Survey regarding limited diagnostic systems for sleep apnea.

T has been considerable controversy about the role of unattended limited recording systems (those that do not record the electroencephalogram [EEG], electrooculogram [EOG], and sub-mental electromyogram [EMG]) for the diagnosis and follow-up of sleep apnea, but little has been written about what signals should be recorded. What basic information is needed to adequately determine if someone has abnormal breathing during estimated or behavioral sleep? The issue of portable monitoring for OSA was first systematically examined by the Standards of Practice Committee of the American Sleep Disorders Association in 1993, leading to a review and recommendations published in 1994.1, 2 They developed a classification of recording systems which was standardized and convenient but was not based on expert consensus of what physiologic information was needed. Nor was it based on outcome studies, of which there were none. Subsequent systematic reviews have continued the rather arbitrary and increasingly dated division of recording systems into only 4 levels. • Level I: Standard polysomnography: Minimal requirements include recording of EEG, EOG, chin EMG, ECG, airflow, respiratory effort, and oxygen saturation. Body position must be documented or objectively measured. Trained personnel must be in constant attendance and able to intervene. Leg movement recording is desirable but optional. • Level II: Comprehensive portable polysomnography: Same as for level I, except heart rate instead of ECG is acceptable, and having trained personnel present and able to intervene is not required for all studies. • Level III: Modified portable sleep apnea testing: Minimum requirements include recording of ventilation (at least 2 channels of respiratory movement, or respiratory movement and airflow), ECG or heart rate, and oxygen saturation. Personnel are needed for preparation, but the ability to intervene is not required for all studies • Level IV: Continuous (single or dual) bioparameter recording: Only 1 or 2 physiologic variables need be recorded. The ability to intervene is not required.