Effect of slow breathing training for a month on blood pressure and heart rate variability in healthy subjects

A Review of:
Nagarjahan, Swarnalatha (2014). Effect of slow breathing training for a month on blood pressure and heart rate variability in healthy subjects. National Journal of Physiology, Pharmacy, & Pharmacology, 4(3) 245-248.

By Anna-Leigh Powell

 

Research on heart rate variability can yield important findings concerning the connection between autonomic functioning and overall health. Heart Rate Variability (HRV) is considered the quantitative measure of vagal activity and vagal nerve activity is correlated with overall health (Karavidas et al., 2008). The literature shows that performing vagal nerve stimulation through surgical procedures results in an increase in HRV (Sackeim et al., 2001). However, this is an expensive and serious process so recently efforts have moved towards studying methods to increase HRV through noninvasive means. The existing study was conducted taking into account these previous findings while focusing specifically on the mechanisms behind the interaction between breathing and HRV (Nagarajan, 2014). It was hypothesized that slow and deep breathing exercises, operationalized by six breaths per minute, would produce an overall increase in HRV and decrease blood pressure.

Utilizing a between subjects design, Nagarajan recruited 8 healthy individuals for the study. Participants were matched with eight control subjects. ECG and respiration were measured before the breathing training to achieve a baseline recording. Data was recorded from a supine as well as standing position. Breathing training was conducted every day for 4 weeks for half an hour. The training was administered via audio guidance from a CD. Measurements of HRV were obtained by the standard deviation of the normal-to-normal RR intervals (SDNN) (Nagarajan, 2014).

Results showed a significant increase in HRV for the standing position from 6.63 ± 4.44 to 46.25 ± 4.20 msec (P < 0.05). It should be noted that an increase in HRV for supine position was also exhibited, however these results were not statistically significant. The mean arterial pressure also decreased significantly from 82.33 ± 3.40 to 79.17 ± 3.64 mm Hg (P < 0.05). Interestingly the mean heart rate was not affected by the training. One possible explanation for this is that 4 weeks of training was not enough time for progress to occur.

Strengths of this particular study include the assessment of body position. Understanding how biostatistics like HRV and BP can be affected by positioning is important in clinical application. Perhaps it is more efficient to measure HRV of patients when standing rather than supine. This study also demonstrated that a significant increase to HRV could occur simply from doing the exercises at home. Previous studies have generally been conducted in a lab following the determination of participant’s resonant frequency. Achieving successful results independent from a lab lends a sense of accessibility to this form of treatment.

Najarahan acknowledges that small sample size may have been a contributing factor in lack of significant results (2014). Several other possible limitations include the assumption that compliance to CD was intact. There was no mention of how specific the audio guidance was. It would be necessary to ensure that the instructions included direction on how to sit and hold one’s self. If such instructions were given, it may be advisable to include a more detailed account of the training. Ideally this could be recreated with biofeedback tools and prompts for more efficient breathing training. It is also important to note that HRV is affected by time of day. This study instructed participants to perform the 30-minute training “at their convenience”(Nagarjahan, 2014). Designating a specific time might add an extra element of control. Along similar lines, the pre-measurement and post-measurements times of day were not listed either. It would be important to ensure that the time of day was consistent during pre and post assessment

Overall this study produced valuable findings. Results support previous data that HRV is linked to cardiovascular health (Shaffer, McCraty, & Zerr, 2014). Narajahan also demonstrates that HRV is an indicator of vagal heart output, lending further support to HRV as a measure of vagal activity. Additionally, the decrease in mean arterial pressure is especially notable as it generally takes multiple means to reduce the MAP of hypertensive patients even a small amount. These findings weigh heavy in the arena of cardiovascular health but could be translated to obesity and mental health as well. Ideas for future research could include factoring in the variables of weight and heart disease; or, to conduct such training but on a clinical population to observe the relationship between mental health and HRV.

 

 

References:

Karavidas, M., Lehrer, P., Vaschillo, E., Vaschillo, B., Marin, H., Buyske, S., Malinovksy, I., Radvanski, D., Hasset, A (2008). Heart rate variability biofeedback for major depression. Biofeedback, 36(1), 18-21.

Sackeim, H., Rush, J., George, M., Marangell, L., Husain, M., Nahas, Z., Johnson, C., Seidman., Giller, C., Haines, S., Simpson., R., Goodman, R. (2001). Vagus nerve stimulation for treatment-resistant depression: efficacy, side effects, and predictors of outcome. Neuropsychopharmacology, 25(5), 713-728.

Nagarjahan, Swarnalatha (2014). Effect of slow breathing training for a month on blood pressure and heart rate variability in healthy subjects. National Journal of Physiology, Pharmacy, & Pharmacology, 4(3) 245-248.

Shaffer, F., McCraty, R., Zerr, C. (2014). A healthy heart is not a metronome: An integrative review of the heart’s anatomy and heart rate variability. Frontiers in Psychology: Psychology for Clinical Settings.

To cite this review, please use this reference: Nagarjahan, Swarnalatha (2014). Effect of slow breathing training for a month on blood pressure and heart rate variability in healthy subjects. Psychology Alert.