A polysomnographic technologist performs overnight polysomnograms on those with suspected sleep disorders. To become a polysomnographic technologist one must receive on-the-job training performing overnight polysomnograms or attend a course in sleep medicine technology.
In the United States, a Registered Polysomnographic Technologist (RPSGT) "is a fully trained sleep technologist who has met the rigorous requirements to become credentialed by the Board of Registered Polysomnographic Technologists". In order to take the registry examination, one must complete a minimum of 6 to 18 months paid clinical experience performing polysomnograms or complete a program in polysomnography that is accredited by the Commission on Accreditation of Allied Health Education Programs. By 2012, only those who have successfully completed a CAAHEP-approved polysomnography program will be eligible to take the BRPT examination in the United States.
Polysomnographic technologists collect data using PSGs (polysomnograms), which collect EEG, EOG, EMG, and ECG as well as respiratory flow and effort. The technologist or an assistant places wired electrodes on the subject's head to collect and score brain wave activity (electroencephalogram or EEG). Then there are electrodes which document eye movement (electrooculogram or EOG), fluctuation of muscle tension usually in the legs and chin (electromyogram or EMG), and heart rate (ECG or electrocardiogram). This information was first collected with analog equipment using needle-and-paper method, but in recent years has been transferred to digital data collection which appears on a computer screen. The technologist applies electrodes by first cleaning the area on the skin or scalp with an exfoliating gel, then applying the electrode with conducting gel (and sometimes a water-soluble glue) that improves the body's electrical impedances, thus giving the computer a better readout.
While the subject is sleeping, the technologist looks for episodes of sleep apnea using pressure-sensitive thoracic and abdominal belts to measure an effort to breathe, thermistors or thermocouples placed over the mouth and nostrils to measure airflow, and a pulse oximeter probe to measure blood oxygen content.
If a patient is apneic, he or she will usually have repeated events throughout the night which are disruptive to the sleep cycle. At the end of an apnea or hypopnea is often an arousal, which is a change in EEG frequency often accompanied by increased EMG frequency for between 3–15 seconds. These arousals are short but often can be frequent throughout the night, causing the person to feel tired despite a full night's sleep.