Medica EasyStat - Troubleshooting Guide; Troubleshooting Introduction and Kit

109
p r i n c i p l e s o f o p e r a t i o n / t h e o r y
r
1
NCCLS: Tentative standard “Definition of quantities and conversions related to blood pH and gas analysis” Vol. 2, No. 10, pages 329-361 (1982)
(National Committee for Clinical Laboratory Standards - Villanova, Pennsylvania, U.S.A.)
2
B.F. Rodak, MS, MT (ASCP) SH: Diagnostic Hematology, W.B. Saunders Co., 1995, pg. 138
3
Tietz, Fundamentals of Clinical Chemistry, 4th ed. 1996
A-aDO
2
The EasyStat analyzer calculates the alveolar-arterial oxygen gradient
according to the following equation
1
:
A-aDO
2
= PAO
2(TC)
- PaO
2(TC)
Alveolar oxygen partial pressure (PAO
2(TC)
) and arte-
rial oxygen partial pressure (PaO
2(TC)
= PO
2
(T)) are
expressed at the patient corrected temperature.
PAO
2(TC)
= (FIO
2
) (BP
(TC)
) - (PaCO
2(TC)
) (FIO
2
+ 1 - FIO
2
)
R
where: A-aDO
2
is expressed in mmHg
BP
(TC)
= Barometric Pressure - Vapor Pressure of water in mmHg
Vapor Pressure of water = 0.4 + antilog (0.0244T + 0.7659)
T = temperature in °C FIO
2
= fraction of inspired oxygen
R = 0.8 = respiratory quotient PaO
2(TC)
= PO
2
(T)
The FIO
2
value used is either the preset 21% or when entered, the
value input from the PATIENT INFORMATION screen.
RI
The EasyStat analyzer calculates the respiratory index according to
the following equation
1
:
RI = A-aDO
2
PaO
2
Anion Gap
The EasyStat (chloride mode) analyzer calculates the Anion Gap
according to the following equation
3
:
([Na
+
] + [K]) - ([HCO
3
-
] + [Cl
-
])