A spirometer is an instrument for measuring the air capacity of the lungs. First attempts to measure lung capacity were made in A.D. 129-200 by Claudius Galen and the first spirometer was invented in the 1840s by John Hutchinson.
As patients perform specific maneuvers whilst using the spirometer, the inspiratory and expiratory airflow is measured and these values are converted into lung health and capacity parameters such as FVC and FEV1. These lung parameters are used for diagnosing and monitoring respiratory diseases such as COPD & asthma.
Spirometers are therefore powerful tools that are used to:
- Determine how well the lungs receive, hold, and utilize air,
- Monitor a lung disease,
- Observe the effectiveness of treatment,
- Determine the severity of lung disease.
Spirometers differ fundamentally based on the type of sensor mechanism used to detect air flow and volume. The two most commonly utilized sensor mechanisms in spirometers are the turbine-based sensors and the ultrasound-based sensors:
- Turbine Spirometers: An infrared detector detects the interruption of an infrared light source by the spinning rotary blades of a turbine that has been propelled by the passing air. This mechanism requires frequent calibrations checks because it is based on a mechanical component.
- Ultrasonic Spirometers: An ultrasonic transmitter and a receiver are placed perpendicular to an airflow and the transit-time flow measurement method is used to determine flow & volume characteristics of the air passing through it. With this method, higher accuracy and repeatability is achieved in results. No re-calibration is required.