Prediction of Long-Term Mortality in Acute Hypercapnic Respiratory Failure with Use of Low-Flow Veno-Venous...

Introduction: Hypercapnic respiratory failure is associated with high morbidity and mortality. Low-flow extracorporeal CO₂ removal (ECCO₂R) has been shown to facilitate lung-protective ventilation or spontaneous breathing. However, three multicenter randomized trials have failed to show benefit which could potentially be a result of patient selection. In this study, we aimed to characterize prognostic scores developed for extracorporeal membrane oxygenation therapy which could potentially assist with the selection of patients for ECCO₂R.

A total of 70 patients admitted to the intensive care unit at the University Hospital of Zurich between 10/2009 and 02/2017 with hypercapnic respiratory failure were treated with ECCO₂R if pH ≤7.25 and/or PaCO₂ ≥ 9 kPa experiencing respiratory exhaustion during spontaneous breathing in obstructive lung disease or reaching the limits of lung protective ventilation (n = 22 and n = 48) in patients with restrictive lung pathologies. Data including baseline characteristics and respiratory parameters were collected prospectively. Scores were calculated retrospectively.

The underlying diseases were acute respiratory distress syndrome (n = 27), chronic-obstructive pulmonary disease (n = 12), bronchiolitis obliterans syndrome (BOS; n = 9), cystic fibrosis (n = 10), pulmonary fibrosis (n = 8), and other causes (n = 4). The 180-day mortality was 45.7% with the highest rate observed in PF and BOS patients as well as in patients who had been mechanically ventilated >6 days before initiation of ECCO₂R. The modified PRedicting dEath for SEvere hypercapnic respiratory failure on vv-ECCO₂R (PRESERVE-CO₂) score differentiated well between survivors and non-survivors (4.3 ± 2.2 vs. 6.9 ± 2.6, p < 0.01), whereas the modified Respiratory ECMO Survival Prediction (RESP-CO₂) score showed no significant distinction. Receiver operating characteristics analysis of the PRESERVE-CO₂ score revealed an area under the curve of 0.78, suggesting a cut-off of 7 points.

Careful selection of patients for ECCO₂R therapy may help to improve outcomes. The proposed PRESERVE-CO₂ score may serve as a guide. A score of 7 points or higher is associated with an unfavorable outcome regarding the 180-day mortality in the specific patient cohort of this study, but future studies to externally validate this score are required.