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Hepatic encephalopathy — USMLE Step 2 CK MCQ

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MediumInternal MedicineHepatic encephalopathyUSMLE Step 2 CK

A 69-year-old man with COPD presents with worsening dyspnea, wheezing, and productive cough. After controlled oxygen, bronchodilators, and systemic glucocorticoids, respiratory rate is 31/min. Arterial blood gas shows pH 7.27, PaCO2 68 mm Hg, and PaO2 64 mm Hg. He is awake, cooperative, hemodynamically stable, and able to protect his airway. Which respiratory intervention is most appropriate?

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Correct answer: E — Start bilevel noninvasive positive-pressure ventilation

This COPD exacerbation has produced acute hypercapnic respiratory failure with respiratory acidosis. Bilevel noninvasive positive-pressure ventilation provides inspiratory pressure support to reduce respiratory muscle work and improve alveolar ventilation while expiratory pressure helps counter intrinsic positive end-expiratory pressure. In appropriately selected patients, it reduces intubation, treatment failure, and mortality. He is an appropriate candidate because he is awake, cooperative, hemodynamically stable, and able to protect his airway. Close monitoring is essential, and worsening mental status, inability to clear secretions, refractory hypoxemia, shock, or failure to improve would prompt endotracheal intubation. CPAP alone does not provide the same ventilatory assistance for hypercapnia. Uncontrolled high-concentration oxygen can worsen carbon dioxide retention; oxygen is generally titrated to an appropriate saturation range. Observation alone is unsafe in a tachypneic patient with a pH of 7.27.

Reference: American Thoracic Society/European Respiratory Society. Clinical Practice Guidelines: Noninvasive Ventilation for Acute Respiratory Failure. https://www.thoracic.org/statements/resources/cc/niv-guidelines.pdf