What is a bronchoscope primarily used for?

A bronchoscope is primarily used for visualizing the airways and taking samples, which makes it an essential tool in diagnosing and treating respiratory issues. This instrument allows healthcare providers to directly observe the interior surfaces of the airways, including the bronchi and bronchioles, helping them identify any abnormalities such as tumors, infections, or inflammation. Additionally, during the procedure, physicians can obtain tissue samples (biopsies) or secretions to test for infections or other conditions.

The other options do not align with the primary function of a bronchoscope. Monitoring oxygen saturation usually involves devices like pulse oximeters, measuring lung capacity typically requires spirometry, and assessing heart function is conducted through techniques such as echocardiograms or cardiac stress tests. Therefore, the specific design and function of the bronchoscope as a visual and sampling instrument are what make it the correct answer in this context.