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  A-a Gradient

 
ExpectedAaG = 2.5 + (0.21 * Age)
MeasuredAaG = (FIO2 * (pAtm - pH2O)) - (pCO2 / RespQuot) + (pCO2 * FIO2 * (1 - RespQuot) / RespQuot) - paO2

 
Input:
 
Age  
Patient Temp  
Elevation  
Percent Inspired O2  
p CO2  
Resp Quot  
p aO2  
Results:
 
Expected AaG  
Measured AaG  
 
Decimal Precision  

 
     
 
Notes

 
References
  1. West JB. Respiratory physiology: the essentials. 7th edition, Philadelphia, Lippincott William & Wilkins 2005, p.170. NLMN: 101205971 NCBI Logo
  2. Kanber GJ, King FW, Eshchar YR, et. al. The alveolar-arterial oxygen gradient in young and elderly men during air and oxygen breathing. Am Rev Respir Dis. 1968 Mar;97(3):376-81. PMID: 5638492 PubMed Logo
  3. Mellemgaard K. The alveolar-arterial oxygen difference: its size and components in normal man. Acta Physiol Scand. 1966 May;67(1):10-20. PMID: 5963295 PubMed Logo
  4. Cole RB, Bishop JM. Variation in alveolar-arterial O2 tension difference at high levels of alveolar O2 tension. J Appl Physiol. 1967 Apr;22(4):685-93. PMID: 6023181 PubMed Logo
  5. Lilienthal JL, Riley RL, et al. An experimental analysis in man of the oxygen pressure gradient from alveolar air to arterial blood during rest and exercise at sea level and at altitude. Am J Physiol. 1946 Sep;147:199-216. PMID: 21000737 PubMed Logo
  6. Le Huu Thien B,Huynh Quang D. Equation des gaz alveolaires et difference alveolo-arterielle en oxygene. J Fran Viet Pneu. 2014; 05(14): 4-10.

 
Associated Medical Subject Headings [MeSH] Terms
 
         Adolescent,   Adult,   Aged,   Aging,   Arteries,   Blood Pressure Determination,   Carbon Dioxide,   Female,   Humans,   Hydrogen-Ion Concentration,   Male,   Middle Aged,   Oximetry,   Oxygen,   Oxygen Consumption,   Partial Pressure,   Pulmonary Alveoli,   Respiration,   Respiratory Function Tests

 
Associated Logical Observation Identifiers Names and Codes [LOINC]
 
Parameter LOINC's and Units
Age 21612-7 : Years old      21612-7 : yr      21612-7 : years      30525-0 : Years old      30525-0 : yr      30525-0 : years      
Patient Temp 8310-5 : degC      
Percent Inspired O2 19993-5 : %O2      19992-7 : %O2      19994-3 : %O2      19996-8 : %O2      19995-0 : %O2      
p CO2 2019-8 : mmHg      34705-4 : mmHg      
p aO2 11556-8 : mmHg      2703-7 : mmHg      19254-2 : mmHg      
Measured AaG 19991-9 : mmHg      53809-0 : mmHg      

 
This material contains content from LOINC® (http://loinc.org). The LOINC table, LOINC codes, and LOINC panels and forms file are copyright © 1995-2014, Regenstrief Institute, Inc. and the Logical Observation Identifiers Names and Codes (LOINC) Committee and available at no cost under the license at http://loinc.org/terms-of-use.

 
Associated ICD9-CM Codes
 
   482.9Bacterial pneumonia nos
   485Bronchopneumonia org nos
   481Pneumococcal pneumonia
   480.9Viral pneumonia nos
   958.1Fat embolism
   673.20Ob pulm embol nos-unspec
   428.0Chf nos

 
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