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Gender Differences in Transfer Functions and Coherencies between RR interval and Blood Pressure during Head up Tilt
Author(s) -
Narasimha Pavan Kumar,
Wang Xue,
Bruce Eugene,
Evans Joyce,
Justice Todd,
Patwardhan A
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a1427-b
We calculated coherencies and transfer functions between RR intervals and systolic blood pressure (SBP) to investigate differences in baroreflex regulation between men and women during orthostasis. Data were collected from 38 normal volunteers (22 men, 16 women) during 10 min in supine posture followed by 30 min of 70 degrees head up Tilt. Non‐invasive continuous blood pressure and ECG were used to compute SBP and RR intervals. Coherence and transfer functions between these variables were averaged within a region defined by mean breathing frequency ± one standard deviation. Average coherencies in men increased from 0.36+/−0.09(Standard Deviation) during supine to 0.49+/− 0.13 during tilt, p<0.05. In women, we did not observe an increase in coherence during tilt, however, the lack of increase was due to women having higher coherence in supine, 0.47+/−0.11, p<0.05. Even though coherence increased in men during tilt, the average coherence in women during tilt was higher than men, 0.52+/−0.11, although not significantly. Transfer function gain increased in men and women during tilt (p<0.005). The gain was higher in men than women in supine (p<0.05) but not during tilt. Although the degree of change in RR interval per unit change in SBP was higher in men, coherencies suggest that the baroreflex is more engaged in women during supine but does not increase further during tilt. This lack of reserve in terms of engagement of the reflex during tilt may underlie the greater incidence of unexplained syncope observed in women than men. Supported by NIH HL65735.