The Role of Spirometry in the Evaluation of Interstitial Lung Disease

Interstitial lung disease, or ILD, is a term defining a group of conditions in which the lung’s ability to expand is compromised due to inflammation and progressive scarring of lung tissue. Since lung scarring is generally non-reversible once it occurs, early detection and treatment are crucial to ensure positive outcomes.

In this scenario, a simple non-invasive test like spirometry may be a key asset in the diagnosis and evaluation of ILD. Let’s explore how and why.

What is Interstitial Lung Disease

Interstitial Lung Disease encompasses a diverse group of disorders characterized by inflammation and scarring of the lung interstitium, a collection of tissues includes the alveolar epithelium, pulmonary capillary endothelium, basement membrane, perivascular and perilymphatic tissues.

The progressive stiffening of lung tissue often leads to impaired gas exchange and reduced lung function, as it becomes harder and harder for the lungs to expand and fill with air. The most common symptoms of Interstitial Lung Disease are dry cough and shortness of breath even at rest.

ILD can be due to different causes, such as:

• Long-term smoking or exposure to hazardous materials
• Autoimmune diseases like rheumatoid arthritis
• Genetic factors and a family history of ILD

Because of the different causes behind the condition, treatments may vary from case to case, though they generally focus on preventing further scarring and managing symptoms. Commonly used medications include antifibrotics and immunosuppressive agents.

Using spirometry to identify restrictive patterns in ILD

Spirometry is a pulmonary function test that measures the volume and flow of air a patient can inhale and exhale by measuring key parameters, such as:

• Forced Vital Capacity (FVC), the total volume of air a patient can exhale forcefully after a deep breath
• Forced Expiratory Volume in one second (FEV1), the volume of air exhaled in the first second of the FVC maneuver
• FEV1/FVC Ratio, the proportion of the previous parameters, a critical metric for differentiating obstructive from restrictive lung patterns

In ILD, the lung’s ability to expand is compromised due to fibrosis and inflammation. Spirometry results typically reveal a restrictive pattern, marked by reduced FVC with a normal or elevated FEV1/FVC ratio. This makes spirometry an essential first-line test for patients experiencing symptoms like chronic cough, dyspnea, or unexplained fatigue.

Although a diagnosis of ILD is usually confirmed with the use of imaging or advanced pulmonary function tests, like DLCO and high-resolution computed tomography (HRCT), a restrictive pattern on spirometry may raise suspicion and prompt further investigations.

The role of spirometry in the management of Interstitial Lung Disease

In the long term, serial spirometry tests may provide a quantitative measure of lung function over time, making spirometry a useful tool to track the progression of Interstitial Lung Disease, with critical insights for clinical decision-making.

In ILD patients undergoing treatment or supportive care, spirometry helps gauge the effectiveness of interventions. Stabilization or improvement in FVC may indicate a positive response, while continued decline may highlight the need for treatment adjustments.

Conclusion

Spirometry plays a pivotal role in the evaluation and management of interstitial lung disease, offering insights into lung function that guide diagnosis, monitor progression, and assess treatment efficacy. When combined with advanced imaging and other pulmonary function tests, spirometry enables a holistic approach to understanding and managing ILD, ultimately improving patient outcomes.