Sleep fragmentation: comparison of two definitions of short arousals during sleep in OSAS patients.

The measurement of arousals during sleep is useful to quantify sleep fragmentation. The criteria for electroencephalography (EEG) arousals defined by the American Sleep Disorders Association (ASDA) have recently been criticized because of lack of interobserver agreement. The authors have adopted a scoring method that associates the increase in chin electromyography (EMG) with the occurrence of an alpha-rhythm in all sleep stages (Université Catholique de Louvain (UCL) definition of arousals). The aim of the present study was to compare the two scoring definitions in terms of agreement and repeatability and the time taken for scoring in patients with obstructive sleep apnoea syndrome (OSAS) of varying severity. Two readers using both ASDA and UCL definitions scored twenty polysomnographies (PSGs) each on two occasions. The PSGs were chosen retrospectively to represent a wide range of arousal index (from 6-82) in OSAS patients. There was no difference in the arousal indices between readers and between scoring methods. The mean+/-SD difference between the two definitions (the bias) was 1.1+/-3.76 (95% confidence interval: -0.66-2.86). There was a strong linear relationship between the arousal index scored with the two definitions (r=0.981, p<0.001). Mean+/-SD scoring duration was significantly shorter for UCL than for ASDA definitions (18.5+/-5.4 versus 25.3+/-6.6 min, p<0.001). In conclusion, it has been found that in obstructive sleep apnoea syndrome patients, the American Sleep Disorders Association and Université Catholique de Louvain definitions were comparable in terms of agreement and repeatability.

Upper airway imaging in sleep apnoea syndrome: clinical applications.

Symptoms of habitual snoring and excessive daytime sleepiness are extremely common in the general population, and have poor predictive value in identifying patients with "true" sleep-related disordered breathing. The upper airways are the main anatomical site responsible for snoring and sleep apnoea; therefore, their examination via different means has been quite extensively assessed. Clinical examination may point to severe micrognathia or retrognathia, grossly hypertrophied tonsils, obvious macroglossia, and oedema and inflammation of the uvula and soft palate. A recently proposed model is promising, but has not been validated independently yet. Endoscopic investigations have been performed in awake as well as in sleeping patients, with the pharynx in relaxed or active states; their predictive value remains poor, both for diagnostic purposes and for identifying patients that may benefit from surgery. Radiographic and magnetic resonance imaging techniques have permitted a detailed understanding of the process of narrowing and collapse of the upper airways. Unfortunately, these techniques do not perform any better than the ones previously cited as clinically efficient tools for diagnosis in the population of patients suspected of sleep-related breathing disorders. In conclusion, clinical examination of the upper airways remains part of the clinical evaluation of patients suspected of sleep-related disordered breathing. Other imaging techniques may be used for research purposes, but do not yet seem to be worth including in the routine assessment of this population.