1. Home
  2. Our Services
  3. A-Z of Services
  4. Respiratory Medicine
  5. Respiratory Patient Information
  6. Overnight oximetry (Sleep study)

Overnight oximetry (Sleep study)

Important information

  • You should not consume any alcohol on the day or night of the test.
  • You should not wear nail varnish or acrylic nails on the night of the test. If you wear nail varnish or acrylic nails the machine will not work.
  • The machine must be returned to Respiratory Physiology after two nights. 

Thank you for your cooperation. This will assist us in getting the most accurate information and enable us to provide you with the most appropriate treatment. 

What is overnight oximetry? 

“Overnight oximetry” is a test designed to assess the level of oxygen in your body when you are asleep.

You will need to use this machine for the two nights after you receive it, and then return it to the hospital.

Why do I need to have this test?

This is a simple non-invasive procedure to check that you are taking in enough oxygen when you are asleep. 

What happens during the test?

At the appointment you will collect an overnight oximetry machine, which will be loaned to you by the hospital. This is used overnight in your own home. The Physiologist will explain the test to you and answer any queries you may have. They will show you how to use the machine. The instructions are also attached to the machine. You will be asked to complete some questionnaires to give you further information about your sleep pattern. 

What does the oximetry machine do?

The oximetry machine assesses your blood oxygen levels, your pulse, and your breathing when you are asleep. This is done using a probe attached to the outside of your finger before you go to sleep in bed. 

Frequently asked questions

Will I experience any discomfort or side effects?

There is no discomfort or any known side effects associated with this test. 

When will I be told the results of the test?

Once you have returned the machine to the hospital, the results will be processed and passed onto the requesting clinician. You are then usually told your results at your next clinic appointment, or a letter may be sent to your GP or the doctor who referred you for the test. 

What happens if I don’t want to have the test?

If you don’t have the test we won’t be able to assess your sleep. This may affect the medical treatment that you receive. 

Instructions 

What will you receive at your appointment?

  1. A pulse oximeter (with a finger probe attached). 
    Our finger probes are available in 2 sizes: regular and large. We have other attachments available such as an earlobe probe. If you have any difficulty using the finger probe, please speak to a member of the team for more information.

    Pulse oximetry machine

  2. Paperwork: Instructions. Epworth Score Assessment. Sleep questionnaire.

    Example of patient questionnaire

What to do part 1

  1. Get ready for bed, take all medication as normal. 
  2. Place the equipment on your left wrist, as if putting on a wrist watch. 
  3. Tighten the band on the equipment so it is comfortable and stable on your wrist. 
  4. Just before you get into bed place the grey probe on your ring finger, so the wire is on the back of the hand. Make sure that your finger is not poking out of the end of the probe.
Pulse oximetry finger probe and wrist attachment

What to do part 2

  1. The machine will then start recording. 
  2. Go to sleep. 
  3. If you wake in the middle of the night, do not take the equipment off. The probe should be attached for at least 5 hours. If the site of the probe becomes uncomfortable, another finger can be used. The other end of the probe is attached to the machine. 
  4. In the morning, when you get up, remove the equipment. 
  5. Repeat the previous steps for the second night. 
  6. If you think that the equipment isn’t working correctly, please contact us (details on the back of this leaflet).

Once your have completed 2 nights wearing the equipment

Please return it to Southmead Hospital “Welcome desk.” This is near the front entrance of the Brunel building, near the Amigos Shop. (Monday to Friday, 7am to 7pm). 

Southmead Hospital Bristol | North Bristol NHS Trust (nbt.nhs.uk)

If you have any issue returning your equipment, please speak to a member of the team.

© North Bristol NHS Trust. This edition published July 2024. Review due July 2027. NBT002589

Contact Respiratory Physiology

Telephone: 0117 414 5400
Email: respiratoryphysiology@nbt.nhs.uk

Overnight oximetry (Sleep study)