The ethnic/racial differences in predisposition to hypertension are widely documented in the literature. On the other hand, it is known that lung functions and capacities are different between people of European, Asian, and African descents. It was demonstrated that slowing breathing to 6 breaths per minute can reduce blood pressure but specific mechanisms remains unclear. It was hypothesized that the effect of slow breathing on blood pressure is different between ethnic/racial groups. Participant cohort included 76 international students recruited from the V.N. Karazin Kharkiv National University. According to requirements of the spirometry system, ECG was continuously recorded in the sitting position for 5 minutes of resting and slow breathing (6 breaths per minute) stages. The tidal volume (TV) and respiratory rate were recorded for one minute at the end of each stage. SBP and DBP were measured with automatic digital sphygmomanometer (OMRON EVOLV, Japan). LF and HF HRV power and minute ventilation (MV) were computed with CardioLab CS and SPIROCOM pc based systems (XAI-Medica, Ukraine). Two-way repeated measures MANOVA with Bonferroni correction (SPSS 22) was used to test for effects of slow breathing and ethnicity/race on HR, SBP, DBP, HRV variables, TV, and MV. Predictors of HR, SBP, and DBP responses to slow breathing were determined using multiple regression analysis. Written informed consent was obtained from each participant. At sitting rest blood pressure was not different between ethnic/racial groups. The slow breathing decreased SBP in European (Ukraine), Arab (Egypt), and Indian students at 4.7±1.4, 6.9±1.7, 3.1±1.6 mm Hg (P=0.001, P<0.001, P=0.049, respectively). In Africans, instead, DBP was reduced (not shown). At rest the LF HRV power was less in Africans compared with other groups (not shown), possible indicating according to our hypothesis described previously, decreased activity of the sympathoinhibitory arm of baroreflex. The TV was similar at rest, but during slow breathing Arabs demonstrated increased TV compared with other groups (Fig. 1A). The MV at rest also was more in Arabs than Africans and Indians, and during slow breathing compared with Africans and Europeans (Fig. 1B). Multiple regression analysis revealed that HR response to slow breathing was positively associated with ∆TV possibly due to temporal decreased venous return and setting on the baroreflex mechanism, and negatively with resting HR and TV (Table 1). The SBP response was associated with resting SBP. This effect dependent on participants’ height, resting TV and LnLF power: the more was resting SBP, height, and resting LnLF power indicating the sympathoinhibitory arm of baroreflex, the more SBP was reduced. Also, ∆SBP was positively associated with resting LnLF by ∆MV interaction. The low values of resting LnLF HRV power in Africans prevented from significant decrease of SBP in this group. The low values of resting MV and ∆MV in African participants lead to decrease of DBP according to positive association between these indices and DBP response (Table 1). Slow breathing decreased SBP in Europeans, Arabs, and Indians. However, African participants, did not demonstrate reduction of SBP due to low resting LnLF HRV power and TV. Instead, Africans demonstrated decreased DBP due to low values of resting MV and LnLF HRV power in this group.
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Open Access
Jun 28, 2021
Yu O Guglya 
