Restrictive lung disease?
Your reply |
It is your belief that restrictive lung disease is present if the FEV1/FVC ratio is high. |
- Caucasian male, age 54 yr, standing height 159 cm, non-smoker.
- breathless on exercise
- shortness of breath on exercise
- no wheezing, no chronic cough or phlegm.
Spirometry |
||
| index | observed | predicted |
| FEV1 | 1.84 L | 3.00 L |
| FVC | 2.13 L | 3.75 L |
| FEV1%FVC | 69% | 78% |
 |
This is not correct. You are quite right that a purely restrictive disorder often presents with a small FEV1, low (F)VC, and a high FEV1/ (F)VC ratio. Conversely, such data may suggest a restrictive disorder. However, spirometric measurements do not include residual volume; we are therefore not informed about the total lung capacity and can therefore not diagnose a restrictive ventilatory defect. In general practice restrictive disorders are rare, and even in clinical practice restrictive lung disease is uncommon (ref. 1). If the spirometric findings suggest a restrictive pattern to you, then by all means check first of all if this is due to poor performance of the FVC maneuver, which may also lead to a low (F)VC and a high FEV1/FVC ratio. Were measurements performed correctly, then look carefully for clinical clues of disease that would lead to a restrictive ventilatory defect. If you are satisfied that the patient does present with a history compatible with disease causing a restrictive disorder, then a chest X-ray and measurement of the TLC, or possibly of the transfer factor of the lung for CO, may be in place if this is clinically relevant. A general rule of thumb is that measurement of lung volumes should only be performed if FEV1%FVC > 55% and FVC%pred < 85%. This rule has a 96% sensitivity for predicting a low TLC and an 98% negative predictive power for excluding restriction (Glady). |
Prevalence of restrictive
disease and cost effectiveness of diagnostic procedures:
Aaron SD, Dales RE, Cardinal P. How accurate
is spirometry at predicting restrictive pulmonary impairment? Chest
1999; 115: 869-873.
Glady CA, Aaron SD, Lunau M, Clinch J, Dales RE. A spirometry-based algorithm to direct lung function testing in the pulmonary function laboratory. Chest 2003; 123: 1939–1946.
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