All Inofab Health spirometers use ultrasonic flow measurement technology in order to deliver the most reliable respiratory measurements possible. Let’s take a look into how this happens exactly, and the logic behind it.
As seen in the representative image above, the SpiroHome spirometer contains 2 ‘transit-time’ ultrasonic transducers (transducer ‘A' and ‘B’) that transmit and receive ultrasonic pulses between each other. When air flows between these transducers, for example during a spirometry test, these ultrasonic pulses experience a slight deviation in travel or ‘transit’ time from one transducer to the other. The degree of change in transit time or ‘time of flight’ of the ultrasonic pulses depends on the rate of air flow. Thus, time-of-flight data from ultrasonic sensors are used to deduce air flow rates.
Zero flow measurement
Right before a spirometry test starts, the device always performs a ‘zero flow measurement’. This step requires the device to first be placed on a flat surface to eliminate any flow of air through the device. The ultrasonic transducers will then transmit/receive ultrasonic pulses during this ‘zero flow’ state. The zero flow measurement of the ultrasonic sensors allows the device to take into account the ambient conditions of the testing environment so that it can be factored out from the airflow measurements taken during the spirometry test.
The start of your spirometry test
Exhaled air reduces the travel time of signals moving from transducer B to A (against breath) and increases the travel time of signals from A to B (with breath).
The difference in the travel times of each signal (from A and B) provides breath flow data.
The air passing through the mouthpiece is sampled 200 times in one second. This means the device can capture even very small deviations in air flow rate.
Processing the flow data
Inofab Health’s SDK (software development kit) runs its algorithm to calculate your spirometric parameters using the flow data captured by the transit time ultrasonic sensors. The spirometry results you see at the end of your spirometry test are the outcome of this state-of-the-art airflow measurement and processing journey.
That is what lies behind the excellent reliability of our process. If you want to delve deeper and learn more, you can check out the paper from a recent study done on SpiroHome Personal and request one for yourself here.