CLEANING AND DISINFECTION OF THE REUSABLE TURBINE
To clean/disinfect the MIR turbine flow sensors you can use any cleaning solution available on the market provided it is not corrosive and it is cold. Any oleil-dimetil-benzil-ammonium chloride cold solution may be used for cleaning/disinfecting the turbine. The solution should be mixed with cold water basing on what specified in the instructions of the solution (generally the solution concentration shouldn’t exceed 15%-20%).
Extract the turbine from the holder and control it visually. Ensure that there are no foreign bodies, hair, sputum, threads or similar objects deposited within the body of the turbine, if this does happen then they must be removed in fact they can slow or even stop the free rotation of the turbine blade and thus compromise the measurements.
Immerse the turbine in a cold sterilizing solution, move it briskly but gently inside the solution to remove impurities. Let it soak for the time specified in the instructions of the solution, generally about 60 min. Rinse well without exposing the turbine to a direct jet of water (no direct jet of water like tap..). Let it dry on a clean surface in an upright position without exposing the turbine to a direct jet of hot air or placing it close to hot air sources (hairdryer, heating, direct sun rays...). The turbine doesn’t need to be completely dry before use. Assemble the turbine again and proceed with new tests.
NO CALIBRATION REQUIRED
The MIR range of spirometers use a digital turbine flow meter working on the infrared interruption principle. Two sets of infrared transmitters (TX) and receivers (RX) detect the rotation of the rotor within the tube (fig1). In normal conditions and with the flow meter undamaged, the measurement depends only and exclusively on the velocity of the air in transit through the turbine tube.
In addition to that, unlike the other kinds of flow meter such as those based on pressure, the measurements made with this mechanical flow meter are NOT influenced in any way by the environmental conditions such as temperature, pressure, humidity and density (or viscosity) of the gas being measured.
Given all of the above, it is possible to confirm that providing the turbine is kept clean and free from foreign bodies, then the response of the turbine set at the factory cannot be modified and thus the turbine does not require calibration.
The only way in which the measurement can change would be by the presence of some kind of "foreign body" within the turbine tube, such as a hair, thread or sputum. This could create a kind of friction which could slow down or even stop the normal rotation of the rotor within the turbine tube.
In order to ensure the absence of some kind of "foreign body" which could slow down or even stop the normal rotation of the rotor, MIR spirometers use a software algorithm which constantly analyses the movement of the rotor and within a certain range of very low flow. The device gives a feedback of an acoustic signal "beep" when the flow is within this range, thus ensuring that the rotor is moving freely and without any friction with possible foreign bodies. Of course, the user is also able to use a calibration syringe to check the correct functioning of the system (see below).
ABOUT TURBINE CALIBRATION CHECK
The accuracy of MIR spirometers can be verified by checking the calibration of the turbine flowmeter and performing maintenance procedures at regular intervals. Frequent calibration checks allow for early identification of equipment problems. The advantage of MIR flow sensor turbine is that calibration check and re-calibration (if required) does not need to be performed by the Manufacturer but can be performed by the user. Just connect your MIR spirometer to a calibration syringe and inject 3L of air at three different speeds. Use winspiroPRO® software, winspiroLIGHT® software or a MIR Spirolab Desktop Spirometer to read the air flows and detect and restore any possible discrepancy with factory values.