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’m coughing mucus sometime with blood

for a year hrct [High Resolution Cat Scan] normal bronchoscopy normal Spirometry jan 17 Fvc 5.24 112% Fev1 4.80 105% Dlco 94% Spirometry aug 17 Fvc 4.80 98% Fev1 4.00 97% Dlco 104% I don’t have a clear diagnostic my dr belive i may have a prolonged infection

Response:  Although both spirometry tests are probably within normal limits you had a significant decrease in FEV1 between January and August (-17%). This isn’t as apparent as it should be since the predicted FEV1 (and FVC) are different for the two tests.  In January the predicted FEV1 was somewhere around 4.57 L and in August it was around 4.12 L so you either had your tests at two different places or they changed reference equations in between.

A decrease in FEV1 like that could be a concern but some people are normally variable, or it could be a difference between testing systems or it actually could indicate a trend.  You won’t know for sure until you are tested again.  At the moment however, your August results, which includes your DLCO, are within normal limits so I wouldn’t be overly concerned about it at this time.

A chronic cough is, unfortunately, a non-specific symptom.  It can be due to a wide variety of lung disorders but just as often it is due to allergies or environmental causes.  Frequent or violent coughing can also cause hemorrhaging of the blood vessels in the airways so the blood in your sputum may be due to the cough and not to an underlying lung disorder.  

It is possible you have a lung infection but these are often difficult to diagnose since there are a wide variety of bacterial, fungal and viral causes.  I’m not up to date on diagnosing lung infections (not my area of expertise anyway) but having your sputum cultured for organisms used to be a relatively common practice.  It would be best if you talked to your physician about this.

2 thoughts on “What is Pulmonary Function Testing?”

  1. hola, soy técnico cardiopulmonar realizo espirometrías en un laboratorio de función pulmonar, tengo una duda que hasta los momentos no he podido aclarar, quería saber si me pueden ayudar.

    al realizar estudios a pacientes he podido evaluar a pacientes con valores por encima de sus capacidades, por ejemplo VEF1 140% CVF 140% y el VEF1% 140%, hay alguna razón especifica por la que pueda ocurrir esto? siendo este un paciente digamos que sin ninguna preparación física como para decir que tiene un desarrollo muscular que pudiera modificar estos valores, es decir son pacientes sedentarios.

    por que pudiera ocurrir que los valores de un paciente estén por encima de sus capacidades?
    y habrá algún limite por encima?

    In English via Google Translate:

    Hello, I am cardiopulmonary technician performed spirometry in a pulmonary function laboratory, I have a doubt that until the moments I could not clarify, I wanted to know if you can help me.

    When conducting patient studies, I have been able to evaluate patients with values above their capacities, for example FEV1 140% FVC 140% and FEV1% 140%, is there any specific reason why this can happen? Being this a patient say that without any physical preparation to say that it has a muscular development that could modify these values, that is to say they are sedentary patients.

    Why could a patient’s values be above his or her abilities?
    And there will be some limit above?

    1. Miguelalfredo –

      First, muscular development has little to do with an elevated FVC and FEV1. Yes, neuromuscular disease can cause low values, but once a certain minimum level of strength has been reached FVC and FEV1 don’t (and can’t) improve since the limiting factor is not strength but the equal pressure point (the point at which the pressure inside the airways is the same as in the surrounding lung tissue) and the resistance of the airways.

      There are several reasons for an elevated FVC and FEV1. First, normal test results are always on a bell-shaped curve and a certain number of people are going to naturally be above 100% or 120% of predicted and that’s reasonably normal. Second, the results for elderly patients are frequently above normal and this is partly because the individual in question has aged well and partly because they are survivors and to have to had good lung function in order to have lived as long as they do. Finally, and what is probably the most likely reason is the reference equations your pulmonary function lab is using. There are numerous different reference equations and the ATS/ERS states that those most relevant to your local population should be used. If you are frequently seeing FVC and FEV1 results that are 140% of predicted then its clear that the wrong reference equations are being used.

      Regards, Richard

      In Spanish via Google Translate:

      Miguelalfredo –

      En primer lugar, el desarrollo muscular tiene poco que ver con una elevada CVF y VEF1. Sí, la enfermedad neuromuscular puede causar valores bajos, pero una vez que se ha alcanzado un cierto nivel mínimo de fuerza, la CVF y el FEV1 no mejoran (y no pueden), ya que el factor limitante no es la fuerza sino el punto de presión igual La presión dentro de las vías respiratorias es la misma que en el tejido pulmonar circundante) y la resistencia de las vías respiratorias.

      Hay varias razones para una CVF elevada y VEF1. En primer lugar, los resultados de las pruebas normales siempre están en una curva en forma de campana y un cierto número de personas van a estar naturalmente por encima del 100% o 120% de lo previsto y eso es razonablemente normal. En segundo lugar, los resultados para los pacientes de edad avanzada son con frecuencia por encima de lo normal y esto se debe en parte a que el individuo en cuestión ha envejecido bien y en parte porque son supervivientes y tener que tener una buena función pulmonar para haber vivido tanto tiempo como lo hacen. Finalmente, y cuál es probablemente la razón más probable es las ecuaciones de la referencia su laboratorio de la función pulmonar está utilizando. Existen numerosas ecuaciones de referencia diferentes y los estados ATS / ERS indican que deben usarse las más relevantes para su población local. Si usted está viendo con frecuencia FVC y FEV1 resultados que son el 140% de lo previsto, entonces su claro que las ecuaciones de referencia equivocada se están utilizando.

      Saludos, Richard

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