Short-term oxygen administration restores blunted baroreflex sensitivity

Short-term oxygen administration restores blunted baroreflex sensitivity in patients with type 1 diabetes - Bernardi et al. (2011)

Key Points

Slow breathing at 6 breaths/min improves autonomic function in type 1 diabetics
Oxygen administration (hyperoxia) also improves autonomic function and to a similar degree as slow breathing
Tissue hypoxia likely plays a key role in abnormal autonomic function in type 1 diabetics

The Breathing Diabetic Summary

We have seen baroreflex sensitivity (BRS) in several studies now. BRS quantifies the body’s ability to keep blood pressure nearly constant under varying conditions. Importantly, BRS is an indicator of overall autonomic function. And, BRS is generally lower in diabetics than in non-diabetics.

The aim of this study was to see how two different protocols, slow breathing and hyperoxia, affected BRS. They studied type 1 diabetics (n=96) and control subjects without diabetes (n=40). Participants were instructed to lie down and breathe naturally for 5 minutes, which then was followed by 2 minutes of reduced breathing at 6 breaths/min. The procedure was then repeated while patients inhaled 100% oxygen at a flow rate of 5 liters/min (hyperoxia).

At baseline, the BRS of the diabetics was significantly lower than the control subjects, which was expected. Remarkably, by breathing slowly (for 2 minutes!) the BRS of the diabetics increased to values similar to the control subjects. The hyperoxia protocol also increased BRS to levels similar to those of the controls. Thus, slow breathing and hyperoxia were both able to quickly improve a key indicator of overall autonomic function in type 1 diabetics.

Both slow breathing and oxygen administration both significantly improved BRS, and they both also increased blood oxygen saturation. This potentially indicates that the source of the diabetics’ autonomic dysfunction is pre-existing tissue hypoxia. Moreover, if chronic tissue hypoxia is present, it will activate the sympathetic nervous system. Thus, the positive results in autonomic function seen here might be due to a combination of improved tissue oxygenation and activation of the parasympathetic nervous system during both slow breathing and hyperoxia.

Overall, this study indicates that by simply breathing slowly diabetics can improve BRS, a key indicator of overall autonomic function, to levels indistinguishable form controls. Further, slow breathing and hyperoxia elicit a similar response and lead to similar improvements in autonomic function. However, we can breathe slowly anytime, without any equipment, making it a simple and practical way to improve autonomic function today. Let’s start practicing Principle 1 (even if only for 2 minutes!) to reverse or avoid autonomic dysfunction associated with diabetes.

Abstract from Paper

Aims/hypothesis We hypothesised that the blunted baroreflex sensitivity (BRS) typical of type 1 diabetes is caused by a higher degree of tissue hypoxia in diabetes, and tested whether oxygen increased BRS and ventilation less, equally or more than in healthy control participants (the latter suggesting higher tissue hypoxia). In addition, we also considered the possible interference between oxygen and breathing pattern.

Methods In 96 participants with type 1 diabetes and 40 agematched healthy controls, we measured BRS (average of six different standard methods), oxygen saturation, end-tidal carbon dioxide and ventilation changes during spontaneous and controlled breathing at 15 and six breaths/min, in normoxia and during 5 l/min oxygen administration.

Results BRS was blunted and blood pressure higher in diabetic participants during spontaneous breathing (p<0.05). BRS increased with oxygen during spontaneous breathing in diabetic (p<0.001) but not in control participants, and with oxygen the difference in BRS was no longer significant. Slow breathing in normoxia restored BRS to a similar extent to giving oxygen. Oxygen increased systolic and diastolic blood pressure, RR interval, heart rate variability, minute ventilation and tidal volume to a greater extent in diabetic patients than in controls, and decreased carbon dioxide similarly to controls.

Conclusions/interpretation The increased response to hyperoxia suggests a pre-existing condition of tissue hypoxia that functionally restrains parasympathetic activity in patients with type 1 diabetes. Autonomic abnormalities can be partially and temporarily reversed by functional manoeuvres such as slow breathing or oxygen administration through enhancement of parasympathetic activity and/ or correction of tissue hypoxia.

Journal Reference:

L. Bernardi, M. Rosengård-Bärlund, A. Sandelin, V. P. Mäkinen, C. Forsblom, and P.-H. Groop, (2011) Short-term oxygen administration restores blunted baroreflex sensitivity in patients with type 1 diabetes, Diabetologia, 54, 2164–2173, DOI 10.1007/s00125-011-2195-4.