A staged combined parenteral and enteral nutritional support strategy in an elderly patient with non-small cell lung cancer, severe pneumonia, type II respiratory failure, and pre-existing malnutrition: a case report

Background: Severe respiratory critical illness with multiple comorbidities poses substantial challenges to nutritional management. Malnutrition is common but often underrecognized, and the optimal nutritional strategy remains unclear in patients with concurrent malignancy and prior gastrointestinal surgery. This case report describes the clinical application of a staged combined parenteral nutrition (PN) and enteral nutrition (EN) strategy in an elderly patient with complex multimorbidity, aiming to illustrate a practical, dynamically adjustable approach to nutritional support in similar settings.

Case Description: A 79-year-old man with a history of gastric malignancy surgery was admitted with coma and dyspnea, and was diagnosed with non-small cell lung cancer, severe pneumonia, type II respiratory failure, and moderate malnutrition [body mass index (BMI) 16.9 kg/m²; Nutritional Risk Screening 2002 (NRS-2002) score 7; Subjective Global Assessment (SGA): moderate malnutrition]. A staged nutritional regimen combining PN and EN via a nasojejunal tube was implemented and dynamically adjusted over three phases based on his gastrointestinal tolerance and clinical evolution. During the intervention, white blood cell count (WBC) decreased from 22.90×10⁹/L to 8.60×10⁹/L and neutrophil percentage from 89.80% to 78.40%, indicating systemic inflammation control. Hemoglobin, total protein, and albumin initially improved but gradually declined with tumor progression. Oxygenation was maintained with peripheral oxygen saturation ≥98.4% under high-flow nasal oxygen after extubation.

Conclusions: This case illustrates that in elderly patients with critical respiratory illness complicated by malignancy, prior gastric surgery, and malnutrition, a staged PN-EN combined strategy can be implemented with dynamic adjustments based on tolerance and clinical changes. However, sustained nutritional improvement may be limited by persistent tumor catabolism and disease-related stress. Nutritional support should be closely coordinated with antitumor and anti-infective therapies. The findings are observational and derived from a single case, and further research is needed to confirm broader applicability.