A-a gradient

Jump to navigation Jump to search

WikiDoc Resources for A-a gradient

Articles

Most recent articles on A-a gradient

Most cited articles on A-a gradient

Review articles on A-a gradient

Articles on A-a gradient in N Eng J Med, Lancet, BMJ

Media

Powerpoint slides on A-a gradient

Images of A-a gradient

Photos of A-a gradient

Podcasts & MP3s on A-a gradient

Videos on A-a gradient

Evidence Based Medicine

Cochrane Collaboration on A-a gradient

Bandolier on A-a gradient

TRIP on A-a gradient

Clinical Trials

Ongoing Trials on A-a gradient at Clinical Trials.gov

Trial results on A-a gradient

Clinical Trials on A-a gradient at Google

Guidelines / Policies / Govt

US National Guidelines Clearinghouse on A-a gradient

NICE Guidance on A-a gradient

NHS PRODIGY Guidance

FDA on A-a gradient

CDC on A-a gradient

Books

Books on A-a gradient

News

A-a gradient in the news

Be alerted to news on A-a gradient

News trends on A-a gradient

Commentary

Blogs on A-a gradient

Definitions

Definitions of A-a gradient

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

Symptoms of A-a gradient

Causes & Risk Factors for A-a gradient

Diagnostic studies for A-a gradient

Treatment of A-a gradient

Continuing Medical Education (CME)

CME Programs on A-a gradient

International

A-a gradient en Espanol

A-a gradient en Francais

Business

A-a gradient in the Marketplace

Patents on A-a gradient

Experimental / Informatics

List of terms related to A-a gradient

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

  1. Costanzo, Linda (2006). Brs Physiology. Hagerstwon: Lippincott Williams & Wilkins. ISBN 0781773113.


Template:WikiDoc Sources