Question

he bicarbonate concentration of the blood would be decreased during a. metabolic acidosis. b. respiratory acidosis. c. metabolic alkalosis. d. respiratory alkalosis.

Short answer

The bicarbonate concentration of the blood would be decreased during metabolic acidosis.

Step-by-step solution

Understanding Metabolic and Respiratory Imbalances

Metabolic imbalances occur when there is a problem with the production or excretion of acids or bases in the body. Respiratory imbalances occur when the lungs cannot efficiently exchange CO2 and oxygen, resulting in a change in the body’s acid-base balance. Acidosis refers to an increase in acidity of the blood, whereas alkalosis refers to a decrease in the acidity of the blood. The main role of bicarbonate (HCO3-) is to act as a buffer, helping to maintain the body's acid-base balance.

Evaluating Option A: Metabolic Acidosis

Metabolic acidosis is a condition where the production of acids in the body exceeds the kidneys' ability to remove them. As a result, the blood becomes more acidic. In this situation, the body would need to compensate by using a buffer which is the bicarbonate (HCO3-) to neutralize excess H+ ions. This compensation would decrease the concentration of bicarbonate in the blood.

Evaluating Option B: Respiratory Acidosis

Respiratory acidosis occurs when the lungs are not able to remove enough CO2, resulting in an accumulation of CO2 in the blood. High levels of CO2 lead to increased production of carbonic acid and therefore more H+ ions, causing acidosis. In this case, the bicarbonate concentration would be increased to buffer the excess acidity.

Evaluating Option C: Metabolic Alkalosis

Metabolic alkalosis is a condition where the body loses acid or gains a significant amount of base, resulting in an alkaline blood pH. During metabolic alkalosis, the HCO3- concentration would be increased to help restore the acid-base balance, so it does not fit the criteria of decreased bicarbonate concentration.

Evaluating Option D: Respiratory Alkalosis

Respiratory alkalosis occurs when the lungs remove more CO2 than necessary, leading to a reduction in carbonic acid and H+ ion concentration in the blood. In this situation, the body compensates by lowering the concentration of bicarbonate to match the reduced H+ ions and maintaining the acid-base balance.

Conclusion

Based on the above evaluation of all the options, we can conclude that the bicarbonate concentration of the blood would be decreased during: a. Metabolic Acidosis

Key concepts

Metabolic Acidosis

Metabolic acidosis occurs when the body produces excessive amounts of acid or when the kidneys cannot excrete sufficient quantities of acid. This leads to a surplus of hydrogen ions (H+), which decreases the pH level of the blood, indicating increased acidity.

There are several causes for metabolic acidosis, including kidney failure, diabetic ketoacidosis, or lactic acidosis. As the body attempts to buffer the increased acidity, bicarbonate ions (HCO3-) in the blood are used to neutralize the excess H+ ions. The chemical reaction forms water and carbon dioxide, reducing the available bicarbonate, which is reflected in a lowered bicarbonate concentration in the bloodstream during metabolic acidosis.

Understanding the Buffering System

The body’s buffering system involves bicarbonate acting as a base to neutralize the added acids. When this system is overwhelmed, the bicarbonate concentration in the blood will drop. Diagnostics of metabolic acidosis often look for a lower blood pH and reduced bicarbonate levels among other signs and symptoms.

Respiratory Acidosis

Respiratory acidosis is characterized by a decrease in the blood's pH level due to impaired lung function and subsequent CO2 retention. The lungs are responsible for expelling carbon dioxide (CO2) as a waste product of respiration. When CO2 is not eliminated effectively, it combines with water (H2O) in the body to form carbonic acid (H2CO3), which dissociates into H+ ions and bicarbonate ions (HCO3-).

This excess CO2 leads to an increase in the production of carbonic acid, tipping the balance towards acidosis. In response, the kidneys work to conserve bicarbonate to act as a buffer and counteract the acidity. Therefore, in the case of respiratory acidosis, the blood bicarbonate concentration would typically be higher, not decreased, as the body attempts to restore acid-base balance.

Acid-Base Balance

Acid-base balance is a crucial aspect of homeostasis, where the body maintains a stable internal environment, including pH levels. The normal pH range of blood is tightly regulated between 7.35 and 7.45. To achieve this, the body utilizes buffer systems, respiratory compensation, and renal compensation mechanisms.

The primary buffer system involves bicarbonate (HCO3-) and carbonic acid (H2CO3), working in conjunction to resist changes in pH. While the respiratory system regulates CO2 (a component of carbonic acid) levels through breathing, the renal system manages the excretion of hydrogen ions and the production/reabsorption of bicarbonate. These systems ensure the blood pH remains within the narrow range necessary for proper physiological function.

The Role of Bicarbonate

Bicarbonate serves as the main buffer in the blood, helping to maintain the delicate acid-base balance. Changes in bicarbonate concentration often signal an underlying issue with either the respiratory or metabolic components of the acid-base homeostasis.

Respiratory Alkalosis

Respiratory alkalosis results from an excess exhalation of CO2, leading to a deficit of carbonic acid (H2CO3) and a decrease in hydrogen ions (H+) concentration, thus causing the blood to become too alkaline (increased pH). Hyperventilation, anxiety, high altitude, or any condition leading to rapid breathing can induce respiratory alkalosis.

As a compensatory mechanism, the kidneys decrease the reabsorption of bicarbonate, directly reducing bicarbonate concentration in the blood. This reduction helps to restore acid-base balance by slightly lowering the pH towards normal levels. Therefore, during respiratory alkalosis, the bicarbonate concentration is decreased as the body attempts to compensate for the lowered level of carbon dioxide and the resultant alkaline state.

Understanding Compensation

In the face of respiratory alkalosis, the mechanism of compensation involves modulating the bicarbonate levels. This response, however, is slower compared to the immediate respiratory responses, and full compensation may take several days to take effect.