How Breathing Regulates the Cardiovascular System and Improves Chemosensitivity

Key Points

• Breathing modulates the cardiovascular system through respiratory sinus arrhythmia

• Slow breathing reduces chemosensitivity to high carbon dioxide and low oxygen

• Controlled breathing could be a beneficial intervention in different pathological states

The Breathing Diabetic Summary

How does breathing affect us physiologically?  Well, the answer to that is complex.  Breathing is felt by various receptors throughout the body, affecting cardiovascular and autonomic variability on many levels. This review study examined these different modulatory effects of breathing through a comprehensive analysis of the peer-reviewed literature.

Breathing and the Cardiovascular System

The cardiovascular system is sensitive to external stimuli. Just picture something scary (like giving a presentation), and your heart rate will likely increase. Consequently, your breathing will also change to match your metabolic needs.

But this is a two-way street. Controlled, rather than reactive, breathing also has profound impacts on the cardiovascular system. This can be temporary, for example, breathing rapidly for one minute, or permanent, for example, developing the behavior/habit of chronic over-breathing.

Knowing that breathing has "direct access" to the cardiovascular system, let's look at how this occurs and how controlled breathing might be beneficial in different pathological states.

Respiratory Sinus Arrhythmia

One way in which breathing permeates the cardiovascular system is through respiratory sinus arrhythmia (RSA). RSA is a measurement of how breathing, heart rate, and blood pressure all interact. In simple terms, RSA refers to the increase in heart rate as you inhale and decrease in your heart rate as you exhale. RSA is thought to be an index of vagal activity and direct measurement of heart rate variability.  

When we breathe so that the length of our inhale matches seamlessly with our heart rate increase and our exhale with our heart rate decrease, we maximize RSA. Typically, this occurs when breathing at around 6 breaths per minute. This coherence among respiration and heart rate leads to the maximization of heart rate variability, improving cardiovascular efficiency.

Breathing and Chemoreflexes

Slow breathing can reduce breathlessness and improve exercise performance in patients with chronic heart failure. These results suggest that slow breathing could be modifying the chemoreflexes, allowing one to tolerate higher concentrations of carbon dioxide and lower concentrations of oxygen.

To test this hypothesis, a study was conducted with yoga trainees and non-yoga trained participants. Both groups performed different breathing protocols to test their response to high carbon dioxide (hypercapnia) and low oxygen (hypoxia). Although none of these participants had heart problems, the goal was to see if slow breathing could reduce chemoreflexes in the controls to the levels seen in yoga practitioners.

As we might expect, the chemoreflexes of the yoga practitioners at baseline were much lower than the non-trained participants.  This means their breathing did not increase as much when exposed to hypercapnia or hypoxia. Interestingly, the chemoreflexes of the controls decreased to levels similar to the yogis when breathing at 6 breaths per minute.  Therefore, the simple act of slow breathing reduced chemosensitivity to carbon dioxide and hypoxia, regardless of previous training.

These results indicate that breathing could represent another way to better coordinate the breathing muscles, improve chemoreflexes, and improve exercise performance in patients with cardiovascular problems. Slow breathing could, therefore, be a practical alternative when other rehabilitation programs are not available.

Breathing Modulates Cardiovascular and Autonomic Control

To summarize, breathing is a potent modulator of cardiovascular and autonomic systems.  Deliberate practice of different breathing patterns (for example, slow breathing) could be beneficial for increasing heart rate variability, improving breathing efficiency, improving chemosensitivity, and enhancing cardio-autonomic control.

Abstract

Respiration is a powerful modulator of heart rate variability, and of baro- and chemoreflex sensitivity. Abnormal respiratory modulation of heart rate is often an early sign of autonomic dysfunction in a number of diseases. In addition, increase in venous return due to respiration may help in maintaining blood pressure during standing in critical situations. This review examines the possibility that manipulation of breathing pattern may provide beneficial effects in terms not only of ventilatory efficiency, but also of cardiovascular and respiratory control in physiologic and pathologic conditions, such as chronic heart failure. This opens a new area of future research in the better management of patients with cardiovascular autonomic dysfunction.

Journal Reference:

L Bernardi, C Porta, A Gabutti, L Spicuzza, P Sleight.  Modulatory Effects of Respiration.  Auton Neurosci. 2001;90(1-2):47-56. doi: 10.1016/S1566-0702(01)00267-3.

Meta-Analysis: Slow Breathing Reduces Systolic Blood Pressure by 5.62 mmHg

Key Points

• Diabetics are at an increased risk of hypertension and its negative cardiovascular outcomes

• Slow breathing reduces systolic blood pressure by 5.62 mmHg and diastolic blood pressure by 2.67 mmHg

• Slow breathing is a simple way to reduce blood pressure and potentially improve cardiovascular outcomes

The Breathing Diabetic Summary

Hypertension is a significant risk factor for cardiovascular disease, which is the leading cause of death in the U.S. For instance, if systolic blood pressure rises from 115 mmHg to 135 mmHg, your risk of cardiovascular disease doubles.

People with diabetes are also much more likely to develop hypertension. Anywhere from 40 to 80% of diabetics have hypertension, a somewhat somber statistic. Moreover, I am writing this in April 2020 during the COVID-19 pandemic. Studies are revealing that hypertension is correlated with more severe complications.

All of this is to say that reducing blood pressure is more important than ever. There are several medications and lifestyle changes available; however, compliance with these approaches are often low. Therefore, alternative therapies are needed. One such treatment is slow breathing.

Slow Breathing and Hypertension

Slow breathing has consistently been shown to reduce blood pressure. In particular, a device called RESPeRATE (which is FDA approved), which slowly reduces breathing rate down to below ten breaths per minute, has been examined extensively. The American Heart Association has even given device-guided slow breathing a “class IIA” rating for reducing blood pressure.  

This meta-analysis provides a concise yet comprehensive summary of studies that have examined slow breathing and hypertension. Their strict search criteria and thorough review of the available randomized controlled trials (RCTs) make this the most robust meta-analysis of slow breathing and blood pressure published to date. 

Study Inclusion and Strict Search Criteria

The authors searched several public databases (e.g., Web of Science, MEDLINE) since their inception until mid-2015. They used a combination of search terms like “hypertension OR prehypertension” and “slow breathing OR device-guided breathing” to identify papers relevant to the meta-analysis.

