Respiratory  |  COPD Pathway - Spirometry Results




Respiratory

COPD Pathway - Spirometry Results

Click here for Interpreting the test

Severity of COPD Classification:

This is based on the post bronchodilator FEV1 result (2005 ATS/ERS taskforce recommendations on the interpretation of lung function tests):

Classification

FEV1/FVC

FEV1

Mild

< 0.7

>=80% predicted

Moderate

< 0.7

50% < FEV1 < 80% predicted

Severe

< 0.7

30% <FEV1 < 50% predicted

Very Severe

< 0.7

FEV1 < 30% predicted or FEV1 < 50% predicted plus
chronic respiratory failure



Measures included in Spirometry results:

Measure

Definition

Vital Capacity (VC)

Measured in Litres

Volume of air expired from a maximal inspiration using a slow/relaxed technique.

FVC Forced Vital Capacity

Measured in Litres

Volume of air exhaled after full inspiration. If low, suggests restrictive pattern.

FEV1 Forced Expiratory Volume in One Second

Volume of air exhaled in first one second of expiration. Important for determining severity of COPD.

FEV1 / FVC ratio

May be reported as FER

( Forced expiratory ratio )

This is the FEV1 expressed as a percentage of FVC

% Predicted

Uses the normal values for age, sex, and height.


Reversibility Testing:

Evaluation of reversibility is a measure of the response to a drug, and often requires withholding of bronchodilators prior to testing.
Significant improvement following bronchodilator is indicated when there is a 12% improvement in FEV1 compared to the baseline measurement, and a minimum of 200mls improvement.

Perform pre-bronchodilator spirometry, give 400 ug of salbutamol, and wait 15 minutes before performing post-bronchodilator spirometry.

Prior to testing, withhold:

  • Short-acting bronchodilators > 4 hours
  • Long-acting bronchodilators for 12 hours

 

Interpreting the test: 

  • In making a diagnosis of COPD , a post bronchodilator FEV1/FVC remains < 0.7 . However FEV1 may improve significantly after bronchodilator . Significant improvement following bronchodilator is indicated when there is a 12% improvement in FEV1 compared to the baseline measurement, and a minimum of 200mls improvement.
  • FVC, FEV1, and FEV1 / FVC ratio: Form the basis for interpretation. Inter-relationships of these measurements may also be of importance diagnostically
  • Assess the response to bronchodilator: a >200 ml and >12% improvement of the FEV1 and/or FVC is significant.
  • Finally, review the indication for the test. Does the result suggest a cause for the patient's respiratory symptoms? Does it confirm or exclude diagnosis of COPD?


Common causes of a restrictive spirometric pattern. 
Link to restrictive:

  • Parenchymal lung disease: pulmonary fibrosis / interstitial lung disease
  • Neuro-muscular disease
  • Morbid obesity
  • Pleural disorders
  • Miscellaneous including heart failure and pneumonia
  • "Pseudo-restriction" Full lung function test does not confirm the spirometric restrictive defect
  • Note: poor spirometry technique can also give a restrictive picture.

    If you have any doubts over interpretation of a spirometry report, contact:

    Whakatane Hospital  Respiratory Physician - fax (07) 306 0903 or
    Tauranga  Hospital Respiratory Services or Medical Support Team - fax(07)579 5718 or

    Request a respiratory specialist case review.

Information:

 



Last updated : Wednesday, March 30, 2016
Next review date : Thursday, March 30,2017


Disclaimer: This site is intended to be flexible and frequently updated. While every effort has been made to ensure accuracy, all information should be verified.