A-a gradient: Difference between revisions
No edit summary |
No edit summary |
||
| (3 intermediate revisions by the same user not shown) | |||
| Line 1: | Line 1: | ||
{{SI}} | {{SI}} | ||
{{CMG}} | |||
==Overview== | ==Overview== | ||
| Line 22: | Line 23: | ||
===Values and Meaning=== | ===Values and Meaning=== | ||
The normal A-a gradient is < 10 mmHg, but can range from 5-20 mmHg in a normal individual. An increased A-a gradient suggests a diffusion defect, V/Q (ventilation/perfusion) defect, or right-to-left shunt.< | The normal A-a gradient is < 10 mmHg, but can range from 5-20 mmHg in a normal individual. An increased A-a gradient suggests a diffusion defect, V/Q (ventilation/perfusion) defect, or right-to-left shunt. <ref>{{cite book | last = Costanzo | first = Linda | title = Brs Physiology | publisher = Lippincott Williams & Wilkins | location = Hagerstwon | year = 2006 | isbn = 0781773113 }}</ref> | ||
==References== | |||
{{reflist|2}} | |||
[[Category:Pulmonology]] | [[Category:Pulmonology]] | ||
[[Category:Overview complete]] | |||
{{WikiDoc Help Menu}} | {{WikiDoc Help Menu}} | ||
{{WikiDoc Sources}} | {{WikiDoc Sources}} | ||
Latest revision as of 14:52, 27 September 2011
|
WikiDoc Resources for A-a gradient |
|
Articles |
|---|
|
Most recent articles on A-a gradient Most cited articles on A-a gradient |
|
Media |
|
Powerpoint slides on A-a gradient |
|
Evidence Based Medicine |
|
Clinical Trials |
|
Ongoing Trials on A-a gradient at Clinical Trials.gov Clinical Trials on A-a gradient at Google
|
|
Guidelines / Policies / Govt |
|
US National Guidelines Clearinghouse on A-a gradient
|
|
Books |
|
News |
|
Commentary |
|
Definitions |
|
Patient Resources / Community |
|
Patient resources on A-a gradient Discussion groups on A-a gradient Patient Handouts on A-a gradient Directions to Hospitals Treating A-a gradient Risk calculators and risk factors for A-a gradient
|
|
Healthcare Provider Resources |
|
Causes & Risk Factors for A-a gradient |
|
Continuing Medical Education (CME) |
|
International |
|
|
|
Business |
|
Experimental / Informatics |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
The Alveolar-arterial gradient (A-a gradient), is used to compare the causes of hypoxemia.
A-a Gradient Equation
A - a gradient = PAO2 - PaO2
Where:
PAO2 = alveolar PO2 (calculated from the alveolar gas equation)
PaO2 = arterial PO2 (measured in arterial blood)
The Alveolar Gas Equation
PAO2 = PIO2 - PACO2/R
Where:
PIO2 = FIO2 x (760 mmHg - 47mmHg) = inspired O2
- FIO2 = 21% at sea level atmospheric pressure = 0.21
- 760 mmHg = atmospheric pressure at sea level
- 47 mmHg = H2O pressure
PACO2 = arterial PCO2 measured in plasma
R = respiratory exchange ratio or respiratory quotient = 0.8 under normal conditions
Values and Meaning
The normal A-a gradient is < 10 mmHg, but can range from 5-20 mmHg in a normal individual. An increased A-a gradient suggests a diffusion defect, V/Q (ventilation/perfusion) defect, or right-to-left shunt. [1]
References
- ↑ Costanzo, Linda (2006). Brs Physiology. Hagerstwon: Lippincott Williams & Wilkins. ISBN 0781773113.