In the identified papers, slow breathing was defined as anything below ten breaths per minute. The subjects had to perform slow breathing at least three times a week for at least 5 minutes each session. They included studies of people with both hypertension and prehypertension. The follow-up period had to be at least 4 weeks and changes in blood pressure had to be reported. They excluded studies of healthy subjects without baseline hypertension or prehypertension

Selecting Relevant Studies and Publication Bias

The authors started with 1,984 studies, but only 17 met their criteria for inclusion in the meta-analysis. Although meta-analyses are some of my favorites, there are caveats that we need to mention for this one.

Of the 17 studies selected, five were abstracts only. Additionally, only two had slow breathing without a device. The other fifteen were device-guided slow breathing using the RESPeRATE, and the maker of the device sponsored six of these. Thus, there was a high risk of publication bias with these studies.

Slow Breathing Significantly Reduces Blood Pressure

Despite these limitations, the collective results were impressive. The average decrease in systolic blood pressure (SBP) across all seventeen studies was 5.62 mmHg. The two non-device slow breathing studies had an even more significant drop of 7.69 mmHg. For diastolic blood pressure, the mean decrease was 2.67 mmHg for the device-guided slow breathing.  

Longer Practice Leads to Better Results

They also examined how the intensity of the slow breathing practice affected results—the conclusion: the longer subjects practiced, the greater their reduction in blood pressure. For example, for slow breathing <100 min a week, the decrease in SBP was 3.01 mmHg, for 100-200 min, it was 6.44 mmHg, and for >200 min, it was 14.00 mmHg.  

Reduced Blood Pressure Reduces Risk of Death

The significance of these findings is that modest reductions in blood pressure lower the chances of strokes, coronary events, heart failure, cardiovascular deaths, and total deaths. This is especially important for diabetics who are at higher risk of developing hypertension and heart disease.

Moreover, the improvements from slow breathing were similar to those seen with antihypertensive medications. Those medications have been shown to improve long-term outcomes in hypertensive and prehypertensive patients. Therefore, slow breathing could potentially provide similar positive results if practiced consistently over a long period.

Slow Breathing is Free and Has No Side Effects

Finally, slow breathing is free, easy to perform, and does not have any side effects. Moreover, the blood-pressure-lowering effects of slow breathing are far-reaching. For example, slow breathing helps with stress, anxiety, and depression, all of which will also help reduce blood pressure.

A Recap of the Main Points 

In summary, slow breathing reduces systolic blood pressure by 5.62 mmHg and diastolic blood pressure by 2.67 mmHg. The more time you practice per week, the greater the blood pressure reductions.  Slow breathing also lowers blood pressure by helping with anxiety, stress, and depression. And by lowering your blood pressure, you reduce the risk of many cardiovascular problems, like stroke or heart disease.

To begin, try breathing at six breaths per minute (4 sec inhale, 6 sec exhale) for five minutes a day and see how you feel. 

Abstract

OBJECTIVES: Interest is increasing in nonpharmacological interventions to treat blood pressure in hypertensive and prehypertensive patients at low cardiac risk. This meta-analysis of randomized controlled trials assesses the impact of device-guided and non-device-guided (pranayama) slow breathing on blood pressure reduction in these patient populations.

METHODS: We searched PubMed, EMBASE, CINAHL, Cochrane CENTRAL, Cochrane Database of Systematic Reviews, Web of Science, BIOSIS (Biological Abstracts) Citation Index and Alt HealthWatch for studies meeting these inclusion criteria: randomized controlled trial or first phase of a randomized cross-over study; subjects with hypertension, prehypertension or on antihypertensive medication; intervention consisting of slow breathing at ≤10 breaths/minute for ≥5 min on ≥3 days/week; total intervention duration of ≥4 weeks; follow-up for ≥4 weeks; and a control group. Data were extracted by two authors independently, the Cochrane Risk of Bias Tool assessed bias risk, and data were pooled using the DerSimonian and Laird random effects model. Main outcomes included changes in systolic (SBP) and/or diastolic blood pressure (DBP), heart rate (HR), and/or decreased antihypertensive medication.

RESULTS: Of 103 citations eligible for full-text review, 17 studies were included in the meta-analysis. Overall, slow breathing decreased SBP by -5.62 mmHg [-7.86, -3.38] and DBP by -2.97 mmHg [-4.28, -1.66]. Heterogeneity was high for all analyses.

CONCLUSIONS: Slow breathing showed a modest reduction in blood pressure. It may be a reasonable first treatment for low-risk hypertensive and prehypertensive patients who are reluctant to start medication.

Journal Reference:

Chaddha A, Modaff D, Hooper-Lane C, Feldstein DA.  Device and non-device-guided slow breathing to reduce blood pressure: A systematic review and meta-analysis.  Complement Ther Med. 2019;45:179-184. doi: 10.1016/j.ctim.2019.03.005.

Slow Breathing at Six Breaths per Minute Improves Baroreflex Sensitivity and Reduces Blood Pressure

Key Points

• Slow breathing improves baroreflex sensitivity, reduces blood pressure, and potentially reduces chemosensitivity

• Slow breathing with ujjayi is not as effective as slow breathing alone in untrained practitioners

• Choose an inhale-to-exhale ratio that is comfortable for you when practicing slow breathing

The Breathing Diabetic Summary

Slow breathing at around 6 breaths/min improves cardiovascular and autonomic functioning. For example, it increases baroreflex sensitivity (BRS), which measures your heart’s ability to adjust your blood pressure in response to changing conditions. Slow breathing also increases parasympathetic tone, leading to better autonomic balance. This study assessed two additional aspects of slow breathing.

First, it evaluated the added effect of “ujjayi” breathing. Ujjayi breathing involves tightening of the throat during the inhale or exhale to make an ocean sound (check out the Wiki article for a simple explanation). It can be somewhat challenging to learn, but many trained yogis use it exclusively during their yoga practice. 

Second, this study examined how the ratio of inhale to exhale affected cardiovascular and autonomic outcomes. Extended exhales are regularly practiced for relaxation. For example, you perform a 4 sec inhale and 8 sec exhale. However, an equal ratio has also been proven to enhance heart rate variability (for example, 5 sec inhale, 5 sec exhale). Here, they assessed these different ratios to help establish the best approach for beginners to slow breathing.

