Pftc1a.htm

Spirometry

Objectives

To detect presence or absence of obstruction in spirometry.
To judge severity of obstruction.
To be able to detect significant change following bronchodilator administration?
To identify patterns of flow volume loops.

History

61 year old male
35 pack years
Shortness of breath on walking one block for 10 years

	Predicted Value	Observed Pre	% Predicted
FVC Liters	5.05	1.56	30
FEV1 Liters	4.03	0.55	13
FEV1/FVC %	77	34	45
FEF25-75 L/S	4.0	0.17	4
PEFR L/S	9.3	1.73	18
FET Secs	-	10.03	-
FIVC L	5.05	1.54	30
PIFR L/S	6.2	2.47	39

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Criteria for Obstruction:

FEV1/FVC observed less than 75% in patients between the ages of 18-65.
%pred between 90-100.

Our patient has observed FEV1/FVC of 34% and % Pred of 45. Hence there is evidence for obstruction.

Criteria for judging severity of Obstruction:

For observed FEV1/FVC
- Severe <40%
- Moderately severe 40-60%
- Mild 60-75%
For % predicted FEV1
- Severe <40%
- Moderately severe 40-60%
- Mild 60-80%
Our patient:
- Observed FEV1/FVC 34
- %Pred FEV1 13
He would be considered to have severe obstructive defect.

Criteria for significant change Never use % change of FEV1/FVC

For (Post-Pre)/Pre expressed as % change significant change is >12%
For change in Post pred - Pre pedicted of 10% is significant

You evaluate for a significant change in the following

FVC
FEV1
FEF25-75

If there is a significant change in 2 of 3 it is a significant bronchodilator response.

If 1 of 3 shows a significant change it is borderline response.

If none of them show a significant change no response.

Our Patient There is no significant change in FVC, FEV1 and FEF 25-75 following bronchodilator administration. Hence this patient will be considered to have no significant response to bronchodilator.

Flow volume loop pattern

The flow volume loop has a typical obstructive pattern as seen in patients with COPD.

Inspiratory limb is normal
There is an exponential drop of flow rates during expiration