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In polysomnography, an oronasal thermal airflow sensor and respiratory inductance plethysmography (RIP) belts at thorax and abdomen are used to detect central sleep apnoea. These sensors are uncomfortable to wear, can disturb the patient’s sleep, and data quality can be significantly di-minished if a sensor slips off the patient. Contactless meas-urements would be a desirable alternative. We utilized a 3D time-of-flight sensor to monitor respiratory-related chest movements to decipher epochs of normal breathing and ap-noea in ten adult patients with a total of 467 apnoea events. Time-synchronized comparisons of 3D measurements of chest movements due to respiration to polysomnography signals from rip belts and nasal airflow proved that the 3D sensor provided largely equivalent results. This new tech-nique could support the diagnosis of central sleep apnoea and Cheyne-Stokes respiration.

Interrater variability of sleep stage scorings has an essential impact not only on the reading of polysomnographic sleep studies (PSGs) for clinical trials but also on the evaluation of patients' sleep. With the introduction of a new standard for sleep stage scorings (AASM standard) there is a need for studies on interrater reliability (IRR). The SIESTA database resulting from an EU-funded project provides a large number of studies (n = 72; 56 healthy controls and 16 subjects with different sleep disorders, mean age +/- SD: 57.7 +/- 18.7, 34 females) for which scorings according to both standards (AASM and RK) were done. Differences in IRR were analysed at two levels: (1) based on quantitative sleep parameter by means of intraclass correlations; and (2) based on an epoch-by-epoch comparison by means of Cohen's kappa and Fleiss' kappa. The overall agreement was for the AASM standard 82.0% (Cohen's kappa = 0.76) and for the RK standard 80.6% (Cohen's kappa = 0.68). Agreements increased from RK to AASM for all sleep stages, except N2. The results of this study underline that the modification of the scoring rules improve IRR as a result of the integration of occipital, central and frontal leads on the one hand, but decline IRR on the other hand specifically for N2, due to the new rule that cortical arousals with or without concurrent increase in submental electromyogram are critical events for the end of N2.

Background: In 2007, the AASM Manual for the Scoring of Sleep and Associated Events was published by the American Academy of Sleep Medicine (AASM). Concerning the visual classification of sleep stages, these new rules are intended to replace the rules by Rechtschaffen and Kales (R&K). Methods: We adapted the automatic R&K sleep scoring system Somnolyzer 24 × 7 to comply with the AASM rules and subsequently performed a validation study based on 72 polysomnographies from the Siesta database (56 healthy subjects, 16 patients, 38 females, 34 males, aged 21–86 years). Scorings according to the AASM rules were performed manually by experienced sleep scorers and semi-automatically by the AASM version of the Somnolyzer. Manual scorings and Somnolyzer reviews were performed independently by at least 2 out of 8 experts from 4 sleep centers. Results: In the quality control process, sleep experts corrected 4.8 and 3.7% of the automatically assigned epochs, resulting in a reliability between 2 Somnolyzer-assisted scorings of 99% (Cohen’s kappa: 0.99). In contrast, the reliability between the 2 manual scorings was 82% (kappa: 0.76). The agreement between the 2 Somnolyzer-assisted and the 2 visual scorings was between 81% (kappa: 0.75) and 82% (kappa: 0.76). Conclusion: The AASM version of the Somnolyzer revealed an agreement between semi-automated and human expert scoring comparable to that published for the R&K version with a validity comparable to that of human experts, but with a reliability close to 1, thereby reducing interrater variability as well as scoring time to a minimum.

FOR APPROXIMATELY 40 YEARS THE ONLY WIDELY ACCEPTED STANDARD FOR DESCRIBING THE HUMAN SLEEP PROCESS WAS THE MANUAL OF SLEEP CLASSIFICATION by Rechtschaffen and Kales.1 On the basis of these scoring rules, sleep recordings are divided into 7 discrete stages (wake, stage 1, stage 2, stage 3, stage 4, stage REM, and movement time). Even though in many cases this standard is useful, the rules of Rechtschaffen and Kales have also been criticized for leaving plenty of room for subjective interpretation, which leads to a great variability in the visual evaluation of sleep stages.2,3 Last but not least, the standard rules were developed for young healthy adults4,5 and do not necessarily directly apply to elderly subjects and patients. The American Academy of Sleep Medicine (AASM)6 modified the standard guidelines for sleep classification by Rechtschaffen and Kales and developed a new guideline for terminology, recording method, and scoring rules for sleep-related phenomena. The manual is the result of a review of literature, analysis and consensus which addresses 7 topics: digital analysis and reporting parameters, visual scoring, arousal, cardiac and respiratory events, movements and pediatric scoring. One of the major changes is a change in terminology: in the AASM classification, sleep stages S1 to S4 are referred to as N1, N2, and N3, with N3 reflecting slow wave sleep (SWS, RK stage REM is referred to as stage R. According to the AASM manual, a minimum of 3 EEG derivations, sampling activity from the frontal, central, and occipital regions, has to be recorded. The recommended derivations are F4-M1, C4-M1, and O2-M1 (right-sided active electrodes and a reference over the left mastoid, rather than the ear).7 The new manual also deals with the definition of the sleep-wake transition, sleep spindles, K-complexes, slow wave sleep, and REM sleep, as well as arousals and major body movements. In summary, the major changes of the new manual comprise EEG derivations, the merging of stages 3 and 4 into N3, the abolition of stage “movement time,” the simplification of many context rules as well as the recommendation of sampling rates and filter settings for polysomnographic (PSG) reporting and for user interfaces of computer-assisted sleep analysis.6 To date there are no studies evaluating the effects of the new standard on sleep scoring data. The aim of the present investigation was to describe in detail differences between visual sleep scoring according to the Rechtschaffen and Kales classification and scoring based on the new AASM guidelines in normal subjects of different age groups and sleep-disturbed patients.