Baroreflex function in sedentary and endurance-trained elderly people

Cardiovascular and respiratory effect of yogic slow breathing in the yoga beginner: what is the best approach?

Slow breathing increases cardiac-vagal baroreflex sensitivity (BRS), improves oxygen saturation, lowers blood pressure, and reduces anxiety. Within the yoga tradition slow breathing is often paired with a contraction of the glottis muscles. This resistance breath “ujjayi” is performed at various rates and ratios of inspiration/expiration. To test whether ujjayi had additional positive effects to slow breathing, we compared BRS and ventilatory control under different breathing patterns (equal/unequal inspiration/expiration at 6 breath/min, with/without ujjayi), in 17 yoga-naive young healthy participants. BRS increased with slow breathing techniques with or without expiratory ujjayi (P < 0.05 or higher) except with inspiratory + expiratory ujjayi. The maximal increase in BRS and decrease in blood pressure were found in slow breathing with equal inspiration and expiration. This corresponded with a significant improvement in oxygen saturation without increase in heart rate and ventilation. Ujjayi showed similar increase in oxygen saturation but slightly lesser improvement in baroreflex sensitivity with no change in blood pressure. The slow breathing with equal inspiration and expiration seems the best technique for improving baroreflex sensitivity in yoga-naive subjects. The effects of ujjayi seems dependent on increased intrathoracic pressure that requires greater effort than normal slow breathing.

Cardiac baroreflex function and dynamic cerebral autoregulation in elderly Masters athletes

Cerebral blood flow (CBF) is stably maintained through the combined effects of blood pressure (BP) regulation and cerebral autoregulation. Previous studies suggest that aerobic exercise training improves cardiac baroreflex function and beneficially affects BP regulation, but may negatively affect cerebral autoregulation. The purpose of this study was to reveal the impact of lifelong exercise on cardiac baroreflex function and dynamic cerebral autoregulation (CA) in older adults. Eleven Masters athletes (MA) (8 men, 3 women; mean age 73 ± 6 yr; aerobic training >15 yr) and 12 healthy sedentary elderly (SE) (7 men, 5 women; mean age 71 ± 6 yr) participated in this study. BP, CBF velocity (CBFV), and heart rate were measured during resting conditions and repeated sit-stand maneuvers to enhance BP variability. Baroreflex gain was assessed using transfer function analysis of spontaneous changes in systolic BP and R-R interval in the low frequency range (0.05–0.15 Hz). Dynamic CA was assessed during sit-stand–induced changes in mean BP and CBFV at 0.05 Hz (10 s sit, 10 s stand). Cardiac baroreflex gain was more than doubled in MA compared with SE (MA, 7.69 ± 7.95; SE, 3.18 ± 1.29 ms/mmHg; P = 0.018). However, dynamic CA was similar in the two groups (normalized gain: MA, 1.50 ± 0.56; SE, 1.56 ± 0.42% CBFV/mmHg; P = 0.792). These findings suggest that lifelong exercise improves cardiac baroreflex function, but does not alter dynamic CA. Thus, beneficial effects of exercise training on BP regulation can be achieved in older adults without compromising dynamic regulation of CBF.

Influence of Seated Rocking on Blood Pressure in the Elderly: A Pilot Clinical Study