Study Details

The study had seventeen participants. Measurements were taken in the supine position while the subjects breathed spontaneously for three minutes. Then, they performed the following breathing protocols: 

• Controlled breathing at 15 breaths/min 

• Controlled breathing at 6 breaths/min with 5 sec inhale and exhale

• Controlled breathing at 6 breaths/min with 3 sec inhale and 7 sec exhale

• Both 6 breaths/min protocols, but with ujjayi.  

The order of the slow breathing was selected randomly for each subject, and there was a two-minute break between each protocol.

Slow Breathing without Ujjayi is More Effective for BRS

The results showed that all of the slow breathing techniques improved BRS. However, there was no added benefit of ujjayi and it actually worsened BRS slightly when compared to slow breathing alone. 

Slow Breathing Reduces Blood Pressure

Interestingly, slow breathing increased heart rate, except when practiced with an equal inhale/exhale.  However, slow breathing reduced diastolic and systolic blood pressures. The decrease was most significant when an equivalent inhale/exhale was used. Again, slow breathing alone outperformed ujjayi.

Slow Breathing & Chemosensitivity

Lastly, they found that slow breathing decreased chemosensitivity. However, the measurement of chemosensitivity was heuristic: it was defined as the tidal volume divided by inhale time. That is, if your tidal volume increased for a given inhale time, that would indicate an increased chemosensitivity (because you are taking a bigger breath over the same inhale time).

Conversely, they also measured end-tidal CO2, and these results showed that all versions of slow breathing significantly reduced CO2 compared to spontaneous breathing. People often overcompensate for the slow breathing rate with bigger breaths, which appears to have happened here. Consistent training or biofeedback can reduce this over-breathing.

In any case, although they concluded that slow breathing reduced chemosensitivity, the significantly decreased end-tidal CO2 does not support this finding in my opinion.

Breathe at a Ratio that is Comfortable to You

To summarize, this study found that slow breathing increased BRS and reduced blood pressure. It also reduced their measure of chemosensitivity.  Although using an equal inhale to exhale ratio showed slightly better results, they suggest that “practitioners can engage in a ratio that is personally comfortable and achieve the same BRS benefit.” 

Interestingly, ujjayi worsened the results when compared to slow breathing alone. They hypothesize that the extra effort needed for ujjayi dampened the parasympathetic response. These results would likely be different in seasoned ujjayi practitioners. 

Therefore, we can conclude that slow breathing at a rate of 6 breaths/min improves cardiovascular and autonomic function. The best way to begin is to choose a ratio that is comfortable for you.

Abstract

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.

Journal Reference:

Mason H, Vandoni M, Debarbieri G, Codrons E, Ugargol V, Bernardi L. Cardiovascular and Respiratory Effect of Yogic Slow Breathing in the Yoga Beginner: What is the Best Approach?  Evid Based Complement Alternat Med. 2013;2013:743504. doi: 10.1155/2013/743504.

Nasal Airflow Activates Broad Regions of the Olfactory Bulb

Key Points

• Nasal breathing information is “encoded” by olfactory sensory neurons in the olfactory bulb

• Breathing activates broad regions of the olfactory bulb, with the intensity changing as total breathing volume changes

• The neural activity stimulated by nasal breathing helps explain how breathing can have immediate physiological effects throughout the body

The Breathing Diabetic Summary

The olfactory bulb (OB) and its neurons (olfactory sensory neurons, OSNs) can sense both odors and airflow.  However, previous studies have rarely examined how airflow is actually encoded by the OB and OSNs.  This study used fMRI and local field potential to figure out how airflow activity is mapped in the OB. 

They studied mice under different airflow stimulation (these can be thought of as different breathing patterns because the mechanical stimulation was occurring through their noses).  The different breathing paradigms included changing respiratory rate, changing tidal volume, or changing both rate and tidal volume while keeping the total airflow the same (that is, keeping Rate X Volume = Constant). 

The results showed that airflow stimulation activated broad regions of the OB.  Odor stimulation, on the other hand, had more localized activity maps.  Furthermore, the overall structure of the activity maps was similar regardless of which breathing paradigm was being studied.  Only the intensity of the signal changed with total airflow.  Greater total volume led to more intense activity in the OB. 

Another interesting result was that nasal airflow affected the physiological state of the mice.  Their resting heart and breathing rates slowed, and EEG power declined in specific ranges. 

These results are important because they show for the first time that nasal breathing information is encoded in the olfactory bulb.  We know that breathing can directly influence emotional state, for example, providing a calming effect.  And, there have been several studies showing a direct correlation between breathing, brain activity, memory, and behavior.  Here, we see why.   

Nasal breathing information is imprinted in the OB.  The OB then projects onto the limbic system, which regulates emotions, olfaction, and the autonomic nervous system.  This helps explain the wide-ranging benefits of slow breathing and how breathing can have such immediate effects on our physiological state.

To summarize, this is the first study to show that nasal airflow elicits broad activity maps in the olfactory bulb.  The patterns are robust and change only in intensity when total airflow is altered.  The effects of nasal respiration on the olfactory bulb are then projected on the limbic system, helping explain how breathing can quickly impact physiological state.

Abstract

Olfactory sensory neurons (OSNs) can sense both odorants and airflows. In the olfactory bulb (OB), the coding of odor information has been well studied, but the coding of mechanical stimulation is rarely investigated. Unlike odor-sensing functions of OSNs, the airflow-sensing functions of OSNs are also largely unknown. Here, the activity patterns elicited by mechanical airflow in male rat OBs were mapped using fMRI and correlated with local field potential recordings. In an attempt to reveal possible functions of airflow sensing, the relationship between airflow patterns and physiological parameters was also examined. We found the following: (1) the activity pattern in the OB evoked by airflow in the nasal cavity was more broadly distributed than patterns evoked by odors; (2) the pattern intensity increases with total airflow, while the pattern topography with total airflow remains almost unchanged; and (3) the heart rate, spontaneous respiratory rate, and electroencephalograph power in the β band decreased with regular mechanical airflow in the nasal cavity. The mapping results provide evidence that the signals elicited by mechanical airflow in OSNs are transmitted to the OB, and that the OB has the potential to code and process mechanical information. Our functional data indicate that airflow rhythm in the olfactory system can regulate the physiological and brain states, providing an explanation for the effects of breath control in meditation, yoga, and Taoism practices.

