The effect of continuous positive airway pressure on spectral encephalogram characteristics in stroke patients with obstructive sleep apnea

Effects of severe obstructive sleep apnea on functional prognosis in the acute phase of ischemic stroke and quantitative electroencephalographic markers

OBJECTIVE

To investigate the effect of severe obstructive sleep apnea (OSA) on functional prognosis in the acute phase and quantitative electroencephalography (EEG) markers during sleep in ischemic stroke patients.

METHODS

This study included 125 mild-to-moderate acute ischemic stroke patients with OSA who underwent polysomnography (PSG) within one week of stroke onset between January 2015 and June 2020. Patients were grouped according to their apnea-hypopnea index (</≥ 30/h). Poor functional prognosis was defined as modified Rankin Scale score ≥3. The EEG recorded by PSG was extracted during different sleep stages for power spectrum analysis. The delta/alpha power ratio (DAR), (delta + theta)/(alpha + beta) ratio (the slowing ratio, TSR), and the relative power (RP) of each frequency band were calculated. Differences in clinical, PSG, and quantitative EEG characteristics were compared between the groups. Additionally, we explored predictors of poor functional prognosis.

RESULTS

Patients with severe OSA had a higher proportion of hypertension, lower relative power of high-frequency bands, and higher delta RP, TSR, and DAR (p < 0.05). Severe OSA was associated with a 3.6-fold increase in risk of poor prognosis (p < 0.05). Increased delta RP and TSR, as well as decreased alpha, beta, and sigma RP, may be independent predictors of a poor functional prognosis.

CONCLUSIONS

Severe OSA is an independent risk factor for a poor functional prognosis in patients with acute ischemic stroke, and quantitative EEG during sleep showed a significant slow wave enhancement, suggesting more severe brain dysfunction. The treatment of severe OSA may improve functional prognosis.

Electroencephalographic Activity and Cognitive Function in Middle-Aged Patients with Obstructive Sleep Apnea Before and After Continuous Positive Airway Pressure Treatment

PURPOSE

To investigate the effect of continuous positive airway pressure (CPAP) on sleep electroencephalogram (EEG) activity in patients with obstructive sleep apnea (OSA) and to examine the correlation between quantitative EEG changes and cognitive function.

PATIENTS AND METHODS

A total of 69 men and 11 women were collected with an average age of 39.61 ± 7.67 years old from among middle-aged patients who had first visits with snoring as their main complaint. All of them completed sleep questionnaires, neurocognitive tests and night polysomnography (PSG). The patients in the OSA group also completed the second night of PSG monitoring under CPAP after pressure titration. A power spectrum analysis of EEG was used, and the correlation between the frequency powers of EEG and the scores of the Epworth Sleepiness Scale (ESS), Pittsburgh Sleep Quality Index (PSQI), Mini-Mental State Examination (MMSE), and the Montreal Cognitive Assessment (MoCA) were further analyzed.

RESULTS

Compared with the control group, the delta/alpha power ratio (DAR) and the (delta + theta)/(alpha + beta) power ratio (the slowing ratio, TSR) of the OSA group before CPAP were higher (P < 0.05). The DAR and TSR of the OSA patients decreased significantly after CPAP. ESS scores were correlated with parameters such as respiratory-related microarousal index (RRMAI), apnea hypopnea index (AHI), and the average absolute power of delta, DAR and TSR (P < 0.05). The PSQI, MMSE and MoCA scores were not correlated with the average absolute power of each frequency band, DAR or TSR (P > 0.05).

CONCLUSION

Patients with OSA have greater slow frequency EEG activity during sleep than the control group. CPAP treatment reversed the slow frequency EEG activity in patients with OSA.

Obstructive Sleep Apnea Syndrome and Features of the Neurophysiological Sleep Pattern

The high prevalence of obstructive sleep apnea syndrome (OSA) causes a steady interest in this pathology. In recent years, one of the urgent problems in modern somnology is the assessment of the main mechanisms of neuronal dysfunction during the day and at night in OSA, the ideas about which, to a large extent, remain contradictory and not fully understood. One of the modern methods for assessing neuronal dysfunction during sleep is the study of the sleep microstructure, and for its assessment, the method of analysis of cyclic alternating pattern (CAP), an EEG marker of unstable sleep, is used. The cyclic alternating pattern is found both in the sleep of adults and children with various sleep disorders and, in particular, with OSAS, therefore, it is a sensitive tool for studying sleep disorders throughout life. With the elimination of night hypoxia against the background of CPAP therapy, the sleep microstructure is restored, the spectral characteristics of the EEG change, and a decrease in the number of EEG arousals after treatment leads to the restoration of daytime functioning. Understanding the role of short-term EEG activations of the brain during sleep can provide significant data on sleep functions in health and disease. Despite the improving diagnosis of sleep disorders using machine algorithms, assessing the relationship of structures and functions of the brain during sleep, neurophysiological data are not entirely clear, which requires further research. In this review, we tried to analyze the results of the main studies of the neurophysiological sleep pattern in OSA against the background of respiratory support during sleep. 

Effects of Continuous Positive Airway Pressure on Sleep EEG Characteristics in Patients with Primary Central Sleep Apnea Syndrome

This study aimed to investigate the effects of continuous positive airway pressure (CPAP) on the electroencephalographic (EEG) characteristics of patients with primary central sleep apnea syndrome (CSAS). Nine patients with primary CSAS were enrolled in this study. The raw sleep EEG data were analyzed based on two main factors: fractal dimension (FD) and zero-crossing rate of detrended FD. Additionally, conventional EEG spectral analysis in the delta, theta, alpha, and beta bands was conducted using a fast Fourier transform. The FD in patients with primary CSAS who underwent CPAP treatment was significantly decreased during nonrapid eye movement (NREM) sleep but increased during rapid eye movement (REM) sleep (p < 0.05). Regarding the EEG spectral analysis, the alpha power increased, while the delta/alpha ratio decreased during REM sleep in patients with CSAS (p < 0.05). In conclusion, CPAP treatment can reduce FD in NREM sleep and increase FD during REM sleep in patients with primary CSAS. FD may be used as a new biomarker of EEG stability and improvement in brain function after CPAP treatment for primary CSAS.