View source for AaDO2

{{Data element
|field_name=AaDO2
|CCMDB_label=<not in CCMDB>
|CCMDB_tab=Apache
|data_type=number
|datafield_length=N/A
|program_collecting=CC
|created_raw=Created
|data_element_sort_index=34
|element_description=The patient's  {{#show: AaDO2 | ?AP phys name}} level in {{#show: AaDO2 | ?AP phys unit}}.
}}
'''AaDO2 - Alveolar-arterial oxygen tension difference
'''
*See [[APACHE Scoring table]]
*See [[FiO2 |APACHE FIO2 Table]]

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 | FIO2]] being administered to a patient is >=50%.

*To calculate the AaDO2: 
**'''AaDO2 =(([[FiO2 | FIO2]] X 713) - [[PaO2]]) - [[PaCO2]]'''
**Example with FIO2 50%, PO2 85 and CO2 40:
**((0.5 X 713)- 85) - 40)) = 231.5 

{{APACHE physiological variable
|AP phys name= Alveolar-arterial oxygen tension difference
|AP phys unit= 
|AP H4= >500
|AP H3= >=350 and <500 
|AP H2= >=200 and <350 
|AP 0= <200 
}}

==Background ==
=== 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.
{{discuss | who = Julie | question = I wonder if "null" is actually intended here, or if it was supposed to be 0. Ttenbergen 14:44, 2017 January 8 (CST)
*AaDO2 is null if there is no data for FIO2, PaO2 and PaCO2. However, no data was set to zero value instead of null.  In addition, AaDO2 and the corresponding score are required only when FIO2 >= 50%, otherwise should be treated as null. (Similarly with PO2 score, it is required when FIO2 < 50% and otherwise should be treated as null. When FIO2 =0, both AaDO2 and its score and PO2 score should be null.)  Are we setting null to zero to facilitate the programming calculation?  Is it possible to differentiate null from valid zero in both L_LOG and created_variables_CC - will the work be big? In L_LOG, these are the FIO2, CO2, PO2 and SerCO2. 14:49, 2017 March 16 (CDT)}}

== Data Integrity Checks ==
{{Data Integrity Check List}}

[[Category: ABG]]
[[Category: APACHE II]]