Blood Pressure and tVNS

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Two common benefits of vagus nerve stimulation are that it usually leads to an improvement  in heart rate variability (HRV) and a drop in blood pressure (BP). Both these ‘biomarkers’ are important indicators of your long term health. 

Knowledge of the importance of maintaining a healthy blood pressure has been well known for a long time. A high BP is often referred to as the ‘silent killer’ because it can go unnoticed for a long time and is strongly associated with heart attacks and strokes. 

HRV is less well known, but more health practitioners are now emphasising its importance in long term health and well being. If you haven’t read our earlier post on HRV, that would be a good place to go either before or after you read this post. 

Improving your BP is all about following the health guidelines that we all know about: improving our diet, regular exercise, avoiding excessive prolonged stress and being well rested. Eating well and exercising is the sort of thing we can all do given a heavy dose of will power. I don’t want to dismiss how difficult that can sometimes be, but in some ways, it’s even harder for us to unwind at the end of our day, relax and get the proper kind of rest we all need to recuperate effectively. 

Our ability to effectively unwinding and relax can be greatly hindered if our parasympathetic nervous system is not working quite how it should be. The resulting fatigue then weakens the parasympathetic system further, creating a vicious cycle that simply exacerbates the problem. 

This is where following a protocol of vagus nerve stimulation can really help. tVNS has a direct positive effect on BP and HRV. We have previously written about the effect of tVNS on HRV and have pointed to recent research that has shown how beneficial it can be. In this post we’re going to take a look at it’s effect on the BP, so that you have some idea of what to expect when you start using the vagus.net stimulator. 

Blood pressure, like HRV, can vary a lot from day to day, or even within the same day. How your BP readings vary will depend on what you’ve eaten, how rested you are and how stressed you are. It’s important therefore to take readings over several days or weeks to get an overall picture. 

As an example, below are two graphs of blood pressure data from one of our test subjects — a 65 year old woman in generally good health. 

The first graph shows her systolic and diastolic blood pressure readings over a ten day period. They are taken at roughly the same time every day in the early evening. The readings show a slightly elevated blood pressure, but nothing out of the ordinary for someone of her age. As you can see, the readings also vary a fair amount.

The next graph shows her readings over a ten day period when she began using our vagus nerve stimulator. The graph shows readings taken just before a 15min stimulation session and just after a stimulation session. The blue and orange lines show systolic and diastolic pressure before; while the red and green lines show readings after stimulation. 

The readings were all taken at roughly the same time each day, in the early evening.

As you can see, there is an overall fall in the BP trend (take note of the change in y-axis scale). It is not always the case that BP after stimulation is lower than BP before a session, but it is so on most occasions. 

There are two effects that are apparent here. The first is the immediate baroreflex. This is the most immediate way in which the body regulates blood pressure and involves the blood vessels dilating to rapidly reduce blood pressure. This mechanism is mediated by the vagus nerve, so stimulating the vagus has an immediate outcome. The second effect is the change in the trend. The overall blood pressure falls during the ten days of stimulation, which shows that the positive effects persist beyond the stimulation session. This is more likely due to an overall strengthening of vagal tone which allows the body to better regulate itself. 

Many people experience such falls in their blood pressure when they start tVNS. But don’t worry if you don’t. Everyone has a slightly different response to tVNS, some more dramatic than others. Studies show that those who have the most to gain usually see the greatest short term changes. But it’s important to remember that the real benefits of tVNS are very much in long term health outcomes. Developing regular, healthy habits will greatly improve your health over time. 

It isn’t essential that you measure your biomarkers. Many people simply find they feel better when they incorporate regular tVNS into their daily routines. And some will use it intermittently to reset their body’s equilibrium from time to time. All these ways of using tVNS can be effective.

However, if you’re one of those people who like to put numbers on things (like we are), we’d recommend that measuring your blood pressure will give a good indication of how you are responding to tVNS. 

In future posts we’ll take a close look at the mechanisms that bring about the changes that we tend to observe in blood pressure and heart rate variability.

References

[1] Ng, F. L., Saxena, M., Mahfoud, F., Pathak, A., & Lobo, M. D. (2016). Device-based Therapy for Hypertension. Current hypertension reports, 18(8), 61. https://doi.org/10.1007/s11906-016-0670-5

[2] Bretherton B, Atkinson L, Murray A, Clancy J, Deuchars S, Deuchars J. Effects of transcutaneous vagus nerve stimulation in individuals aged 55 years or above: potential benefits of daily stimulation. Aging (Albany NY). 2019; 11:4836-4857. https://doi.org/10.18632/aging.102074

[3] https://www.sciencedirect.com/topics/neuroscience/baroreflex

[4] Antonino D, Teixeira AL, Maia-Lopes PM, Souza MC, Sabino-Carvalho JL, Murray AR, Deuchars J, Vianna LC. Non-invasive vagus nerve stimulation acutely improves spontaneous cardiac baroreflex sensitivity in healthy young men: A randomized placebo-controlled trial. Brain Stimul. 2017 Sep-Oct;10(5):875-881. doi: 10.1016/j.brs.2017.05.006. Epub 2017 May 19. PMID: 28566194.

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Getting On Your Nerves

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