Author: Debeer Yaro
To simulate a real patient, certain modifications need to be made to the testing setup used previously on other machines. A COVID-19 patient typically has fluid build-up into his/her lungs. To test whether the sensors/machine can handle this high air humidity, water is poured into the test lung. To evaporate the water and ensure a relative humidity in the air of +/- 100%, the lung is emerged into heated water of 80°C (seen on picture 1). The water is kept at this temperature thanks to an immersible electric water heater.
After 12 hours of using the setup where the PCB of the flow/pressure sensor was facing towards the ceiling (as seen on picture 1), no errors/alarms or failures were detected. When checking the tubes, condensation was clearly visible.
The test was done over again but this time the flow/pressure sensor was taped down so that the PCB was facing towards the ground (as seen on picture 2). Unfortunately, after coming back after a few hours the flow and pressure sensor gave no readings. It seems in this setup the measuring canal of the flow/pressure sensor is blocked more easily due to the water in the air (seen on picture 3). After blowing air trough the sensor grid and clearing the canal, the sensor critically failed (seen on picture 4). This setup could occur in the worst case scenario, when turning the patient on his chest, thus the sensor must work in these conditions.