Relationship between ventilatory thresholds and systolic blood pressure variability.

During exercise, an increase in respiratory rate amplifies the blood pressure oscillations. This phenomenon is usually intensified when exercise rate exceeds the ventilatory thresholds (VTs). The present study examined whether VTs assessment was possible from systolic blood pressure variability (SBPV) analysis to give blood pressure ventilatory thresholds (BPVTs). Blood pressure, ECG, and Ventilatory equivalents (VE/VO2, VE/VCO2) were collected from 15 well-trained subjects during an incremental exhaustive test performed on a cycloergometer. The "Short-Time Fourier Transform" was applied to SBP series to compute the instantaneous high frequency SBPV power (HF-SBPV). BPVTs were determined in all but 3 subjects. For the 12 remaining subjects, visual examination of ventilatory equivalents and HF-SBPV power revealed 2 thresholds for both methods. There was no difference between the first (VT1 235+/-60 vs. BPVT1 226+/-55 W, p=0.063) and second (VT2 293+/-67 vs. BPVT2 301+/-66 W, p=0.063) thresholds. However, BPVT1 was slightly underestimated compared to VT1 (9.9+/-15.4 W) given lower limit of agreement (LOA) at -19.9 W and higher at 40.4 W. BPVT2 was over-estimated compared to VT2 (-8.8+/-11.2 W) given lower LOA at -30.9 W and higher at 13.4 W. Thus, BPVTs determination appears useful in conditioning programs with sedentary or pathological subjects but probably not with trained subjects.