Sleep recordings in the laboratory and home: a comparative analysis

Night to night variability of pulse oximetry features in children at home and at the hospital

Objective. Investigation of the night-to-night (NtN) variability of pulse oximetry features in children with suspicion of Sleep Apnea.Approach. Following ethics approval and informed consent, 75 children referred to British Columbia Children's Hospital for overnight PSG were recorded on three consecutive nights, including one at the hospital simultaneously with polysomnography and 2 nights at home. During all three nights, a smartphone-based pulse oximeter sensor was used to record overnight pulse oximetry (SpO2 and photoplethysmogram). Features characterizing SpO2 dynamics and heart rate were derived. The NtN variability of these features over the three different nights was investigated using linear mixed models.Main results. Overall most pulse oximetry features (e.g. the oxygen desaturation index) showed no NtN variability. One of the exceptions is for the signal quality, which was significantly lower during at home measurements compared to measurements in the hospital.Significance. At home pulse oximetry screening shows an increasing predictive value to investigate obstructive sleep apnea (OSA) severity. Hospital recordings affect subjects normal sleep and OSA severity and recordings may vary between nights at home. Before establishing the role of home monitoring as a diagnostic test for OSA, we must first determine their NtN variability. Most pulse oximetry features showed no significant NtN variability and could therefore be used in future at-home testing to create a reliable and consistent OSA screening tool. A single night recording at home should be able to characterize pulse oximetry features in children.

Validity of a newly developed ultraminiature cordless EMG measurement system

To verify validity of a newly developed ultraminiature EMG measurement system (BMS), the ability of BMS to record masseteric EMG was compared with that of a conventional polygraph system (PG) in the daytime. Effective distance between the transmitter unit and receiver unit of BMS was also examined. Subjects were 12 healthy volunteers. During tapping, maximum clenching, and gum chewing of all subjects, distinct bursts were observed in EMG recorded by BMS as well as PG. RMS values of maximum clenching measured by BMS and PG showed a linear and significant correlation, and there was no significant difference between the data of BMS and PG. When distance between the transmitter unit and receiver unit of BMS was 100 cm or less, no artifact signal was observed. Having obtained these findings suggesting ability for precise measurement in the daytime, we are planning to use BMS in home sleep studies in the next step.

Nightly variability of sleep-disordered breathing measured over 3 nights

OBJECTIVE

To examine the nightly variability of sleep-disordered breathing (SDB) as measured by the apnea-hypopnea index (AHI).

STUDY DESIGN AND SETTING

Retrospective comparison of 3 sequential nights of testing performed in the home in 1091 patients who were referred for diagnostic testing of SDB.

RESULTS

The Pearson and Intraclass correlation coefficients ranged between 0.88 and 0.90 for each pair of nights. Based on night 1, approximately 90% of patients were classified consistently with "AHI-high" (the highest AHI measured across the 3 nights) using an AHI threshold of 5. However, 10% were misclassified on night 1 relative to the highest AHI level.

CONCLUSION AND SIGNIFICANCE

These findings suggest that (1) 1 night of diagnostic testing for SDB is not sufficient to diagnosis SDB in approximately 1 of every 10 cases, and (2) there is little, if any, significant nightly change in SDB in the home environment.

EBM RATING

D.

Periodic leg movements during sleep in the elderly

Periodic leg movements in sleep (PLMS) occur frequently in the sleep of elderly persons but their significance is unknown. In this study, 63 elderly persons with symptoms of insomnia but without history of renal disease were evaluated polysomnographically. All received laboratory evaluations for blood urea nitrogen (BUN) and creatinine and completed a questionnaire on sleep complaints. Results indicated a positive relationship between PLMS and urea nitrogen in elderly women. In addition, symptoms of leg twitching and prolonged sleep latency could distinguish arbitrarily formed high and low PLMS groups. These results suggest that PLMS could be a window on the age-related decline in renal function and that these movements are related to several highly specific symptoms of geriatric insomnia.

Issues in the diagnosis and treatment of insomnia

Most people attribute a restorative function to sleep. This is because experimental or clinical sleep disturbance is usually followed by annoying symptoms of fatigue and sleepiness the following day. Can these daytime changes be documented objectively? In the past several years, the Multiple Sleep Latency Test (MSLT) has been developed and validated as an objective quantitative measure of sleepiness. Multiple assessments of sleep latency yield a profile of sleepiness across the day. This profile changes in the predicted direction with acute total and partial sleep deprivation, chronic sleep deprivation, sleep satiation, and in comparisons between hypersomnia patients and controls. Sleep and wakefulness are complementary phases in the daily cycle of human existence. Adequacy of sleep and energetic wakefulness next day are interacting phases in this cycle. Insomnia can be seen as a perception of disturbed sleep with daytime consequences, but is essentially also a symptom. This paper reviews a number of issues in the diagnosis and treatment of insomnia. The dimensions, daytime consequences and longitudinal aspects of insomnia are considered. Most investigations to date have been geared towards the problem of chronic insomnia and yet we are all likely to suffer from transient insomnia at some point. Psychiatric and psychophysiological disorders have been shown to be the most frequent causes of disorders of initiating and maintaining sleep. Moreover, there is an apparent disparity between subjective and objective sleep parameters with, for example, objectively disturbed sleep in noncomplaining subjects. The criteria of hypnotic efficacy and the effects of triazolam and flurazepam on sleep and daytime alertness have been investigated in normals, chronic insomniacs and the elderly. In general, chronic insomniacs showed all degrees of daytime alertness regardless of nocturnal sleep parameters. About one-third could be classified as fully alert all day long in spite of their complaints. The effect of flurazepam and triazolam on sleep (improvement) was essentially the same. Daytime effects were most closely related to half-life. The long-acting benzodiazepine, flurazepam, impaired daytime alertness although nocturnal sleep was improved. Triazolam improved not only nighttime sleep but also daytime alertness.