Clinical Reasoning: Young healthy woman with difficult-to-wean acute ventilator dependence

A 25-year-old woman with a history of occipital headaches and chronic smoking (2 pack-years) was found unconscious at home following a week of fatigue and drowsiness. She was intubated on-scene and admitted to the medical intensive care unit (ICU) for hypercapnic respiratory failure. CT scan of the chest revealed bibasilar opacities, leading to empiric treatment of pneumonia despite absence of fever and cough. Pulmonary opacities and mental status improved with treatment, but the patient failed multiple attempts to wean from ventilation before ultimate extubation. The patient then experienced sleep apnea as witnessed by hospital staff and remained persistently hypercapnic, requiring biphasic positive airway pressure (BiPAP) support. Bedside ultrasound revealed severe bidiaphragmatic weakness, prompting neurologic consultation for apparent neuromuscular respiratory failure. On examination, cranial nerves were intact. The patient had normal muscle tone, 4/5 strength in the right deltoid and right intrinsic hand muscles, no fatigable oculobulbar weakness, diffuse hyperreflexia (3/4 in bilateral brachioradialis, biceps, and triceps, 4/4 in both patellars, with 5–6 beats of clonus in both ankles), and bilateral Babinski sign. The patient had no cerebellar signs.