Spirometers have evolved through the years with advancements in technology allowing for the development of spirometers that are more accurate, portable, easier to use and which can be integrated into digital platforms. Spirometers operate on the basic principle of detecting flow and volume information of air exhaled/inhaled through the device, and converting this into spirometric data indicative of the patient’s lung function. 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-based spirometers out date ultrasound-based spirometers, but with the increased capacity for higher accuracy and repeatability results with ultrasound-based spirometers, ultrasound-based spirometers are gaining preference and popularity.
The turbine-based sensor involves an infrared detector detecting the interruption of an infrared light source by the spinning rotary blades of a turbine that has been propelled by passing air. This mechanism is relatively simple to construct and use, however, as it is essentially based on a mechanical component, regular re-calibration of the setup is required. Turbine-based spirometers therefore require frequent calibration checks to ensure that its accuracy is preserved. Ultrasound-based spirometers place an ultrasonic transmitter and receiver perpendicular to an airflow, and use the transit-time flow measurement method to determine flow and volume characteristics of the air passing through it. This type of technology does not require re-calibration, which is one of the key reasons for why ultrasonic spirometers are becoming increasingly popular.