Which description best defines respiratory alkalosis in acid-base balance?

• A. A primary decrease in plasma bicarbonate $H_{2}C{O}_3$ due to diarrhea, causing decreased blood pH
• B. A primary increase in arterial $P_{aC{O}_2}$ due to hypoventilation, causing decreased blood pH
• C. A primary decrease in arterial $P_{aC{O}_2}$ due to hyperventilation, causing increased blood pH
• D. A primary increase in plasma bicarbonate $H_2^{+}C{O}_3$ due to loss of gastric acid, causing increased blood pH

Answer: (C)

Verified step by step guidance

1. Understand that respiratory alkalosis is a condition related to the acid-base balance in the blood, specifically caused by changes in carbon dioxide (CO2) levels due to respiratory activity.
2. Recall that CO2 in the blood combines with water to form carbonic acid, which dissociates into hydrogen ions (H+) and bicarbonate (HCO3-), influencing blood pH. The relevant equilibrium is: \(\mathrm{CO_2 + H_2O \leftrightarrow H_2CO_3 \leftrightarrow H^+ + HCO_3^-}\).
3. Identify that respiratory alkalosis occurs when there is a primary decrease in arterial partial pressure of CO2 (\(P_{a}CO_2\)), typically due to hyperventilation, which causes less CO2 to be present in the blood.
4. Recognize that a decrease in \(P_{a}CO_2\) shifts the equilibrium to the left, reducing hydrogen ion concentration and thus increasing blood pH (making it more alkaline).
5. Evaluate the answer choices by matching the description of decreased \(P_{a}CO_2\) due to hyperventilation and increased blood pH, which correctly defines respiratory alkalosis.