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Background: The low- to high-frequency components ratio (LF/HF) of heart rate variability reflects the balance between sympathetic and parasympathetic activity. The autonomic response in individuals with obstructive sleep apnea (OSA) may lead to sympathetic activation demonstrated by an increase in the LF/HF ratio. Studies examining autonomic function during sleep and wake in children with OSA are relatively scarce. Aim: A meta-analysis of the relevant available publications. Methods: A MEDLINE search from 2000 through 2013 at PubMed (NLM) was performed. A search for the index terms ('sleep disordered breathing' OR 'obstructive sleep apnea') AND 'heart rate' in all fields was done. Studies that included comparisons between children with and without diagnosed OSA were included into the analysis. Types of 'outcome measures' were the values of the LF/HF indices in different states of the sleep-wake cycle. Results: Four studies met the inclusion criteria. A total of 518 control children and 272 children with different degrees of OSA whose mean age ranged between 4.2 and 9.8 years were reported in the studies. Large inconsistencies concerning the effect sizes across publications were found. Meta-regression revealed a statistically significant association between calculated values of the effect sizes and the reported mean values of the apnea-hypopnea indices in the OSA groups (intercept: − 0.11826, regression coefficient: 0.01667, p = 0.048). Conclusion: Power analysis of heart rate variability in children with OSA may help to provide further information regarding neural control mechanisms that are altered in OSA. The LF/HF index may serve as an indicator of OSA severity and as a possible marker for risk stratification in children with OSA. [ABSTRACT FROM AUTHOR]

Question of the study The assessment of blood pressure, heart rate parameters, and baroreflex sensitivity is an interesting and as yet little-known field of investigation in children with obstructive sleep apnoea syndrome (OSAS). We raised the question whether children with OSAS show changes of autonomic regulation compared to healthy probands. Patients and methods Fourteen patients with OSAS aged 9.6 ± 3.6 years (range: 5-15; 11 boys, 3 girls) were compared to 29 healthy controls aged 9.5 ± 3.4 years (range: 5 17; 20 boys, 9 girls) with negative polysomnographic findings. Continuous beat-to-beat finger pressure and heart rate were recorded by the volume clamp method (Portapres; TNO Biomedicals, Amsterdam) during NREM 4 sleep stage and at daytime (7 rain supine position, 5 rain uptight position). From the recordings during NREM 4 sleep and during daytime, intervals of 2 min -- excluding apnoea and hypoventilation -- have been chosen for a newly developed spectral analysis method on the basis of trigonometric regression with moving time windows (MTRS) to gain HRV parameters. Results (i) Increase of sympathetic activity of systolic and diastolic BP and heart rate during NREM 4 sleep stage in the OSAS group; (it) decrease of parasympathetic activity of the heart rate in OSAS patients in NREM sleep; (iii) higher diurnal sympathetic activity level in diastolic BP in the upright position and in systolic BP in both positions in the sleep-healthy group; (iv) Reduction of baroreflex activity at daytime in the upright position with decrease of the parasympathetic level in OSAS patients. Conclusions Obstructive sleep apnoea in children leads to a higher sympathetic activity during NREM 4 sleep, whereas the sympathetic level seems to be lower at daytime. Thus, young OSAS patients do present a disturbance of autonomic regulation mechanisms in NREM 4 sleep stage and at daytime. A decrease in baroreflex sensitivity is shown for the alert state but not in NREM 4 sleep. The results suggest that pathophysiology in OSAS patients is influenced by the vasomoturic, i.e. sympathetic, part (short-term effect) rather than by the parasympathetically regulated baroreflex sensitivity (long-term effect). [ABSTRACT FROM AUTHOR]

Presents a study that discussed appropriate measures for heart rate variability (HRV) monitoring of infants in sleep laboratories. Recommendations for data acquisition, pre-processing and analysis of data; Importance of R-wave detection for HRV-analysis; Strategies for measuring HRV in the time and frequency domain.

Presents information on a study which investigated the stability of parameters of the heart rate variability during NREM 4 sleep stage. Methodology; Results and discussion; Conclusions.

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Copyright of Somnologie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Question of the study We investigated the influence of radiofrequency electromagnetic fields emitted by digital mobile telephones on heart rate variability (HRV) during sleep in healthy young men. Subjects and methods For each subject, two polysomnographies were carried out in the sleep laboratory under field and sham exposure, respectively. Field intensity was weak so that thermal effects could be excluded. HRV was assessed from the electrocardiogram both in the time and in the frequency domain. Results For most HRV parameters, significant differences between sleep stages were found. Particularly, on the basis of spectral analysis of the RR intervals, slow wave sleep was characterized by a low LF/HF ratio of the low- and high-frequency components of HRV, indicating a predominance of the parasympathetic over the sympathetic activity in autonomic cardiac control. During REM sleep, the balance was shifted in favour of the sympathetic tone. For all HRV parameters, no significant differences were found between field and sham exposure. Conclusions Under the given experimental conditions, no influence of weak radiofrequency electromagnetic fields on cardiac autonomic activity could be proven. [ABSTRACT FROM AUTHOR]

Copyright of Somnologie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Somnologie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Somnologie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Somnologie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Somnologie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Somnologie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Somnologie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Somnologie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Somnologie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Somnologie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Somnologie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Somnologie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Somnologie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Question of the study There are differing opinions regarding the accuracy required of sampling frequencies in ECG signals. The question of this study was whether sampling frequencies of 100 Hz or 40 Hz would significantly influence the results of spectral analysis of R-R intervals. Patients and methods Thirty subjects underwent polysomnographic recordings in the sleep laboratory, sampled at a frequency of 100 Hz using the Alice 3.0 system. Two different sampling frequencies were used to assess the effects on a subsequent spectral analysis of R-R intervals. Repetition using a different sampling frequency was performed with a simulation technique. The study was performed on the total group (N = 30) and on two different subgroups (mean R-R > 900 ms; n = 15 and mean R-R < 900 ms; n = 15), respectively. Results Although different means of R-R intervals influence the following spectral parameters in different ways, there are only small changes in the time domain. Differences > 5% in analyses using two different sampling frequencies was found only in the UHF band (very high frequency band > 0.40 Hz) in time series with short R-R intervals. In LF band and HF band, the differences varied between 1% and 3%. Conclusions Using the simulation technique, we found only small changes in the spectral analysis parameters. The selection of a correct mathematical approach seems to be an important precondition. Additional comparative studies using different sampling frequencies for the same data segment are necessary to confirm these results in real-time conditions. [ABSTRACT FROM AUTHOR]