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Table 1 Heart rate variability time domain measures when supine and during head-up tilt, with and without a respiratory acidosis induced by inhalation of 5%CO2 in normoxic air

From: Indirect measures of human vagal withdrawal during head-up tilt with and without a respiratory acidosis

Supine Head-up tilt
Mean (ms) SD R–R (ms) Median (ms) RMSSD Heart rate beats min−1 Mean (ms) SD R–R (ms) Median (ms) RMSSD Heart rate beats min−1
Room air
 1,042 (219) 64 (19) 1,044 (221) 71 (37) 60 (13) 794 (182) 72 (29) 790 (186) 56 (32) 79 (16)
5%CO2
 979 (202) 98 (40) 1,036 (216) 112 (61) 63 (12) 788 (164) 79 (44) 776 (170) 61 (38) 79 (14)
  1. Reported values are mean (SD) for 14 subjects