19 - 4
• The watertrap collects water drops condensed in the sample line and therefore prevents them from
entering the module. To avoid blocking the airway, empty the watertrap container whenever half
full. Dispose of accumulated fluids in accordance with hospital policy or your local regulations.
• The watertrap has a filter preventing bacterium, water and secretions from entering the module.
After long-term use, dust or other substances may compromise the performance of the filter or even
block the airway. In this case, replace the watertrap. Replacing the watertrap once a month is
recommended.
• Do not apply adult or pediatric watertrap to the neonate patient. Otherwise, patient injury could
result.
• To extend the lifetime of the watertrap and module, disconnect the watertrap from the module and
set the operating mode to Standby when AG monitoring is not required.
19.7 Zeroing the AG Module
The AG module performs a zero calibration automatically when needed. Once the zero calibration is started, the
AG module stops measuring and “Zeroing” is displayed in the AG numeric area.
After the zero calibration is completed, the AG module reacquires the AG readings. During the reacquisition
period, “Zero Recovering” is displayed in the AG numeric area. Valid data will reappear 30 seconds after the zero
calibration is started. You can hide the display of the “Zero Recovering” message, but values displayed during
the reacquisition period may not be accurate. .
The automatic zero calibration will not start under the following conditions:
■ Physiological alarms related to CO
2
or AG are active.
■ An apnea alarm is active.
■ No breath has been detected for over 30 seconds.
You can also perform the zero calibration manually.
19.8 MAC Values
Minimum alveolar concentration (MAC) is the minimum concentration of the agent in the alveoli. It is a basic
index to indicate the depth of anesthesia. The standard ISO 80601-2-55 defines MAC as this: alveolar
concentration of an inhaled anesthetic agent that, in the absence of other anesthetic agents and at equilibrium,
prevents 50% of patients from moving in response to a standard surgical stimulus.
MAC values are listed below:
* indicates 1 MAC nitrous oxide can only be reached in hyperbaric chamber.
• The MAC values shown in the table above are those published by the U.S. Food and Drug
Administration for a healthy 40-year-old adult male patient.
• In actual applications, the MAC value may be affected by age, weight and other factors.
The formula to calculate the MAC value is as follows:
Where N is the number of all agents (including N
2
O) that the AG module can measure, EtAgent
i
is the
concentration of each agent, and AgentVol
age
i is the concentration of each agent at 1 MAC with age correction.
The formula for calculating age correction of 1 MAC is:
Agent Des Iso Enf Sev Hal
N
2
O
1 MAC 6% 1.15% 1.7% 2.1% 0.77% 105%*
MAC
EtAgent
AgentVol
age
i
-------------------------------------
i0
=
N1
–
=
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