A polysomnographic technologist (or PSGT) runs overnight polysomnograms on those with suspected sleep disorders or have been ordered to do so by a physician. To become a PGTT one must, in most cases, perform overnight polysomnograms for 6 months or attend and graduate from a school of sleep medicine. This differs from a Registered Polysomnographic technician (RPSGT) in that they have not yet performed overnight polysomnograms for 18 months and passed their registry exam through the Board of Registered Polysomnographic Technologists or BRPT. Taking the registry exam requires one to first complete guidelines per BRPT rules.
Polysomnographic technologists collect data using PSG's (polysomnograms), which collect EEG, EOG, EMG, and ECG as well as respiratory flow and effort. The technologist or an assistant places wired electrodes on one'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.
One of the largest growing areas in sleep medicine is in the area of sleep-disordered breathing, especially Obstructive Sleep Apnea Syndrome (OSAS), sometimes referred to as Obstructive Sleep Apnea/Hypopnea Syndrome (OSAHS). An apnea is a cessation of either one or both respiratory effort and airflow for 10 seconds or longer.
An obstructive apnea is usually caused by excess cell tissue lining the upper airway, abnormal airway anatomy, oropharyngeal crowding, or sometimes even enlarged tonsils. The technologist will observe continued respiratory effort (measured using pressure-sensitive thoracic and abdominal belts) but no airflow (measured with a thermistor or thermocouple placed over the mouth and nostrils).
A central apnea is complete cessation of respiratory effort resulting in flat lines in the espiratory belt and flow channels. The person is not respiring.
A hypopnea is a partial obstruction associated with a 4 percent or greater continuous desaturation in blood oxygen percentage (measured with a pulse oximeter probe (POX) usually placed on the finger, which measures blood oxygen content by reflecting light from the bloodstream).
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.