SIGNIFICANCE STATEMENT Presentation of odor information in the olfactory bulb has been well studied, but studies about breathing features are rare. Here, using blood oxygen level-dependent functional MRI for the first time in such an investigation, we explored the global activity patterns in the rat olfactory bulb elicited by airflow in the nasal cavity. We found that the activity pattern elicited by airflow is broadly distributed, with increasing pattern intensity and similar topography under increasing total airflow. Further, heart rate, spontaneous respiratory rate in the lung, and electroencephalograph power in the β band decreased with regular airflow in the nasal cavity. Our study provides further understanding of the airflow map in the olfactory bulb in vivo, and evidence for the possible mechanosensitivity functions of olfactory sensory neurons.

Journal Reference:

Wu R, Liu Y, Wang L, Li B, Xu F.  Activity patterns elicited by airflow in the olfactory bulb and their possible functions.  J Neurosci. 2017;37(44):10700-10711. doi: 10.1523/JNEUROSCI.2210-17.2017.

Yoga breathing program significantly reduces PTSD in Australian Vietnam veterans

Key Points

• A 6-month yoga-breathing program (SKY) significantly reduced PTSD as assessed by the CAPS score

• Yoga breathing could be a valuable complementary therapy for the treatment of PTSD

The Breathing Diabetic Summary

It is estimated that ~7-8% of the U.S. population will have post-traumatic stress disorder (PTSD) at some point in their life.  And it is not just limited to military and first responders.  PTSD can happen to anyone who experiences a traumatic event. 

Even with the universal awareness of PTSD and its negative side effects, conventional treatments are often insufficient, and many patients remain chronically ill. 

However, before we review this research, I don’t want anyone to have the impression that breathing will cure PTSD.  What we’re looking for is a complementary therapy that can be integrated as part of a complete treatment plan to aid in healing.

This study chose the Sudarshan Kriya Yoga (SKY) program as that complementary therapy.  Their version of the SKY program involved slow and fast breathing, mobility exercises, and group therapy sessions.  The researchers also incorporated warrior values to make it more appealing to veterans. 

They studied 25 male Vietnam veterans from Australia.  The subjects participated in a 22-hour SKY training course spread out over 5 days.  After that, they met once a week for one month, and then once a month for the following 5 months.  The entire program lasted 6 months.  The subjects were encouraged to practice yoga breathing for 30 minutes a day on their own time, but there was no record of their compliance.  No changes were made to their medication throughout the study.

Their breathing protocol started with Ujjayi breathing (ocean breathing) with a 4 sec inhale, 4 sec hold, 6 sec exhale, 2 sec hold.  After that, they performed 20 fast breaths at 50-60 breaths/min and then rested for 30 seconds before starting over.  They did not give the exact times for each breathing practice, but it looks like they completed this cycle several times over 30 minutes. 

In any case, because there were several therapeutic components to the SKY program, we cannot isolate breathing alone for any changes observed.

The researchers made several assessments of PTSD, but the one they focused on most was the CAPS score.  The Clinician Administered PTSD Scale is a 30-question interview to assess PTSD severity.   The average CAPS score at the beginning of the study was 56.3.  At week 6, the average scores had significantly fallen down to 42.1.  Finally, at the end of the 6 months, the average scores had dropped to 26.2.

An interesting result was that the effect size (ES) of the difference in baseline CAPS scores and 6-month CAPS scores ranged from 0.88 to 2.9.  Anything above 0.8 is considered a “large” effect.  Most antidepressant trials achieve an ES of around 0.5.  

Overall, the SKY program significantly reduced PTSD severity as measured by the CAPS score.  Because yoga breathing techniques are simple and have almost no side effects, the authors suggest that they could easily be incorporated into the military health care system and serve as a valuable complementary therapy for treating PTSD.

Abstract

Objective: It is appropriate to acknowledge that despite treatment, Post Traumatic Stress Disorder (PTSD) continually debilitates many Vietnam veterans. Although therapies have been developed, remission is hard to obtain with either pharmacotherapy or psychotherapy. Evidence has suggested that some forms of yoga may reduce sympathetic overactivity and increase parasympathetic activity, thereby improving stress resilience. Sudarshan Kriya Yoga (SKY) was hypothesized in this study to be potentially useful for lessening symptom severity on the Clinician Administered PTSD Scale (CAPS) in Vietnam veterans with treatment-resistant PTSD. Method: Fifty male Vietnam veterans with PTSD (DSM-IV) were referred to the study. Thirty-one participants meeting criteria were subsequently randomized to either the SKY Intervention (adapted for veterans) group or a 6-week wait-list Control. The intervention consisted of 22 hours of guided group yoga instruction over a duration of 5 days, followed by a 2-hour group session which following 5 months. Severity of PTSD symptoms was assessed at pre-intervention, 6-week post-intervention, and 6-month follow-up for both groups using the CAPS. Additional questionnaires to measure PTSD, depression, quality of life, and alcohol consumption were administered at pre-intervention, post-intervention and follow-up time frames as well. Results: completed the study, of which 14 received immediate intervention while 11 constituted the Control group. The Intervention group intervention completion, while the Control group had zero decline within this period. At this point, the Control group received the SKY improvements were maintained in both groups 6 months following receipt of treatment. The results indicate that multi-component interventions with yoga breath techniques may offer a valuable adjunctive treatment for veterans with PTSD.

Journal Reference:

Carter JJ, Gerbarg PL, Brown RP et al.  Multi-Component Yoga Breath Program for Vietnam Veteran Post Traumatic Stress Disorder: Randomized Controlled Trial.  J Trauma Stress Disor Treat.  2013;2(3).  doi:http://dx.doi.org/10.4172/2324-8947.1000108.

How slow breathing improves physiological and psychological well-being (hint: it might be in your nose)

Key Points

• Slow breathing increases heart rate variability, respiratory sinus arrhythmia, and alpha brain wave activity

• These physiological changes lead to improved behavioral outcomes

• The nose links slow breathing to these positive physiological and psychological outcomes

The Breathing Diabetic Summary

I think this paper wins “Best Title Ever” award!

