Objective: To evaluate the impact of body position on the arterial stiffness indices provided by radial applanation tonometry in pregnant and nonpregnant women.
Methods: Twenty-four young women (18–30 years) in the third trimester of a normal pregnancy and 20 healthy nonpregnant women of the same age were enrolled. In each, applanation tonometry was carried out in the sitting and supine position. The following stiffness indices were analyzed: systolic augmentation index (sAix), sAix adjusted for heart rate (sAix@75) and diastolic augmentation index (dAix), all expressed in % of central aortic pulse pressure.
Results: The sAix was apparently not influenced by body position, but the transition from seated to supine was associated with a substantial decrease in heart rate. When correcting for this confounder by calculating the sAix@75, systolic augmentation was substantially lower when individuals were supine (mean ± SD: nonpregnant 3.0 ± 14.4%, pregnant 8.8 ± 9.7%) than when they were sitting (nonpregnant 5.7 ± 13.0%, pregnant 11.1 ± 83%, P = 0.005 supine vs. seated in both study groups, P > 0.2 for pregnant vs. nonpregnant). The influence of body position on the dAix went in the opposite direction (supine: nonpregnant 9.7 ± 6.6%, pregnant 4.4 ± 3.5%; seated: nonpregnant 7.7 ± 5.8%, pregnant 3.3 ± 2.4%, P < 0.00001 supine vs. seated in both study groups, P = 0.001 for pregnant vs. nonpregnant).
Conclusion: Body position has a major impact on the pattern of central aortic pressure augmentation by reflected waves in healthy young women examined either during third trimester pregnancy or in the nonpregnant state.
aDivision de Physiopathologie Clinique, Département de Médecine
bService de Médicine intensif adulte
cDépartement de Gynécologie-Obstétrique-Génétique, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Lausanne, Switzerland
Correspondence to François Feihl, MD, Associate Professor, PPA, BH10-701, CHUV, 1011 Lausanne, Switzerland. Tel: +41 21 314 1423; fax: +41 21 314 1432; e-mail: Francois.Feihl@chuv.ch
Abbreviations: dAix, diastolic augmentation index; dMTT, mean transit time of diastolic reflection wave; dT1r, onset time of diastolic reflected wave; PPA, pulse pressure amplification; sAix, systolic augmentation index; sAix@75, sAix corrected for the influence of heart rate; sT1r, onset time of systolic reflected wave
Received 25 February, 2011
Revised 18 January, 2012
Accepted 16 February, 2012