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 infant'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. Your appointment letter will give you the specific fasting times, so please read this carefully.

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. Before the day of testing the team will call to make sure your child is well for the test and is not on a course of antibiotics.

If your child is found to be unwell on clinical examination during the day of testing, it may be the procedure will have to be postponed and re-booked for another day.

For more information on the infant lung function procedure Lung function tests (infants)

The person bringing your child for the test should have ‘Parental Responsibility’ for them. Parental Responsibility refers to the individual who has legal rights, responsibilities, duties, power and authority to make decisions for a child. If the person bringing your child does not have Parental Responsibility, we may have to cancel the test.

Will my child be given any medication before the procedure?

Your child will be given chloral hydrate, a short acting sedative, to help them into a deeper sleep during the lung function test. 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.

Are there any side effects associated with the medication?

Side effects are uncommon 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. Throughout the test we will monitor their oxygen saturations and heart rate.

What happens after the procedure?

After the procedure your child will be awake naturally but may remain drowsy for a few hours as the effects of the medicine wear off. You should not leave your child alone 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 Unit in collaboration with the Child and Family Information Group
Last review date:
November 2022