Question

When you hold your breath, carbon dioxide gas is trapped in your body. Does this increase or decrease your blood \(\mathrm{pH}\) ? Does it lead to acidosis or alkalosis? Explain your answers.

Short answer

Breath holding decreases blood pH and leads to acidosis.

Step-by-step solution

Understanding Blood pH

Blood pH measures the acidity or alkalinity of blood, with a normal range of about 7.35 to 7.45. A decrease in pH means the blood is becoming more acidic, while an increase means it is becoming more basic (alkaline).

Effect of Carbon Dioxide on Blood pH

CO2 in the blood reacts with water to form carbonic acid according to the reaction: CO2 + H2O ⇌ H2CO3. Carbonic acid then dissociates to release H+ ions, which lowers the pH of the blood, making it more acidic.

Holding Breath and CO2 Levels

When you hold your breath, CO2 levels increase in the body because breathing out is the primary method of expelling CO2. This buildup leads to more carbonic acid formation.

Conclusion on Blood pH

An increase in CO2 due to holding your breath leads to an increase in blood acidity and therefore, a decline in blood pH.

Identifying the Condition: Acidosis vs. Alkalosis

Acidosis is a condition in which the blood becomes more acidic (lower pH), whereas alkalosis is when the blood becomes more basic (higher pH). Since holding your breath increases acidity, it leads to acidosis, not alkalosis.

Key concepts

carbon dioxide (CO2)

Carbon dioxide, commonly referred to as CO2, is a gas that plays a vital role in the body's respiratory process. It is a byproduct of cellular respiration, the process by which our cells generate energy. Normally, CO2 is expelled from the body through the lungs when we breathe out. However, its role doesn’t end here. When CO2 is dissolved in the blood, it participates in a reversible chemical reaction with water to form carbonic acid (H2CO3). This is expressed in the reaction: \[ \mathrm{CO_2 + H_2O \rightleftharpoons H_2CO_3} \] Carbonic acid can further break down into hydrogen ions (H+) and bicarbonate ions (HCO3-). The presence of hydrogen ions directly influences blood pH, making the blood more acidic. This process helps to regulate pH levels in the blood, maintaining a delicate balance that is crucial for normal bodily functions. Changes in CO2 levels can therefore have significant effects on blood pH.

acidosis

Acidosis is a condition characterized by an increase in the acidity of the blood. Normally, the blood maintains a slightly alkaline pH of about 7.35 to 7.45. When the level of acidity rises, this pH value falls below the normal range, indicating acidosis. There are several causes of acidosis, but when related to CO2, it involves respiratory mechanisms. During instances like holding your breath, CO2 accumulates because it is not expelled from the lungs. This results in more CO2 reacting with water to form carbonic acid, leading to an increased release of hydrogen ions which then decreases the blood pH. Key points to remember about respiratory acidosis include:

• Caused by inadequate ventilation or situations where CO2 cannot be expelled efficiently.
• Traditionally, it involves an increase in blood CO2 that results in increased acidity.
• Treatment often involves improving airway ventilation to decrease CO2 levels in the blood.

alkalosis

In contrast to acidosis, alkalosis refers to a condition where the blood becomes more alkaline (or basic) than normal, with pH values higher than the usual 7.45. It can result from a decrease in hydrogen ion concentration or an increase in bicarbonate ions. There are two distinct types of alkalosis—metabolic and respiratory. Here, we'll focus on respiratory alkalosis as it relates to CO2. In cases where a person hyperventilates, CO2 is expelled more rapidly than it’s produced. This reduces carbonic acid (since less CO2 is available to react with water), resulting in a higher blood pH and a less acidic environment. Essential aspects of respiratory alkalosis include:

• Generally due to increased ventilation or excessive breathing rates.
• Leads to a decrease in CO2 levels and subsequent rise in blood pH.
• Can be managed by controlling breathing rates and ensuring a constant CO2 level in the body.

Given that holding your breath leads to acidosis rather than alkalosis, understanding the balance of CO2 provides a clear picture of how these conditions manifest and how they can be managed.