Overview of Acid-Base Balance - Hormonal and Metabolic

What is Acid-Base Balance? What is this medical term referring to? If you’re looking for the answer to this question, you’re in the right place, because that is what this study guide is all about.

Acid-Base Balance 

Acid-Base Balance refers to the degree of acidity or alkalinity in the body. Without the right balance, our organs and systems cannot function properly. In this article, we are going to cover acidosis, alkalosis, and acid-base balance on the pH scale. So if you’re ready, let’s get started.

What is Acid-Base Balance?

Acid-Base Balance refers to the degree of acidity or alkalinity in the human body. It is measured by the pH scale. The pH scale ranges from 0, which is very acidic, to 14, which is very alkaline.

Blood in the human body is typically slightly more alkaline than acidic. A normal pH ranges from 7.35 to 7.45. The goal of the body is to maintain the blood pH as close to 7.40 as possible.

How is an Acid-Base Balance Analysis Performed?

An acid-base balance analysis can be performed by looking at the results of an Arterial Blood Gas (ABG). It’s is a test that measures the blood levels of oxygen (PaO2), carbon dioxide (PaCO2), and acid-base balance (pH) in the body.

A sample of blood is collected and the results are used to assess how well oxygen is being distributed throughout the body and how well carbon dioxide is being removed.

This is why ABG Interpretation is a very important skill for Respiratory Therapists and medical professionals.

What are the Normal Values for Acid-Base Balance?

After an arterial blood sample is collected, it should be analyzed and interpreted by the practitioner. The following are the ABG normal values:

• pH: 7.35-7.45
• Partial Pressure of Oxygen (PaO2): 75-100 mmHg
• Partial Pressure of Carbon Dioxide (PaCO2): 35-45 mmHg
• Bicarbonate (HCO3-): 22-26 mEq/L
• Oxygen Saturation (SpO2): 94-100%

The human body strives to regulate the amount of carbon dioxide and bicarbonate in the blood in order to keep the pH within the normal range.

What are the Steps for Acid-Base Balance?

• Step 1 – Collect and Analyze an ABG Sample 
• Step 2 – Determine if the pH is Alkalosis or Acidosis
• Step 3 – Determine if the Issue is Respiratory or Metabolic
• Step 4 – Determine if it’s Compensated or Uncompensated
• Step 5 – Perform the treatment modalities recommended by the physician

We have an ABG Calculator tool that can help you with this process. With that said, it is best if you learn to perform an ABG Analysis on your own. Our complete guide on Arterial Blood Gases can help.

How Does the Body Maintain Acid-Base Balance?

Acid-Base Balance is controlled by the lungs, kidneys, and buffer systems. The lungs help with ventilation and oxygenation by providing the blood with oxygen and removing carbon dioxide on exhalation.

The kidneys help to regulate blood pH by excreting acids or bases in order to maintain a proper balance. Buffer systems help maintain proper pH balance by guarding against sudden swings in acidity and alkalinity

What are the Types of Acid-Base Disorders?

There are two types of abnormalities when it comes to maintaining Acid-Base Balance:

1. Acidosis
2. Alkalosis

Acidosis means that the blood has either too much acid, or too little bases, which results in a decreased pH. Alkalosis means that the blood has too much base, or too little acid, which results in a decreased pH.

There are also two types of Acid-Base Disorders:

1. Respiratory
2. Metabolic

Metabolic acidosis or alkalosis occurs when there is an imbalance in the production of acids or bases that results from a lack of excretion by the kidneys.

Respiratory acidosis or alkalosis occurs when the lungs are removing too much or too little carbon dioxide due to breathing disorders.

Respiratory Acidosis:

	pH	PaCO2	HCO3
Acute (Uncompensated)	< 7.35	> 45	Normal
Partially Compensated	< 7.35	> 45	> 26
Chronic (Fully Compensated)	Normal	> 45	> 26

Respiratory Alkalosis:

	pH	PaCO2	HCO3
Acute (Uncompensated)	> 7.45	< 35	Normal
Partially Compensated	> 7.45	< 35	< 22
Chronic (Fully Compensated)	Normal	< 35	< 22

Metabolic Acidosis:

	pH	PaCO2	HCO3
Acute (Uncompensated)	< 7.35	Normal	< 22
Partially Compensated	< 7.35	< 35	< 22
Chronic (Fully Compensated)	Normal	< 35	< 22

Metabolic Alkalosis:

	pH	PaCO2	HCO3
Acute (Uncompensated)	> 7.45	Normal	> 26
Partially Compensated	> 7.45	> 45	> 26
Chronic (Fully Compensated)	Normal	> 45	> 26

What is Required for the Body to be in Acid-Base Balance?

The production of hydrogen ions is exactly offset by their loss. This means that, for the body to be in acid-base balance, the level of hydrogen ions must reach equilibrium.

The kidneys maintain acid-base balance by excreting hydrogen ions and generating bicarbonate. This phenomenon maintains blood plasma pH within the normal range.

Which Two Body Systems Contribute to the Acid-Base Balance of Blood?

There are two primary systems in the body that contribute to acid-base balance. They are:

1. Respiratory System
2. Urinary System