Common testing problems that you can have

In order to perform any Pulmonary Function Test you will need to breathe in very specific ways and at very specific times. The technician performing your tests should be able to explain how and when you are supposed to breathe. The ways in which you will need to breathe may often seem peculiar but there are good reasons for every breathing maneuver you will be asked to perform.

Most everybody is able to perform these breathing maneuvers either right away or with some practice. Occasionally however, you can have some difficulty performing these tests. There are several relatively common reasons that this can happen.


A cough is probably the second most common reason that your doctor will order Pulmonary Function tests for you. It can be a symptom of a lung disorder but is often due to just a cold or allergies. Taking a deep breath or blowing your air out really fast can sometimes trigger a cough, particularly if it’s the reason you are having tests in the first place.

Having a glass of water and resting for a moment can help. Taking a steady deep breath in instead of a fast one can also help. There are still times when you will need to blow your air out as fast as possible and this still may trigger a cough but this shouldn’t prevent you from trying your best.

Epiglottal Closure:

The epiglottis is a flap of cartilage that covers your airway and prevents food from going down your airway when you swallow. To some extent you can control how it works and you can see this if you take a breath in and then bear down without letting any air out. The epiglottis is only partially under conscious control however, and sometimes if you really tense up when you try to blow out hard it can become activated and close even though you don’t want it to.

When this happens it’s best to take a moment to relax, and in particular relax your shoulders and neck, then focus on breathing with your diaphragm and stomach.


In order for the test equipment to be able to measure your air you have to breath through a mouthpiece but this can be difficult for individuals with a hyperactive gag reflex. You will probably know this is a problem for you if you have trouble with gagging while seeing a dentist or swallowing pills. Like epiglottal closure a normal gag reflex prevents choking and keeps food and liquids from entering the airways. For most people the gag reflex is usually triggered by the presence of an unusually large object at the back of the throat but 10%-15% of the human population is hypersensitive and will gag when almost anything is placed in their mouth. The reasons that a hyperactive gag reflex occurs are unclear but are not under your conscious control.

If a hyperactive gag reflex is a problem then try not to place the mouthpiece any deeper in your mouth than absolutely necessary. It also tends to improve with practice.

Shortness of breath (SOB):

The sensation of shortness of breath is most often caused by:

  • Too much carbon dioxide in your blood stream.
  • Too little oxygen in your blood stream.

For different breathing tests you will need to keep blowing your air out or to hold your breath for what may seem like very long periods of time.  These long breathing maneuvers can increase the amount of carbon dioxide or decrease the amount of oxygen in your blood, particularly if your lung already has a problem with exchanging these gases.

In addition, shortness of breath can also be caused by:

  • Anything that prevents your lungs from expanding when you take a breath.
  • Anything that increases the amount of work that you need to breathe.

Different lung disorders can decrease your ability to take a deep breath or can make your respiratory muscles work hard in order for you to breathe and this can make it easier for you to feel short of breath.  

If you get short of breath please remember that none of the breathing maneuvers are dangerous, only uncomfortable, and that you should be given time to rest and let your breathing return to normal between tests.


When you are already short of breath anything that seems like it might threaten your ability to get enough air may cause you to become claustrophobic.  This can happen when you are asked to breathe through a mouthpiece with your nose clipped or when you have to enter the booth of a plethysmograph.  A feeling of claustrophobia is not under your control and can happen to anyone that is short of breath.

Although you may feel claustrophobic none of the breathing tests should actually prevent you from getting enough air.  If you do become claustrophobic you should be given time to relax and accomodate yourself to the needs of the test you will be performing.

What Blowing Means:

Unfortunately, there are a limited number of words than can be used to describe the breathing maneuvers you will be asked to perform. “Blow” is the most common of these but it has a number of different meanings and this can lead to misunderstanding how a test should be performed.

Most importantly a breathing test is not like blowing up a balloon. When you blow up a balloon you are trying to blow a small amount of air with a lot of pressure. When you perform a breathing test you should be trying to get the most amount out (or in) that you possibly can in the least amount of time. Unlike a balloon there is very little resistance when you blow your air out so tensing and pushing down really hard doesn’t really help. When you are asked to blow out fast and hard think instead of keeping everything wide open and huffing your air out.

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Coughing, epiglottal closure, gagging, shortness of breath and claustrophobia are common problems that can occur when performing Pulmonary Function tests.   If any of these happen please remember that these feelings are not your fault and they are not under your conscious control. They are your body’s automatic response to a situation that it perceives to be a threat to your breathing.  

Good quality Pulmonary Function tests require your cooperation and both you and your physician needs accurate results. If you are distressed by any of these sensations then this will make it more difficult for you to perform the tests correctly. Please take a moment and relax.  This kind of testing means you’re going to have to breathe in unusual and occasionally uncomfortable ways but none of the tests are in any way dangerous or life-threatening and everybody survives the experience.  

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PFT Patient by Richard Johnston is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.