RCT of Effects of Device-guided Breathing on Ambulatory BP

Although drug therapies have greatly improved blood pressure (BP) control and reduction of
cardiovascular events, as many as 50% of hypertensives on drug treatment have inadequately
controlled BP due to poor adherence, insufficiently aggressive treatment, and an aversion on
the part of many patients to drug treatment. Device-guided breathing is a behavioral
intervention that guides the breathing into the 6 per minute range, inducing respiratory
sinus arrythmia (RSA), which is the natural cycle of arrythmia that occurs through the
influence of breathing on the flow of sympathetic and vagus impulses to the sinoatrial node
of the heart. It has been shown in several small trials to have substantial effects on BP
reduction, has no known side-effects, and may represent a cost-effective adjunctive
treatment for hypertension. an important consideration is that, often, behavioral
interventions are given for a brief amount of time, but are expected to have long-term
effects. This does not hold true for medication; one would not give anti-hypertensive
medication for eight weeks and expect an effect on BP several months later. The development
of behavioral interventions needs to take into account methods to sustain long-term effects.

Our aim is to conduct a randomized controlled trial (RCT) to test the efficacy of a guided
breathing intervention on ambulatory BP (ABP) in hypertensives drawn from primary care and
specialty hypertension practices, using a sample size powered to detect effects at 8 weeks
and 4-month follow-up. We also propose to study a physiological mechanism, baroreflex
sensitivity, that may mediate the effect of the intervention on BP. The design calls for
two control groups: Usual Care (UC) and a placebo condition (using a device that gives the
same type of feedback sounds as the guided breathing feedback device, but modified to pace
the breathing at approximately 13 breaths per minute, a normal resting rate.) There are two
intervention conditions using the RESPeRate device that guides the breath into the 6
breaths/minute range. In both, the initial intervention lasts eight weeks, following which
participants are further randomized to either: 1) ending the intervention; of 2) continuing
the intervention for the next 8 weeks. The main outcomes are the change in systolic and
diastolic BP (measured by Ambulatory BP monitoring) during the waking hours. Outcomes are
measured at baseline, 8 weeks, and 16 weeks