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Abstract

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.

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U. Rajendra Acharya, K. Paul Joseph, N Kannathal … (2006)

Heart rate variability (HRV) is a reliable reflection of the many physiological factors modulating the normal rhythm of the heart. In fact, they provide a powerful means of observing the interplay between the sympathetic and parasympathetic nervous systems. It shows that the structure generating the signal is not only simply linear, but also involves nonlinear contributions. Heart rate (HR) is a nonstationary signal; its variation may contain indicators of current disease, or warnings about impending cardiac diseases. The indicators may be present at all times or may occur at random-during certain intervals of the day. It is strenuous and time consuming to study and pinpoint abnormalities in voluminous data collected over several hours. Hence, HR variation analysis (instantaneous HR against time axis) has become a popular noninvasive tool for assessing the activities of the autonomic nervous system. Computer based analytical tools for in-depth study of data over daylong intervals can be very useful in diagnostics. Therefore, the HRV signal parameters, extracted and analyzed using computers, are highly useful in diagnostics. In this paper, we have discussed the various applications of HRV and different linear, frequency domain, wavelet domain, nonlinear techniques used for the analysis of the HRV.

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V Somers, M Dyken, A Mark … (1993)

The early hours of the morning after awakening are associated with an increased frequency of events such as myocardial infarction and ischemic stroke. The triggering mechanisms for these events are not clear. We investigated whether autonomic changes occurring during sleep, particularly rapid-eye-movement (REM) sleep, contribute to the initiation of such events. We measured blood pressure, heart rate, and sympathetic-nerve activity (using microneurography, which provides direct measurements of efferent sympathetic-nerve activity related to muscle blood vessels) in eight normal subjects while they were awake and while in the five stages of sleep. The mean (+/- SE) amplitude of bursts of sympathetic-nerve activity and levels of blood pressure and heart rate declined significantly (P < 0.001), from 100 +/- 9 percent, 90 +/- 4 mm Hg, and 64 +/- 2 beats per minute, respectively, during wakefulness to 41 +/- 9 percent, 80 +/- 4 mm Hg, and 59 +/- 2 beats per minute, respectively, during stage 4 of non-REM sleep. Arousal stimuli during stage 2 sleep elicited high-amplitude deflections on the electroencephalogram (called K complexes), which were frequently associated with bursts of sympathetic-nerve activity and transient increases in blood pressure. During REM sleep, sympathetic-nerve activity increased significantly (to 215 +/- 11 percent; P < 0.001) and the blood pressure and heart rate returned to levels similar to those during wakefulness. Momentary restorations of muscle tone during REM sleep (REM twitches) were associated with cessation of sympathetic-nerve discharge and surges in blood pressure. REM sleep is associated with profound sympathetic activation in normal subjects, possibly linked to changes in muscle tone. The hemodynamic and sympathetic changes during REM sleep could play a part in triggering ischemic events in patients with vascular disease.

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Risk factors for central and obstructive sleep apnea in 450 men and women with congestive heart failure.

D Sin, F. Fitzgerald, J. Parker … (1999)

In previous analyses of the occurrence of central (CSA) and obstructive sleep apnea (OSA) in patients with congestive heart failure (CHF), only men were studied and risk factors for these disorders were not well characterized. We therefore analyzed risk factors for CSA and OSA in 450 consecutive patients with CHF (382 male, 68 female) referred to our sleep laboratory. Risk factors for CSA were male gender (odds ratio [OR] 3.50; 95% confidence interval [CI], 1.39 to 8.84), atrial fibrillation (OR 4.13; 95% CI 1.53 to 11. 14), age > 60 yr (OR 2.37; 95% CI 1.35 to 4.15), and hypocapnia (PCO(2 ) 35 kg/m(2), 6.10; 95% CI 2.86 to 13.00); whereas, in women, age was the only important risk factor (OR for age > 60 yr, 6.04; 95% CI 1.75 to 20.0). We conclude that historical information, supplemented by a few simple laboratory tests may enable physicians to risk stratify CHF patients for the presence of CSA or OSA, and the need for diagnostic polysomnography for such patients. Sin DD, Fitzgerald F, Parker JD, Newton G, Floras JS, Bradley TD. Risk factors for central and obstructive sleep apnea in 450 men and women with congestive heart failure.