Table 7.

BRS measures and arterial stiffness parameters

Author (s)	Years	Parameters involved		Experiment protocol		Association between BRS measure and arterial stiffness parameter	Other findings
		BRS measure	Arterial stiffness	BRS measure	Arterial stiffness
Cunha et al. [34]	1997	BRS sequence method	cf-PWV	Continuous measurements of blood pressure for 20 min in the supine position to calculate beat-to-beat SBP, DBP and RRI; Spontaneous breathing	PWV between the carotid and femoral arteries was determined by the foot-to-foot method	Significant negative correlation between PWV and BRS in hypertensive subjects	–
Lantelme et al. [36]	2002	BRS sequence method (BRS-s) BRS alpha-index (BRS-a)	cf-PWV	Beat-to-beat measurements of SBP and RRI for 10 min in the supine position and 5 min in the standing position; Spontaneous breathing	PWV between the carotid and femoral arteries was determined by the foot-to-foot method	Significant negative correlation between both supine and standing BRS-s (not BRS-a) and PWV in hypertensive subjects	Significant increase in SBP, reduction in RRI, BRS-s and BRS-a from supine to standing
Siegelova et al. [38]	2004	BRS spectral method	Pulse pressure Carotid IMT	Continuous measurements of blood pressure for 5 min in the supine position; metronome-controlled breathing 0.33 Hz	B-mode ultrasonography was performed in the supine position on both the right and left common carotid artery Average carotid IMT was determined from 5 measurements	No specific analysis on the association between BRS measures and carotid IMT or pulse pressure was reported	Treated hypertensives with a higher pulse pressure are older, have a lower gain of the baroreflex and have a larger IMT
Labrova et al. [39]	2005	BRS spectral method BRSf	Carotid IMT	Continuous measurements of RR-intervals, beat-to-beat SBP and DBP in the sitting position at rest during a 5 min period; metronome-controlled breathing 0.33 Hz	B-mode ultrasonography was performed in the supine position on both the right and left common carotid artery Average carotid IMT was determined from 5 measurements	Significant negative correlation between carotid IMT and both BRS and BRSf in the whole group but not in hypertensive group	Decreased BRS and BRSf in hypertensive patients Positive correlation between age and IMT; negative correlation between age and BRS and BRSf in the whole group. However, age-related BRS was significantly weakened in the hypertensives due to an age-dependent prolongation of mean RRI
Novakova et al. [40]	2005	BRS spectral method BRSf	Carotid IMT	Continuous measurements of RR-intervals, beat-to-beat SBP and DBP in the sitting position at rest during a 5 min period; metronome-controlled breathing 0.33 Hz	B-mode ultrasonography was performed in the supine position on both the right and left common carotid artery Average carotid IMT was determined from 5 measurements	Significant negative association between BRS, BRSf and carotid IMT in the whole group (both measurements in a period of 1 year)	Greater IMT, decreased BRS and BRSf in hypertensive patients compared to normotensive subjects (both measurements in a period of 1 year, 2004–2005)
Labrova et al. [41]	2005	BRS spectral method BRSf	Carotid IMT	Continuous measurements of RR-intervals, beat-to-beat SBP and DBP in the sitting position at rest during a 5 min period; metronome-controlled breathing 0.33 Hz	B-mode ultrasonography was performed in the supine position on both the right and left common carotid artery Average carotid IMT was determined from 5 measurements	Significant negative correlation between carotid IMT and BRS and BRSf in the whole group but not in hypertensive group	Greater IMT, decreased BRS and BRSf in hypertensive patients compared to normotensive subjects
Chan et al. [42]	2005	BRS sequence method	TAC	RRI and SBP were derived from continuous ECG and non-invasive BP measurements, respectively, at two timepoints: (i) baseline: while receiving conventional hemodialysis ($\ge$ 18 h after the session); and (ii) 2 months after a stable dose of nocturnal hemodialysis ($\ge$ 4 h after the session) Spontaneous breathing	TAC (SV/PP)	Significant positive correlation between BRS and TAC in hypertensive subjects with ESRD	Following conversion from conventional hemodialysis to nocturnal hemodialysis, mean HR remains unaffected, SBP and DBP decreased, while BRS and TAC increased