This was a review study that pulled together all of the scientific literature on slow breathing and psychological/behavioral outcomes.  They were trying to answer the following question: What physiological changes are common to all slow breathing studies that have shown improvements in stress and anxiety?

After using some rather rigorous criteria for their literature search, they reduced 158 potential papers down to only 15. 

The physiological outcome parameters they focused on were heart rate variability (HRV), respiratory sinus arrhythmia (RSA), and brain wave activity.  The studies they examined also used several different subjective questionnaires to assess stress, anxiety, depression, and well-being.

As it is with science, there was a lot of nuance and many contradictory findings.  However, several common results did emerge.

First, slow breathing was associated with increases in HRV, particularly in the low frequency (LF) band.  Second, it was associated with increases in RSA.  Finally, slow breathing was associated with increases in alpha brain wave activity (brain waves associated with “flow”) and decreases in theta brain wave activity. 

All of these common physiological changes observed during/after slow breathing were associated with improved psychological and behavioral outcomes.  For example, several studies showed reductions in anxiety, improvements with depression, reduced anger, and increased relaxation.

Thus, slow breathing consistently increases HRV, RSA, and alpha brain wave activity.  These physiological changes then improve psychological and behavioral outcomes.

From a practical perspective, all of the studies used breathing rates of 3-6 breaths/min.  With practice, we can use an app (such as Breathing Zone) to achieve these rates.

Lastly, they examined the importance of the nose.  They reviewed studies showing that nasal breathing has a direct relationship with brain activity, which goes away when the nasal cavity tissue is numbed.  Moreover, certain areas of the brain follow oscillations that match breathing…but only with nasal respiration.  In fact, simply puffing air into the nostrils activates the brain at those “puff” oscillations (independent of actually breathing).

The authors hypothesize that the nose is the link between slow breathing, brain and autonomic functioning, and positive emotional outcomes.

From all of this, we find that slow breathing through the nose at 3-6 breaths/min (Principle 1) has positive effects on HRV, RSA, and brain wave activity.  These benefits then lead to improved psychological and behavioral outcomes.

Abstract

Background: The psycho-physiological changes in brain-body interaction observed in most of meditative and relaxing practices rely on voluntary slowing down of breath frequency. However, the identification of mechanisms linking breath control to its psychophysiological effects is still under debate. This systematic review is aimed at unveiling psychophysiological mechanisms underlying slow breathing techniques (<10 breaths/minute) and their effects on healthy subjects. Methods: A systematic search of MEDLINE and SCOPUS databases, using keywords related to both breathing techniques and to their psychophysiological outcomes, focusing on cardio-respiratory and central nervous system, has been conducted. From a pool of 2,461 abstracts only 15 articles met eligibility criteria and were included in the review. The present systematic review follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Results: The main effects of slow breathing techniques cover autonomic and central nervous systems activities as well as the psychological status. Slow breathing techniques promote autonomic changes increasing Heart Rate Variability and Respiratory Sinus Arrhythmia paralleled by Central Nervous System (CNS) activity modifications. EEG studies show an increase in alpha and a decrease in theta power. Anatomically, the only available fMRI study highlights increased activity in cortical (e.g., prefrontal, motor, and parietal cortices) and subcortical (e.g., pons, thalamus, sub-parabrachial nucleus, periaqueductal gray, and hypothalamus) structures. Psychological/behavioral outputs related to the abovementioned changes are increased comfort, relaxation, pleasantness, vigor and alertness, and reduced symptoms of arousal, anxiety, depression, anger, and confusion. Conclusions: Slow breathing techniques act enhancing autonomic, cerebral and psychological flexibility in a scenario of mutual interactions: we found evidence of links between parasympathetic activity (increased HRV and LF power), CNS activities (increased EEG alpha power and decreased EEG theta power) related to emotional control and psychological well-being in healthy subjects. Our hypothesis considers two different mechanisms for explaining psychophysiological changes induced by voluntary control of slow breathing: one is related to a voluntary regulation of internal bodily states (enteroception), the other is associated to the role of mechanoceptors within the nasal vault in translating slow breathing in a modulation of olfactory bulb activity, which in turn tunes the activity of the entire cortical mantle.

Journal Reference:

Zaccaro A, Piarulli A, Laurino M, et al.  How Breath-Control Can Change Your Life: A Systematic Review on Psycho Physiological Correlates of Slow Breathing.  Front Hum Neurosci.  2018;12:353.

Diaphragmatic breathing improves subjective and physiological indicators of anxiety

Key Points

• Diaphragmatic breathing reduces anxiety as measured on the Beck Anxiety Inventory

• Diaphragmatic breathing reduces physiological indicators of anxiety, including breathing rate, heart rate, and skin conductance

The Breathing Diabetic Summary

We’ve all been told to just “take a deep breath.”  As I’ve argued before, that’s not always the best advice.  However, it might not be the worst advice either.

We know that controlling your breath improves autonomic balance and improves several markers of cardiovascular function.  This paper wanted to examine the effects of diaphragmatic breathing on both subjective and physiological indicators of anxiety.

To do this, they studied 30 patients with mild-to-moderate anxiety.  The participants were broken up into a control (n=15) group and diaphragmatic breathing relaxation (DBR; n=15) group.

The DBR group was given instruction on diaphragmatic breathing over an 8-week period.  They also were instructed to practice DBR twice daily, completing 10 breaths with each practice.

(Here is my only qualm with this paper. They did not describe exactly what the DBR technique was.  They just said that the patients received DBR training and were instructed to practice at home and during training sessions with the investigators.  Therefore, we cannot replicate their DBR exercise for ourselves.)

After the 8-week program, the participants in the DBR group significantly reduced their anxiety on the Beck Anxiety Inventory (BAI), a standardized questionnaire used to assess anxiety.  Their average scores dropped from ~19 down to ~5 (lower is better).

Moreover, physiological indicators of anxiety also reduced in the DBR group.  For example, heart rate, breathing rate, and skin conductivity all decreased, indicating reductions in anxiety.

