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Fig. 1 | The Journal of Physiological Sciences

Fig. 1

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

Fig. 1

Representative primary data recordings of heart rate variability in time (upper) and frequency (lower) domains during 5 min supine (left) and 5 min head-up tilt (right) epochs when breathing room air. The upper tachograms plot the R–R interval for successive heart beats, and the frequency spectrum of this tachogram shown below is banded into very low frequency (0–0.04 Hz), low frequency (0.04–0.15 Hz), and high frequency (0.15–0.4 Hz). Data shown are from a male (28 years) and the mean heart rate was 53 beats min−1 with HF and LF components of 56.8NU and 39.1NU respectively, when supine. During HUT, the mean heart rate was 86 beats min−1 with HF and LF components of 28.6NU and 63.4NU respectively

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