Negative Pressure Pulmonary Oedema Mimicking Infectious Pneumonia: Diagnostic Value of Ground-Glass Opacity Distribution in Acute Respiratory Failure.

Abstract

Background

Diffuse ground-glass opacities (GGOs) on thoracic imaging are a common but non-specific finding in patients presenting with acute respiratory failure and may result from infectious, inflammatory, or oedematous lung diseases. In young adults with substance abuse, differentiating among aspiration syndromes, opportunistic infections, drug-induced lung injury, and pulmonary oedema can be particularly challenging. Recognition of radiological distribution patterns may provide important diagnostic clues and facilitate early diagnosis.

Case Report

A L A 26-year-old male heavy-vehicle driver with a history of recreational drug use was admitted with acute respiratory distress, altered consciousness, profound hypoxaemia (oxygen saturation 48%), hypotension, and frothing from the mouth. Examination revealed complete upper airway obstruction caused by tongue collapse and secretions. Chest radiography showed bilateral diffuse pulmonary opacities. High-resolution computed tomography (HRCT) showed bilateral dependent GGOs with patchy consolidations which was predominantly seen involving the posterior basal lung segments. Initial differential diagnoses included aspiration pneumonia with Pneumocystis jirovecii pneumonia. Urine toxicology positive for benzodiazepines. The patient received oxygen therapy, flumazenil, and non-invasive ventilation, resulting in rapid clinical improvement within hours. Repeat chest radiography and follow-up computed tomography showed near-complete resolution of pulmonary infiltrates. The combination of acute upper airway obstruction, characteristic gravity-dependent imaging distribution, rapid radiological improvement and prompt response to positive-pressure ventilation supported a diagnosis of negative pressure pulmonary edema (NPPE) secondary to benzodiazepine-associated airway obstruction. The patient was subsequently referred for rehabilitation.

Conclusion

NPPE is an important, potentially reversible cause of acute respiratory failure that may mimic infectious and aspiration-related lung diseases. Careful assessment of the distribution of GGOs, particularly gravity-dependent involvement, together with clinical context and rapid response to treatment, can facilitate accurate diagnosis, prevent unnecessary antimicrobial therapy, and enable timely management.