From the Guidelines
The pulmonary function test results indicate a restrictive pattern, with a severely reduced FVC at 41% of predicted and an elevated FEV1/FVC ratio at 86%, suggesting a restrictive lung disorder rather than obstructive disease. The FVC is severely reduced, while the FEV1 is also severely reduced at 47% of predicted. This pattern is commonly seen in conditions such as pulmonary fibrosis, chest wall disorders, neuromuscular diseases, pleural diseases, or severe obesity 1. According to the European Respiratory Journal, a reduced VC does not prove a restrictive pulmonary defect, but it may be suggestive of lung restriction when FEV1/VC is normal or increased 1.
Key Findings
- FVC: 41% of predicted
- FEV1: 47% of predicted
- FEV1/FVC ratio: 86%
- The FEV1/FVC ratio is elevated, indicating a restrictive pattern rather than an obstructive one 1
- The American Thoracic Society recommends that only FVC, FEV1, and FEV1/FVC need to be routinely reported for spirometry, and that measurement of slow VC and calculation of FEV1/VC are a useful adjunct in patients with suspected airflow obstruction 1
Clinical Implications
- Further evaluation is recommended, including complete pulmonary function tests with lung volumes and diffusion capacity, chest imaging, and clinical correlation to determine the specific cause of the restriction
- Treatment would depend on the underlying cause but might include anti-inflammatory medications, antifibrotics for certain interstitial lung diseases, or addressing any reversible factors contributing to the restriction
- The use of a uniform format for the presentation of PFT results, as recommended by the American Thoracic Society, can help reduce potential miscommunication or misunderstanding 1
From the Research
Interpretation of FVC, FEV1/FVC, and FEV1 Values
- FVC (Forced Vital Capacity) of 41: This value is lower than the normal range, indicating a potential restrictive pattern [(2,3)].
- FEV1/FVC (Forced Expiratory Volume in 1 second/Forced Vital Capacity) ratio of 86: This value is higher than the normal range, indicating a potential restrictive pattern rather than an obstructive pattern [(2,3)].
- FEV1 (Forced Expiratory Volume in 1 second) of 47: This value is lower than the normal range, which could be indicative of either a restrictive or obstructive pattern [(3,4)].
Determining the Presence of a Restrictive Pattern
- A study published in 2010 2 found that in patients with a low FVC and a normal or elevated FEV1/FVC ratio, the restrictive pattern can be identified with confidence using an algorithm that takes into account the clinical diagnosis and certain spirometry measurements.
- Another study published in 2014 3 states that a restrictive pattern is indicated by an FVC below the fifth percentile based on NHANES III data in adults, or less than 80% in patients five to 18 years of age.
Considerations for Airflow Limitation
- A 2019 study 4 found that using the slow vital capacity (SVC) instead of FVC in the FEV1/VC ratio can enhance the yield of spirometry in detecting mild airflow obstruction in younger and obese subjects.
- However, the same study 4 notes that the FEV1/SVC ratio should be used with caution in elderly subjects with preserved FEV1/FVC, as a low value may represent a false-positive finding for airflow limitation.
Reference Values for Lung Function
- A 1999 study 5 compared lung-function reference values and found that the European Respiratory Society (ERS) values for FVC, FEV1, and FEV1%FVC should be verified, and the formulas of Brändli et al. are recommended.