Reproducibility Of Near Infra-red Spectroscopy In Children

Abstract

PURPOSE: Near infrared spectroscopy (NIRS) is a non invasive widely used device for the monitoring of muscular oxygenation. It should be an interesting investigation method in children. Although some studies investigated muscle oxygenation in children, no study has focused on the reproducibility of the NIRS measure in children. Then, this study was designed in order to test the reproducibility of muscle oxygenation in children. METHODS: 12 children (10.3 ±0.9yrs) first performed an incremental test to determine power associated to ventilatory threshold (PVT). Then, for each of the four following sessions, subjects performed two 6min moderate intensity exercises separated by 6min of recovery. The intensities were respectively set at 70 and 90% of PVT. The oxygenation was measured by using a continuous-wave near-infrared spectrophotometer (Artinis, Oxymon - Netherlands) that generates light at 905, 850 and 770nm. Three parameters were measured: the relative concentration changes in deoxy- (HHb), oxy- (O2Hb) and total hemoglobin (Hb) and myoglobin (Mb) (Hbtot). The optodes were firmly attached at the same place in the vastus lateralis of the right leg. The reliability of each variable, averaged every 10s, was determined by the intraclass correlation coefficient (ICC, model 2.1). The ICC coefficient, based on a random effect two-way analysis of variance (tests x mean intervals) model, is a measure of variance between the repeated measures according to the equation: ICC(2.1) = (BMS - EMS) / (BMS + (k - 1)EMS + k(JMS - EMS)/n) where BMS is the between-subject mean square, EMS: the residual mean square, JMS: the treatments mean square, k: the number of tests (4), and n: the number of subjects (12). RESULTS: ICC for 70%VT test were 0.958 for Hb, 0.924 for HbO2 and 0.953 for Hbtot. ICC for 90%VT test were 0.938 for Hb, 0.920 for HbO2 and 0.957 for Hbtot. CONCLUSIONS: Based on four repetitions of two intensities, this study has highlighted that for moderate intensity exercises, oxygenation measure is reproducible in children during dynamic exercise.