Cardiorespiratory effects of breathing and relaxation in myocardial infarction patients - van Dixhoorn (1998)

Key Points

  • Breathing and relaxation reduce heart rate, reduce breathing rate, and increase respiratory sinus arrhythmia in patients who have suffered a heart attack

  • These positive improvements might be the results of improved autonomic cardiac balance

  • Breathing and relaxation, combined with an exercise program, are beneficial for rehabilitation in heart attack patients

The Breathing Diabetic Summary

I am always on the lookout for ways to improve autonomic function and balance.  Thus, even when papers are not directly related to diabetes, they are often extremely applicable to us.  In this case, this study looks at the rehabilitation program of patients who have suffered a heart attack.  Because autonomic imbalance plays a big role in heart disease, the goals of rehabilitation are often similar to what we seek as diabetics: improved cardiac autonomic balance.

The study included 39 patients in an experiment group and 37 in a control group, all of whom were rehabilitating from heart attack.  Both groups were prescribed an exercise program as part of their rehabilitation (30 minutes of cycling every day).  The experiment group was also taught relaxation and breathing exercises.  The relaxation protocol involved actively flexing and passively relaxing muscles.  The breathing protocol had two different exercises.  The first was to breathe through pursed lips to make each breath audible.  The second was to incorporate a body movement into the breathing movements, for example, flexing the foot while exhaling.  They took measurements of the patients before rehabilitation, after 5 weeks of rehabilitation, and then at a 3-month follow-up.  

Overall, the patients found the relaxation/breathing intervention fairly easy to implement, with 41% of patients using it successfully, 44% partially successfully, and the rest unsuccessfully.  Moreover, almost 80% of the patients reported practicing it every day.

From this practice, the results showed that patients lowered their natural breathing rate (~2 breaths/min less).  Both groups lowered their heart rate, but adding relaxation/breathing onto the exercise program reduced heart rate even more.  In addition, the resting heart rate of the breathing/relaxation group was significantly lower at the 3-month follow-up when compared to the exercise group.  Lastly, the respiratory sinus arrhythmia (RSA) of the experiment group was significantly larger than that of the control group at the 3-month follow-up.  This final result is perhaps unsurprising since RSA is a measure of how heart rate varies synergistically with breathing.

Although they could not make conclusive statements on the causes of these improvements, the authors suspect that the patients were eliciting the “relaxation response” more frequently and thus increasing parasympathetic activity and decreasing sympathetic activity.  The overall effect would be improved cardiac autonomic balance.  This hypothesis is supported by the study of Joseph et al. (2005), which found that 2 minutes of slow breathing could restore autonomic and respiratory balance.

Overall, this study found that regular practice of relaxation and breathing could lower heart rate, lower breathing rate, and increase respiratory sinus arrhythmia in patients rehabilitating from a heart attack. The authors suspect that these positive results are due to an improvement in cardiac autonomic balance, which clearly would benefit us as diabetics.

Abstract from Paper

The effect of individual instruction in relaxation and breathing, additional to an exercise training program, was investigated in 76 post-myocardial infarction patients after rehabilitation and at 3 months follow-up. Respiration rate (RR), heart rate (HR) and respiratory sinus arrhythmia (RSA) were the outcome variables used to compare experimental (exercise plus relaxation) and control (exercise without relaxation) groups. HR and RR decreased slightly during 20-min sessions of supine measurement. This response did not vary between sessions (pre-rehabilitation, post-rehabilitation and after 3-month follow-up). RSA tended to decrease during the sessions. The within-session reduction in RSA became more apparent in the control group after treatment and less so in the experimental group. RR decreased in the experimental group after rehabilitation, but not in the control group. HR decreased for all patients, but the decrease was larger in the experimental group. This effect was associated with the lower RR. RSA did not change in the control group but increased in the experimental group, during both normal and deep breathing. This effect was also associated with a slower RR and became marginally significant when RR was statistically controlled for. We conclude that the relaxation intervention induced a slower breathing pattern which was associated with beneficial effects on resting HR and RSA. Further study is warranted to clarify the degree to which reduced respiration rate is an indicator of lower sympathetic arousal or merely a concomitant of the learned breathing technique.

Journal Reference:

van Dixhoorn, J., (1998) Cardiorespiratory effects of breathing and relaxation in myocardial infarction patients, Biological Psychology, 49(1-2), 123 – 135.