In patients with chronic bronchitis, what is the FEV1/FVC ratio typically?

• A. Greater than 80%
• B. 70%-80%
• C. Less than 70%
• D. Equal to 100%

Answer: (C)

In patients with chronic bronchitis, the FEV1/FVC (Forced Expiratory Volume in one second to Forced Vital Capacity) ratio is typically less than 70%. This reduction in the ratio indicates an obstructive pattern of lung disease. Chronic bronchitis is characterized by inflammation and narrowing of the airways, which leads to increased resistance to airflow during exhalation. As a result, patients experience difficulty in expelling air from their lungs, causing a decrease in FEV1 (the volume of air that can be forcibly exhaled in one second) relative to FVC (the total volume of air exhaled after taking a deep breath).

In obstructive lung diseases like chronic bronchitis, the FEV1 is often reduced more significantly than the FVC, leading to a lower ratio. A ratio less than 70% is used as a diagnostic criterion to classify the presence of obstructive lung impairment. Therefore, understanding this ratio is crucial for diagnosing and assessing the severity of chronic bronchitis and other similar conditions, highlighting the obstructive nature of the disease and its impact on lung function.