Overall, these results indicate that diaphragmatic breathing improves anxiety from both subjective and physiological perspectives.  That is, it works.  Thus, we can use deep breathing anytime we (or our clients or friends) feel overwhelmed and know that we are changing our physiology to promote a more relaxed state.

Abstract from Paper

PURPOSE: To evaluate the effectiveness on reducing anxiety of a diaphragmatic breathing relaxation (DBR) training program.

DESIGN AND METHODS: This experimental, pre-test-post-test randomized controlled trial with repeated measures collected data using the Beck Anxiety Inventory and biofeedback tests for skin conductivity, peripheral blood flow, heart rate, and breathing rate.

FINDINGS: The experimental group achieved significant reductions in Beck Anxiety Inventory scores (p < .05), peripheral temperature (p = .026), heart rate (p = .005), and breathing rate (p = .004) over the 8-week training period. The experimental group further achieved a significant reduction in breathing rate (p < .001).

PRACTICE IMPLICATIONS: The findings provide guidance for providing quality care that effectively reduces the anxiety level of care recipients in clinical and community settings.

Journal Reference:

Chen YF, Huang XY, Chien CH, Cheng JF. The effectiveness of diaphragmatic breathing relaxation training for reducing anxiety. Perspect Psychiatr Care. 2017;53(4):329-336.

Treat & reverse the root cause of diabetic complications (tissue hypoxia) with slow breathing

Key Points

• Type-1 diabetics exhibit lower resting oxygen saturation, lower cardiovascular control, reduced hypoxic chemoreflexes, and enhanced hypercapnic chemoreflexes

• The root cause of these problems is resting tissue hypoxia, which causes over-activation of the sympathetic nervous system and autonomic and cardiovascular dysfunction

• Autonomic imbalance in diabetes is largely functional, and therefore reversible

The Breathing Diabetic Summary

This is a follow-on to our previous paper on cardio-respiratory control in diabetes.  This paper, however, is a clinical study rather than a literature review.

Previous studies have shown respiratory problems in diabetics.  Previous studies also have shown cardiovascular dysfunction in diabetics.  However, no studies simultaneously examined both of these factors in an integrated fashion.  Thus, the aim of this study was to comprehensively examine cardio-respiratory function in type-1 diabetics.

The key measurements from this paper were resting oxygen saturation, baroreflex sensitivity (BRS; a marker of cardiovascular and autonomic control), and both hypoxic and hypercapnic chemoreflexes (markers of respiratory control). 

Their hypothesis: If the BRS and chemoreflexes were suppressed in diabetics, this would indicate nerve damage was present.  However, if cardiovascular function was suppressed, while chemoreflexes were enhanced, this would indicate autonomic imbalance that has a functional cause.  In this latter case, therapies aimed at restoring cardio-respiratory control (for example, slow breathing) could help prevent diabetic complications.

The study had 46 patients with type-1 diabetes and 103 age-matched control subjects.  The participants went through a variety of tests to evaluate baroreflex functioning and chemoreflexes.  For example, to measure the patients’ hypercapnic chemoreflex, oxygen was kept constant while CO2 was gradually increased.  The chemoreflex can then be measured as the slope of the relationship between minute ventilation and change in CO2 (or oxygen in the case of the hypoxic chemoreflex).  A large change in minute ventilation for a small change in CO2 would represent an enhanced hypercapnic chemoreflex.

Interestingly, the results showed that although diabetics displayed larger breathing volumes than controls, they had slightly higher CO2 levels and reduced oxygen saturation.  However, they did have an enhanced hypercapnic chemoreflex, meaning they could not tolerate changes in CO2 as well as controls.  And, somewhat surprisingly, they had a reduced hypoxic chemoreflex, meaning they could tolerate lower oxygen levels without increasing their breathing as much as controls.

The diabetics also exhibited a lower resting oxygen saturation. This is fascinating because the lower resting oxygen saturation implies a significantly reduced partial pressure of oxygen (due to the oxyhemoglobin dissociation curve). This would result in tissue hypoxia. What’s more, they cite a paper (which is now near the top of my reading list) that shows that a high HbA1c also reduces tissue oxygenation by increasing oxygen’s affinity to hemoglobin (shifting the dissociation curve to the left). 

The authors suggest that their results can be interpreted as follows: Resting tissue hypoxia, combined with a suppressed hypoxic chemoreflex, leads to an enhanced compensatory hypercapnic chemoreflex and chronic activation of the sympathetic nervous system.  This, in turn, leads to a suppression of the cardiovascular system (reduced BRS and reduced heart rate variability).  It’s a vicious cycle.

However, this is actually great news.  Their results suggest that diabetic autonomic imbalance is largely functional and not related to nerve damage.  (Remember, both the cardiovascular reflexes and the chemoreflexes would have been suppressed with nerve damage).  In fact, the authors suggest that this imbalance likely leads to nerve damage rather than being the result of it. Therefore, therapies targeting cardio-respiratory control could help reverse/prevent diabetic complications.

Finally, the authors suggest that breathing control and physical exercise could be two such therapies to restore cardio-respiratory function.  We know that slow breathing has many therapeutic benefits for the cardiovascular, autonomic, and respiratory systems.  And, we know that slow, light breathing increases CO2 and increases tissue oxygenation (due to the Bohr effect).  Now, we know that these positive benefits have the potential to stop or reverse diabetic complications. 

Abstract from Paper

BACKGROUND: Cardiovascular (baroreflex) and respiratory (chemoreflex) control mechanisms were studied separately in diabetes, but their reciprocal interaction (well known for diseases like heart failure) had never been comprehensively assessed. We hypothesized that prevalent autonomic neuropathy would depress both reflexes, whereas prevalent autonomic imbalance through sympathetic activation would depress the baroreflex but enhance the chemoreflexes.

METHODS: In 46 type-1 diabetic subjects (7.0±0.9year duration) and 103 age-matched controls we measured the baroreflex (average of 7 methods), and the chemoreflexes, (hypercapnic: ventilation/carbon dioxide slope during hyperoxic progressive hypercapnia; hypoxic: ventilation/oxygen saturation slope during normocapnic progressive hypoxia). Autonomic dysfunction was evaluated by cardiovascular reflex tests.

