Which instrument is used for measuring air entering and leaving the lungs?

The spirometer is the correct instrument for measuring air entering and leaving the lungs. It is specifically designed to assess various lung functions by measuring the volume of air inhaled and exhaled. This makes it a vital tool in diagnosing and monitoring respiratory conditions such as asthma and chronic obstructive pulmonary disease (COPD).

The spirometer can provide both static lung volumes and dynamic measurements like forced expiratory volume, which are essential in evaluating how well the lungs are working. Understanding these measurements helps healthcare providers tailor treatment plans for patients with respiratory issues.

In contrast, a stethoscope is primarily used for listening to internal sounds of a patient's body, including heart and lung sounds, but it does not measure air volumes. A bronchoscope is a device used to visualize the airway and lungs through a flexible tube, allowing for direct observation and sampling but is not intended for measuring airflow. A respirator, or ventilator, is utilized to support or control breathing in patients who are unable to breathe adequately on their own but does not measure lung function.