Slow breathing reduces chemoreflex response to hypoxia and hypercapnia, and increases baroreflex sensitivity.
OBJECTIVE
To investigate whether breathing more slowly modifies the sensitivity of the chemoreflex and baroreflex.


METHODS
University of Pavia, IRCCS Policlinico S. Matteo.


METHODS
Fifteen healthy individuals.


METHODS
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.).


METHODS
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.
Bernardi
L
L
Department of Internal Medicine, University of Pavia and IRCCS Ospedale S. Matteo, Pavia, Italy. lbern1ps@unipv.it
Gabutti
A
A
Porta
C
C
Spicuzza
L
L
D000328:Adult; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure; D002628:Chemoreceptor Cells / Q000503:physiopathology*; D005260:Female; D006339:Heart Rate; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology*; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D012018:Reflex / Q000502:physiology*; D012119:Respiration; D013997:Time Factors