Slow breathing reduces chemoreflex response to hypoxia and hypercapnia, and increases baroreflex sensitivity.


Author: Bernardi L1, Gabutti A, Porta C, Spicuzza L

Affiliation: <sup>1</sup>Department of Internal Medicine, University of Pavia and IRCCS Ospedale S. Matteo, Pavia, Italy. lbern1ps@unipv.it
Conference/Journal: J Hypertens.
Date published: 2001 Dec
Other:
 Volume ID: 19   ,  Issue ID: 12   ,  Pages: 2221-9   ,  Word Count: 193  
    OBJECTIVE: To investigate whether breathing more slowly modifies the sensitivity of the chemoreflex and baroreflex.



DESIGN SETTING: University of Pavia, IRCCS Policlinico S. Matteo.



PARTICIPANTS: Fifteen healthy individuals.



INTERVENTIONS: Progressive isocapnic hypoxia and progressive hyperoxic hypercapnia were measured during spontaneous breathing and during a breathing rate fixed at 6 and 15 breaths per minute (b.p.m.).



MAIN OUTCOME MEASURES: Variations in chemo- and baroreflex sensitivity (by monitoring ventilation, oxygen saturation, end-tidal carbon dioxide, R-R interval and blood pressure) induced by different breathing rates.



RESULTS: Breathing at 6 b.p.m. depressed (P < 0.01) both hypoxic and hypercapnic chemoreflex responses, compared with spontaneous or 15 b.p.m. controlled breathing. Hypoxic and hypercapnic responses during spontaneous breathing correlated with baseline spontaneous breathing rate (r = -0.52 and r = +0.51, respectively; P = 0.05). Baroreflex sensitivity was greater (P < 0.05) during slow breathing at baseline and remained greater at end rebreathing.



CONCLUSIONS: Slow breathing reduces the chemoreflex response to both hypoxia and hypercapnia. Enhanced baroreflex sensitivity might be one factor inhibiting the chemoreflex during slow breathing. A slowing breathing rate may be of benefit in conditions such as chronic heart failure that are associated with inappropriate chemoreflex activation.



PMID: 11725167  DOI: 10.1097/00004872-200112000-00016