Exploring mechanisms of blood pressure regulation in response to device-guided and non-device-guided slow breathing: A mini review.

Background: Hypertension is a widespread disease that, if persistent, increases the risks of coronary heart disease mortality and morbidity. Slow breathing is a recommended blood pressure-lowering strategy though the mechanisms mediating its effects are unknown.

Objective: This review aims to evaluate autonomic and vascular function as potential mediators driving BP adaptive responses with slow breathing.

Methods: We searched EBSCO host, Web of Science, Cochrane Central Register of Controlled Trials, and PubMed using key words for optimized search results.

Results: Nineteen studies were included in this review (11 device-guided; 8 non-device-guided breathing). Though some studies showed increased vagally mediated components of heart rate variability during slow breathing, results from acute and long-term studies were incongruent. Increases in baroreflex sensitivity (BRS) following a single device-guided slow breathing bout were noted in normotensive and hypertensive adults. Long-term (4 weeks to 3 months) effects of slow breathing on BRS were absent. Device-guided breathing resulted in immediate reductions in muscle sympathetic nerve activity (MSNA) in normo- and hyper-tensive adults though results from long-term studies yielded inconsistent findings. Non-device-guided slow breathing posed acute and chronic effects on vascular function with reductions in arterial stiffness in adults with type I diabetes and increases in microvascular endothelial function in adults with irritable bowel syndrome. Non-device guided breathing also reduced pro-inflammatory cytokines in healthy and hypertensive adults in acute and chronic studies. No adverse effects or non-adherence to treatment were noted in these trials.

Conclusion: Device-guided slow breathing is a feasible and effective modality in improving BRS, HRV, and arterial stiffness though its long-term effects are obscure. Though less evidence exists supporting the efficacy of non-device-guided slow breathing, acute and chronic studies demonstrate improvements in vascular function and inflammatory cytokines. More studies are needed to further explore the long-term effects of slow breathing in general and non-device-guided breathing in particular.