GE HEALTHCARE B20, User'S Reference Manual

Page: 291 / 320

Airway gas
17-23
Airway gases calculations
•
MAC =
where AA
1
=primary agent, AA
2
=secondary agent, x(AA) is Hal=0.75%, Enf=1.7%,
Iso=1.15%, Sev=2.05%, Des=6.0% and N
2
O=100%.
•
MACage (volatile agent) = (0.05T-0.85) A (1.32 x 10 -0.00303age )
where T=temperature, A=MAC
•
MACage (N2O)
=
•
Balance gas (EtBal) = 100-EtCO
2
-EtO
2
-EtN
2
O-EtAA
(pri)
-EtAA
(sec)
where EtAA
(pri)
and EtAA
(sec)
are the primary and secondary end tidal values for the
measured anesthetic agent.
Unit conversions
NOTE: 47 mmHg is the partial pressure of the saturated water vapor at 37°C.
The following lists the relationship between gas concentration and its partial pressure:
Reading in mmHg (dry gas) =
(ambient pressure in mmHg) x (gas concentration in%)
100
Reading in mmHg (water vapor saturated gas) =
(ambient pressure in mmHg - 47 mmHg) x gas concentration in%
100
Reading in kPa (dry gas) =
(ambient pressure in mmHg) x (gas concentration in%)
750
Reading in kPa (water vapor saturated gas) =
((ambient pressure in mmHg - 47mmHg) x (gas concentration in%)
750
NOTE: 47 mmHg is the partial pressure of the saturated water vapor at 37°C.
atmN 2 O
1.14 1.378 10
0.00347 age
–
×
( )
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