A nurse is reviewing the arterial blood gas (ABG) results of a client who the provider suspects has respiratory alkalosis. Which of the following results should the nurse expect to see to confirm respiratory alkalosis?

Choice A rationale While a pH value above 7.45 signifies an alkalotic state where the blood is excessively basic, this finding alone does not distinguish between a respiratory or metabolic cause. Alkalosis indicates a hydrogen ion concentration decrease, but the nurse must evaluate the carbon dioxide and bicarbonate levels to determine the origin of the imbalance. In respiratory alkalosis, the elevation in pH is specifically driven by the excessive loss of carbon dioxide through the lungs during hyperventilation. Choice B rationale The PaO2 value represents the partial pressure of oxygen in arterial blood and is used to assess oxygenation status rather than acid-base balance. A level below 70 mm Hg indicates hypoxemia, as the normal range is typically 80 to 100 mm Hg. While hypoxemia can sometimes trigger hyperventilation leading to respiratory alkalosis, the low oxygen level itself is not the diagnostic criteria for alkalosis. The focus must remain on the relationship between pH and carbon dioxide. Choice C rationale Bicarbonate (HCO3) is the metabolic component of the acid-base balance, and its normal range is 22 to 26 mEq/L. A bicarbonate level above 26 mEq/L would suggest a metabolic alkalosis or a compensatory mechanism for chronic respiratory acidosis. In the acute stage of respiratory alkalosis, the bicarbonate level usually remains within the normal range because the kidneys require several days to compensate by excreting excess base to bring the pH back toward the normal physiological range. Choice D rationale Respiratory alkalosis is defined by a primary decrease in the partial pressure of arterial carbon dioxide (PaCO2) below the normal reference range of 35 to 45 mm Hg. This occurs when hyperventilation causes the lungs to exhale carbon dioxide faster than the body produces it, leading to a deficit of carbonic acid. The reduction in PaCO2 directly causes the arterial pH to rise above 7.45, confirming that the alkalotic state is respiratory in origin rather than metabolic. .