278 MEASUREMENT OF FUNCTIONAL RESIDUAL CAPACITY (FRC) WITH HELIUM|[sol]|OXYGEN (HELIOX) AS A WASHOUT GAS IN A MECHANICAL LUNG MODEL

摘要

OBJECTIVE: To test, whether FRC measurement by heliox washout is as reliable as with the standard oxygen washout technique, because even short term lung measurements with hyperoxic condition are potentially harmful to premature infants.METHODS: We used a mixture of helium/oxygen (60/40) in an open circuit N2 washout technique. N2 was continuously measured with a N2-UV-analyzer and FRC calculated with a standard lung function cart (Sensormedics 2600). Using a calibrated syringe (20-80 ml) as a model lung of spontaneous breathing and a rubber lung (48 ml) as a model of the ventilated lung different volumes were washed out, the initial FiO2 in the “lung” varying between .21 and .75.RESULTS: Using the same calibration volumes the heliox technique yielded more N2 counts and the calibration line was steeper as compared to the O2 washout. With 10 measurements for each setting deviation of the mean volume from the expected volume ranged from ?11.5 to 6.1% for the spontaneous breaths and from ?17.2 to ?7.6% for the ventilated lung. Maximal coefficient of variation was 9.1%.CONCLUSION: Heliox used as a washout gas gives reproducible results with high accuracy in FRC measurement of low volumes, even with elevated FiO2 and although a mass spectrometer is not used for N2 detection.(Supported by Deutsche Forschungsgemeinschaft He 1835/1-1)