Salt sensitivity of blood pressure is accompanied by slow respiratory rate: results of a clinical feeding study

Sleep-disordered breathing has been implicated in hypertension, but whether daytime breathing is a factor in blood pressure (BP) regulation has not been investigated to date. The present study sought to determine the role of breathing pattern in salt sensitivity of BP. Thirty-six women, ages 40 to 70, were placed on a 6-day low-sodium/low-potassium diet followed by a 6-day high-sodium/low-potassium diet. Breathing pattern at rest and 24-hour ambulatory BP were monitored at baseline and after each 6-day diet period. Respiratory rate (but not tidal volume or minute ventilation) was an inverse predictor of systolic (r = -0.50; P < .001) and diastolic (r = -0.59; P < .001) blood pressure sensitivity to high sodium intake. Respiratory rate was positively associated with hemoglobin (r = + 0.38; P < .01), and the salt-induced change in hemoglobin was associated with salt-induced change in BP (r = -0.35; P < .05). These findings indicate that a pattern of slow breathing not compensated by increased tidal volume is associated with salt sensitivity of BP in women. Breathing patterns could play a role in the hypertensive response via sustained effects on blood gases and acid-base balance, and/or be a marker for other biological factors mediating the cardiovascular response to dietary salt intake. (C) 2007 American Society of Hypertension. All rights reserved.