Pftc5a.htm

Bronchodilator response

Objectives

To select the tests to observe for the change following bronchodilator administration.
To identify a significant change
Learn to grade the response
Understand the significance of bronchodilator response

History

58 year old female
25 pack years of smoking
Shortness of breath on walking one block for 5 years
Wheezing while short of breath
Family history of Asthma
Had Asthma during childhood

	Predicted Value	Observed Pre	% Predicted
FVC Liters	3.29	1.66	50
FEV1 Liters	2.61	1.25	47
FEV1/FVC %	76	75	98
FEF25-75 L/S	2.55	1.14	44
PEFR L/S	6.05	3.46	57
FET Secs	-	5.42	-
FIVC L	-	1.75	-
PIFR L/S	4.04	3.08	76

Which measurements do you look at to decide whether there is a bronchodilator respose?

FVC
FEV1
FEF25-75

We should also pay attension to changes in FRC and Inspiratory fows, but we dont on routine examination.

Never use FEV1/FVC.

What is a significant change for a given test?

There are two ways of looking for a significant change.

((Post value-Prevalue)/Pre value) expressed as % change from baseline. Recent ATS criteria for a significant change is 12%.
Change greater than 200 ml
% predicted change of 10%

I was taught to use the last criteria. 2 standard deviation for repetetive performance of these tests is 10%. Hence it stands to reason that we can consider a change as significantr only when it is over 10% of predicted change. Most of the Pulmonologists will use a combination first two criteria to assess a significant change.

Some patients can deflate following relief of obstruction and can increase inspiratory flow rates. Look at the flow volume loop for these changes.

What criteria do you use to classify a response as significant, borderline and no response?

Indices we are looking at are:

FVC
FEV1
FEF25-75

Significant: 2 of 3 indices shows a significant change.
Moderate:1 of 3 indices shows a significant change
No response: None of the 3 indices show a significant change

Be careful with FEF25-75. If the FVC volume changes you cannot use the change in FEF25-75. The mid portion of FVC (FEF25-75) can shift to left (steep portion) or right (flat portion) if the FVC volume changes.

What is the significance of assessing a bronchodilator response?

When there is a significant bronchodilator response we can ssume patient has reactive airway disease namely Asthma.
Borderline response is seen in patients with COPD.

Lack of response does not rule out Asthma. Patient could have been already on maximal bronchodilator therapy or may be refractory at the time of bronchodilator administration.

At present paying too much attenstion to a bronchdilator response is not a meanigful exercise for management of patients. We give bronchodilators to all patients who are obstructed irrespective of the results from PFT study.