Home Sleep Study (HST) or Polysomnogram (PSG)
There are two types of sleep studies. An at home sleep study (HST) and a sleep clinic study called a Polysomnogram (PSG).
Home Sleep Tests are exactly what they sound like: sleep tests that are taken from the comfort of one’s own home. Patients receive their testing kit in the mail with detailed instructions on usage. After the sleep study is performed it is simply mailed back in a pre-paid envelope. The data is read by a board-certified sleep physician.
Home Sleep Study Benefits
The patient self-administers the home sleep test, and is able to spend the night in the patient’s own bed in familiar surroundings (reducing first night effect).
Home sleep testing, a home sleep study, can be advantageous for those with trouble arranging time out of their schedules to spend the night in-lab.
The typical cost of a home sleep test or a home sleep study is only a fraction of the cost of an in-lab sleep study, and typically yields similar results in the diagnosis of Obstructive Sleep Apnea.
Because a HST is used strictly for diagnosing breathing disorders, it requires far less equipment. A HST comes in a small package that includes devices that are easy for patients to apply themselves including:
- a small nasal cannula to measure airflow
- a belt around the upper chest to measure respiratory effort
- a finger clip to measure the oxygen saturation in the blood
A polysomnogram is an overnight sleep study that records brain activity, eye movements, heart rate, blood pressure, oxygen levels, body movement, and more. This is an in-lab sleep study. The patient must come to the sleep lab for an overnight study. Patients arrive between 8-9 p.m. to fill out paper work and be given an overview of the procedure by a sleep technologist. Patients will have to spend the night in the facility as the test usually concludes around 6-7 a.m. You will be hooked up to numerous wires and straps, have to sleep in a strange bed and sleep while someone is watching you.
The PSG involves:
- 2 elastic belts around your chest and stomach to measure breathing effort.
- A nasal cannula (clear plastic tubing) and small heat monitor to measure all breathing activity.
- A wire electrode on each leg to measure body movement/muscle activity.
- Wires with small cup electrodes attached to your scalp with a conductive paste to measure brain activity.
- Wire electrodes are taped to your face near the eyes and chin to show muscle activity. These electrodes are used to measure eye movements, which also give clues to sleep stages, as well as chin movements which can observe possible nocturnal teeth grinding as well as other sleep disorders related to muscle activity.
- A monitor taped to your finger to detect oxygen levels during the study.
- 2-3 lead EKG monitors to show heart rate and rhythm.
- A small mic applied to your throat to detect snoring.
- Once you have been hooked up to the various machines you are encouraged to sleep, the technician will begin monitoring the data from another room.
Polysomnogram Information from the sleep test:
Apnea-Hypopnea index (AHI) : apnea events plus hypopnea events divided by the number of hours slept.
OSA severity is measured AHI
- Mild: 5 14 events per hour
- Moderate: 15-29 events per hour
- Severe: 30+ events per hour
Arousal : an abroubt change in brainwave activity (EEG) indicating a change from sleep to wakefulness, or from a deepr to lighter stage of sleep. A documented arousal must be greater than three seconds.
Arousal index : the number of arousals per hour divided by number of hours slept. Arousals may be spontaneous or related to respiratory or movement events.
Blood Oxygen Saturation : level of oxygen in the blood, normal concentration should not go below 90% or drop more than 4% with apnea events.
- 85 – 90 % = Mild
- 80 – 85 % = Moderate
- 80 % or lower = Severe