(1128) Negative-Pressure Pulmonary Edema: A Post-Extubation Complication

Introduction: Negative pressure pulmonary edema (NPPE) is a potentially life-threatening post-extubation complication if not diagnosed promptly.

Description: The patient is a 40-year-old male with a past medical history of anxiety, bipolar disorder, and nicotine dependence, who was admitted for hypoxia post laparoscopic appendectomy. He was witnessed biting on the endotracheal tube (ET) during extubation with resultant pink frothy secretions and a requirement for 4-liter supplemental oxygen (SO) via nasal cannula. Post-extubation exam was notable for tachycardia and bilateral lung crackles. Chest x-ray (CXR) showed diffuse bilateral patchy alveolar opacities. Computed tomography angiography showed relatively diffuse ground-glass opacities and consolidative airspace disease. Brain natriuretic peptide and echocardiogram were unremarkable, confirming the diagnosis of noncardiogenic pulmonary edema (NCPE), which in this setting would be NPPE due to post-extubation laryngospasm (PEL). Pulmonology recommended supportive care with SO, bronchodilators, and diuretics. The patient was diuresed for 48 hours and was weaned off SO; a clinical course consistent with NPPE.

Discussion: NPPE is NCPE due to inspiratory effort against an obstructed airway, leading to very negative intrathoracic pressures increasing transvascular fluid filtration, shifting it into the pulmonary interstitium. The etiology can be any cause of upper airway obstruction (UAO) such as upper airway infection, tumor, or laryngospasm, specifically PEL. PEL can be due to secretions irritating the larynx, rapid influx of cold air, or foreign body (e.g. ET). Only 0.1% of PEL cases cause NPPE, often in healthy men possibly due to their ability to achieve very negative airway pressures. Oropharyngeal aspiration of secretions and small dose steroids or propofol pre-extubation can lower the risk. NPPE presents as acute hypoxemia with signs of UAO, such as wheezing, crackles, and pink frothy sputum. CXR supports the diagnosis. Management is supportive with SO, bronchodilators, and diuretics, although diuretic use is controversial as it may worsen hypovolemia. Patients typically recover within 12-48 hours. In refractory cases, positive pressure ventilation can be used. In emergency cases, reintubation and prolonged mechanical ventilation may be required.