PFT Findings in Obstructive and Restrictive Lung Diseases
| Obstructive Lung Disease | Restrictive Lung Disease | |
| FEV1 | <80% | <80% |
| FEV1/FVC | <70% or < LLN | ≥ 70% or ≥ LLN |
| FVC | Normal to Increased (i.e. ≥ LLN) | <80% (i.e. < LLN) |
| Examples | COPD (i.e. emphysema and chronic bronchitis) Asthma Bronchiectasis α1-antitrypsin deficiency Bronchiolitis obliterans Cystic fibrosis Silicosis (early) |
There are three basic categories of restrictive lung diseases: Intrinsic lung disease, chest wall deformities, and neuromuscular disorders. Chest wall (Ankylosing spondylitis; Kyphosis; Morbid obesity; Scoliosis Interstitial lung disease (Asbestosis; Berylliosis; Eosinophilic pneumonia; Hypersensitivity pneumonitis; pneumoconiosis; Idiopathic pulmonary fibrosis; Sarcoidosis; Silicosis (late)) Neuromuscular disorders (Amyotrophic lateral sclerosis; Guillain-Barré syndrome; Muscular dystrophy; Myasthenia gravis) Adverse Drug Reaction ( Amiodarone; Methotrexate; Nitrofurantoin) |
Diffusing capacity of the Lung for Carbon Monoxide (DLCO).
DLCO is a test that determines how much oxygen travels from the alveoli of the lungs to the blood vessels surrounding the alveoli. It is a quantitative measure of gas exchange in the lungs. “Diseases that decrease blood flow to the lungs or damage alveoli will cause less efficient gas exchange, resulting in a lower DLCO measurement.” AFP
“Idiopathic pulmonary fibrosis, asbestosis, hypersensitivity pneumonitis, and sarcoidosis are restrictive lung diseases with a low diffusion capacity due to alveolar damage.
COPD and asthma are both obstructive lung diseases, but can be associated with an abnormal DLCO. Morbid obesity causes a restrictive lung disease associated with a normal DLCO. The presence of chronic pulmonary emboli is associated with a low DLCO due to pulmonary vascular disease, but PFTs are normal.” ABFM
Read AAFP, 2014
Pulmonary Function Test Interpretation
From AAFP 2014 article above.
| TEST RESULTS BASED ON AGE | SUGGESTED DIAGNOSIS | |
|---|---|---|
| FVC | FEV1/FVC RATIO* | |
|
5 to 18 years: ≥ 80% |
5 to 18 years: ≥ 85% |
Normal |
|
Adults: ≥ LLN |
Adults: ≥ LLN or ≥ 70% |
|
|
5 to 18 years: ≥ 80% |
5 to 18 years: < 85% |
Obstructive defect |
|
Adults: ≥ LLN |
Adults: < LLN or < 70% |
|
|
5 to 18 years: < 80% |
5 to 18 years: ≥ 85% |
Restrictive pattern |
|
Adults: < LLN |
Adults: ≥ LLN or ≥ 70% |
|
|
5 to 18 years: < 80% |
5 to 18 years: < 85% |
Mixed pattern |
|
Adults: < LLN |
Adults: < LLN or < 70% |
|
FEV1 = forced expiratory volume in one second; FVC = forced vital capacity; LLN = lower limit of normal (defined as below the fifth percentile of spirometry data obtained from the Third National Health and Nutrition Examination Survey).
*—The 70% criteria should be used only for patients 65 years and older who have respiratory symptoms and are at risk of chronic obstructive pulmonary disease (i.e., current or previous smoker)
References
Johnson JD, Theurer WM: A stepwise approach to the interpretation of pulmonary function tests. Am Fam Physician 2014;89(5):359-366. http://www.aafp.org/afp/2014/0301/p359.html