What device is used to measure the flow of air in and out of the lungs?

The spirometer is the correct device used to measure the flow of air in and out of the lungs. It functions by quantifying the volume of air inhaled and exhaled during breathing. Spirometry is a common pulmonary function test that provides valuable information about lung capacity and airflow, helping to diagnose conditions such as asthma, chronic obstructive pulmonary disease (COPD), and other respiratory issues. By measuring various aspects of lung function, such as forced vital capacity (FVC) and forced expiratory volume (FEV1), a spirometer assists healthcare providers in assessing respiratory health and determining appropriate treatment plans.