SpO2/RR index in choosing the method for correction of acute respiratory failure in COVID-19 patients

Objective. To study advisability of the SpO2/RR index in COVID-19 patients with spontaneous breathing and various severity of ARF regarding achievement of parameters of effective standard oxygen therapy and non-invasive ventilation. Material and methods. A single-center prospective study included 84 patients of both sexes with severe course of new coronavirus infection and symptoms of ARF. Upon admission to the ICU, all patients underwent standard oxygen therapy (SOT) and non-invasive ventilation if necessary. We analyzed RR, SpO2, SpO2/RR, SpO2/FiO2, SpO2/FiO2/RR (ROX index), PaO2/FiO2 in patients with effective and ineffective therapy. The Wilcoxon test and the Mann—Whitney U-test were used for statistical analysis. Results. In patients with spontaneous respiration and ARF, SOT was effective in case of baseline SpO2/RR index >3.4—3.5. In patients with ineffective SOT, non-invasive ventilation was successful in case of SpO2/RR index within 2.5—3.5. Conclusion. The SpO2/RR index can be used to choose the method for correction of ARF in COVID — 19 patients with spontaneous breathing. The SpO2/RR index >3.5 increases the likelihood of saturation >92% under SOT while index >2.5 indicates higher probability of saturation >92% under non-invasive ventilation.