Novel Computerized Method for Automated Determination of Ventilatory Threshold and Respiratory Compensation Point

Introduction: The ventilatory threshold (named as VT(1)) and the respiratory compensation point (named as VT(2)) describe prominent changes of metabolic demand and exercise intensity domains during an incremental exercise test. Methods: A novel computerized method based on the optimization method was developed for automatically determining VT(1) and VT(2) from expired air during a progressive maximal exercise test. A total of 109 peak cycle tests were performed by members of the US astronaut corps (74 males and 35 females). We compared the automatically determined VT(1) and VT(2) values against the visual subjective and independent analyses of three trained evaluators. We also characterized VT(1) and VT(2) and the respective absolute and relative work rates and distinguished differences between sexes. Results: The automated compared to the visual subjective values were analyzed for differences with t test, for agreement with Bland–Altman plots, and for equivalence with a two one-sided test approach. The results showed that the automated and visual subjective methods were statistically equivalent, and the proposed approach reliably determined VT(1) and VT(2) values. Females had lower absolute O(2) uptake, work rate, and ventilation, and relative O(2) uptake at VT(1) and VT(2) compared to men (p ≤ 0.04). VT(1) and VT(2) occurred at a greater relative percentage of their peak VO(2) for females (67 and 88%) compared to males (55 and 74%; main effect for sex: p < 0.001). Overall, VT(1) occurred at 58% of peak VO(2,) and VT(2) occurred at 79% of peak VO(2) (p < 0.0001). Conclusion: Improvements in determining of VT(1) and VT(2) by automated analysis are time efficient, valid, and comparable to subjective visual analysis and may provide valuable information in research and clinical practice as well as identifying exercise intensity domains of crewmembers in space.