I write this blog post today to help you understand the differences among home testing devices circulating in the community.
In today’s economy, some have turned to home testing as a less costly option for sleep apnea screening. Here is Medicare’s definition of the different categories of sleep testing:
Type I – “gold standard” for sleep studies – Provided by the St. Joseph Center for Sleep Medicine
This is an attended study, performed in a sleep lab with the oversight of a sleep technologist with full sleep staging. This test monitors the transition through all your stages of sleep. It includes the use of an electroencephalograph (EEG) brain wave monitor which tells the technologist when you are asleep and when you are awake. Type I devices must also include the following channels:
• EOG – monitors eye movement
• ECG –monitors heart rate and rhythm
• Chin EMG – monitors muscle activity
• Limb EMG – monitors leg or arm movement
• Respiratory effort at thorax and abdomen – monitors breathing
• Nasal air flow
• Pulse Oximetry – records your oxygen levels
• Additional channels for CPAP/BiPap levels, CO2, pH and pressure
Type II home sleep test (HST) studies – Provided by the St. Joseph Center for Sleep Medicine
With a Type II portable monitor, unattended studies can be performed at home without the oversight of a sleep technologist. These devices have a minimum of seven channels. Type II devices must include the following channels:
• EEG – monitors brain waves to tell a professional if you are awake or asleep
• EOG – monitors eye movement
• ECG – monitors heart rate and rhythm
• EMG – monitors muscle activity
• Respiratory effort
• Pulse oximetry – records your oxygen levels during sleep
Type III home sleep test (HST)
With a Type III portable monitor, unattended studies are performed with a minimum of four channels. Type III devices must include the following channels:
• 2 respiratory movement/airflow channels
• ECG/heart rate
• Pulse oximetry
The home sleep test was initially developed for screening. Now, type II or III home tests are being used increasingly for diagnosis of sleep apnea. Although less costly, the home sleep test is not always the best method to diagnose a sleep disorder. For example, the Type III test does not monitor brain activity so the professional is not aware if the patient is actually asleep or not; this can affect the test’s accuracy, possibly resulting in prescribing unnecessary therapy.
As I stated at the beginning, the Type I testing – a full test in a lab under the supervision of a technologist – is the gold standard. In many cases, we can still recommend the type II home test, which still monitors brain activity, so the results will show the patient’s sleep-awake patterns – which in turn will provide a more accurate result than the type III device.
Till next time, keep dreaming!
Kevin Hammond RPSGT, CRT
Lead Polysomnographic Technologist
St. Joseph Center for Sleep Medicine