Tests · Sleep
Sleep study: the sleep test carried out at home
A sleep study records what happens in the body during a night's sleep and is the test used to investigate obstructive sleep apnoea. Clínica Rhinus performs the type IV version, carried out at the patient's home with a portable device that records oxygenation and airflow. It is the modality indicated where clinical suspicion of apnoea is high.
Medically reviewed by Prof. Aline Bittencourt, MD, PhD, CRM-MA 7562 · RQE 1832 Updated on
What is a sleep study?
It is the test that records what happens in the body during a night’s sleep. From that recording, the number of breathing pauses per hour is calculated — the figure that defines the presence and severity of obstructive sleep apnoea.
Sleep tests are classified by how many signals they record simultaneously. The more channels, the more detailed the reading of the night.
Which sleep study does Clínica Rhinus perform?
The type IV, carried out at the patient’s home. It is a portable device, with few sensors, that you take home and use in your own bed. It generally records:
- Blood oxygenation, via a finger sensor.
- Airflow through the nose.
- Heart rate.
With these it is possible to identify the drops in oxygen and the interruptions in airflow that characterise breathing pauses.
Sleeping in your own bed is a real advantage: sleep tends to be closer to normal than on a night spent away from home.
How it works in practice
- You collect the device at the clinic and receive instructions on how to fit it.
- At night, at home, you position the sensors as instructed and sleep normally.
- The following morning you remove the device and return it to the clinic.
- The recording is analysed and the report is discussed at the consultation.
What it shows and what it does not
| What to compare | Full study, in a laboratory | Type IV, at home |
|---|---|---|
| Where it is done | In a sleep laboratory | At the patient’s home |
| Breathing pauses | Yes | Yes |
| Oxygenation | Yes | Yes |
| Sleep stages | Yes | No |
| Leg movements | Yes | No |
| Other sleep disorders | Yes | No |
The main limitation follows from one thing alone: without recording sleep stages, the device cannot distinguish time asleep from time awake in bed. Since the event index is calculated per hour of sleep, that uncertainty can make the result come out lower than reality.
How the result is read
The principal index is the number of breathing events per hour of sleep:
| Events per hour | Classification |
|---|---|
| Fewer than 5 | Within expected limits for adults |
| 5 to 15 | Mild apnoea |
| 15 to 30 | Moderate apnoea |
| Above 30 | Severe apnoea |
These values apply to adults; in children the criteria are different and stricter.
The classification does not decide treatment on its own. Mild apnoea with marked daytime sleepiness may weigh more, in practice, than a higher index in someone without symptoms. This is why the result is read at the consultation, alongside the clinical picture.
When the full study is necessary
The home test does not suit every situation. The full laboratory study is indicated where there is:
- Significant cardiac or pulmonary disease.
- Neuromuscular disease.
- Suspected central, rather than obstructive, apnoea.
- Significant associated insomnia.
- Suspicion of sleep disorders other than apnoea.
- A normal home test result in someone with persistent marked symptoms.
In those cases, assessment is carried out at the clinic and the patient is advised on referral to a sleep laboratory.
Where it is carried out
The device is supplied by Clínica Rhinus, in the Renascença district of São Luís, and the test takes place at your home. The result is interpreted at the consultation with the ENT specialist.
This test is carried out on a self-pay basis only. The consultation may be covered by your health plan, according to its rules. Contact our team to arrange booking.
How should I prepare for this test?
- Bring the medical request: it is required.
- Collect the device at the clinic and receive instructions on how to fit it.
- Avoid coffee, energy drinks and alcohol from the afternoon onwards.
- Do not nap during the day of the test.
- Keep your usual night-time routine: same time, same bed, same pillow.
- Continue your usual medication, unless advised otherwise.
- Return the device the following day, at the agreed time.
Sources: Brazilian Association of Otorhinolaryngology and Cervico-Facial Surgery (ABORL-CCF) · Flint PW, Francis HW, Haughey BH, et al. Cummings Otolaryngology: Head and Neck Surgery. 7th ed. Elsevier; 2020. · Bento RF, Bittencourt AG, Voegels RL. Seminários em Otorrinolaringologia. Fundação Otorrinolaringologia.
Frequently asked questions
Questions about sleep
What is a sleep study and how do I prepare for it?
It is a recording of sleep using sensors that monitor breathing, oxygenation and heart rate over one night. At Clínica Rhinus it is carried out at home, with a portable device. Preparation is simple: no coffee or alcohol from the afternoon, no daytime nap, and keep your normal sleep routine.
What is the difference between the home test and the full study?
The full study is carried out in a sleep laboratory and also monitors brain activity, which allows sleep stages to be identified and other sleep disorders to be detected. The type IV records few channels and answers the central question well — are there breathing pauses? — but it does not describe the architecture of the night.
Why can the home test underestimate apnoea?
Because without recording sleep stages, the device does not know how long you actually slept. If you were awake for part of the night, events are divided by a longer period than the true sleep time, and the index comes out lower. That is why a normal result in someone with marked symptoms usually calls for the full study.
When is the home test the right choice?
When clinical suspicion of obstructive apnoea is high — loud snoring, pauses observed by a bed partner, daytime sleepiness — and there are no other conditions complicating interpretation. In those cases it answers the question at lower cost and without leaving home.
In which situations is the full study necessary?
In people with significant cardiac or pulmonary disease, neuromuscular disease, suspected central apnoea, significant insomnia, or suspicion of sleep disorders other than apnoea. In those cases the clinic assesses the patient and advises on referral to a sleep laboratory, where the full study is carried out.
Can I sleep with the sensors on?
Most people can, and sleeping in your own bed helps considerably. The portable device has few sensors, they are lightweight, and they allow you to turn over during the night. Even sleep that is somewhat worse than usual is generally sufficient, because what is analysed are the breathing events across the night.