Q.39 Hyperventilation (breathing rapidly and deeply) causes which of the following
event(s) in the arterial blood?
(A) Decrease in CO2 concentration
(B) Decrease in proton concentration
(C) Increase in pH
(D) Increase in O2 concentration
Hyperventilation rapidly expels excess CO₂ from the lungs, leading to respiratory alkalosis in arterial blood. This causes a decrease in CO₂ concentration, a drop in proton (H⁺) concentration, and an increase in pH, while arterial O₂ concentration sees minimal change. The correct answers for this CSIR NET Life Sciences question are (A), (B), and (C).
Option Analysis
Option (A): Decrease in CO₂ concentration
Hyperventilation increases alveolar ventilation, accelerating CO₂ removal and lowering arterial partial pressure of CO₂ (PaCO₂), known as hypocapnia. This is the primary mechanism driving respiratory alkalosis. Correct.
Option (B): Decrease in proton concentration
Lower PaCO₂ shifts the carbonic acid equilibrium (CO₂ + H₂O ⇌ H₂CO₃ ⇌ H⁺ + HCO₃⁻) leftward, reducing H⁺ (proton) concentration. This alkalizes the blood. Correct.
Option (C): Increase in pH
The drop in H⁺ directly raises blood pH above 7.45, defining acute respiratory alkalosis. Symptoms like dizziness may follow. Correct.
Option (D): Increase in O₂ concentration
Hyperventilation has little effect on arterial O₂ partial pressure (PaO₂) or saturation, as these are already near saturation on room air. Any minor PaO₂ rise is clinically insignificant. Incorrect.
Hyperventilation, characterized by rapid deep breathing, disrupts arterial blood gas balance primarily through hyperventilation effects on arterial blood. This condition lowers CO2 concentration in arterial blood by excessive exhalation, triggering respiratory alkalosis—a rise in pH due to decreased proton concentration. While O2 concentration remains largely unchanged, these shifts are critical for exams like CSIR NET Life Sciences.
Physiological Mechanism
Excess ventilation reduces PaCO₂ (hypocapnia), shifting the bicarbonate buffer system to consume H⁺ ions, thus decreasing proton concentration and elevating pH. Arterial blood pH rises quickly, often above 7.45.
Clinical Implications
Common in anxiety or hypoxia, it causes symptoms like paresthesia. Treatment involves rebreathing CO₂ to normalize gases.
Exam Relevance
For CSIR NET, recognize (A) decrease in CO2 concentration, (B) decrease in proton concentration, and (C) increase in pH as true; (D) increase in O2 concentration is false due to hemoglobin saturation limits.
