Effect of slow breathing on the blood pressure and the Valsalva ration in prehypertensive Indian students
Keywords: Prehypertension, slow breathing, Valsalva ratio, HRV
AbstractThe purpose of this study was to evaluate the effect of slow breathing and prehypertension (PHT) on cardiovascular and HRV variables and on the Valsalva ratio (VR). ECG was recorded in 39 normotensives and 35 prehypertensives at 5 min resting and slow breathing (6 breaths/min) stages to obtain HR, LF and HF power; SBP and DBP were recorded at the end of each stage. The Valsalva manoeuvre was performed after resting and slow breathing stages. Two-way repeated MANOVA was used to test for the effects of PHT and slow breathing. Stepwise multiple linear regression analysis was used to reveal predictors of HR, SBP and DBP. The normotensives and the prehypertensives demonstrated reduction of SBP during slow breathing (117.95 ± 0.73 vs. 115.18 ± 0.91 mm Hg, P = 0.001 and 130.09 ± 0.08 vs. 125.91 ± 0.96 mm Hg, P < 0.001, respectively). At rest, the VR was lower in prehypertensives (1.69 ± 0.05 vs. 1.87 ± 0.05, P = 0.009). After slow breathing, the VR increased significantly only in prehypertensives (P = 0.008), it was no longer different from that of normotensives (1.82 ± 0.06 vs. 1.90 ± 0.06, P = 0.346). The LnLF power, interpreted according to our hypothesis described previously as sympathoinhibition, increased in both groups. Slow breathing reduced SBP in normotensives and prehypertensives as a result of an increase in sympathoinhibition in both groups and VR, considered as a surrogate marker of the baroreflex activity, in prehypertensives.