The gold standard of sleep diagnostic procedures is known as a whole-night polysomnography (PSG). It consists of an overnight stay in a medical facility with a supervising technician who oversees a suite of monitoring mechanisms. A sleep technology expert scores the data offline and a sleep physician interprets the results. In spite of the high cost and the amount of work needed for such a study, the results maybe not be representative of a typical night’s sleep at home.
A representative test requires sleeping in one’s own bed with familiar routines and schedules. That’s of course not possible in a sleep facility. The full lab-based polysomnography should be reserved for sleep disorders that cannot be detected with a partial home study or with other objective methods that allow a patient to remain in his/her normal sleep environment.
A whole-night PSG typically records the following:
- Signals that enable the evaluation of sleep architecture and quality
- 6 electroencephalography (EEG) channels (at a minimum)
- 2 electrooculography (EOG) eye movement channels
- 1 electromyography (EMG) chin muscle activity channel
- Signals that enable the evaluation of respiration during sleep
- mouth and nose airflow
- nasal pressure
- chest and abdominal movement (2 channels)
- oxygen saturation
- body position
- Signals that enable the evaluation of limb movements
- 1-4 EMG channels for muscle activity
- 1-2 electrocardiogram (ECG) channels for heart electrical activity
The attending lab technician monitors these recordings overnight and corrects problems with signal quality or disconnections.
A sleep technology expert scores the study afterwards. This is a manual process, though some computerized tools can make the job easier and faster. But overall, whole-night polysomnography is burdensome and expensive; and the scoring process is costly and complicated. As well, there have always been some concerns about recording quality variability and differences in skill levels across sleep technology experts.
Partial sleep studies at home that are administered by sleep clinics seem to be a superior alternative for cost and efficiency reasons. The use of partial sleep studies is increasing, though important quality and reimbursement issues must first be resolved.