Sympathetic neural outflow and chemoreflex sensitivity are related to spontaneous breathing rate in normal men - Narkiewicz et al. (2006)
Key Points
Higher resting breathing rates are associated with higher resting sympathetic activity
A 1 breath/min increase in breathing rate is associated with a 1.4 bursts/min increase in sympathetic activity
We can train ourselves to breathe slowly 24/7 and thus reduce resting sympathetic activity
The Breathing Diabetic Summary
We have seen in previous studies (e.g., Oneda et al., 2010) that slow breathing can temporarily lower sympathetic activity. However, these authors wanted to investigate if spontaneous breathing rate was linked to resting sympathetic activity. That is, if a person breathes slower 24/7, will they have lower sympathetic activity than someone who breathes faster?
They studied 69 men with a mean age of about 30 years old. They divided the men into three groups based their resting respiratory rate: <13 breaths/min, 13-16 breaths/min, and >16 breaths/min. They had the participants lay down for 10 minutes while they recorded measurements of muscle sympathetic nerve activity (MSNA), blood pressure, breathing rate, and heart rate. They did not have the participants change their breathing.
(Although I do not cover it here, they also tested how spontaneous breathing rate affected the participants’ reaction to hypercapnia and hypoxia. They results were pretty interesting, and I will be covering them in future notes on breathing and blood alkalinity.)
The results showed that higher respiratory rate (the >16 breaths/min group) was associated with higher sympathetic activity. They performed a statistical analysis that included age, body mass index, blood pressure, and breathing rate, and breathing rate was the only variable that could explain the increased sympathetic activity. This statistical analysis showed that for an increase of 1 breath/min, there was a corresponding MSNA increase of 1.4 bursts/min. That’s pretty remarkable! Obviously, this is only one group of people and one study, but to show a numerical value for how sympathetic activity increases with resting breathing rate is pretty awesome.
Overall, the important finding from this study is that our spontaneous breathing rate is linked to our resting sympathetic activity. What makes this so important is that we can change our resting breathing rate. The authors even speculate that long-term behavioral changes could be useful in slowing down the breathing rate of people who have, for example, cardiovascular disease, to help lower sympathetic activity. For us diabetics who also have higher baseline sympathetic activity, let’s start practicing Principle 1 today to train ourselves to breathe slowly all the time. While we’re at it, let’s tape our mouths at night to continue training and reap the benefits of a lower sympathetic tone and deeper sleep!
Abstract from Paper
Respiration contributes importantly to short-term modulation of sympathetic nerve activity. However, the relationship between spontaneous breathing rate, chemoreflex function, and direct measures of sympathetic traffic in healthy humans has not been studied previously. We tested the hypothesis that muscle sympathetic nerve activity and chemoreflex sensitivity are linked independently to respiratory rate in normal subjects. We studied 69 normal male subjects aged 29.6+-8.1 years. Subjects were subdivided according to the tertiles of respiratory rate distributions. Mean respiration rate was 10.6 breaths/min in the first tertile, 14.8 breaths/min in the second tertile, and 18.0 breaths/min in the third tertile. Subjects from the third tertile (faster respiratory rate) had greater sympathetic activity than subjects from the first tertile (slower respiratory rate; 29+-3 versus 17+-2 bursts/min; P<0.001). Stepwise multiple linear regression analysis revealed that only respiratory rate was linked independently to sympathetic activity (r=0.42; P<0.001). In comparison to subjects with slow respiratory rate, subjects with fast respiratory rate had greater increases in minute ventilation during both hypercapnia (7.3+-0.8 versus 3.2+-1.0 L/min; P=0.005) and hypoxia (5.7+-0.8 versus 2.4+-0.7 L/min; P=0.007). Muscle sympathetic nerve activity and chemoreflex sensitivity are linked to spontaneous respiratory rate in normal humans. Faster respiratory rate is associated with higher levels of sympathetic traffic and potentiated responses to hypoxia and hypercapnia. Spontaneous breathing frequency, central sympathetic outflow, and chemoreflex sensitivity exhibit significant and hitherto unrecognized interactions in the modulation of neural circulatory control.
Journal Reference:
Krzysztof Narkiewicz, Philippe van de Borne, Nicola Montano, Dagmara Hering, Tomas Kara, and Virend K. Somers, (2006) Sympathetic neural outflow and chemoreflex sensitivity are related to spontaneous breathing rate in normal men, Hypertension, 47, 51-55, DOI: 10.116110.1161/01.HYP.0000197613.47649.02.