Asthma and COPD Q 26

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A nurse reviews the ABG values and notes a pH of 7.50, a PCO2 of 30 mm Hg, and an HCO3 of 25 mEq/L. The nurse interprets these values as indicating:

  

     A. Respiratory acidosis uncompensated

     B. Respiratory alkalosis uncompensated

     C. Metabolic acidosis uncompensated

     D. Metabolic acidosis partially compensated.

    

    

Correct Answer: B. Respiratory alkalosis uncompensated

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In respiratory alkalosis, the pH will be higher than normal and the PCO2 will be low. Respiratory alkalosis is by definition a disease state where the body’s pH is elevated to greater than 7.45 secondary to some respiratory or pulmonary process. herefore, respiratory alkalosis is a decrease in serum CO2. While it is theoretically possible to have decreased CO2 production, in every scenario this illness is a result of hyperventilation where CO2 is breathed away.

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Option A: The primary disturbance is an elevated arterial partial pressure of carbon dioxide (pCO2) and a decreased ratio of arterial bicarbonate to arterial pCO2, which results in a decrease in the pH of the blood. To compensate for the disturbance in the balance between carbon dioxide and bicarbonate (HCO3-), the kidneys begin to excrete more acid in the forms of hydrogen and ammonium and reabsorb more base in the form of bicarbonate. This compensation helps to normalize the pH.

Option C: Acidemia refers to a pH less than the normal range of 7.35 to 7.45. In addition, metabolic acidosis requires a bicarbonate value less than 24 mEq/L. Metabolic acidosis is due to alterations in bicarbonate, so the pCO2 is less than 40 since it is not the cause of the primary acid-base disturbance. In metabolic acidosis, the distinguishing lab value is a decreased bicarbonate (normal range 21 to 28 mEq/L).

Option D: Respiratory compensation is the physiologic mechanism to help normalize metabolic acidosis, however, compensation never completely corrects an acidemia. It is important to determine if there is adequate respiratory compensation or if there is another underlying respiratory acid-base disturbance.

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