Infant lung function tests with chloral hydrate 

This information from Great Ormond Street Hospital (GOSH) explains about lung function tests with chloral hydrate – a short acting sedative. This sedative helps your child sleep during the lung function test measurements.

What do I need to do before coming to GOSH for my child’s lung function test?

It is important that your child does not eat or drink anything for a few hours before the sedation. This is called ‘fasting’ or ‘nil by mouth’. Fasting reduces the risk of stomach contents entering the lungs during and after the procedure. You will be informed the day before the procedure of the time that your child should be ‘nil by mouth’ – in other words, have nothing to eat or drink before the sedation. Fasting times are provided in your admissions letter  in broad terms, this is four hours for food (including milk) and two hours for clear fluids and breast milk before the procedure.

It is equally important to keep giving your child food and drink until those times to ensure they remain well hydrated and get adequate nutrition. This may involve waking your child earlier than normal to give them a drink, which we recommend.

Will my child be given any medication before the procedure?

Your child will be given chloral hydrate, a short acting sedative, to help them sleep during the lung function test measurements so that it does not distress them. Please let us know if your child has any allergies so that we can check to make sure that the medicine is safe to give. This medicine usually works within 10 to 30 minutes. Chloral hydrate has a bitter taste, however a small amount of ribena or squash can be used to mask the taste. We use chloral hydrate routinely without any complications.

Are there any side effects associated with the medication?

As we are only giving one dose of chloral hydrate, side effects are highly unlikely however it is still important to be aware of them:

  • „„rash
  • „„headache
  • „„nausea and vomiting
  • „„tummy upset (feeling bloated, passing wind)

What will happen during the procedure?

During the procedure, your child will be asleep while we measure their lung function. As your child will be sedated, their oxygen saturations and heart rate will be monitored throughout the test.

What happens after the procedure?

After the procedure your child will be awake but may remain drowsy for a few hours as the effects of the medicine wear off. You should not leave your child’s side during this time as they will be unsteady on their feet.

When will we find out about the result of the test?

The lung function results will be discussed with you at your next clinic appointment. If we have any concerns we will contact you sooner.

Compiled by: 
The Lung Function Test team in collaboration with the Child and Family Information Group
Last review date: 
February 2015


Please note this is a generic GOSH information sheet. If you have specific questions about how this relates to your child, please ask your doctor. Please note this information may not necessarily reflect treatment at other hospitals.