Respiratory acidosis develops when the blood pH is:
(a) Increased due to a decreased blood P𝒸ₒ₂ level
(b) Decreased due to an increased blood P𝒸ₒ₂ level
(c) Increased due to an increased blood P𝒸ₒ₂ level
(d) Decreased due to a decreased blood P𝒸ₒ₂ level

Verified step by step guidance

1. Step 1: Understand the definition of respiratory acidosis. Respiratory acidosis occurs when there is an accumulation of carbon dioxide (CO\_2) in the blood, leading to an increase in hydrogen ion concentration and thus a decrease in blood pH.
2. Step 2: Recall the relationship between CO\_2 and blood pH. CO\_2 reacts with water in the blood to form carbonic acid, which dissociates into hydrogen ions (H\^+) and bicarbonate (HCO\_3\^-). An increase in CO\_2 shifts this equilibrium, increasing H\^+ concentration and lowering pH.
3. Step 3: Analyze each option in terms of CO\_2 levels and pH changes: (a) Increased pH with decreased CO\_2 is alkalosis, not acidosis; (b) Decreased pH with increased CO\_2 matches respiratory acidosis; (c) Increased pH with increased CO\_2 is contradictory; (d) Decreased pH with decreased CO\_2 is unlikely.
4. Step 4: Conclude that respiratory acidosis is characterized by a decreased blood pH due to an increased blood CO\_2 level.
5. Step 5: Therefore, the correct description of respiratory acidosis corresponds to option (b): decreased pH due to increased blood P\_CO\_2.

Key Concepts

Respiratory Acidosis

Respiratory acidosis is a condition where the blood becomes more acidic due to impaired lung function, leading to an accumulation of carbon dioxide (CO₂). This excess CO₂ increases hydrogen ion concentration, lowering blood pH below the normal range (7.35-7.45). It typically results from hypoventilation or respiratory diseases.

Blood pH and Acid-Base Balance

Blood pH measures the acidity or alkalinity of blood, with normal values around 7.4. A decrease in pH indicates acidosis, while an increase indicates alkalosis. The body maintains pH balance through respiratory and renal mechanisms that regulate CO₂ and bicarbonate levels.

Partial Pressure of Carbon Dioxide (P𝒸ₒ₂)

P𝒸ₒ₂ represents the amount of CO₂ gas dissolved in the blood and is a key factor in respiratory regulation of acid-base balance. Elevated P𝒸ₒ₂ (hypercapnia) leads to increased acidity (lower pH), while decreased P𝒸ₒ₂ (hypocapnia) causes alkalinity (higher pH).