Abstract
BackgroundHigh normal resting pCO2 is a risk factor for salt sensitivity of blood pressure (BP) in normotensive humans and has been associated with higher resting systolic BP in postmenopausal women. To date, however, no known studies have investigated the effects of regular practice of voluntary mild hypocapnic breathing on BP in hypertensive patients. The objective of the present research was to test the hypothesis that capnometric feedback training can decrease both resting pCO2 and 24-h BP in a series of mildly hypertensive postmenopausal women.MethodsA small portable end tidal CO2 (etCO2) monitor was constructed and equipped with software that determined the difference between the momentary etCO2 and a pre-programmed criterion range. The monitor enabled auditory feedback for variations in CO2 outside the criterion range. 16 mildly hypertensive postmenopausal women were individually trained to sustain small decreases in etCO2 during six weekly sessions in the clinic and daily sessions at home. 24-h BP monitoring was conducted before and after the intervention, and in 16 prehypertensive postmenopausal women in a control group who did not engage in the capnometric training.ResultsFollowing the intervention, all 16 capnometric training participants showed decreases in resting etCO2 (− 4.3 ± 0.4 mmHg; p < .01) while 15 showed decreases in 24-h systolic BP (− 7.6 ± 2.0 mmHg; p < .01). No significant changes in either measure was observed in the control group. In addition, nighttime (− 9.5 ± 2.6; p < .01) and daytime (− 6.7 ± 0.2 mmHg) systolic BP were both decreased following capnometric training, while no significant changes in nighttime (− 2.8 ± 2.2 mmHg; p = .11) or daytime (− 0.7 ± 1.0 mmHg; p ≤ .247) systolic BP were observed in the control group.ConclusionsThese findings support the hypothesis that regular practice of mild hypocapnic breathing that decreases resting etCO2 reliably decreases 24-h blood pressure in hypertensive postmenopausal women. The extent to which these effects persist beyond the training period or can be observed in other hypertensive subgroups remains to be investigated.
Highlights
Primary hypertension is chronically elevated blood pressure (BP) of unknown origin
Baseline demographics and physiological measures for the intervention and control groups Table 1 shows that baseline means of age, body mass index, body surface area, resting etCO2, resting breathing rate, 24-h diastolic pressure and 24-h heart rate for the capnometric training group and the control group were not significantly different
This study found that 6 weeks of regular practice of hypocapnic breathing reliably decreased 24-h systolic BP in postmenopausal hypertensive women
Summary
Primary hypertension is chronically elevated blood pressure (BP) of unknown origin. It is the most common cardiovascular disorder, and a major risk factor for stroke and coronary heart disease [1]. Clinically oriented studies addressed the blood pressure (BP) effects of a slowed breathing rate that decreases SNS activity. Preliminary successes were reported in several studies which showed that breathing interventions could decrease resting BP (reviewed by Shi et al [7] and Park et al [8]). None of these studies reported decreases in 24-h BP, leading some to conclude that the era of breathing interventions in hypertension was over [9]. The objective of the present research was to test the hypothesis that capnometric feedback training can decrease both resting pCO2 and 24-h BP in a series of mildly hypertensive postmenopausal women
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