Which device measures expiratory volume and airflow in patients?

A spirometer is the device specifically designed to measure expiratory volume and airflow in patients. It assesses how much air a person can breathe in and out and how quickly they can breathe out, providing crucial information about lung function and respiratory efficiency. This measurement helps in diagnosing respiratory conditions, tracking pulmonary recovery, and guiding treatment decisions.

In contrast, an oximeter is used to measure the oxygen saturation level in a patient's blood, important for assessing respiratory efficiency but does not provide direct measurements of airflow or volume. An electrocardiogram (ECG) records the electrical activity of the heart, unrelated to lung function, while a thermometer measures body temperature, also not relevant to respiratory measurements. Thus, the spirometer is the clear choice for evaluating expiratory volume and airflow.