Controlled breathing lowers sympathetic activity, even when performed at a relatively fast pace

Key Points

• Controlled breathing reduces sympathetic activity, even when performed at a relatively fast pace

• The reduction in sympathetic activity might be due to increased focus or increased tidal volume

The Breathing Diabetic Summary

Several studies have shown the positive effects of slow, controlled breathing.  For example, Oneda et al. (2010) showed that slow breathing reduced blood pressure, heart rate, and sympathetic activity in hypertensive patients.  A study published in Nature showed that slow breathing increased autonomic function, arterial function, and blood oxygen saturation in type 1 diabetics.

However, in most studies looking at controlled breathing, the breathing rate is controlled and reduced.  The current study examined the role of the “controlled” part.  That is, are the benefits due to controlling respiration or slowing it down?

To do this, they had participants breathe both spontaneously and at a controlled pace of 12 breaths/min.  A rate of 12 breaths/min was chosen because it is a “typical” breathing rate given in most physiological textbooks.

They found that the controlled breathing lowered sympathetic activity, but it did not lower blood pressure.  Thus, this relatively “fast” pace compared to other studies (typically 6 breaths/min) still lowered sympathetic activity.

Interestingly, several patients actually had a slower spontaneous breathing rate (~5-9 breaths/min) than the controlled pace.  But, even in these patients, their sympathetic activity was lowered when they switched to the controlled pace.  This suggests that there is a “meditative/focus” aspect of controlling your breath that relaxes you and lowers sympathetic activity.

Overall, this study shows that simply controlling your breathing rate can lower sympathetic activity.  Therefore, if you are not yet able to drop into the 4-6 breaths/min range (which is usually suggested), there are still benefits to using an app to control your breathing rate at a pace that is comfortable to you. 

Abstract

Controlled or paced breathing is often used as a stress reduction technique but the impact on blood pressure (BP) and sympathetic outflow have not been consistently reported. The purpose of this study was to determine whether a controlled breathing (12 breaths/min, CB) rate would be similar to an individual’s spontaneous breathing (SB) rate. Secondly, would a CB rate of 12 breaths/min alter heart rate (HR), BP, and indices of muscle sympathetic nerve activity (MSNA). Twenty-one subjects (10 women, 11 men) performed two trials: SB, where the subject chose a comfortable breathing rate; and CB, where the subject breathed at a pace of 12 breaths/min. Each trial was 6 min during which respiratory waveforms, HR, BP (systolic, SBP; diastolic, DBP), and MSNA were recorded. During CB, the 6 min average breathing frequency (14±4 vs 12±1 breaths/min, P<0.05 for SB and CB, respectively), MSNA burst frequency (18±12 vs 14±10 bursts/min, P<0.01) and MSNA burst incidence (28±19 vs 21± 6 bursts/100 heart beats, P<0.01) were significantly lower than during SB. HR (66±9 vs 67±9 beats/min, P<0.05) was higher during CB. SBP (120±13 vs 121±15 mmHg, P=0.741), DBP (56±8 vs 57±9 mmHg, P=0.768), and MSNA total activity (166± 94 vs 145±102 a.u./min, P=0.145) were not different between the breathing conditions. In conclusion, an acute reduction in\ breathing frequency such as that observed during CB elicited a decrease in indices of MSNA (burst frequency and incidence) with no change in BP.

Journal Reference:

McClain SL, Brooks AM, Jarvis SS. An acute bout of a controlled breathing frequency lowers sympathetic neural outflow but not blood pressure in healthy normotensive subjects. Int J Exerc Sci. 2017;10(2):188-196.

Breathing center in brain has powerful effects on higher-order brain functions

Key Points

• The breathing center in the brain has a powerful effect on higher-order brain functions

• Slow and regular breathing promotes calmness, where as rapid breathing promotes arousal

The Breathing Diabetic Summary

Anytime a study gets featured in Science, we know it’s time to sit up straight and read closely.  This paper is no exception.   

The first observation they made was that slower breathing was associated with calm behaviors, whereas faster breathing was associated with active behaviors. This sounds obvious, but it gets interesting.

They found that if they removed a certain cluster of brain neurons (Cdh9/Dbxl preBotC), they were able to turn off this active mode, and subsequently promote slow breathing and calm behaviors.  Thus, they isolated the exact cluster of brain neurons that promote an active, aroused state. Interestingly, these neurons are also controlled by breathing.  What’s more, the authors showed that these “breathing neurons” are a gateway to the rest of the brain, helping explain how slow breathing is able to calm you down.

What does this mean for us?  Essentially, their results show that we can calm ourselves by breathing slow, or excite ourselves by breathing fast, something we probably already knew by now.  However, they are showing the exact set of neurons controlling this process and showing that these neurons give the breath “direct access” to higher-order brain function.  That’s pretty amazing and definitely Science worthy.

Abstract

Slow, controlled breathing has been used for centuries to promote mental calming, and it is used clinically to suppress excessive arousal such as panic attacks. However, the physiological and neural basis of the relationship between breathing and higher-order brain activity is unknown.We found a neuronal subpopulation in the mouse preBötzinger complex (preBötC), the primary breathing rhythm generator, which regulates the balance between calm and arousal behaviors. Conditional, bilateral genetic ablation of the ~175 Cdh9/Dbx1 double-positive preBötC neurons in adult mice left breathing intact but increased calm behaviors and decreased time in aroused states. These neurons project to, synapse on, and positively regulate noradrenergic neurons in the locus coeruleus, a brain center implicated in attention, arousal, and panic that projects throughout the brain.

Journal Reference:

Yackle K, Schwarz LA, Kam K, Sorokin JM, Huguenard JR, Feldman JL, Luo L, Krasnow MA. Breathing control center neurons that promote arousal in mice. Science. 2017;355(6332):1411-1415.