Cardiovagal outflow impacts bronchial tone: ethnical/racial aspect
Authors: Amaechi Fechukwu Gift , Shekh Vera Evgenievna , Odelola Inioluwa Faith , Ekwealor Esther Ekenechukwu , Shchyrova Larisa Semyonovna 
Published: April 2020

It is well documented that Africans have a prevalence of hypertension despite the high parasympathetic activity. The HRV analysis is a perspective noninvasive tool for the determination of ANS outflow. Till now it is not known if HF HRV power indicating cardiovagal outflow impacts bronchial tone. Orthostatic test is accompanied with a decrease of HF HRV power. The aim of the study was to evaluate if cardiovagal outflow impacts bronchial tone in sitting and upright position and whether this interaction may be associated with prevalence of hypertension in Africans.

A total of 19 Caucasian, 17 African, 20 Arabic, and 22 Indian men were recruited from V.N. Karazin Kharkiv National University student population. No significant differences were in age, BMI and height of participants. In the sitting and upright positions ECG, tidal volume (TV), and respiratory rate was continuously recorded, LF and HF HRV power in absolute units and minute ventilation (MV) were computed with CardioLab CS and SPIROCOM pc based systems (XAIMedica, Ukraine). The sitting position was taken as a baseline according to requirements of the spirometry system. The SBP and DBP were recorded my means automatic digital sphygmomanometer (Nissei WS‐1011, Japan) at 4.5 minute of each 5 min stage. Two‐way repeated measures MANOVA with Bonferroni correction was used to test for effects of orthostasis and ethnicity/race on cardiovascular, respiratory, and HRV variables, multiple regression analysis was used to determine predictors of MV. All analyses were conducted using SPSS 22. Written informed consent was obtained from all participants.

The highest values of LnHF were observed in Africans, the significant difference was between them and Indians at rest indicating high parasympathetic activity in Africans in congruence with previous reports (Fig.
1). Upon assuming the upright position LnHF power was significantly reduced in all the groups showing decreased cardiovagal outflow necessary to keep blood pressure and brain perfusion at normal level. Upon standing the LnLF power was reduced only in Africans. In accordance with our hypothesis, decrease of LnLF, possibly indicating decrease of inhibitory influence on sympathetic nervous system, in Africans, represented one more mechanism opposing effect of gravity and providing normal perfusion of tissues in standing position.

The MV was significantly lower in Africans than in Arabs and Indians and TV was less in Africans compared with Caucasians and Arabs in both positions (Fig.
2). Our data from multiple regression analysis revealed that MV in sitting and standing positions was negatively associated with LnHF HRV power indicating that parasympathetic outflow to bronchial smooth muscle works in parallel with cardiovagal outflow. The orthostatic stress did not modulate this autonomic‐respiratory interaction.

In conclusion, it is suggested that parasympathetic outflow impacts simultaneously bronchial tone and cardiovascular system. High parasympathetic activity in Africans reduced significantly tidal volume and minute ventilation and might cause activation of chemoreflex and explain increased blood pressure in this group.

Effect of ethnicity/race and orthostasis on LnLF HRV power (A) and LnHF HRV power (B) in young men. *P<0.05, *** P<0.001. Data are expressed as means±SE.

Figure 1

Effect of ethnicity/race and orthostasis on minute ventilation (A) and tidal volume (B) in young men. *P<0.05, ** P<0.01. Data are expressed as means±SE.

Figure 2