In mechanical ventilators, the inspiratory and expiratory volumes (Vti, Vte) and minute volumes (Vi and Ve) must be precisely checked using gas flow analyzers or ventilator testers.
Ventilator testers from different manufacturers can measure flow and volume. However, flow accuracy is strongly temperature-dependent and requires temperature compensation. This is particularly important because turbine-operated ventilators raise the gas temperature above the ambient temperature.
A turbine-driven homecare ventilator, such as the Resmed Stellar (shown above), raises the temperature of the respiratory gas to 30.2°C due to the turbine. (Settings: IPAP = 30 cmH2O, EPAP = 7 cmH2O, rate = 15 bpm)
The IMT Analytics FlowAnalyser PF-300 PRO measures flow with an accuracy of 1.65% of reading, while the CITREX H5 (shown above) measures flow with an accuracy of 1.9% of reading.
A Fluke Biomedical VT650 or VT900A measures flow with an accuracy of only 2% of reading if the gas temperature is between 19 and 27°C. At a gas temperature of 30°C, a VT650 or VT900A measures flow with an accuracy of 2.6% of reading (2% + 3 x 0.2%), as the flow accuracy must be corrected by 0.2% per degree Celsius (see VT900A user manual, page 41). This indicates a significant difference in accuracy between devices when measuring flow in turbine ventilators.
Summary:
The temperature influence on flow and volume measurement in ventilator testers must always be considered, especially when testing turbine-driven ventilators that deliver gas temperatures above ambient. All IMT Analytics Gas Flow Analyzers feature an advanced, patented temperature compensation for flow measurement, to guarantee constant flow accuracy over a wide temperature range.