Honzikova et al. [43]	2006	BRS spectral method	Carotid IMT	Continuous measurements of RR-intervals, beat-to-beat SBP and DBP in the sitting position at rest during a 5 min period; metronome-controlled breathing 0.33 Hz	B-mode ultrasonography was performed in the supine position on both the right and left common carotid artery Average carotid IMT was determined from 5 measurements	Significant negative correlation between carotid IMT and BRS in the normotensive and whole groups, but not in hypertensive group	BRS was negatively correlated with age and IMT in normotensive subjects and in the whole group, but not in hypertensive subjects
Michas et al. [44]	2012	BRS alpha-index	cf-PWV	Continuous measurements of RR-intervals, beat-to-beat SBP and DBP in the sitting position at rest during a 5 min period; metronome-controlled breathing 0.25 Hz	PWV between the carotid and femoral arteries was determined by the foot-to-foot method	No separate association analysis was reported between the two study groups Significant negative correlation between PWV and BRS in the whole group (normotensives and hypertensives)	Hypertensive patients were significantly older, had higher PWV and lower BRS than normotensive subjects
Celovska et al. [45]	2012	BRS sequence method BRS spectral method BRSf	Carotid IMT	Continuous measurements of RRI, SBP and DBP for three sequential periods of 5 min each in the supine position; metronome-controlled breathing 0.33 Hz	mean of the maxima at 4 sites of both common carotid artery and carotid bulb	Significant negative correlation between all BRS measures and carotid/carotid bulb IMT in hypertensive with stroke patients in comparison with stroke-free hypertensives	The higher the grade of hypertension, the lower the BRS/BRSf values Significant association between reduced BRS and increased SBP, PP and carotid IMT in hypertensives with stroke
Okada et al. [47]	2013	BRS sequence method (assessed by averaging the values of the slope of the linear correlation between RRI and beat-by-beat SBP during the two VM (phase IV))	cf-PWV	Continuous measurements of HR and BP during these tests: (i) 6 min of spontaneous breathing; (ii) two VM at 40 mmHg for 20 s with 5 min apart and (iii) 60° upright tilt for 10 min (MSNA data were collected during the last 3 min of tilting) Spontaneous breathing	PWV between the carotid and femoral arteries was determined by the foot-to-foot method	No specific analysis on the association between BRS measures and cf-PWV was reported	Higher cf-PWV and lower sympathetic BRS in hypertensive patients compared to normotensive subjects, but similar morning HR increase and cardiovagal BRS between both groups. Upright sympathetic BRS was smaller and %TPR/%MSNA by 60° HUT was higher in hypertensive subjects with greater morning surge than those with lesser morning surge. No difference in supine or upright MSNA between the groups. Significant positive correlation between morning surge and cf-PWV and sympathetic BRS in hypertensive subjects only. Sympathetic BRS, but not %TPR/%MSNA, was correlated with cf-PWV in hypertensive subjects.
Celovska et al. [49]	2017	BRS Sequence method; BRS Spectral method	Carotid IMT	Continuous measurements of RRI, SBP and DBP for three sequential periods of 5 min each in the supine position; metronome-controlled breathing 0.33 Hz	Measured on the far wall of common carotid artery along 1 cm long section proximal to the carotid bulb Mean of 3 single measurements at the side (left and right common carotid) with greater IMT was calculated	No specific analysis on the association between BRS measures and carotid IMT was reported	Significant negative correlation between spectral BRS, sequence BRS and systolic BP as well as mean BP in hypertensives Prehypertensive and hypertensives with critical BRS ≤ 5 ms/mmHg have significantly increased carotid and carotid bulb IMT

BP blood pressure, BRS baroreflex sensitivity, cf-PWV PWV between carotid and femoral arteries, DBP diastolic blood pressure, HR heart rate, IMT intima–media thickness, MSNA muscle sympathetic nervous activity, PP pulse pressure, PWV pulse wave velocity, rel relative unit, RRI RR-intervals, SBP systolic blood pressure, TAC total arterial compliance (SV/PP), TPR total peripheral resistance, VM Valsalva maneuver