Whenever the Agent sensor changes from a steady state condition, the system will perform an zero
reference adjustment to restabilize the sensor readings. During this time it is possible for a false
identification and concentration value to occur. Change from a steady state condition may occur
During the first hour after the system has been turned on and flowing oxygen greater than 50
percent, the CO2 waveform periodically baselines to complete reference measurement; however,
the measurement numeric values remain. Once the system reaches ambient temperature this
condition will cease to occur.
To perform a manual zero reference adjustment
Breath Rate Distortion
The effect of rise time distortion to the gas curve becomes apparent when the breathing rate
increases so that the time for a full inspiratory or expiratory event gets shorter. In those
situations, due to the effect of the rise time, the gas curve does not reach the true end‐tidal (or
first inspired value) and the end‐tidal gas value may then be underestimated. Correspondingly,
the first inspired value may be overestimated. Below is an exaggerated illustration of the effect.
Expression MR400 Instructions for Use
– Applying a sampling line for the first time.
– Switching from one agent to another.
– Going from high agent concentrations to low or off.
Select the CO2 VS box.
The CO2 menu appears. Current settings are displayed.
Select Zero Cal.
Allow the process to complete, typically 10–12 seconds.
Monitoring Agents and Gases (AGENT Option) 9‐3