Final answer:
A spirometer is the instrument that measures lung volumes, such as FEV and FVC, and their ratios to diagnose or monitor respiratory diseases.
Step-by-step explanation:
The instrument that measures and records the volume of air that moves in and out of the lungs is a spirometer. The spirometry test results can be extremely useful for diagnosing respiratory diseases, such as asthma, emphysema, and fibrosis, or for assessing the effectiveness of their treatment. By measuring the forced expiratory volume (FEV) and the forced vital capacity (FVC), as well as calculating the FEV1/FVC ratio, healthcare professionals can determine if there's a problem with lung compliance or resistance within the respiratory system.