Pulmonary function tests are central to establishing the type of lung disorder during the diagnostic phase. They may prove very useful during environmental (natural) avoidance-challenge techniques to determine causative environments and effectiveness of remediation efforts. These tests may be the only effective measurement of progression or non-progression as the patient is followed over time with interstitial lung disease.
Spirometry: This is the most common pulmonary function test that is utilized to determine if there has been any damage done to the lung. There are 4 important measurements of spirometry that are very useful in the diagnosis, treatment, and monitoring of respiratory tract disorders caused by an environmental contamination. These measurements include an FVC (Forced Vital Capacity), FEV1 (Forced Expiratory volume in the first second), FEV1/FVC ratio, and a response to an inhaled broncho-dilator.
Forced Vital Capacity: This is a component of spirometry that measure the amount of air expelled when taking a deep breath and forcibly blowing out as much air as possible. The FVC is usually abnormal in the interstitial lungs diseases. Early in the course of many cases of interstitial lung disease this measurement may be within normal range. Some cases may persist for years on treatments without development of an abnormality.
Forced Expiratory Volume in the First Second: This is a component of spirometry that measures the amount of air expelled in the first second of the forced vital capacity (FVC). The FEV1 measures the rate of air blown out in the first second during spirometry.
FEV1/FVC ratio: This ratio is helpful in differentiating between obstructive lung diseases (emphysema and asthma) and the restrictive lung diseases. The ratio is reduced in the obstructive lung diseases and may be better than predicted normal in the restrictive diseases.
Response to Bronchodilators: This response should be measured to determine if these medications would be helpful in a symptomatic fashion as many patients with an inflammatory lung disorder may have a non-specific reactive lower airway manifested by cough, chest tightness, mucous production, and wheezing.
Lung Volumes: These measurements become important during the diagnosis phase of an evaluation to differentiate between an obstructive defect with air trapping and a true reduction in total lung capacity. Lung volumes are usually reduced in interstitial lung diseases and may be increased in obstructive lung diseases.
Diffusion Studies: These measurements may be done at rest and with exercise. These tests measure the ability to move gases (oxygen and carbon dioxide) from inside the lung to inside the bloodstream. Diffusion studies are usually reduced in interstitial lung diseases and may be reduced in severe obstructive lung diseases, as well.
