Reliability and Responsiveness of the Ventilatory Threshold in Cancer Survivors Treated with Hematologic Stem Cell Transplantation

Abstract

Purpose: We assessed the reliability and responsiveness of 2 methods used to measure the ventilatory threshold (VT) in sedentary adult cancer survivors treated with hematological stem cell transplantation (HSCT). Methods: Thirteen volunteers (mean age=50.6 years, SD=12) treated with HSCT at least 6 months prior to recruitment participated in this study. Two blinded raters assessed VT using 2 methods: v-slope and ventilatory equivalents. Results: The Ventilatory equivalents (Veq) method consistently produced higher values for VT than the v-slope method. Both methods demonstrated excellent consistency between observers (interrater ICC2,1 >.90; SEM 49-93 ml/min) but we found only moderate stability between assessment sessions separated by an interval of 1 week (test-retest ICC2,1= .56 -.83; SEM 112-191 ml/min). Responsiveness (Guyatt's Index) to 12 weeks of home-based aerobic training ranged from 0.47 to 0.51 for the v-slope method and 0.22-0.33 for the Veq method. Conclusion: The v-slope method appears to be a somewhat more conservative and a substantially more responsive measure of VT than the Veq method. Results from this study generally support the usefulness of VT as an outcome measure in clinical trials of aerobic training for HSCT recipients.