The flow variable's accuracy is verified by which instrument?

The rotameter is the correct instrument for verifying the accuracy of flow variables. It is a device specifically designed to measure the flow rate of gases and liquids. The mechanism involves afloat that moves within a tapered transparent tube; as the flow increases, the float rises to a position that correlates to the flow rate on the calibrated scale of the device. This direct visual indication allows for precise determination of flow accuracy, making it a valuable tool in settings such as mechanical ventilation.

While other instruments like a pneumotachometer and spirometer measure flow and volume, they serve slightly different purposes; the pneumotachometer primarily measures the airflow through the respiratory system, and the spirometer measures the volume of air inhaled and exhaled. The pressure gauge, on the other hand, indicates the pressure of a gas but does not measure flow directly. Therefore, when it comes to verifying the flow variable's accuracy, the rotameter stands out as the most appropriate choice.