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Sleep and Lung function tests

Pulmonary function tests

Pulmonary Function Tests or “Lung Function Tests” are breathing measurements to assess how well your lungs are working.  They help the doctor to: diagnose a chest condition e.g. asthma, measure response to treatment, and monitor your progress.

It is advisable to;

  • Not smoke for 24 hours prior to your appointment
  • Not eat a large meal 2 hours prior or wear tight restrictive clothing
  • Not to drink alcohol for at least 4 hours prior

If possible do not take the following inhalers prior to the tests;

  • Ventolin (Salamol, Salbutamol) or Bricanyl for at least 6 hours prior
  • Atrovent (Ipratropium), Duovent or Combivent for at least 8 hours prior
  • Seretide, Fostair (purple), Symbicort, and Theophylline for  12 hours prior
  • Spiriva (Tiotropium) or Seebri for 24 hours prior

If you feel you need to take any of these inhalers on the day of your tests or the day prior because of breathlessness then please do, but try to remember which one you have taken and at what time.

These tests take about 30 – 60 minutes.  We measure your height and weight, then sit you in front of a machine and talk you through various breathing manoeuvres.  For example, during one measure you have to hold your breath for a few seconds whereas on a different one you’ll be asked to “blow!” the air out.  These are different measurements to those performed in your GP Surgery. 

You will be asked to repeat each measure several times so that we record the best possible results.  We are aware this may be difficult for some patients but always encourage you to try your best.  The measures are harmless and generally cause no pain.

Sometimes we perform a measurement “post bronchodilator”.  If we did this with you, you would use an inhaler like unit to breath in a medication, wait for 20 minutes then repeat one of the breathing manoeuvres.


Simple exercise

This is usually a “six minute walk test”.  Suitable foot wear should be worn.  You will not be on a treadmill for this test.  It entails wearing a little monitor on your wrist and walking as far as you possibly can in a straight flat corridor for 6 minutes.  We cannot tell you how long you have been walking for but the idea is to achieve as much distance as possible.  However, if you need to stop to catch your breath you may do so but then try to restart walking as soon as possible.  The monitor on your wrist will measure your pulse rate and oxygen levels.  Before and after the walk test we will also ask you to rate how your legs and breathing feel.


Airways challenge

The airways challenge tests involves performing several maximal exhalations (i.e. blow’s out).  In between each effort you will breathe in a sweet sugar like powder.  The test will assess how sensitive (or irriatable) your airways are.  There is strict preparation for this test;

  • you should not be pregnant
  • you should be free from chest infection for at least 6 weeks prior
  • perform no vigorous exercise on the day of the test
  • no smoking for 6 hours prior the test
  • no caffeinated foods/drinks (e.g. tea, coffee, cola, chocolate) on the day of the test.

Also for the Airways Challenge test “inhalers and antihistamine need to be stopped”, follow the table below;


Withholding Time

Singulair (Montlukast)

4 days

Antihistamines (Cetirizine/Zyrtec, Fexofenadine/Telfast, Loratadine/Claratyne)


3 days

Spiriva (Tiotropium), Seebri

3 days

Seretide, (Purple inhaler), Symbicort (white with red bottom inhaler)

24 hours

Serevent (Green inhaler),  Oxis, Onbrez

24 hours

Nuelin (Theophylline)

24 hours

Flixotide, Becotide, Becloforte, Qvar, Pulmicort (brown/red inhalers)

12 hours

Atrovent (Ipratropium)

12 hours

Ventolin (Blue inhalers) or Bricanyl (terbutaline, white & blue)

8 hours

Intel  (Sodium Cromoglycate) or Tilade (nedcocromil sodium)

8 hours

If you have any concerns with withholding medications prior to the airways challenge test please have your current prescription to hand and ring the department on 01493 453055, you will need to speak to one of the lung technicians/physiologists.

The most common side effect during the airways challenge test is cough, sometimes it can cause mild shortness of breath, wheeze or chest soreness.  If these side effects occur they are mild, last only a few minutes, and disappear following breathing a medication we have to hand if necessary.  Many patients do not experience any of these side effects at all.


Hypoxic Challenge (part of Flight Assessment)

When travelling in an aeroplane there is less oxygen available due to the effect of altitude. This means some people with a lung condition may require additional oxygen during air travel.  The hypoxic challenge test helps your consultant assess whether or not in-flight oxygen may benefit you, however even if in-flight oxygen is advised and arranged it does not guarantee your safety during air travel. 

For this test you should take your usual medications but call us to reschedule if you have had an chest infection or admission to hospital within 4 weeks of your appointment date.

The test takes 60 – 90 minutes.  You sit quietly with a small finger probe on which measures your oxygen levels and pulse.  For about 20-30 minutes you’ll have a soft little clear mask face mask on that simulates the aircraft environment, your oxygen levels will be monitored throughout.   After this, sometimes a doctor will also take a blood sample using a needle to gain more detailed information about your blood oxygen levels.

The hypoxic challenge test has no side effects associated with it.  It is not a painful test, if a blood sample needs to be taken this may cause brief discomfort.  If you do not attend for this test the doctor may not be able to advise you on air travel with your lung condition.


Respiratory Muscle Function

These are a specific type of Pulmonary/Lung Function test.  They require maximal effort and cooperation.  If you are booked in for this test you may take medications as normal.  One of the tests we perform may require you to brief lay flat on a couch and perform a long blowing out manoeuvre. 


Overnight Pule Oximetry

For this you will attend the clinic for about 15 minutes to collect a small wrist monitor.  You then wear it overnight whilst at home to measure your oxygen levels and pulse rate during sleep.  You or a family member will need to return the monitor the following day.   It is a harmless and painless test.  There are many reasons why the doctor might have asked for this to be done and they will let you know the results.


Home sleep study

You will need to attend the clinic for about 30 minutes.  A technician will ask you a few questions and show you how to wear the sleep study equipment which is about the size of a mobile phone.  The monitor can be worn over bed clothes/pyjamas.   It will measure certain signals (e.g. oxygen level and breathing pattern) during your sleep and is very simple to use (ON/OFF button).  You will be required to sign for the equipment and confirm it will be returned the following day by an agreed timeso it can be prepared for the next patient awaiting a study.  We also ask patients to write a brief note on how the night went, for example,  what time did you go to bed, was it a usual night for you.  A consultant will review the study and inform you of the results at his outpatient clinic.  


Inpatient sleep study

Sometimes the doctor would like to measure more signals than what can be done during a home study, in this case he will request an “inpatient sleep study” be performed.  This will require a one night stay at the hospital on the ward in a side room.  When coming in for the night you must take and/or bring your usual medications.  Your sleep will also be video recorded to help the doctor assess your sleep.   Our coordinator will provide you with more information about this type of study when they call to arrange it.  A consultant will review the study and inform you of the results at his outpatient clinic.  


CPAP Therapy

“CPAP” stand for Continuous Positive Airway Pressure.  This is a specific therapy used by thousands of people in the UK to control a common sleep breathing condition.   A consultant at the hospital will refer you to this clinic.  Your first appointment will take about 60 minutes and follow up visits take 30 minutes.  If this therapy is appropriate for you the consultant will explain this at a clinic appointment. 


If you have any questions, or any other concerns about any of these services please contact us on 01493 453055 during office hours.

Please note the Sleep & Lung Function telephone lines have been temporarily reduced. You can still contact the team on this number however there is currently no facility to leave voicemail messages. Apologies for any inconvenience this may cause.