EvitaXL

The difference between measured values under NTPD and
BTPS conditions is typically approx. 12 %.
Example: heating up 500 mL tidal volume NTPD to 37 o C and
moistening it to 100 % rel. humidity produces 564 mL BTPS.
EvitaXL doses the tidal volume so that the set tidal volume
under BTPS is effective in the lung.
The expiratory measurement is performed on the basis of saturated
gases at 30 o C.
Measurement principles
Flow Measurement
The expiratory flow is measured with a hot-wire anemometer.
The energy needed to keep the hot wire at a temperature of
180 oC represents the flow flowing through the sensor and
cooling the hot wire.
O2 measurement
The oxygen measurement is based on the principle of a galvanic
cell. The monitored gas diffuses through a membrane
into the electrolyte in the sensor. The electrolyte contains a
working electrode and a reference electrode. The oxygen is
reduced electrochemically and the resultant current is proportional
to the O2 partial pressure in the gas.
CO2 measurement
CO2 is measured in the main stream and is based on an
absorption measurement. A spectrum is output by a light
source while two detectors register the characteristic absorption
spectrum and generate electrical signals as a function of
the CO2 concentration. These signals are evaluated and displayed.
Condensation is prevented by heating the CO2
measuring unit.
Measurements
Flow Measurement
Measurement principles
Instructions for Use EvitaXL 219