RESULTS: Resting oxygen saturation and baroreflex sensitivity were reduced in the diabetic group, whereas the hypercapnic chemoreflex was significantly increased in the entire diabetic group. Despite lower oxygen saturation the hypoxic chemoreflex showed a trend toward a depression in the diabetic group.

CONCLUSION: Cardio-respiratory control imbalance is a common finding in early type 1 diabetes. A reduced sensitivity to hypoxia seems a primary factor leading to reflex sympathetic activation (enhanced hypercapnic chemoreflex and baroreflex depression), hence suggesting a functional origin of cardio-respiratory control imbalance in initial diabetes.

Journal Reference:

Bianchi L, Porta C, Rinaldi A, Gazzaruso C, Fratino P, DeCata P, Protti P, Paltro R, Bernardi L. Integrated cardiovascular/respiratory control in type 1 diabetes evidences functional imbalance: Possible role of hypoxia. Int J Cardiol. 2017;244:254 – 259.

Slow breathing improves blood sugar by reducing body’s endogenous production of glucose

Key Points

• Slow breathing lowers blood sugar by reducing the liver’s production of glucose

• Slow breathing increases insulin sensitivity

• Slow breathing might be a no-cost beneficial intervention for diabetics

Breathing Blueprint Summary

This is a follow on to the previous Wilson et al. (2013) paper that described how a relaxation breathing exercise improved glycemic response in healthy college-aged humans.  In this review, the authors examine key evidence showing that breathing can potentially improve glycemic response and insulin sensitivity.  

Let’s start with some statistics. Can you believe that in 2013, ~9.3% of Americans had diabetes?!?  That’s insane.  And, pharmacy costs added up to ~$18 billion!  Breathing might not cure diabetes, but it might help reduce the costs and negative side effects of diabetics by improving our insulin sensitivity and glycemic control. Which is exactly what this paper examined.

One mechanism they found that explains why slow, relaxation breathing lowers blood sugar is reduction in sympathetic nervous system activity.  In short, the liver generates glucose via a process called gluconeogenesis.  When the sympathetic nervous system is activated, it increases this process, increasing the body’s endogenous production of glucose.  Other stress hormones, such as adrenaline, also increase the liver’s production of glucose.  By breathing slowly, we shift out of this sympathetic state, reducing the amount of glucose produced by the liver and helping reduce our blood sugar.

They also examined several studies showing that slow breathing can restore insulin sensitivity.  There were no clear mechanisms as to how slow breathing improved insulin sensitivity, but the take-home point was that it does. We will have to wait on future studies to identify exactly what’s going on “under the hood.”

Overall, this review showed scientific evidence that breathing exercises can improve glycemic control and increase insulin sensitivity.  The glucose-lowering effect of slow breathing is likely due to reduced sympathetic activity and reduced glucose production by the liver.  The improved insulin sensitivity might also be related to this, but the precise mechanism is unknown.

In any case, I think it’s safe to say that practicing Principle 1 and Principle 2 is a good idea, especially for diabetics, to improve glycemic control and insulin sensitivity.

Abstract from Paper

This is the first review of the literature on the effects of slow breathing on glycemic regulation and insulin sensitivity. While many studies have investigated the effects of yoga on individuals with diabetes, few studies have specifically focusing on the isolation of slow breathing as the principle factor in their intervention. While it is difficult to separate the exercise-related effects of yoga, there is considerable evidence that a breathing intervention is capable of increasing insulin sensitivity and improving glycemic regulation. This appears to be true both acutely and chronically in healthy individuals and those with diabetes. Yoga pranayama and the slow breathing practices that are fundamental to yoga represent a relatively low-cost and under-utilized intervention for individuals with conditions related to altered glycemic regulation and insulin sensitivity. More studies should focus on pranayama and slow breathing maneuvers to better clarify the role of respiratory modulation on glucose metabolism and insulin response.

Journal Reference:

Wilson T, Kelly KL, Baker SE. Review: Can yoga breathing exercises improve glycemic response and insulin sensitivity?. J Yoga Phys Ther. 2017;7(2). DOI: 10.4172/2157-7595.1000270.

Breathe slowly (and pause) to improve heart rate variability

Key Points

• Slow breathing at ~6 breaths/min increases heart rate variability (HRV)

• Including a post-exhalation pause enhances relaxation and makes it easier to breathe slowly

• A post-exhalation pause also enhances some HRV parameters more than continuous breathing

The Breathing Diabetic Summary

We don’t want our hearts to beat like a metronome, but to constantly be changing and adapting to the current conditions.  One way to measure this is through heart rate variability (HRV), which represents the changes in time between heartbeats.  HRV is a marker of overall health: Higher HRV is associated with better health. 

Many studies have shown that slow breathing can increase HRV.  Depending on the individual, it appears that breathing at a pace between 4 and 6 breaths/min maximizes HRV.  However, there are many ways to achieve a breathing rate of 4-6 breaths/min. 

For example, you can inhale for 5 sec, and exhale for 5 sec.  Inhale for 4 sec, exhale for 6 sec, etc.  But, these different methods might not necessarily be the best way to maximize HRV.  The current study set out to see if including a post-exhalation pause would increase HRV compared to continuous breathing with equal inhales and exhales.

Specifically, they tested two different methods for breathing at 5.5 breaths/min: 5-5 and 4-2-4.  The 5-5 protocol used a 5 sec inhale and 5 sec exhale.  The 4-2-4 protocol used a 4 sec inhale, 2 sec exhale, and 4 sec post-exhalation pause. 

Forty subjects performed the breathing protocols in a seated upright position.  They performed each breathing protocol for 6 min, followed by a 5 min rest period before starting the next one.  Along with measuring several different HRV parameters, the authors also evaluated which breathing protocol the subjects found more relaxing and easier to perform.

68% of the participants found the 4-2-4 cycle easier to follow and 63% found it more relaxing.  The authors suspect that this is a result of the shorter inhalation period, which caused less strain on the breathing muscles.  They also suspect that the post-exhalation rest period reduced the risk of hyperventilation.

There is no one single measurement for HRV.  There are high and low frequency bands, along with other parameters such as the standard deviation of the NN intervals.  In this study, they found that the 4-2-4 cycle significantly improved one aspect of HRV (high-frequency HRV), whereas the 5-5 cycle improved another (low-frequency HRV).  Thus, although the title of the paper suggests that the rest period is critical, it is important to note that both breathing protocols improved HRV in different ways.

