What is Pulmonary Function Testing?

A Pulmonary Function test is a breathing test that measures how well your lungs are working.  There are many reasons why your physician may need to have you perform a Pulmonary Function test.  The most common of these are:

  • shortness of breath
  • cough
  • wheeze

You may need to have Pulmonary Function tests performed regularly if you have been diagnosed with a lung disease like:

  • asthma
  • COPD
  • pulmonary fibrosis

You may also need to have Pulmonary Function tests performed in order to obtain a baseline for:

  • surgery
  • chemotherapy
  • radiation therapy

Some tests can be performed in your physician’s office but many will need to be performed in a Pulmonary Function Lab by trained technicians.  Your physician will order the tests that he believes will be most helpful in diagnosing or monitoring your condition.  

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


Latest Q & A:

I just took the PFT yesterday and my doctors app is not for a month.

Could you tell me if there is anything serious from these test results.  [results were placed in a table and edited for clarity]

Test: Predicted: Pre-BD Observed: %Predicted: Post-BD: %Predicted: %Change:
FVC(L): 3.57 2.08 58% 2.46 69% +19%
FEV1(L) 2.85 1.59 56% 1.80 63% +13%
FEV1/FVC: 80 77 96% 73 91% -9%
FEF25-75: 2.94 1.31 45% 1.20 41% -9%
FEF25%: 6.97 3.98 57% 6.36 91% +60%
FEF50%: 3.68 1.94 53% 1.72 47% -12%
FEF75%: 1.28 0.48 37 0.41 32 -13%
PEF (L/sec): 7.64 5.37 70% 7.40 97% +38%
FIVC (L): 3.57 2.08 58% 2.38 67% +14%
MVV (L/min): 123 57 46%
TLC (L): 5.76 8.45 147% 4.88 85% -42%
VC(L): 3.57 2.22 62% 2.50 70% +13%
IC (L): 2.72 2.18 80% 2.38 87% +9%
FRC (L): 2.38 6.27 263% 2.50 105% -60%
ERV (L): 0.11 0.12 18%
RV(L): 2.20 6.23 283% 2.37 108% -62%
RV/TLC: 39 74 191% 49 126% -34%
DLCO: 28.0 21.6 77%
DLCO/VA: 3.70 5.18 140%
VA: 4.18
RAW: 216 12.14 561% 585 270% -52%
GAW: 0.571 00.82 14% 0.171 30% +108%
sRAW: 5.15 79.04 1535% 16.02 311% -80%
sGAW: 0.194 0.013 7% 0.062 32% +393%
MIP (cm H2O) 108 113 105%
MEP (cm H2O): 202 90 45%

Response:  To start with I am going to ignore your pre-BD TLC, FRC and RV because I think they were seriously overestimated due to problems with your testing (see What’s the frequency, plethysmograph for a technical and in-depth explanation of the probable cause).  Your post-BD TLC, FRC and RV look much more realistic.

I am also going to ignore your airway resistance measurements (RAW, GAW, sRAW, sGAW) partly because the test quality looks very poor but also because these measurements aren’t usually very helpful in general.

In my lab this would be interpreted as “Moderately severe airway obstruction with a mild gas exchange defect and normal lung volumes.  The significant increase in FVC and FEV1 following inhaled bronchodilator indicates an element of airway hyperreactivity.  Respiratory muscle strength is within normal limits.”  

This could be consistent with COPD but fits several other lung disorders as well.

FYI, although your MEP is only 45% of predicted, the predicted value is too high and values above 70 cm H2O are within normal limits.  I also see some math errors in the DLCO/VA but that doesn’t change how the DLCO would be interpreted. 

 

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