Difference Between Metabolic and Respiratory Acidosis

The main difference between metabolic and respiratory acidosis is that the metabolic acidosis occurs due to the production of organic acids such as lactic acid and ketone bodies whereas the respiratory acidosis occurs when lungs have failed to remove excess carbon dioxide from the blood. Furthermore, metabolic acidosis lasts for a short time while respiratory acidosis is the main reason for the acid-base imbalance in the body.

Metabolic and respiratory acidosis are two types of acidic conditions that can occur in the body due to the drop in body pH from its regular level, 7.4.

Key Areas Covered

1. What is Metabolic Acidosis
     – Definition, Causes, Role in the Body
2. What is Respiratory Acidosis
     – Definition, Causes, Role in the Body
3. What are the Similarities Between Metabolic and Respiratory Acidosis
     – Outline of Common Features
4. What is the Difference Between Metabolic and Respiratory Acidosis
     – Comparison of Key Differences

Key Terms

Carbonic Acid, Metabolic Acidosis, Organic Acids, pH, Respiratory Acidosis

What is Metabolic Acidosis

Metabolic acidosis occurs due to the increased production of acids such as lactic acid and ketone bodies in the body. It may also occur when the body cannot excrete excess acids through urine. Several types of metabolic acidosis can be identified such as:

1. Lactic acidosis – develops due to the anaerobic respiration inside the muscle cells.
2. Diabetic acidosis or diabetic ketoacidosis (DKA) – develops due to the production of ketone bodies due to uncontrolled diabetes.
3. Hyperchloremic acidosis – develops due to the increased loss of sodium bicarbonate in severe diarrhea.
   

   Figure 1: Metabolic Acidosis Parameters

4. Acidosis in DCT and PCT – develops due to kidney disease.
5. Poisoning of aspirin, ethylene glycol or methanol
6. Acidosis caused by severe dehydration.

What is Respiratory Acidosis

Respiratory acidosis is the condition of having high concentrations of carbon dioxide in the blood. It is caused by the alveolar hypoventilation arisen due to the defectiveness of the nervous or respiratory system, brain injuries or asthma. Carbon dioxide is the waste of cellular respiration produced during the production of ATP energy for the body. It is excreted from the body to the external environment during exhalation.

Figure 2: Respiratory Acidosis Parameters

The accumulated carbon dioxide in the blood reacts with water to form carbonic acid, which dissociates into H⁺ and HCO^3-. The increased H⁺ concentration leads to a drop in the blood pH. When the partial pressure of CO₂ increases 60 mmHg above, respiratory acidosis occurs.  

Similarities Between Metabolic and Respiratory Acidosis

• Metabolic and respiratory acidosis are two types of acidic conditions that can occur in the body due to the drop in pH below 7.35.
• Both make urinary pH acidic.

Difference Between Metabolic and Respiratory Acidosis

Definition

Metabolic acidosis refers to a condition that occurs when the body produces excessive quantities of acid or when the kidneys are not removing enough acid from the body while respiratory acidosis refers to a condition that occurs when the lungs can’t remove enough of the carbon dioxide produced by the body.

Main Factor

The main factor of metabolic acidosis is organic acids such as lactic acid and ketone bodies while the main factor of the respiratory acidosis is dissolved carbon dioxide or carbonic acid in the blood. This is the main difference between metabolic and respiratory acidosis.

Response of the Body

Furthermore, a low pH due to metabolic acidosis stimulates the respiratory center of the brain to increase the rate of breathing while a low pH due to respiratory acidosis increases the exchange of H⁺ and Na⁺ in the kidney, increasing the formation of ammonia in the body.

Effect

Metabolic acidosis lasts for a short period of time while respiratory acidosis is the main reason for the acid-base imbalance in the body.

Conclusion

Metabolic acidosis is the drop in body pH due to the increased production of organic acids such as lactic acid and ketone bodies. The reduced excretion of acids from the body also leads to metabolic acidosis. On the other hand, respiratory acidosis occurs due to the impaired removal of carbon dioxide from the blood during respiration. The main difference between metabolic and respiratory acidosis is the type of conditions that lead to each type of acidosis.

Reference:

1. “What Is Metabolic Acidosis?” WebMD, WebMD, Available Here
2. “Respiratory Acidosis: Types, Symptoms, and Causes.” Healthline, Healthline Media, Available Here

Image Courtesy:

1. “Davenport Fig 12” By Jimmy Martenson. Frame limits and equations based off of similar figures in Horace W. Davenport. The ABC of Acid-Base Chemistry: The Elements of Physiological Blood-Gas Chemistry for Medical Students and Physicians. Sixth Edition. The University of Chicago Press. 1974. – English Wikipedia (http://en.wikipedia.org/wiki/File:Davenport_Fig_12.jpg) (CC BY-SA 3.0) via Commons Wikimedia 
2. “Davenport Fig 11” By K90 – Own work (CC BY-SA 3.0) via Commons Wikimedia