High-flow nasal cannula-based support for suspected severe immune-related pneumonitis in a patient with small cell lung cancer: a case report

Severe immune-related pneumonitis (IRP) is difficult to diagnose in patients with lung cancer and competing causes of respiratory failure. We report a 69-year-old man with recurrent small cell lung cancer who developed acute hypoxemic and hypercapnic respiratory failure after multiple immunotherapies and thoracic radiotherapy. Severe IRP was suspected, although infection, tumor-related airway obstruction, mucus retention, radiation injury, and cardiac involvement remained alternative or concurrent explanations. After invasive ventilation was declined, high-flow nasal cannula (HFNC) support was provided alongside corticosteroids, antimicrobials, tocilizumab, and intravenous immunoglobulin. Nursing care emphasized respiratory assessment, secretion clearance, humidification, and recognition of deterioration. Respiratory status initially improved, permitting HFNC withdrawal and discharge without supplemental oxygen. Subsequent respiratory deterioration occurred, and the patient died 178 days after admission from an unknown cause. This case highlights diagnostic uncertainty and the importance of multidisciplinary reassessment during HFNC support; concurrent treatments preclude attribution of improvement to any single intervention.