A Sleep Tech's Guide to In-Lab Sleep Studies
Sleep medicine is a rapidly expanding and fascinating field of expertise. Today, the advances in sleep technology and medicine, as well as the developing public awareness of sleep disorders and how they affect a patient's health, are increasing. Because of this, there's a growing need for qualified sleep technologists and in-lab sleep studies.
An in-lab sleep study provides you with a comprehensive evaluation of your patient's sleep. It's an effective way to properly diagnose the patient with a sleep disorder. As a sleep technologist, you're required to have expertise in preparing and monitoring the recording of normal and abnormal sleep through collective medical and technical monitors.
You need to recognize when medical intervention is needed and respond to it based on certain protocols given to you by the medical director. When you're properly trained to conduct a polysomnography or other type of in-lab sleep study, it provides physicians and patients with the highest quality clinical tool.
Sleep technicians often have questions about how to perform in-lab sleep studies correctly, and this guide was developed to help.
Overview of In-Lab Sleep Studies
As a registered sleep technologist, you might perform an in-lab sleep study to:
- Test for certain sleep-related breathing conditions.
- Diagnose hypersomnia or narcolepsy with a sleep study followed by a Multiple Sleep Latency Test (MSLT).
- Evaluate sleep behaviors related to parasomnias.
- Determine why a sleep disorder treatment isn't working.
- Calibrate or titrate continuous positive airway pressure (CPAP) levels in patients who're receiving CPAP therapy due to a sleep-related breathing disorder.
Types of In-lab Sleep Studies
A sleep study or Polysomnogram (PSG) is an overnight sleep study that records the patient's eye movements, brain activity, EKG, body movement, oxygen levels and more. Polysomnograms are used to diagnose various disorders including:
- Obstructive sleep apnea (OSA) and other sleep-related breathing disorders
- Seizure disorders versus parasomnias occurring during sleep
- Sleep-related breathing disorders that may cause excessive daytime sleepiness (EDS)
- Periodic limb movement disorder (PLMD) and other sleep-related movement disorders
There are a number of different sleep study tests you may conduct including:
- Overnight Sleep Study
- Seizure VS Parasomnia Monitoring
- CPAP Titration
- Split Night CPAP Titration Study
- Maintenance of Wakefulness Testing (MWT)
- Multiple Sleep Latency Testing (MSLT)
Below is an overview of each test:
Overnight Sleep Study
This study allows you to measure how well your patient sleeps and how much, and assess breathing and other physiological functions such as EKG. It's also referred to as an all-night polysomnogram.
Seizure VS Parasomnia Monitoring
You perform this all-night polysomnogram with additional EEG monitoring. If your patient is having seizures, extended EEG monitoring using a more extensive group of electrodes on their scalp along with video monitoring can help to differentiate these two similar disorders.
This is an all-night polysomnogram with titration of PAP therapy, which you'll introduce to them during this study. During the study the patient’s breathing is monitored to determine the pressure required to maintain on open airway and regular breathing.
Split Night Study
You perform this all-night test along with CPAP titration together in one night. However, you need to meet certain criteria during the diagnostic portion of the patient's in-lab sleep study in order to start CPAP therapy on the same night.
Maintenance of Wakefulness Testing (MWT)
During this test, you'll have the patient stay awake and sit in bed for four, 40-minute sessions every two hours over the day. This study is sometimes done on workers in the transportation industry to evaluate if the patient can fly or drive safely.
Multiple Sleep Latency Testing (MSLT)
You'll perform this test after the all-night sleep study to evaluate how quickly and often the patient falls asleep during the day in quiet situations. This study is used to detect sleep architecture abnormalities that come with narcolepsy and document daytime sleepiness and its severity.
Preparing for the Study
To ensure the study is completed accurately, it's important that you prepare your equipment and patient properly. Contact your patient before the study and go over what they need to prepare and what to expect during the study.
On the day of the patient's in-lab sleep study, advise them to:
- Avoid napping.
- Shower or avoid using hair products like gel or hairspray that may interfere with the recording.
- Follow their regular routine as much as they can.
- Avoid caffeine use after lunch.
- Inform you of any medications they’re taking.
You'll want to ensure the patient is as comfortable as possible during the study. Before they report for the sleep study, encourage them to bring along any items they use during their nightly routine such as:
- Comfortable clothing or pajamas to sleep in.
- Toothpaste, toothbrush, and dental floss.
- Clean clothing for the morning.
- Reading material.
- Makeup remover.
Explain to them what happens during their sleep study, describe the sensors you'll be attaching and the types of equipment you'll use. Check the equipment before the study to ensure its working correctly.
