What is the best indicator of the adequacy of alveolar ventilation?

• A. Tidal volume
• B. Color
• C. PaCO2 from an arterial blood gas analysis
• D. Respiratory rate

Answer: (C)

The adequacy of alveolar ventilation is primarily indicated by the levels of carbon dioxide (PaCO2) in the arterial blood. When assessing ventilation, the body’s ability to expel carbon dioxide effectively is crucial, as it directly relates to how well the lungs are functioning to remove CO2 produced by metabolism. A normal PaCO2 range (typically 35-45 mmHg) indicates that ventilation is adequate; deviations from this range can signal respiratory inadequacy.

If the carbon dioxide level is elevated (hypercapnia), it suggests that ventilation is insufficient and CO2 is not being removed adequately, which can lead to respiratory acidosis. Conversely, low levels of carbon dioxide (hypocapnia) might indicate hyperventilation and excessive loss of CO2. Therefore, monitoring PaCO2 through arterial blood gas analysis provides a direct and reliable assessment of ventilatory function and helps in diagnosing respiratory conditions.

While tidal volume, color of the patient, and respiratory rate provide some information about a patient's respiratory status, they are not as definitive in assessing the adequacy of alveolar ventilation as PaCO2 levels. Tidal volume refers to the amount of air exchanged in a single breath but does not account for its effectiveness in gas exchange. The color may