T. Penzel

The SIESTA project polygraphic and clinical database

The SIESTA project had two major goals: developing new tools for analyzing computer-based sleep recordings and creating a reference database for sleep-related features. Basically, both goals have been reached, although validation and fine tuning of the sleep analyzer is still on-going. Investigations on the Web interface will be finished soon and a documentation of the database (including a CD-ROM with all test forms and all clinical, psychometric and actigraphic data as well as all R&K-scorings) will be published. Besides its scientific impact, the SIESTA project also emphasizes two other important aspects: the need of national and international cooperation between different experts and disciplines and the importance of standardized methods in scientific and clinical research.

Interrater reliability between scorers from eight European sleep laboratories in subjects with different sleep disorders.

Interrater variability of sleep stage scorings is a well‐known phenomenon. The SIESTA project offered the opportunity to analyse interrater reliability (IRR) between experienced scorers from eight European sleep laboratories within a large sample of patients with different (sleep) disorders: depression, general anxiety disorder with and without non‐organic insomnia, Parkinsons disease, period limb movements in sleep and sleep apnoea. The results were based on 196 recordings from 98 patients (73 males: 52.3 ± 12.1 years and 25 females: 49.5 ± 11.9 years) for which two independent expert scorings from two different laboratories were available. Cohens κ was used to evaluate the IRR on the basis of epochs and intraclass correlation was used to analyse the agreement on quantitative sleep parameters. The overall level of agreement when five different stages were distinguished was κ = 0.6816 (76.8%), which in terms of κ reflects a ‘substantial’ agreement ( Landis and Koch, 1977 ). For different groups of patients κ values varied from 0.6138 (Parkinsons disease) to 0.8176 (generalized anxiety disorder). With regard to (sleep) stages, the IRR was highest for rapid eye movement (REM), followed by Wake, slow‐wave sleep (SWS), non‐rapid eye movement 2 (NREM2) and NREM1. The results of regression analysis showed that age and sex only had a statistically significant effect on κ when the (sleep) stages are considered separately. For NREM2 and SWS a statistically significant decrease of IRR with age has been observed and the IRR for SWS was lower for males than for females. These variations of IRR most probably reflect changes of the sleep electroencephalography (EEG) with age and gender.

Sleep fragmentation and daytime vigilance in patients with OSA treated by surgical maxillomandibular advancement compared to CPAP therapy

Impaired vigilance is a frequent daytime complaint of patients with obstructive sleep apnoea (OSA). To date, continuous positive airway pressure (CPAP) is a well established therapy for OSA. Nevertheless, in patients with certain craniofacial characteristics, maxillomandibular advancement osteotomy (MMO) is a promising surgical treatment. Twenty‐four male patients with OSA (pretreatment respiratory disturbance index (RDI) 59.3 SD±24.1 events/h) participated in this investigation. The mean age was 42.7±10.7 years and the mean body mass index was 26.7±2.9 kg/m2. According to cephalometric evaluation, all patients had a narrow posterior airway space, more or less due to severe maxillary and mandibular retrognathia. All patients except two were treated first with CPAP for at least 3 months and afterwards by MMO. Two patients only tolerated a CPAP trial for 2 nights. Polysomnographic investigation and daytime vigilance were assessed before therapy, with CPAP therapy and 3 months after surgical treatment. Patients’ reports of impaired daytime performance were confirmed by a pretreatment vigilance test using a 90‐min, four‐choice reaction‐time test. The test was repeated with effective CPAP therapy and postoperatively. Daytime vigilance was increased with CPAP and after surgical treatment in a similar manner. Respiratory and polysomnographic patterns clearly improved, both with CPAP and after surgery, and showed significant changes compared to the pretreatment investigation. The RDI decreased significantly, both with CPAP (5.3±6.0) and postoperatively (5.6±9.6 events/h). The percentages of non‐rapid eye movement Stage 1 (NREM 1) sleep showed a marked decrease (with CPAP 8.2±3.6% and after MMO 8.2±4.4% vs. 13.3±7.4% before treatment), whereas percentages of slow wave sleep increased significantly from 8.0±6.1% before therapy to 18.2±12.8 with CPAP and 14.4±7.3% after MMO. The number of awakenings per hour time in bed (TIB) was significantly reduced after surgery (2.8±1.3), compared to both preoperative investigation (baseline 4.2±2.0 and CPAP 3.4±1.5). Brief arousals per hour TIB were reduced to half with CPAP (19.3±20.0) and after MMO (19.7±13.6), compared to baseline (54.3±20.0). We conclude that the treatment of OSA by MMO in carefully selected cases has positive effects on sleep, respiration and daytime vigilance, which are comparable to CPAP therapy.

