The ABC of Acid-base balance

Hello there, weary traveller, and welcome!

You are standing (or, more likely, sitting) in front of what has literally been termed as the most basic physiologic phenomenon described and quantified in this hopefully useful study-helper. But do not let that fool you! Things could get really sour if you take it too lightly.

We are well aware that you are most likely anxious to dive into the good stuff, so we are going to keep this intro short and give you the bullet points you are going to need on your way down this delightful physiological rabbit hole. Also, we assume that if you are a student and are using this mostly for the sake of passing an exam, you would prefer us to get to the point as quickly as possible.

So, without further ado, here is the promised bare minimum of knowledge you need to equip yourself with in order to find your way in the dark depths of protons, graphs and equations:

1. Hydrogen ions (from here on simply called protons for obvious reasons) are the culprits that determine pH – the relationship is a logarithmic one. The proton concentration is in the nanomolar range, while most of the other parameters are described in the milimolar range.
2. The normal reference range for blood pH lies from 7,37 to 7,43. We chose 7,4 for our starting point. It is also the midpoint of the normal reference range, so you could say it is “the normalest”.
3. Buffers are substances that work hard all day and night to minimise any changes to the pH in a solution – the solution of interest here being human blood in its natural environment. The buffers in our bodies are crudely separated into bicarbonate and non-bicarbonate buffers.
4. There are four basic acid-base disturbances that can befall an unsuspecting victim: metabolic acidosis, respiratory acidosis, metabolic alkalosis, and respiratory alkalosis. And because life is never just plain metabolic or respiratory, mixed disturbances also exist.
5. Our bodies of course do their best to adhere to a physiologically modified Le Chatelier's principle and compensate for the disturbance. Here the lungs and kidneys take turns in the “worker of the month” section of the body's acid-base newspaper.
6. Multiple approaches are used to interpret acid-base changes in humans. All of them are explained and described a little further down the road.

The chapter of our application you are about to explore is subdivided into five parts (counting this introduction) that are organised in a way that can build and strenghten your knowledge step by step. With this in mind, our recommendation is to master them one at a time in the order that they are listed. You can of course jump back and forth as you please or only use the ones you deem worthy of your time.

The first section covers two approaches to the interpretation of acid-base physiology, namely the Physiological Boston approach and the Base excess Copenhagen approach, using the Davenport diagram. The second one takes a look at the third, Quantitative Stewart approach, with the help of the Gamble diagram. In the final round, all three of these approaches to acid-base interpretation collide in an epic battle of wits, hopefully leaving you wiser than you were before you stumbled upon this simulator.

If you came here with the intent to learn, please continue and enjoy the experience. If you came by accident, by all means, continue all the same.