A method of determining anaerobic threshold from percutaneous oxygen saturation

The anaerobic threshold (AT) is the point of the aerobic-to-anaerobic metabolic switch. Despite the many clinical applications of AT, this measurement requires sophisticated equipment and skills. Here, we investigated a simple measurement method for AT using percutaneous oxygen saturation (SpO 2 ) and pulse rate (PR) with a pulse oximeter in a study of exercise stress on healthy volunteers. Twenty individuals (ten men and ten women) were included in the study. Various respiratory parameters, including AT, were measured using conventional analytical methods. The SpO 2 threshold (ST) was calculated using the SpO 2 -Slope method. The mean ± standard deviations SpO 2 at ST was 97.8% ± 0.3% in men and 99.0 ± 0.3% in women. The concordance and interchangeability between ST and various five different types of AT, the ventilatory equivalent for oxygen (VE/VO 2 _AT), V-Slope (V-Slope_AT), ventilatory equivalent (VE_AT), respiratory exchange ratio (R_AT), and partial pressure of end-tidal oxygen (PETO 2 _AT) were generally high, with positive correlation coefficients in the range of [0.68–0.80]. These findings suggest that the SpO 2 -Slope method with a pulse oximeter may be a useful and simple method to determine AT compared to conventional methods.