Chapter 18: Pulmonary Diagnostic Procedures

The patient's arterial blood gas (ABG) values on room air are PaO2, 70 mm Hg; pH, 7.31; PaCO2, 52 mm Hg; and HC03-, 24 mEq/L. What is the interpretation of the patient's ABG? a. Uncompensated metabolic alkalosis. b. Uncompensated respiratory acidosis. c. Compensated respiratory acidosis. d. Compensated respiratory alkalosis. - Answer: b. Uncompensated respiratory acidosis. Rationale: The pH is closer to the acidic level, so the primary disorder is acidosis. Uncompensated respiratory acidosis values include a pH below 7.35, PaCO2 above 45 mm Hg, and HC03- of 22 to 26 mEq/L. Compensated respiratory acidosis values include a pH of 7.35 to 7.39, PaCO2 greater than 45 mm Hg, and HC03- greater than 26 mEq/L. Compensated respiratory alkalosis values include a pH of 7.41 to 7.45, PaCO2 below 35 mm Hg, and HC03- below 22 mEq/L. Uncompensated metabolic alkalosis values include a pH above 7.45, PaCO2 of 35 to 45 mm Hg, and HC03- above 26 mEq/L. On admission, a patient presents with a respiratory rate of 24 breaths/min, pursed-lip breathing, heart rate of 96 beats/min in sinus tachycardia, and a blood pressure of 110/68 mm Hg. The patient's arterial blood gas (ABG) values on room air are PaO2, 70 mm Hg; pH, 7.38; PaCO2, 52 mm Hg; and HC03- , 34 mEq/L. What diagnoses would be most consistent with the above arterial blood gas values? a. Acute pulmonary embolism. b. Acute myocardial infarction. c. Congestive heart failure. d. Chronic obstructive pulmonary disease. - Answer: d. Chronic obstructive pulmonary disease. Rationale: The fact that the HC03- level has increased enough to compensate for the increased pCO2 level indicates that this is not an acute condition because the kidneys can take several days to adjust. The other choices would present with a lower HC03- level. The values indicate respiratory acidosis, and one of the potential causes is chronic obstructive pulmonary disease. Potential causes for respiratory alkalosis are pulmonary embolism, acute myocardial infarction, and congestive heart failure.