Patients with Alzheimer’s disease (AD) who rock for 1—2 hr per day in a rocking chair demonstrate significant improvements in depression, anxiety, and balance and a decrease in pain medication usage; however, the underlying basis for their responses remains unclear. Rocking with plantar flexion uses the calf muscles, enhancing lower limb fluid return to the heart, which should increase blood pressure (BP) and may, then, also increase cerebral perfusion. Accordingly, we tested the efficacy of rocking activity for increasing BP in healthy, older persons. In a pilot laboratory study of 24 healthy, White men and women aged 55—87 years, we observed that 30 min of steady rocking led to an average 12 mmHg increase in systolic blood pressure (SBP, p < .001) and a 3.6 mmHg average increase in diastolic blood pressure (DBP, p < .001). To determine the effect of using this intervention in a nonclinical setting, we tested a similar group of 7 participants at a senior center. In this setting, we observed an average increase in SBP of 27 mmHg (p < .001) and in DBP of 2.5 mmHg (p < .001) after 30 min of rocking. In a subgroup (n = 8) of hypotensive individuals (SBP < 110 mmHg after sitting quietly for 30 min) extracted from both settings, rocking raised the average SBP from <100 mmHg to approximately 120 mmHg. These results are consistent with the hypothesis that rocking can increase BP and, therefore, may enhance cerebral perfusion. This observation may play a fundamental role in designing nursing interventions focused on improvement of symptoms associated with AD.

Arterial baroreflex control of cardiac vagal outflow in older individuals can be enhanced by aerobic exercise training

Maintained cardiac vagal function is critical to cardiovascular health in human aging. Aerobic exercise training has been considered an attractive intervention to increase cardiovagal baroreflex function; however, the data are equivocal. Moreover, if regular exercise does reverse the age-related decline in cardiovagal baroreflex function, it is unknown how this might be achieved. Therefore, we assessed the effects of a 6-month aerobic training program on baroreflex gain and its mechanical and neural components in older individuals (5 women and 7 men, aged 55 to 71 years). We assessed baroreflex function using pharmacological pressure changes (bolus nitroprusside followed by bolus phenylephrine) and estimated the integrated gain (Delta R-R interval/Delta systolic blood pressure) and mechanical (Delta diameter/Delta pressure) and neural (Delta R-R interval/Delta diameter) components via measurements of carotid artery diameter in previously sedentary older individuals before and after 6 months of aerobic training. There was a significant 26% increase in baroreflex gain that was directly related to the amount of exercise performed and that was derived mainly from an increase in the neural component of the arterial baroreflex (P<0.05). We did find changes in the mechanical component, but unlike integrated gain and the neural component, these were not related to the magnitude of the exercise stimulus. These results suggest that exercise training can have a powerful effect on cardiovagal baroreflex function, but a sufficient stimulus is necessary to produce the effect. Moreover, adaptations in the afferent-efferent baroreflex control of cardiac vagal outflow may be crucial for the improvement in arterial baroreflex function in older humans.

Interval training in elderly men increases both heart rate variability and baroreflex activity

AIMS

Autonomic nervous system activity decreases continuously with age and appears to be a powerful predictor of disease and death. Attempts are thus made to reactivate autonomic drive with the intent of improving health.

METHODS

We assessed maximal oxygen consumption (VO2max), autonomic nervous system activity by heart rate variability (HRV) analysis and spontaneous cardiac baroreflex activity (SBR) in eleven elderly men (73.5+/-4.2 years) before and after a 14-week program of intensive cycloergometer interval training. The standard HRV indices were calculated using time domain (mean RR, PNN50, RMSSD, SDNN, SDANN and SDNNIDX), and Fourier transform (total power, ULF,VLF, LF, LFnu, HF, HFnu and LF/HF) analyses of 24-hour, daytime and nighttime Holter recordings. The SBR was calculated from 15-minute recordings of spontaneous blood pressure and RR interval variations using the sequence (slope, slSBR) and cross-spectral (alphaSBRHF and alphaSBRLF) methods.

RESULTS

After the training period,VO2max increased by 18.6 % (26.8+/-4.4 to 31.8+/-5.2 ml.kg(-1).min(-1), p<0.01). The nocturnal parasympathetic indices of HRV increased (PNN50: 3.05+/-2.21 to 5.00+/-2.87%, RMSSD: 29.1+/-7.6 to 38.8+/-10.9 ms, HF: 117+/-54 to 194+/-116 ms2/Hz, all p<0.05) as did the SBR indices (slSBR: 7.0+/-1.8 to 9.8+/-2.1 ms.mmHg(-1), p<0.01; alphaSBRHF: 6.9+/-2.2 to 10.5+/-3.7 ms.mmHg(-1), p<0.05; alphaSBRLF: 5.3+/-2.3 to 6.9+/-3.1 ms.mmHg(-1), p=0.22).

