOA=-3.24±6.63 and -0.98±5.76mmHg; R 2 =0.57 and 0.75, P<0.001, respectively). This equation closely predicted V D at rest and peak exercise (bias±95%LOA=-0.03±0.06 and -0.02±0.13L; R 2 =0.86 and 0.83, P<0.001, respectively).
Conclusions: These data suggest predicted PaCO 2 and V D based on breath-by-breath gas exchange and ventilatory responses demonstrate acceptable agreement with criterion measurements at peak exercise in HF patients. Routine assessment of PaCO 2 and V D can be used to improve interpretability of exercise ventilatory responses in HF.
(Copyright © 2017 Elsevier Ireland Ltd. All rights reserved.)
Databáze: MEDLINE
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