During the In-Lab Sleep Study
When your patient arrives for the study have them complete the pre-study questionnaire. Escort the patient to their room where you'll be conducting the study and allow them time to get settled. Once they're settled and ready for bed, attach the sensors to them so you can monitor their sleep activity.
Types of Sensors and Equipment
The type of equipment and sensors you'll use for the in-lab sleep study will depend on the study you're conducting; however, they will usually include:
- Small electrodes and wires that you attach to their scalp using a conductive paste for measuring their brain activity. These help you determine if the patient is asleep and the sleep stage they're in.
- Small electrodes that you tape to their face near their chin and eyes for measuring eye movement and muscle activity. You'll be measuring their eye and chin movements to determine sleep stages. Chin muscle activity can also determine if nocturnal teeth grinding is present during sleep.
- Two belts that you put around their stomach and chest for measuring their breathing effort.
- A small thermal sensor and clear plastic tube (nasal cannula) for measuring their breathing activity.
- Two electrodes that you'll attach on each of their legs for measuring muscle activity and limb movement.
- A monitor that you'll tape to their finger for detecting oxygen levels.
- Two electrocardiogram (EKG) monitors for showing their heart rhythm and rate.
- A small microphone that you'll attach to their neck for detecting snoring.
After you hook up the patient to the various sensors, you’ll go into another room to monitor the data. You can communicate with the patient through an intercom system and complete a series of tests to adjust the equipment as needed. Once you've adjusted the equipment, encourage your patient to go to sleep.
After the Study
Once you complete the study, take the time to complete the necessary comments to the physician regarding the study. Next the study is scored. This is where you'll mark the patient's stages of sleep and identify any scorable events. Submit the study information to the physician so they can interpret the data.
Some of the data you'll be presenting in the sleep study report includes:
Quantity of Sleep
This is an objective measure of the patient's total sleep time (TST) during the study based on the scored EEG data.
Sleep Efficiency and Latency
This is the ratio between the patient's TST and total recording time (TRT) known as the sleep efficiency. Diminished sleep efficiency is where the patient has significant difficulty either getting to sleep or staying asleep and is often related to certain disorders and conditions such as insomnia or sleep apnea.
You'll record the sleep onset latency as well. This is the number of minutes it takes for the patient to fall asleep after you turn the lights out. Generally, it takes around 15 minutes to fall asleep, however, if the patient has a shorter sleep onset latency (they fall asleep the minute their head hits the pillow), it may be a sign of sleep deprivation often caused by a sleep disorder.
The patient will progress through four stages of sleep once they fall asleep. These stages will increase to deep, dreamless sleep and gradually proceed to rapid eye movement (REM) sleep. Throughout the night, a person cycles between non-REM and REM sleep in approximately 90 minute cycles. The structure of these cycles reveals whether the person is getting enough healthy restorative sleep.
Arousals and Awakenings
Interruptions in sleep that last between 3 to 15 seconds long can spontaneously occur and are sometimes due to a sleep disorder. You score the number of the patient's arousals and awakenings in the study and report the arousal index (frequency per hour of sleep and the total number). The higher this index, the more tired the patient will most likely feel depending on their sleep disruption tolerance level. A person can feel chronically sleepy with an arousal index of as few as 5 arousals per hour. Some people even have an arousal index of higher than 100 which is the worst case.
A glitch in the patient's central nervous system can cause breathing abnormalities that can cause arousals and awakenings. This glitch, for example, can be the brain "forgetting" to breathe or they may have a mechanical cause which is more common.
You’ll report how many times each occur as an index of events per hour (respiratory disturbance index or apnea-hypopnea index) and as a nighttime total. If the patient has an apnea-hypopnea index between 5 to 14, this indicates they have a mild level of sleep and breathing disturbance. If the number is 15 to 30, it's a moderate level and anything greater than 30 is a severe level of sleep disordered breathing.
You'll also measure the desaturations (drops in blood oxygen levels associated with sleep disordered breathing disturbances). Around 95 percent is normal saturation, 86 percent is mildly abnormal, 85 to 80 percent is moderate and anything below 79 percent is severe.
What you've learned:
- In-lab sleep studies are important for diagnosing sleep related breathing and other sleep disorders.
- There are several different types of sleep studies used to diagnose sleep disorders.
- It's important to properly prepare the patient and your equipment before the in-lab study.
- It's important to score the study accurately for proper diagnosis.
For more information on conducting an in-lab sleep study and the proper guidelines, check out the American Association of Sleep Technologist’s Learning Center.