CONCLUSION

Intensive endurance training in elderly men enhanced parasympathetic parameters of HRV and, interestingly, of SBR. Physiological mechanisms and long-term clinical effects on health status should be further investigated.

Dose-response relationship of the cardiovascular adaptation to endurance training in healthy adults: how much training for what benefit?

Occupational or recreational exercise reduces mortality from cardiovascular disease. The potential mechanisms for this reduction may include changes in blood pressure (BP) and autonomic control of the circulation. Therefore, we conducted the present long-term longitudinal study to quantify the dose-response relationship between the volume and intensity of exercise training, and regulation of heart rate (HR) and BP. We measured steady-state hemodynamics and analyzed dynamic cardiovascular regulation by spectral and transfer function analysis of cardiovascular variability in 11 initially sedentary subjects during 1 yr of progressive endurance training sufficient to allow them to complete a marathon. From this, we found that 1) moderate exercise training for 3 mo decreased BP, HR, and total peripheral resistance, and increased cardiovascular variability and arterial baroreflex sensitivity; 2) more prolonged and intense training did not augment these changes further; and 3) most of these changes returned to control values at 12 mo despite markedly increased training duration and intensity equivalent to that routinely observed in competitive athletes. In conclusion, increases in R-wave-R-wave interval and cardiovascular variability indexes are consistent with an augmentation of vagal modulation of HR after exercise training. It appears that moderate doses of training for 3 mo are sufficient to achieve this response as well as a modest hypotensive effect from decreasing vascular resistance. However, more prolonged and intense training does not necessarily lead to greater enhancement of circulatory control and, therefore, may not provide an added protective benefit via autonomic mechanisms against death by cardiovascular disease.

Relationship of baroreflex sensitivity and blood pressure in an older population

OBJECTIVES

Ageing and hypertension are associated with reduced baroreflex sensitivity (BRS) in young and middle-aged populations. The effects of blood pressure level on BRS in the older population are unclear. We examined the association between blood pressure and BRS in older persons with blood pressure below 180 mmHg.

METHODS

BRS, high (alphaHF 0.15-0.4 Hz) and low (alphaLF 0.04-0.15 Hz) frequency alpha-index, was determined in 75 normotensive subjects (aged 75 +/- 4 years, 41% female, 131 +/- 10/74 +/- 7 mmHg) and 64 untreated hypertensive subjects (aged 76 +/- 5 years, 48% female, 165 +/- 7/ 88 +/- 7 mmHg) by spectral analysis of 20 min continuous blood pressure and heart rate recordings using finger plethysmography. Subjects were recruited from 10 general practices and were taking no cardiovascular medications.

RESULTS

High but not low frequency alpha-index was significantly blunted in hypertensive subjects (alphaHF 5.1 +/- 3.1 versus 8.4 +/- 7.4 ms/mmHg, P< 0.001 and alphaLF 4.7 +/- 3.0 versus 5.8 +/- 3.9 ms/mmHg, P= 0.07). Multivariate analysis of the relationship between age and blood pressure demonstrated systolic and to a lesser extent diastolic blood pressure were significant predictors of variance in BRS for alphaHF [systolic blood pressure (SBP) P< 0.0001, diastolic blood pressure (DBP) P< 0.05, r2 = 0.1] and alphaLF (SBP P=0.01, DBP P<0.05, r2 = 0.04). Age was not a significant predictor for either measure, in the 20 year range studied.

CONCLUSIONS

In an older population blood pressure is associated with reduced BRS, particularly for the high frequency component. Such a change may place older subjects with hypertension at increased risk of orthostatic hypotension, vasovagal syncope and sudden cardiac death.