Biomedical subjects

Josiane Castells

Publications and source records attributed to Josiane Castells.

2 recordsLinked to original sources

PubMed2003

Decrease in peak heart rate with acute hypoxia in relation to sea level VO(2max).

The aim of this study was to evaluate the influence of arterial oxygen saturation ( SaO(2)) on maximal heart rate during maximal exercise under conditions of acute hypoxia compared with normoxia. Forty-six males were divided into three groups depending on their sea level maximal oxygen consumption ( VO(2max)): high [GH, VO(2max)=64.2 (3.3) ml x min(-1) x kg(-1)], medium [GM, 50.8 (3.9) ml x min(-1) x kg(-1)] and low [GL, 41.0 (1.9) ml x min(-1) x kg(-1)]. All subjects performed a maximal exercise test in two conditions of inspired oxygen tension ( PIO(2), (149 mmHg and 70 mmHg). Among the GM group, seven subjects performed five supplementary incremental exercise tests at PIO(2) 136, 118, 104, 92, and 80 mmHg. Measurements of VO(2max) and SaO(2) using an ear-oxymeter were carried out at all levels of PIO(2). The decrease in SaO(2 )and peak heart rate (HR(peak)) with PIO(2) became significant from 104 and 92 mmHg. SaO(2) correlated with the decrease in HR(peak). For PIO(2)=70 mmHg, the decrease in VO(2max), SaO(2) and HR(peak) was, respectively, 44%, 62%, and 17.0 bpm for GH, 38%, 68%, and 14.7 bpm for GM, and 34%, 68%, and 11.8 bpm for GL. During maximal exercise in hypoxia, SaO(2) was lower for GH than GM and GL ( p<0.01). Among subjects in GH, five presented exercise-induced hypoxemia (EIH) when exercising in normoxia. The EIH group exhibited a greater decrement in HR(peak) than the non-EIH group at maximal hypoxic exercise (21.2 bpm vs. 15.0 bpm; p<0.05). When subjects are exposed to acute hypoxia, the lower SaO(2), due either to lower PIO(2) or to training status, is associated with lower HR(peak).

Acute Disease↗

PubMed2003

A methodology to assess the accuracy of a portable metabolic system (VmaxST).

PURPOSE: Validity of a portable metabolic system (VmaxST) was investigated during gas exchanges simulations by a mechanical system (GESS) and during human exercise. METHODS: Three tests were conducted while gas exchanges were measured continuously by VmaxST. Test 1 was composed of six simulations of gas exchanges during steady-state exercise (20 min at V̇E = 80 L.min-1). Test 2 was composed of seven simulations of gas exchanges during incremental exercise (V̇O(2) from 300 to 5600 mL.min-1). In the human trial, 11 subjects performed an incremental running exercise on a treadmill while gas exchanges were measured at the end of each stage with the Douglas bag method (DBM). RESULTS: Test 1 showed that the VmaxST measurements were stable, despite inaccurate measurements of gas concentrations at the start of the test. During test 2, the mean error (difference between measured and predicted value) and the upper and lower limits of agreement were -8.0%, -12.6%, and -3.4% for V̇O(2); -4.6%, -12.0%, and +2.8% for V̇CO(2); and -0.7%, -4.7%, and +3.3% for V̇E. During the human trial, no significant difference was shown between V̇O(2) measured by VmaxST and by DBM at any stage of exercise. The mean difference and the upper and lower limits of agreement between the VmaxST and the DBM measurements were -0.5%, -14.3%, and +13.3% for V̇O(2); -6.3%, -20.9%, and +8.3% for V̇CO(2); and -9.9%, -25.5%, and +5.7% for V̇E. CONCLUSIONS: The use of GESS showed that measurements of V̇O(2) by VmaxST could be biased in a standardized condition. In more realistic condition of use, this bias was lower but the accuracy of measurements was impaired.

Adult↗