A preliminary study on the influence of obstructive sleep apnea upon cumulative parasympathetic system activity

Changes in the heart rate variability in patients with obstructive sleep apnea and its response to acute CPAP treatment

Introduction

Obstructive Sleep Apnea (OSA) is a major risk factor for cardiovascular disease. The goal of this study was to demonstrate whether the use of CPAP produces significant changes in the heart rate or in the heart rate variability of patients with OSA in the first night of treatment and whether gender and obesity play a role in these differences.

Methods

Single-center transversal study including patients with severe OSA corrected with CPAP. Only patients with total correction after CPAP were included. Patients underwent two sleep studies on consecutive nights: the first night a basal study, and the second with CPAP. We also analyzed the heart rate changes and their relationship with CPAP treatment, sleep stages, sex and body mass index. Twenty-minute segments of the ECG were selected from the sleep periods of REM, no-REM and awake. Heart rate (HR) and heart rate variability (HRV) were studied by comparing the R-R interval in the different conditions. We also compared samples from the basal study and CPAP nights.

Results

39 patients (15 females, 24 males) were studied. The mean age was 50.67 years old, the mean AHI was 48.54, and mean body mass index was 33.41 kg/m² (31.83 males, 35.95 females). Our results showed that HRV (SDNN) decreased after the use of CPAP during the first night of treatment, especially in non-REM sleep. Gender and obesity did not have any influence on our results.

Conclusions

These findings support that cardiac variability improves as an acute effect, independently of gender or weight, in the first night of CPAP use in severe OSA patients, supporting the idea of continuous use and emphasizing that noncompliance of CPAP treatment should be avoided even if it is just once.

Autonomic cardiovascular tests in children with obstructive sleep apnea syndrome

STUDY OBJECTIVES

The aim of our study was to investigate cardiovascular autonomic activity during wakefulness, using cardiovascular tests, in a population of children with OSAS.

DESIGN

Prospective study.

SETTING

Sleep unit of an academic center.

PARTICIPANTS

We included 25 children (mean age 10.2 +/- 2.3 years) undergoing a diagnostic assessment for OSAS, and 25 age-matched healthy control subjects. All subjects underwent an overnight polysomnography and autonomic cardiovascular tests using parts of the Ewing test battery, which is a physiological test used for the assessment of autonomic function (head-up tilt test, Valsalva maneuver, deep breathing test).

MEASUREMENTS AND RESULTS

Eighteen of 25 children with OSAS (11 males, mean age 9.4 +/- 1.7 years) concluded the study. OSAS patients had higher systolic blood pressure, diastolic blood pressure, baseline heart rate, the 30:15 index (which represents the RR interval at the 15th and 30th beats during the head up tilt test), and delta diastolic and systolic blood pressure during the head-up tilt test, while the heart rate variability during the deep breathing test was lower, compared with controls. A positive correlation between systolic and diastolic blood pressure and the apnea-hypopnea index (AHI), and negative between AHI and both the 30:15 index and Valsalva ratio, were found. Stepwise linear regression analysis detected a negative correlation between AHI and the 30:15 index and Valsalva ratio, a positive correlation between overnight mean oxygen saturation and delta heart rate, and between AHI and delta systolic blood pressure.

CONCLUSIONS

Our data point to an increase in basal sympathetic activity during wakefulness and to an impaired reaction to several physiological stimuli, which is dependent on the severity of OSAS.

The autonomic nervous system and ischemic stroke: a reciprocal interdependence

Signs and symptoms of autonomic nervous system (ANS) dysfunction are frequently reported after ischemic or haemorrhagic stroke and in many cases they exhibit peculiar patterns in relationship with the site and the extension of brain lesion. However if an ANS disorder can cause or predispose to a stroke is far from being correctly known. Evidences in favor of a pathogenetic mechanism of an ANS dysfunction are reported for myocardial infarction and such data are likely to be appropriate also for atherothrombotic type of ischemic stroke. On the other hand, it is well known that many risk factors for this pathology are strongly correlated with an altered functioning of ANS so that a reciprocal interdependence between ANS and stroke can be hypothesized. This review points to evidence the possible relationship existing between these two conditions and suggests a quite different diagnostic and therapeutic approach to both on the basis of their pathogenetic mechanisms.