Reliability of a new device to assess the oxygen consumption of human respiratory muscles. Med. Sci. Sports Exerc., Vol. 31, No. 7, pp. 1076-1082, 1999.
This study tests the reliability of a new device for assessing the oxygen consumption of the respiratory muscles (O2 resp.).
Fourteen healthy male volunteers participated in the study. The device consists of an expandable external ventilatory dead space created with pieces of plastic tubing and a spirometer filled with 100% oxygen. It also incorporates a carbon dioxide absorber. Total O2 (O2 tot.) was recorded from the spirometric closed circuit and ventilation (E), from the spirometer tracing. For each subject the test procedure was carried out in duplicate (T1 and T2) after an overnight fast. The dead space was increased at a constant rate of 260 mL every 90 s, and O2 tot. and E increased progressively. Because log O2 tot. was linearly related to E, we calculated the slope value (log O2-E) and the Y-intercept (E = 0) of the semilog regression representing, respectively, O2 resp. and metabolic O2 (O2 met.).
When compared with values in the literature, these values did not differ from those recorded in subjects of a similar age group. The O2 resp. and O2 met. calculated in T1 and T2 were not different (O2 resp. = 0.0066 ± 0.0005 for T1 vs 0.0067 ± 0.0005 log mL·min−1/L·min−1 for T2 and O2 met. = 269.3 ± 28.6 for T1 vs 281.9 ± 24.1 mL·min−1 for T2). The coefficients of variation were: 25% at T1 and 23% at T2 for O2 resp. and 34% at T1 and 29% at T2 for O2 met. Moreover, significant correlations (r = 0.96, P < 0.001 for O2 resp., r = 0.95, P < 0.001 for O2 met.), high coefficients of determination (r2 = 0.92 for O2 resp., r2 = 0.90 for O2 met.) and negligible SEE (0.0005 for O2 resp., 0.2 mL·min−1 for O2 met.) were found between the two tests. When we plotted the mean values of O2 resp. and O2 met. measured at T1 and T2 against their respective differences, more than 95% of the slight differences ranged between the limits defined by mean value ± 2 SD, reflecting the small discrepancy between duplicate measurements.
The results confirm that the test performed with this device is useful and reliable for assessing the O2 resp. in healthy subjects.
TEF-Adaptations Physiologiques et Comportementales, Faculté de Médecine (EA 2088), Université de Picardie Jules Verne, 80036 Amiens, FRANCE; Laboratoire de Physiologie des Interactions (EA 701), Service d'Explorations Fonctionnelles Respiratoires, Hôpital Arnaud de Villeneuve, 34295 Montpellier, FRANCE; Service d'Explorations Fonctionnelles Cardio-pulmonaires Pédiatriques, Hôpital Nord, 80000 Amiens, FRANCE; Faculté des Sciences du Sport, Université de Picardie Jules Verne, 80025 Amiens, FRANCE
Submitted for publication July 1997.
Accepted for publication December 1997.
The authors gratefully thank the medical and technical staff of the service "Explorations Fonctionnelles Cardio-pulmonaires Pédiatriques," particularly Ms. and Mr. Goin and the subjects for their generous cooperation with our project. We also thank Ms. Stott Carmeni, Mr. Telliez, Mr. Bouferrache, and Mr. Bosle for valuable technical assistance.
Address for correspondence: Prof. S. Ahmaidi, Ph.D., Faculté des Sciences du Sport, Allée P. Grousset, 80025, Amiens Cedex 1, France. E-mail: Said.Ahmaidi@ca.u-picardie.fr.