Overall, this study shows that you can improve HRV by slowing down your breath.  Whether you adopt a post-exhalation rest or simply do slow continuous breathing is up to you. Either way, you can rest assurred you will be improving this critical indicator of overall health.

Let’s wrap up with a quote from the end of the paper that is one of my new favorites:

“With breathing interventions being relatively rapid interventions to implement and also demonstrating a wide range of positive clinical outcomes, breathing interventions warrant closer consideration from healthcare professionals.”

Abstract from Paper

Heart rate variability (HRV) is associated with positive physiological and psychological effects. HRV is affected by breathing parameters, yet debate remains regarding the best breathing interventions for strengthening HRV. The objective of the current study was to test whether the inclusion of a postexhalation rest period was effective at increasing HRV, while controlling for breathing rate. A within-subject crossover design was used with 40 participants who were assigned randomly to a breathing pattern including a postexhalation rest period or a breathing pattern that omitted the postexhalation rest period. Participants completed training on each breathing pattern, practiced for 6 min, and sat quietly during a 5-min washout period between practices. Participants were given instructions for diaphragmatic breathing at a pace of six breaths/minute with or without a postexhalation rest period. Recordings of heart rate, breathing rate, HF-HRV, RMSSD, LF-HRV, and SDNN were collected before and during each of the breathing trials. HRV indices were derived from Lead 1 ECG recordings. Pairwise contrasts showed that inclusion of a postexhalation rest period significantly decreased heart rate (p<.001) and increased HF-HRV (p<.05). No differences were found for breathing rates (p>.05), RMSSD (p>.05), and SDNN (p>.05). Results indicated that omission of the postexhalation rest period resulted in higher LF-HRV (p<.05). A postexhalation rest period improves HF-HRV, commonly associated with self-regulatory control, yet the importance of a postexhalation rest period requires further exploration.

Journal Reference:

Russell MEB, Scott AB, Boggero IA, Carlson CR. Inclusion of a rest period in diaphragmatic breathing increases high frequency heart rate variability: Implications for behavioral therapy. Psychophysiology, 2017;54:358 – 365.

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.

Slow breathing improves autonomic function in type 1 diabetics

Key Points

• Slow breathing increased autonomic function, arterial function, and blood oxygen saturation in type 1 diabetic patients

• Slow breathing stimulates the parasympathetic nervous system and suppresses the sympathetic nervous system, providing an antioxidant effect

• “Slow breathing could be a simple beneficial intervention in diabetes.”

Breathing Blueprint Summary

The last key point above, taken directly from the abstract, says it all. This paper was published in Nature, one of the most prestigious scientific journals around, and they are highlighting the usefulness of slow breathing for diabetes and autonomic function in general.  Pretty awesome.

Diabetics suffer from an enhanced risk for cardiovascular disease, which is associated with autonomic dysfunction.  However, slow breathing has been shown to restore autonomic balance, suggesting that it might be applicable in type 1 diabetes.

Participants in the study performed 5 minutes of spontaneous breathing, followed by 2 minutes of slow breathing at 6 breaths/min.  That is a very short amount of time, yet they still got fairly remarkable results. 

During spontaneous breathing, diabetics had worse baseline data than controls.  For example, diabetics had a lower resting blood oxygen saturation and higher blood pressure.  The main marker of autonomic function that they measured was the baroreflex sensitivity (BRS). BRS measures your body’s ability to quickly adjust your blood pressure to match the current circumstances.  At baseline, the diabetics’ had a lower BRS score.

However, after just 2 minutes of slow breathing, their BRS increased to values similar to those of the controls during spontaneous breathing.  The authors believe this occurred due to a reduction in sympathetic nervous system activity and an increase in parasympathetic activity.

They also provide evidence that this shift in autonomic activity has a direct antioxidant effect.  Because diabetics (and really anyone with a chronic disease) suffer from excess oxidative stress and free radicals, this aspect of slow breathing is extremely important for improving our overall health and well-being.

Lastly, slow breathing also improved the arterial function and blood oxygen saturation of the diabetics. The authors suspect the improvements in oxygen saturation were due to improved ventilation perfusion (i.e., better matching of air and blood flow in the lungs). 

In summary, with only 2 minutes of slow breathing, type 1 diabetics were able to improve autonomic function, enhance antioxidant capacity, and improve blood oxygen saturation. These results provide practical evidence that slow breathing can improve the overall health of diabetics.

Abstract from Paper

Hyperoxia and slow breathing acutely improve autonomic function in type-1 diabetes. However, their effects on arterial function may reveal different mechanisms, perhaps potentially useful. To test the effects of oxygen and slow breathing we measured arterial function (augmentation index, pulse wave velocity), baroreflex sensitivity (BRS) and oxygen saturation (SAT), during spontaneous and slow breathing (6 breaths/min), in normoxia and hyperoxia (5 L/min oxygen) in 91 type-1 diabetic and 40 age-matched control participants. During normoxic spontaneous breathing diabetic subjects had lower BRS and SAT, and worse arterial function. Hyperoxia and slow breathing increased BRS and SAT. Hyperoxia increased blood pressure and worsened arterial function. Slow breathing improved arterial function and diastolic blood pressure. Combined administration prevented the hyperoxia-induced arterial pressure and function worsening. Control subjects showed a similar pattern, but with lesser or no statistical significance. Oxygen-driven autonomic improvement could depend on transient arterial stiffening and hypertension (well-known irritative effect of free-radicals on endothelium), inducing reflex increase in BRS. Slow breathing-induced improvement in BRS may result from improved SAT, reduced sympathetic activity and improved vascular function, and/or parasympathetic-driven antioxidant effect. Lower oxidative stress could explain blunted effects in controls. Slow breathing could be a simple beneficial intervention in diabetes.

Journal Reference:

Bernardi L, Gordin D, Bordino M, Rosengård-Bärlund M, Sandelin A, Forsblom C, Per-Henrik Groop PR. Oxygen-induced impairment in arterial function is corrected by slow breathing in patients with type 1 diabetes. Sci Rep. 2017;7:6001. DOI:10.1038/s41598-017-04947-4.