Spontanous periodic breathing is associated with sympathetic hyperreactivity and baroreceptor dysfunction in hypertension

Abstract

OBJECTIVES: Intermittent periods of hypoxemia such as during periodic breathing are associated with hypertension and increased sympathetic activity. In patients with sleep apnea syndrome, hypertension is common. Treating apnea improves hypertension and reduces sympathetic outflow. The aim of the present study was to investigate the phenomenon and mechanisms of spontaneous periodic breathing in patients with hypertension. METHOD: We examined 43 hypertensive patients with untreated hypertension without left-ventricular dysfunction, heart failure or sleep apnea syndrome. Muscle sympathetic nerve activity (MSA), heart rate (HR), blood pressure (BP) and respiration were continuously recorded at rest and during cold-pressor testing. Oxygen and a CO2-enriched gas were used to test central and peripheral chemoreceptors, respectively. Baroreceptor gain was measured using the alpha method. RESULTS: Seven out of 43 patients showed spontaneous periodic breathing while awake. No difference in MSA, HR and BP was seen between patients with and without periodic breathing at rest except the breathing pattern. However, the cold-pressor test caused a larger increase of MSA in patients with periodic breathing (203 +/-62 vs. 62 +/-8%, P < 0.0001 by ANOVA), as well as systolic (46 +/-6 vs. 25 +/-3 mmHg, P = 0.002) and diastolic BP (26 +/-5 vs. 12 +/-1 mmHg, P = 0.004, ANOVA). Baroreceptor gain was markedly higher in patients with periodic breathing. Chemoreceptor sensitivity was comparable. CONCLUSION: Spontaneous periodic breathing is relatively common in patients with hypertension and is associated with greatly enhanced responses to cold-pressor testing. We suggest increased baroreceptor gain and sympathetic outflow as a cause for the oscillatory respiration pattern via barorespiratory coupling.

Peripheral chemoreflex activation contributes to sympathetic baroreflex impairment in chronic heart failure

“…We have shown that chronic renal failure or anemia in CHF patients lead to tonic activation of peripheral chemoreceptors and subsequently to MSNA elevation [6,10]. On the basis of our results, it could be hypothesized that in these and other similar patients (CHF or hypertensive patients with Cheyne-Stokes pattern of respiration or with central sleep apnea), oxygen delivery could lead to beneficial changes in the progression of the disease or outcome [29]. Second, oxygen administration also tested the effect of chemoreflex inactivation on baroreflex sensitivity.…”

Tonic activity of carotid body chemoreceptors contributes to the increased sympathetic drive in essential hypertension

“…18 Hypertensive patient 100 % Oxygen 21 % Oxygen Tonic chemoreflex activation in hypertension M Siński et al However, in this study patients were of an advanced age and on antihypertensive medication, which may influence sympathetic activity. In the recent study by Binggeli et al, 19 the authors used hyperoxic stimuli in hypertensive subjects with and without periodic breathing, and did not find a significant reduction of MSNA in the group without periodic breathing. However, this study was not designed to test our hypothesis, was not placebo-controlled and was not a crossover design with inclusion of control normotensive patients.…”

Periodic breathing in healthy humans at exercise in hypoxia*

“…It is interesting to note that in the present study, an increase in cardiac output (as expected during exercise) exacerbated the oscillations, whereas in patients with cardiac failure, the predominant hypothesis to explain the Cheyne-Stokes breathing pattern is an increase in time delay due to low cardiac output (11,18). A phase shift between the various physiological signals involved in the control loop might contribute to the instability of the system as observed with heart rate and blood pressure, with arterial O 2 saturation, or tidal volume in normal subjects during sleep in hypoxia (3,29), or in patients with cardiac failure (4,36). The observation that exercise appears to increase ventilation oscillations suggests that whatever effect enhances oscillations is strong enough to offset the stabilizing effect of the reduced phase shift.…”