A 65-year-old woman comes to the office reporting progressively increasing orthopnea, daytime fatigue, and morning headache for the last month. She has had no chest pain or problems with swallowing or speech. Medical conditions include myocardial infarction, type 2 diabetes, hypertension, and amyotrophic lateral sclerosis. Temperature is 37 C (98.6 F), blood pressure is 130/70 mm Hg, pulse is 88/min, and respirations are 16/min. Pulse oximetry shows 95% on room air. BMI is 24 kg/m². Examination shows normal jugular venous pressure, clear lungs, and normal heart sounds. There is no peripheral edema. Neurologic examination shows 3/5 power in right lower extremity and 4/5 power in left lower extremity and muscle atrophy, unchanged from her last examination 2 months ago. Laboratory results are as follows: Which of the following is the most appropriate next step in management?

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Explanation: This patient with amyotrophic lateral sclerosis (ALS) (asymmetric muscle strength, muscle atrophy) has manifestations of early respiratory insufficiency. Patients with ALS, a terminal neurodegenerative disease that affects both upper and lower motor neuron function, most often die of respiratory failure, which is caused by multiple factors: Inspiratory muscle (eg, diaphragm) atrophy and weakness, which leads to poor inspiratory strength Expiratory muscle weakness, which leads to an ineffective cough and poor bronchial clearance Bulbar muscle weakness, which leads to dysphagia and chronic aspiration Because gravity is not assisting with lung expansion, respiratory symptoms are often more pronounced when patients are supine. In addition, sleep further contributes to respiratory insufficiency because the accessory respiratory muscles are less active during REM sleep, and relaxation of the weakened upper airway musculature results in airway collapse and obstruction. Therefore, early respiratory insufficiency may manifest as orthopnea and appear similar to obstructive sleep apnea (eg, daytime fatigue, morning headache), as seen in this patient. Treatment focuses on improving respiratory function, which both prolongs survival and improves quality of life. Noninvasive positive-pressure ventilation (NIPPV) improves respiratory function by opening the upper airway and providing positive end-expiratory pressure to improve atelectasis. NIPPV is considered first-line therapy for ALS patients with respiratory insufficiency; it can be used intermittently at night but may need to be used more frequently as the disease progresses. Hypoxia and hypercarbia are late signs of respiratory failure; treatment should be initiated prior to the development of abnormal vital signs or CO₂ retention. ₂ (Choice A) Furosemide is used to treat heart failure, which can present with orthopnea and fatigue. However, this patient has no jugular venous distension, no peripheral edema, and a normal b-type natriuretic peptide level, making heart failure unlikely. (Choice B) Home oxygen therapy is not recommended in patients with ALS due to the risk of decreasing the ventilatory drive, which may worsen carbon dioxide retention and potentially lead to hypercapnic coma. (Choice C) Modafinil is sometimes used to treat fatigue associated with ALS. However, this patient's symptoms of orthopnea, fatigue, and headache are more likely related to respiratory insufficiency, which is better treated with NIPPV. (Choice E) Tiotropium is a long-acting bronchodilator used in patients with chronic obstructive pulmonary disease or asthma, but this patient's symptoms are due to respiratory muscle weakness rather than bronchoconstriction. (Choice F) Tracheostomy and invasive mechanical ventilation can be considered for patients with contraindications to NIPPV (eg, inability to clear secretions, severe bulbar dysfunction) or those with progressive respiratory failure despite NIPPV. Most patients with advanced disease choose to forgo these options given the associated complications (eg, increased caregiver burden) and terminal nature of ALS. Educational objective: Amyotrophic lateral sclerosis can cause respiratory insufficiency due to respiratory muscle weakness. Noninvasive positive-pressure ventilation prolongs survival and improves quality of life. References: Respiratory failure in amyotrophic lateral sclerosis. (http://www.ncbi.nlm.nih.gov/pubmed/29990478)

A 65-Year-Old Woman Comes to the Office Reporting Progressively Increasing