The IV Pole Top
The IV Pole Base
Acid-Base Balance

by "Grog" (Alan W. Grogono), Professor Emeritus, Tulane University Department of Anesthesiology

Acid-Base Balance Tutorial Home Page

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Home IconThis Website mixes serious learning with a little fun. Enough: 'An author who speaks about his own books is almost as bad as a mother who talks about her own children' – Benjamin Disraeli. Nov 19th 1873.

Exciting News

Treat High Altitude patients using our new High Altitude Diagram. It shows the usual PCO2 and Base Excess for high altitudes and that allows the patient to be treated appropriately.


The devastating 1952 poliomyelitis epidemic in Copenhagen (Danish: København) demonstrated the critical need for accurate acid-base assessment. About 3,000 people were infected, of whom roughly one in ten had respiratory paralysis due to bulbar poliomyelitis and about one in hundred died. The story of how 1,500 medical and dental students provided 24-hour manual ventilation and saved about 100 lives (Berend 2018) is summarized in greater detail at the start of the History Section. The author's own involvement in critical care, the creation of ventilators, and the design of acid-base diagrams is at the foot of the History Section

Acid-Base Balance Diagram: Typical Zones
Acid-Base Balance Diagram: Typical Zones

Acid-Base Balance Diagram: Typical Zones


This tutorial was completely rewritten in March 2018 with new text, diagrams, fonts, and colors. It explains clinical acid-base balance and features the Sea Level Acid-base Diagram (on the right) that now displays typical clinical disturbances in both Metric and US Units. The small icons and diagrams throughout the website provide additional information – sometimes serious, sometimes light-hearted!

The website also focuses on the many Unfortunate Historical Decisions whose legacy still complicates this subject.

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The Bird's Eye-View, Two Components

Lungs "Breath out the CO2."

Respiratory: When breathing is inadequate carbon dioxide accumulates. The extra CO2 molecules combine with water to form carbonic acid, also known as respiratory acid, which contributes to an acid pH. The treatment, if all else fails, is to lower the PCO2 by breathing for the patient using a ventilator.

Kidney "Either treat, or wait and watch."

Metabolic: When normal metabolism is impaired acid forms, e.g., poor blood supply stops oxidative metabolism and lactic acid forms. This acid is not respiratory so, by exclusion, it is "metabolic." If severe, the patient may be in shock and require treatment, possibly by neutralizing this excess acid with bicarbonate, possibly by allowing time for excretion/metabolism.

Six Sentences "Just six Sentences!"

That's It: we just covered the whole of acid-base balance in six sentences. As you explore this site, keep this bird's eye-view in mind. We will also consider low levels of metabolic and respiratory acid (alkalosis) – but clinical problems usually result in acidosis, which justifies focusing on acidosis.

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Why do we care?

Heart "Are they diseases themselves?"

Variations in pH or PCO2 used to be thought of as pathological entities. Experiments by Xu et al have shown, however, that very low pH and very high PCO2 may both be well tolerated when circulation and oxygenation are maintained. The implication is that abnormal levels of PCO2 or pH are best regarded as indicators of serious trouble, but not as pathology in themselves.

Getting Started

Start "How wonderful it is that nobody need wait a single moment before starting to improve the world." Anne Frank (1929 - 1945), Diary of a Young Girl, 1952.

It will depend on what you know and how you like to learn. History, Physiology, and the Interactive Diagram are all good places to start.

Alternatively, use the Index to select a particular topic that interests you most.

Interactive Acid-Base Diagram

Diagram "Interactive – like a game!"

The Acid-Base Diagram is a Major Feature of this website. It shows characteristic zones on an interactive diagram and simultaneously provides continuous text interpretation.

In addition to showing the Classical Zones, it provides Self Testing, Examples, a Large Teaching Version, a High Altitude Version, and the option to Enter Your Own Data.

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Computing Techniques

Computer "Explained as simply as possible!"

The mathematics and programming underlying the interactive diagrams and equations are described on a separate page.

This site employs Javascript, and Pop-Ups. To get the best out of this website, these must be active.


Mail "Correspond, touch, associate, connect." Contact me if you wish. I appreciate feedback, especially if you have ideas comments or suggestions, or if you find errors or spelling mistakes. Thank you.

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Med Ed Portal
Peer-reviewed accepted 11/21/06:
MedEdPORTAL. Number: 402.

Peer Reviewed by AAMC MedEdPORTAL

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Acknowledgements and Thanks

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Same Author:

Animated Knots by Grog
Animated Napkins by Grog
Stereo Art
Magic Squares

About the Author:

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Acid-Base Tutorial
Alan W. Grogono
Small Logo Copyright Jan. 2020.
All Rights Reserved
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