Predictors of invasive mechanical ventilation requirement and mortality in hypercapnic respiratory failure: A...

While hypercapnic respiratory failure (HRF) has been widely studied in emergency department (ED) populations, the prognostic significance of metabolic compensation and lactate levels remains unclear. This study aimed to evaluate the association of creatinine, bicarbonate (HCO₃), chloride, and lactate levels with the need for invasive mechanical ventilation (IMV) and inhospital mortality in patients with HRF.

This single-center, cross-sectional study included adult patients who presented to the ED with respiratory distress and arterial partial pressure of carbon dioxide >50 mmHg between 2020 and 2023. The relationships between initial laboratory parameters and clinical outcomes were analyzed.

A total of 420 patients were included (median age: 77 years [interquartile range: 68-85]; 51.4% female). The mortality rate among bedridden patients was 55.9% and 34.3% among patients diagnosed with pneumonia. Creatinine ≥1.6 mg/dL was associated with inhospital mortality (odds ratio [OR]: 3.7; 95% confidence interval [CI]: 2.044-6.696) and IMV requirement (OR: 2.323; 95% CI: 1.216-4.439). Lactate >1.5 mmol/L was also associated with higher mortality (OR: 10.441; 95% CI: 5.739-18.996). Delta HCO₃ (ΔHCO₃) <-7.5 mEq/L predicted mortality (OR: 2.965; 95% CI: 1.756-5.008) and IMV need (OR: 10.181; 95% CI: 5.709-18.156). Low ΔHCO₃, hemoglobin, pH levels, elevated lactate, creatinine levels, and immobility are the independent risk factors for mortality. The AUC values of lactate levels for predicting mortality were higher than those of pH (0.662 vs. 0.655).

In patients with HRF, ΔHCO₃, hemoglobin, pH, lactate and creatinine levels, and immobility are strong predictors of poor outcomes. Lactate is a robust and independent predictor of poor outcomes, with prognostic accuracy comparable to that of pH, and may be valuable for clinical risk stratification.