med 610 clinical respiratory diseases & critcare med

Pulmonary Function Testing

Case 3 Answer

A 60 year-old man presents to his primary care provider with complaints of increasing dyspnea on exertion. He has a 40 pack-year history of smoking and is retired following a career as a building contractor.

His pulmonary function testing is as follows:

  Pre-Bronchodilator (BD) Post- BD
Test Actual Predicted % Predicted Actual % Change
FVC (L) 1.89 4.58 41 3.69 96
FEV1 (L) 0.89 3.60 25 1.89 112
FEV1/FVC (%) 47 79      
RV (L) 5.72 2.31 248    
TLC (L) 7.51 6.41 117    
RV/TLC (%) 76 37      
DLCO* corr 20.73 33.43 62    
*DLCO is measured in ml/min/mmHg
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His flow volume loops is as follows:

flow volume loop graph

Case 3 Interpretation

This patient has markedly abnormal spirometry. The FVC is only 41% predicted while the FEV1 is only 25% predicted, well below the lower limit of normal of 80% predicted. In addition, the FEV1/FVC ratio is markedly reduced. The combination of the low FEV1, FVC and reduced FEV1/FVC ratio is consistent with a diagnosis of airflow obstruction. With an FEV1 of 25% predicted, this would be classified as “severe” airflow obstruction.

The patient also meets criteria for reversible airflow obstruction as both the FEV1 and FVC improve by over 200 ml and 12% following administration of a bronchodilator.

In addition to these abnormalities on spirometry, the patient has a markedly elevated residual volume (RV), a finding that is indicative of air-trapping. The total lung capacity (TLC) is somewhat elevated at 117% predicted but it is still shy of the 120% predicted level used to define hyperinflation.

 

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