Use of ROX index in predicting the failure of non-invasive respiratory support for patients with COVID-19

ABSTRACT

Introduction: COVID-19 patients are at risk of respiratory deterioration requiring higher level of care. Decisions around timing of intubation and invasive ventilation remain a challenge. NEWS2 is a well-established physiology scoring system used to detect the deteriorating patient [1]. New evidence suggests ROX index may be more reliable than NEWS2 to identify patients at risk of treatment failure of non-invasive respiratory support (NIRS) [2]. Another study has suggested the use of a nomogram for predicting NIRS failure [3]. Methods: Data were collected retrospectively from 81 COVID-19 patients admitted to a general critical care unit. Vasopressor use, comorbidities and worst physiological parameters in the first 24 h of instituting NIRS were recorded and used to calculate NEWS2, ROX index, nomogram scores and P/F ratio. NIRS failure, length of therapy and survival status at the end of critical care admission were recorded. Results: Area under the receiver operating characteristic (AUROC) curves were calculated for NIRS failure prediction. For nomogram AUROC was 0.701 (95% CI 0.584-0.818) p = 0.0033, ROX index AUROC 0.810 (95% CI 0.708-0.908) p = < 0.0001, NEWS2 AUROC 0.688 (95 CI 0.574-0.802) p = 0.0051, P/F AUROC 0.748 (95% CI 0.638-0.858). Conclusions: ROX index is an easily calculated score and a better predictor of NIRS failure than nomogram, NEWS2 scores and P/F ratio. NEWS2 is not calibrated for this patient population and is not specific for those requiring respiratory support. The ROX index is easier to calculate than a recently developed nomogram [3] and performs better. Patients in respiratory support units (RSU) in the United Kingdom do not have arterial lines sited routinely. ROX-index would therefore be a useful score to help predict treatment failure of NIRS in RSU's and facilitate decision making for escalation of care.