Clinical Briefs: Hyper (-ventilation and -tension)
December 1, 2005 3 minutes read
Clinical Briefs: Hyper (-ventilation and -tension)
With Comments from Russell H. Greenfield, MD. Dr. Greenfield is Medical Director, Carolinas Integrative Health, Carolinas HealthCare System, Charlotte, NC, and Clinical Assistant Professor, School of Medicine, University of North Carolina, Chapel Hill, NC.
Source: Joseph CN, et al. Slow breathing improves arterial baroreflex sensitivity and decreases blood pressure in essential hypertension. Hypertension 2005;46: 714-718.
Goal: To determine whether breathing at a rate of 6 cycles/min decreases blood pressure in healthy and hypertensive individuals.
Design: Single intervention clinical trial.
Subjects: Subjects included adults older than age 50 years with essential hypertension (n = 20) or acting as normal controls (n = 26).
Methods: Following a brief period of acclimation to the lab, recordings and measurements were initiated (ECG, respirations as measured with inductive belts, end-tidal CO2 as determined with capnography, and blood pressure) during: 1) 5 minutes of spontaneous breathing, 2) 2 minutes of controlled breathing at 6 cycles/min, and 3) 2 minutes of controlled breathing at 15 cycles/min. Breathing was controlled using visual instructions and under continuous monitoring with the capnograph; arterial baroreflex sensitivity was measured via a reportedly accepted method of spectral analysis.
Results: In the hypertensive group, slow breathing significantly decreased both systolic (from 149.7 ± 3.7 to 141.4 ± 4 mm Hg) and diastolic (from 82.7 ± 3 to 77.8 ± 3.7 mm Hg) blood pressure with no significant impact on R-R interval. A similar reduction in systolic, but not diastolic, blood pressure was found in hypertensive subjects during controlled breathing at 15 breaths/min and was associated with a shortening of the R-R interval. Control subjects showed similar trends only for R-R interval changes. Baroreflex sensitivity was depressed in hypertensive subjects during spontaneous breathing compared with controls, but slow breathing improved baroreflex sensitivity to values similar to those of the control group during spontaneous breathing (apparent normalization). Controlled breathing at 15 breaths/min resulted in no significant change in baroreflex sensitivity. Hypertensive subjects had significantly higher resting respiratory rates and lower end-tidal CO2 values compared with controls; during slow breathing, however, there were no significant changes in end-tidal CO2 or minute volume (related to increased tidal volume).
Conclusions: People with hypertension exhibit signs of spontaneous hyperventilation. Slow, regular breathing at 6 cycles/min reduces blood pressure in hypertensive subjects in association with increased baroreflex sensitivity (vagal arm).
Study strengths: Degree of monitoring and methods employed for data collection.
Study weaknesses: Intervention was extremely limited (2 minutes duration), thus addressing only acute effects, not longstanding impact.
Of note: Slow breathing has been shown to enhance arterial baroreflex sensitivity, reduce sympathetic activity, and lessen chemoreflex activation in normal subjects as well as people with heart failure; subjects in the hypertensive group weighed significantly more than those in the control group; examinations took place during late morning hours; indirect methods were utilized to measure minute ventilation and tidal volume so as to avoid the use of a pneumotachograph, which can alter spontaneous breathing patterns; improved baroreflex sensitivity in this study was dependent upon slow breathing rate and not the regular rhythmic nature of the breath, since there was no improvement in sensitivity at a faster fixed rate (15 cycles/min); interestingly, in hypertensive subjects, controlled breathing at a rapid rate also resulted in decreased systolic blood pressure; there was no decrease in heart rate noted with slow breathing.
We knew that: Sympathetic hyper-activity and parasympathetic withdrawal may result in sustained blood pressure elevation related to changes in arterial baroreflex sensitivity, as well as chemoreflex-induced hyperventilation; impairment of the baroreflex is directly related to increased blood pressure variability, which in turn is related to an increase in end-organ dysfunction; device-guided breathing that produces slow, regular breathing appears to reduce blood pressure in hypertensive subjects; prior data suggest that slow breathing also inhibits chemoreflex activation.
Clinical import: The prevalence of hypertension remains very high, as does the rate of noncompliance with medical regimens used to treat hypertension. Given the opportunity to participate in a program to effectively lower blood pressure without medication, most hypertensive patients would jump at the chance, especially if the program is offered by their doctors. The simple act of controlled, slow breathing appears to have beneficial effects on blood pressure, at least acutely. Whether long-term effects on blood pressure can be expected with specialized training and regular use of slow breathing remains to be seen. So don't hold your breath (at least not yet ).
What to do with this article: Keep a copy of the abstract on your computer.
Greenfield RH. Hyper (-ventilation and -tension). Altern Med Alert 2005;8(12):143.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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