What is the interpretation of a Forced Vital Capacity (FVC) of 41%, Forced Expiratory Volume in one second (FEV1) to Forced Vital Capacity (FVC) ratio of 86%, and Forced Expiratory Volume (FEV) of 47%?

From the Guidelines

The pulmonary function test results show a restrictive pattern, with a significantly reduced FVC at 41% of predicted, an elevated FEV1/FVC ratio at 86%, and a reduced FEV1 at 47% of predicted, suggesting a restrictive lung disease rather than obstructive disease. The FVC is significantly reduced, while the FEV1/FVC ratio is elevated, which is consistent with a restrictive lung disease pattern 1. This pattern suggests that the patient has a condition that limits the total amount of air that can be inhaled, while maintaining relatively normal airflow rates. The high FEV1/FVC ratio, combined with reduced lung volumes, points to conditions that may include pulmonary fibrosis, chest wall disorders, neuromuscular diseases, or pleural diseases. Further evaluation is needed, including complete pulmonary function tests with lung volumes and diffusion capacity, chest imaging, and clinical correlation 1. Management depends on the underlying cause but may include treating inflammation, preventing progression, and providing supportive care. Patients with restrictive lung disease often benefit from pulmonary rehabilitation, supplemental oxygen if hypoxemic, and treatment of the specific underlying condition. It is essential to note that the diagnosis of restrictive lung disease should be made with caution, considering the patient's clinical presentation, medical history, and other diagnostic tests, as a low FEV1/VC ratio can also be seen in healthy subjects, and the meaning of a low FEV1/FVC ratio in healthy subjects is unclear 1. However, in patients with respiratory diseases, a low FEV1/VC ratio, even when FEV1 is within the normal range, predicts morbidity and mortality 1. Therefore, a comprehensive evaluation and management plan should be tailored to the individual patient's needs, taking into account the severity of the disease, symptoms, and overall health status. The most recent and highest-quality study 1 provides the best guidance for interpreting lung function tests and diagnosing restrictive lung disease. Key points to consider in the diagnosis and management of restrictive lung disease include:

• The FEV1/VC ratio is a critical parameter for identifying obstructive impairment, but a high ratio can also be seen in restrictive lung disease 1
• The FVC is often reduced more than IVC or SVC in airflow obstruction, but in restrictive lung disease, the FVC is significantly reduced 1
• Additional parameters, such as peak expiratory flow and maximum inspiratory flows, may assist in diagnosing extrathoracic airway obstruction 1
• A comprehensive evaluation, including complete pulmonary function tests, chest imaging, and clinical correlation, is essential for diagnosing and managing restrictive lung disease 1.

From the Research

Interpretation of Spirometry Results

The given spirometry results are FVC 41, FEV1/FVC 86, and FEV 47. To interpret these results, we need to consider the normal values and the ratios between different parameters.

Normal Values and Ratios

• FVC (Forced Vital Capacity) is the total amount of air that can be exhaled from the lungs after a maximum inhalation. A normal FVC value is typically above 80% of the predicted value.
• FEV1 (Forced Expiratory Volume in 1 second) is the amount of air that can be exhaled from the lungs in the first second of a forced exhalation. A normal FEV1 value is typically above 80% of the predicted value.
• FEV1/FVC ratio is the ratio of FEV1 to FVC, which is used to diagnose obstructive and restrictive lung diseases. A normal FEV1/FVC ratio is typically above 70% 2.

Diagnosis

Based on the given results:

• FVC is 41, which is lower than the normal value.
• FEV1/FVC ratio is 86, which is higher than the normal value.
• FEV is 47, which is lower than the normal value.

These results suggest a restrictive lung disease pattern, as indicated by the low FVC and high FEV1/FVC ratio 3. However, the diagnosis of restrictive lung disease should be confirmed by other tests, such as total lung capacity (TLC) measurement, as a low FVC can also be seen in obstructive lung diseases with airway hyperinflation 2.

Possible Causes

The possible causes of these results include:

• Restrictive lung diseases, such as interstitial lung disease or pulmonary fibrosis 4, 5.
• Obstructive lung diseases with airway hyperinflation, such as chronic obstructive pulmonary disease (COPD) or asthma 2, 6.
• Other conditions, such as neuromuscular disorders or obesity, which can affect lung function 4, 3.

Further Evaluation

Further evaluation, including clinical history, physical examination, and additional tests, such as TLC measurement, diffusing capacity of the lung for carbon monoxide (DLCO), and chest imaging, is necessary to confirm the diagnosis and determine the underlying cause of the abnormal spirometry results 4, 3, 5.