Nocturnal Hemodynamics in Patients with Sleep Apnea

Sleep apnea, a nocturnal disturbance of the respiratory regulation, has effects on the hemodynamics during sleep as well as during the day. The first systematic inquiries into these relationships were conducted as early as 1965 by Jung and Kuhlo [1]. In 1972, the research team of Coccagna and Lugaresi used direct measurements to document the blood pressure behavior during individual apnea episodes [2].

Acquisition of biomedical signals databases

Aspects to consider when building a database are presented. The work is based on experiences from the SIESTA project which identified sleep disorders.

Standards for biomedical signal databases

This article presents some requirements imposed on data format specifications derived from different biosignal recording environments. This is followed by a review of four particularly interesting data formats and some notes about other specifications. Finally, the merits of different formats are discussed and some views about future developments are given.

A new design of a polysomnography-based multi-center treatment study for the restless legs syndrome

Periodic limb movements (PLM) cause sleep disorders and daytime symptoms and are frequently associated with restless legs syndrome (RLS). Treatment of RLS with increased PLM during sleep (PLMS) has been evaluated in studies limited in size, methodology and study length. This long-term, placebo-controlled, multi-center, study with polysomnography (PSG) recordings has been designed in order to assess efficacy and safety parameters of pergolide treatment in RLS. This novel approach for a study was created to assure consistently high quality of sleep recording and analysis. Using defined criteria, 21 sleep centers were approved for the study after a pilot phase. Seventeen centers with 16 different PSG systems randomized 100 patients. Digital sleep recordings from 4 visits (baseline, 6 weeks, 6 months, 1 year) were submitted to one central evaluation center following previously defined standardized operating procedures. Visual scoring of all recordings was performed by one independent scorer. Reliability of scoring was evaluated for 20 randomly selected baseline recordings. The mean epoch by epoch agreement for sleep stages was 88% (range 81-96%), mean arousal re-scoring differed by 0.5 (range: -16 to 20), and mean PLM index re-scoring differed by 0.1 (range: -1.5 to 2.1). Using one scorer with a demonstrated high reliability in PSG scoring for all sleep recordings was very effective in terms of study cost, study duration, and data quality.

A Device For Ambulatory Heart Rate, Oxygen Saturation And Snoring Recording

Sleep related breathing disorders (SRBD) are of high prevalence in the male population. Obstructive sleep apnea is the most prominent finding in these patients. A new ambulatory system for preselection and therapy control of these patients was deviced - the MESAM IV. The new system records heart rate, snoring sounds, oxygen saturation and body position up to 18 hours. In a sleep laboratory 68 patients were recorded in parallel with conventional polysomnography to compare the results in terms of apnea and hypopnea detection. Visual evaluation of recorded data resulted in a good agreement whereas automatic analysis needs further improvement.

Multimedia database "Marburg Respiratory Sounds (MARS)"

Lung sounds and their relation with the pulmonary pathology make their accurate interpretation crucial. The traditional method of auscultation with the stethoscope is rather subjective and requires long experience. For the development of advanced detection algorithms of pathological lung sounds a large number of validated lung sound recordings are needed. In contrast to existing commercial lung sound CDs we compiled a database which contains many cases with typical auscultation findings and findings with difficult evaluation. A novelty is the combination between auscultation results and lung function parameters.

Vigilance stages and performance in OSAS patients in a monotonous reaction time task

OBJECTIVES To develop improved methods for objective assessment of daytime vigilance. This is important in the diagnosis and therapy control of sleep disorders associated with excessive daytime sleepiness (EDS). METHODS Twenty-one patients with EDS due to obstructive sleep apnea were recorded during a daytime 90 min reaction time (RT) test in a monotonous situation. Two EEG, two EOG and a submental EMG channel were recorded simultaneously. The recordings were divided into short, stationary segments of variable length (0.5-2 s) and classified into 7 stages using our previously described system, which includes additional stages for drowsiness. RESULTS The duration of RT was linearly correlated to the vigilance state (P<0.05). The appearance of slow eye movements (SEM) was more consistently related to performance impairment than EEG changes. CONCLUSIONS Our system can provide a better tracking of vigilance changes than the standardized sleep stage scoring. A 1-2 h test is useful in the assessment of the performance of a subject suffering from EDS. We found that SEMs indicate more sensitive and consistent EDS-related performance impairment than changes in EEG activity.