Obstructive lung disease is characterized by FEV1/FVC values of:

Obstructive lung disease is defined by an impairment in airflow that significantly affects the patient's ability to exhale air from the lungs. The FEV1/FVC ratio, which compares the amount of air a patient can forcibly exhale in one second (FEV1) to the total volume of air they can exhale after a deep breath (FVC), is a crucial indicator in diagnosing obstructive lung diseases, such as asthma and chronic obstructive pulmonary disease (COPD).

In instances of obstructive lung disease, the FEV1 is reduced more than the FVC, leading to a decrease in the FEV1/FVC ratio. A value of less than 70% is typically indicative of obstructive disease, as it demonstrates that the patient has a significant limitation in airflow. This threshold helps clinicians determine the presence of obstruction and the severity of the condition. Understanding this ratio is essential for effective diagnosis and management of lung diseases.

For context, the other values mentioned are associated with different pulmonary conditions: a ratio more than 80% typically suggests normal pulmonary function; normal values indicate no obstruction; and a ratio between 70% and 80% can be seen in patients with mild obstructive lung disease or restrictive lung disease, but