Association between Prehospital Arterial Hypercapnia in Acute Heart Failure and Admission to Acute Care Units : A Retrospective Cohort Study

Abstract Background: Acute Heart Failure (AHF) is a common condition that often manifests by acute respiratory distress and requires urgent medical evaluation and treatment. Arterial hypercapnia is common in AHF. It has been associated with a higher rate of intubation and non-invasive ventilation in the Emergency Room (ER), but its prognostic value has never been studied in the prehospital setting. Methods: A retrospective study was performed on the charts of all patients taken care of by a physician-staffed prehospital mobile unit between June 2016 and September 2019 in Geneva. After approval by the ethics committee, charts were screened to identify all adult patients with a diagnosis of AHF. The main predictor was prehospital hypercapnia. The primary outcome was admission rate in an acute care unit (ACU, composite of intensive care or high-dependency units). Secondary outcomes were ER length of stay (LOS), orientation from ER (intensive care unit, high-dependency unit, general ward, discharge home), intubation rate at 24 hours, hospital LOS and hospital mortality. Results: A total of 104 patients with a diagnosis of AHF were included. Hypercapnia was found in 59 (57%) patients and vital signs were more severely altered in this group. The overall ACU admission rate was 47%, with a statistically significant difference between hypercapnic and non-hypercapnic patients (58% vs 33% respectively, p=0.014). ER LOS was shorter in hypercapnic patients (5.5 hours vs 8.9 hours, p=0.008). Conclusions: There is a significant association between prehospital arterial hypercapnia and acute care unit admission in AHF patients. Trial Registration:This study was approved on 20.08.2019 by the institutional ethics committee of Geneva, Switzerland (Project ID 2019-01559)