|Data Element (edit)|
|CCMDB Label:||<not in CCMDB>|
The patient's Alveolar-arterial oxygen tension difference level in . AaDO2 - Alveolar-arterial oxygen tension difference
Measures the difference in the partial pressure of oxygen between the alveoli and the arteries. This measures the efficiency of the oxygen exchange between the lung alveoli and the pulmonary capillaries.
- A calculated component of APACHE II score when FIO2 being administered to a patient is >=50%.
- To calculate the AaDO2:
|Apache Physiological Variable|
|variable name||Alveolar-arterial oxygen tension difference|
|absolute max allowed|
|high score 4||>500|
|high score 3||>=350 and <500|
|high score 2||>=200 and <350|
|high score 1|
|low score 1|
|low score 2|
|low score 3|
|low score 4|
|AP phys warnMin|
|AP phys absMin|
This value is used to generate the APACHE Score.
Collecting Apache physiological variables
There are some specific rules to follow in choosing which one of several lab results to collect.
See APACHE physiological variable collection for details.
Rules described in APACHE_physiological_variable_collection#Exceptionally_high_or_low_values are implemented by Check APACHE physiological variable high low.
Why the constant 713?
The value 713 mmHg is the barometric pressure (Pb) used in the AaDO2 formula.
Normal Sea level Pb is 760 mmHg. (Winnipeg is close to sea level. We don't adjust for different elevations around the city nor do we adjust this value for the constant changes in Pb).
The barometric pressure is corrected for water vapor pressure (Pbc).
- (vapor pressure is 47 mmHg @ a temperature of 37C).
- (760-47)= Pbc of 713 mmHg.
can be less than 0
*4 AaDO2 can be 0 or negative
Unlike other physiological variables AaDO2 can be 0 or negative, so onlike the others the score for a 0 AaDO2 is 0 if AaDO2 < 200, which includes AaDO2<=0.
Note for programming only: The score is still null if the AaDO2 is null.
Data Integrity Checks
Data Integrity Checks (SMW)
|Check APACHE physiological variable high low||CCMDB.accdb||implemented|