Reproducibility of the exponential rise technique of CO 2 rebreathing for measuring P v CO 2 and C v CO 2 to non-invasively estimate cardiac output during incremental, maximal treadmill exercise

Abstract

The purpose of this study was to determine the reproducibility of the indirect Fick method for the measurement of mixed venous carbon dioxide partial pressure (P(v)CO(2)) and venous carbon dioxide content (C(v)CO(2)) for estimation of cardiac output (Q(c)), using the exponential rise method of carbon dioxide rebreathing, during non-steady-state treadmill exercise. Ten healthy participants (eight female and two male) performed three incremental, maximal exercise treadmill tests to exhaustion within 1 week. Non-invasive Q(c) measurements were evaluated at rest, during each 3-min stage, and at peak exercise, across three identical treadmill tests, using the exponential rise technique for measuring mixed venous PCO(2) and CCO(2) and estimating venous-arterio carbon dioxide content difference (C(v-a)CO(2)). Measurements were divided into measured or estimated variables [heart rate (HR), oxygen consumption (VO(2)), volume of expired carbon dioxide (VCO(2)), end-tidal carbon dioxide (P(ET)CO(2)), arterial carbon dioxide partial pressure (P(a)CO(2)), venous carbon dioxide partial pressure ( P(v)CO(2)), and C(v-a)CO(2)] and cardiorespiratory variables derived from the measured variables [Q(c), stroke volume (V(s)), and arteriovenous oxygen difference ( C(a-v)O(2))]. In general, the derived cardiorespiratory variables demonstrated acceptable (R=0.61) to high (R>0.80) reproducibility, especially at higher intensities and peak exercise. Measured variables, excluding P(a)CO(2) and C(v-a)CO(2), also demonstrated acceptable (R=0.6 to 0.79) to high reliability. The current study demonstrated acceptable to high reproducibility of the exponential rise indirect Fick method in measurement of mixed venous PCO(2) and CCO(2) for estimation of Q(c) during incremental treadmill exercise testing, especially at high-intensity and peak exercise.

Derivation of physiological inhalation rates in children, adults, and elderly based on nighttime and daytime respiratory parameters

“…Values for H F of 0.2057 ± 0.0018 L of O 2 /kcal (n = 31) and H P of 0.2059 ± 0.0019 L of O 2 /kcal (n = 1245) were then calculated. The H P value was calculated by using published data for individuals aged 2 h to 73 years (n = 327) in the supine position and 8.8-81 years (n = 918) in the upright position (Tenney and Miller 1956;Baker et al 1957;Spurr et al 1957;Emirgil et al 1967;Pernow and Saltin 1971;Oren et al 1981;Allen et al 1984;Capderou et al 1997;Treuth et al 1998;Gisolf et al 2003;Cade et al 2004;Shiou-Liang et al 2005; other references are underlined in the appendix). During the postprandial phase, VO 2 , E, and RER values of 0.184 ± 0.011 L/min, 0.90 ± 0.04 kcal/ min, and 0.866 ± 0.074, respectively, were calculated for individuals in the supine position, compared with a VO 2 of 0.291 ± 0.013 L/ min, an E of 1.41 ± 0.05 kcal/min, and a RER of 0.817 ± 0.050 for subjects in the upright position.…”

Resting and exercise cardiorespiratory function in survivors of congenital diaphragmatic hernia

“…The exponential CO 2 rebreathing method was refined in the 1980s, 35 and was found to be reliable in progressive exercise in adults and children. [36][37][38] The technique assumes a single-compartment physiology, and might thus be vulnerable to ventilation-perfusion mismatch, but reasonable estimations of cardiac output could be obtained in individuals with mild to moderate airway obstruction. 39,40 It has not been evaluated, however, in patients with PHT, who characteristically exhibit increasing dead-space ventilation with exercise, as reflected by increasing respiratory equivalents.…”

Exploratory Study on Oxygen Consumption On-kinetics During Treadmill Walking in Women With Systemic Lupus Erythematosus

“…Peak heart rate was determined electronically from an electrocardiogram by multiplying the six-second cardiac cycle rate by 10. Peak cardiac output (Qt) was measured by the exponential rise CO 2 rebreathing technique38 applied at peak exercise. Peak arteriovenous oxygen difference (a-vO 2 ) was calculated by dividing peak VO 2 by peak Qt.…”