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1. A 65-year-old man with a history of chronic obstructive pulmonary disease (COPD) and
hypertension presents to the emergency department with dyspnea, chest pain, and cough. He
is diagnosed with acute pulmonary embolism (PE) and started on anticoagulation therapy. His
arterial blood gas (ABG) results are: pH 7.32, PaCO2 50 mmHg, PaO2 60 mmHg, HCO3 26
mEq/L, SaO2 90%. Which of the following statements is true about his ABG results?
A) He has respiratory acidosis with partial compensation.
B) He has respiratory alkalosis with partial compensation.
C) He has metabolic acidosis with partial compensation.
D) He has metabolic alkalosis with partial compensation.
Answer: A) He has respiratory acidosis with partial compensation. Rationale: Respiratory
acidosis is caused by hypoventilation, which leads to increased PaCO2 and decreased pH. The
kidneys try to compensate by retaining HCO3, which increases the base excess. However, the
compensation is incomplete because the pH is still below the normal range (7.35-7.45).
2. A 45-year-old woman with a history of asthma and diabetes mellitus is admitted to the
intensive care unit (ICU) with severe acute respiratory distress syndrome (ARDS) due to COVID19 infection. She is intubated and mechanically ventilated with a tidal volume of 6 mL/kg, a
positive end-expiratory pressure (PEEP) of 10 cm H2O, and a fraction of inspired oxygen (FiO2)
of 0.8. Her ABG results are: pH 7.28, PaCO2 48 mmHg, PaO2 55 mmHg, HCO3 22 mEq/L, SaO2
88%. Which of the following interventions is most appropriate to improve her oxygenation?
A) Increase the tidal volume to 8 mL/kg.
B) Increase the PEEP to 15 cm H2O.
C) Decrease the FiO2 to 0.6.
D) Decrease the respiratory rate to 10 breaths/min.
Answer: B) Increase the PEEP to 15 cm H2O. Rationale: ARDS is characterized by alveolar
collapse and pulmonary edema, which impair gas exchange and cause hypoxemia. PEEP helps
to recruit collapsed alveoli and increase functional residual capacity, which improves
oxygenation. Increasing the tidal volume or decreasing the respiratory rate would worsen
ventilation-perfusion mismatch and increase the risk of ventilator-induced lung injury.
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