Table 3 Heart rate variability during the head-up tilt test.

From: Sleep apnea is associated with reduced daytime blood pressure variability in adults with Down syndrome

 

Position

No or mild SA (n = 7)

Moderate to severe SA (n = 21)

p-value

RR intervals (ms)

Supine

886.3 ± 169.8

962.5 ± 123.1

0.072

Orthostatic

719.9 ± 176.3

739.4 ± 97.6

0.796

HR (bpm)

Supine

70.2 ± 12.7

63.9 ± 7.2

0.092

 

Orthostatic

87.4 ± 17.6

83.2 ± 11.3

0.559

RMSSD (ms)

Supine

50.0 ± 26.3

43.8 ± 26.6

0.332

Orthostatic

29.0 ± 12.1

25.8 ± 22.8

0.175

pNN50 (%)

Supine

20.6 ± 15.1

20.8 ± 17.6

0.678

Orthostatic

9.2 ± 9.5

5.4 ± 8.6

0.408

LFRR (nu)

Supine

61.5 ± 18.3

59.6 ± 19.1

0.499

Orthostatic

69.5 ± 17.1

72.5 ± 10.6

0.466

HFRR (nu)

Supine

38.4 ± 18.3

40.8 ± 18.8

0.456

Orthostatic

30.4 ± 16.9

27.5 ± 10.6

0.465

LFRR/HFRR

Supine

2.1 ± 1.2

2.0 ± 1.5

0.469

Orthostatic

3.2 ± 2.2

3.3 ± 1.9

0.500

  1. HFRR High frequencies, LFRR Low frequencies, LFRR/HFRR Sympathovagal balance, pNN50  The proportion of differences greater than 50 ms between successive RR intervals, RMSSD  The root mean square of successive RR intervals, SA   sleep apnea.
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