Effect of skin pressure caused by the cuff on female heart rate variability

The study was undertaken to focus on investigating whether skin pressure caused by the cuff would affect the global autonomic nervous system (ANS) by means of heart rate variability (HRV) power spectral analysis and further objectively evaluate the physiological threshold of skin pressure on the female abdomen and lateral waist respectively. Eight healthy females were chosen as the subjects. HRV signals of each subject in a completely relaxed sitting condition were collected during 11 kinds of skin pressures (0, 3, 6, 9, 12, 15, 18, 21, 24, 27, 30mmHg) caused by the cuff on the abdomen and lateral waist. Three frequency-domain parameters of HRV: normalized low frequency component (LFnorm), normalized high frequency component (HFnorm) and the ratio of low frequency component to high frequency (LF/HF) were evaluated. Results showed that for the female abdomen, HFnorm was increased and LFnorm was declined before the skin pressure was up to 15mmHg. When the skin pressure was more than 15mmHg, HFnorm went down and LFnorm went up gradually. It suggested that parasympathetic autonomic nervous system (PNS) activity was stimulated when skin pressure at the abdomen was increased by degrees. But after the skin pressure exceeded 15mmHg, PNS activity came to be weak. For the female lateral waist, both HFnorm and LFnorm were not significantly varied before the skin pressure was up to 18mmHg. But when the skin pressure exceeded 18mmHg, HFnorm was obviously declined and LFnorm was increased. This finding indicated that PNS activity was significantly inhibited when skin pressure at the lateral waist exceeded 18mmHg. Therefore, in order to reduce the negative effect of skin pressure on the female body, the skin pressure should be less than 15mmHg on the abdomen and less than 18mmHg on the lateral waist.