Measurement of regional tissue bed venous weighted oximetric trends during exercise by near infrared spectroscopy

Background: Cardiopulmonary exercise testing (CPET) is limited to children able to tolerate the equipment. Modification of instrumentation to reduce invasiveness will open CPET to a wider population. Near Infrared Spectroscopy (NIRS) devices measure regional oxyhemoglobin saturation (rSO2). We aim to predict anaerobic threshold (AT) during CPET using multiorgan NIRS monitoring. Methods and Results: Nineteen subjects were recruited. NIRS probes were placed on the forehead, para vertebral space, vastus lateralis, and deltoid muscle (rSO2 C, rSO2 R, rSO2 L and rSO2 A). rSO2 was recorded at six second intervals at rest, exercise, and through a five minute recovery period. The AT was computed using the v-slope method. AT was also predicted using NIRS data by identifying the inflection point of the rSO2 trends for all the four sites. AT can be estimated by the point of slope change of rSO2 R, rSO2 C and the four-site composite measure. Conclusions: Multisite NIRS monitoring of visceral organs is a potential predictor of AT. This allows for monitoring in all forms of exercise over a wide age range.