key: cord-1039833-4hmcxmq8 authors: Fink, Douglas L.; Goldman, Nina R.; Cai, James; El-Shakankery, Karim H.; Sismey, George E.; Gupta-Wright, Ankur; Tai, Charlotte X. title: Ratio of Oxygen Saturation Index to Guide Management of COVID-19 Pneumonia date: 2021-03-30 journal: Ann Am Thorac Soc DOI: 10.1513/annalsats.202008-934rl sha: d55930d78d486290b08142c4df8e825222cc08f4 doc_id: 1039833 cord_uid: 4hmcxmq8 nan Coronavirus disease (COVID-19) caused by novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged from China in December 2019, leading to a global pandemic (1) . Approximately 17% of patients admitted to hospital require critical care, the majority of whom undergo mechanical ventilation (MV) for pneumonia complicated by hypoxemia (2) . High-flow nasal cannula (HFNC) and continuous positive airway pressure (CPAP) are recognized treatments for hypoxemic respiratory failure caused by community-acquired pneumonia (CAP) (5) (6) (7) . HFNC and CPAP may represent definitive therapy, avoiding unnecessary MV, or provide bridging respiratory support that offsets the need for immediate MV, preserving finite critical care resources. The ratio of oxygen saturation (ROX) index is used to predict the failure of HFNC in the treatment of CAP (6, 7) . There are little published data describing the use of the ROX index to guide use of HFNC to treat COVID-19-associated respiratory failure; we provide further evidence to validate ROX index use in this setting (8, 9) . The ROX index was developed as a simple bedside test to predict the failure of HFNC and need for MV, although patients with viral pneumonia were likely underrepresented in derivation and validation studies (6) . We undertook a retrospective observational study of individuals with laboratory-confirmed COVID-19 presenting to a single East LondonhospitalbetweenMarch16,2020,andApril6,2020.Patientswho received HFNC, CPAP, or MV were identified. Electronic notes review captured demographic data and clinical and respiratory parameters. Of 393 inpatients with laboratory-confirmed COVID-19 during the study period, 255 individuals (255/393; 65.0%) were eligible for HFNC or CPAP as determined by the treating clinicians, consistent with national and local guidelines (10) . A total of 108 individuals (108/255, 42.4%) received HFNCorCPAP;69individualsreceivedHFNConly(63.8%),18 received CPAP only (16.7%), and 21 received both devices (19.4%; Table 1 ). The majority of individuals receiving HFNC and/or CPAP experienced severe outcomes, defined as mortality or MV at 30-day follow-up (77/108; 71.3%). Most individuals who were deemed eligible for CPAP and HFNC at the time of admission were judged by treating clinicians not to require devices (147/255; 57.6%), and the majority of these individuals experienced nonsevere outcomes (138/147; 93.8%). (Table 2 ) (6, 7). A ROX index of less than 4.88 at 2 hours after HFNC initiation had the highest positive predictive value for severe outcome (91.2%; CI, 76.3-98.1%) of the respiratory variables analyzed. These results demonstrated comparable accuracy in sensitivity analyses for individuals receiving HFNC alone and individuals receiving both CPAP and HFNC (data not shown). For patients receiving HFNC, intubation-freesurvivalwassignificantlyreducedforindividualswithaROXindexof less than 4.88 at the time of device initiation (P = 0.0020) and at 2 hours after device initiation (P = 0.0154; Figure 1 ). For individuals receiving only CPAP, neither ROX index at any time-point nor arterial oxygen pressure/fraction of inspired oxygen ratio at admission or at device initiation were associated with severe outcome. Rationing of HFNC and CPAP on the basis of suitability for MV has been a strategy used widely even in high-resource settings (11) . It is critical to explore the role and outcomes of HFNC and CPAP in the management of COVID-19 hypoxemic respiratory failure for patients deemed not suitable for MV. As expected, individuals who had HFNC and CPAP documented as the ceiling of care at admission (i.e., do-not- survived, highlighting the complex nature of decisions in the current COVID-19 landscape. The major limitation of our study is its retrospective and singlecenter nature. There were a number of variables inadequately recorded in electronic notes. There are missing clinical observation data; however, these missing data are clearly highlighted in our summaries and do not prevent analysis. Our study suggests that theROX indexis a useful predictor of failure of HFNC in COVID-19 respiratory failure to identify patients early who are likely to require MV, as suggested in earlier studies, and warrants prospective validation studies in this setting. In addition to existing literature, our data also support HFNC use guided by ROX index in individuals who have do-not-intubate orders as the ceiling of care, who have hitherto been excluded from published analyses. Further studies are required to characterize the role of the ROX index and risk stratification of HFNC failure to guide resource management and palliative care decision-making in patients deemed not suitable for MV. Coronaviridae Study Group of the International Committee on Taxonomy of Viruses. The species severe acute respiratory syndrome-related coronavirus: classifying 2019-nCoV and naming it SARS-CoV-2 Features of 16,749 hospitalised UK patients with COVID-19 using the ISARIC WHO Clinical Characterisation Protocol Treatment of acute hypoxemic nonhypercapnic respiratory insufficiency with continuous positive airway pressure delivered by a face mask: a randomized controlled trial High-flow oxygen through nasal cannula in acute hypoxemic respiratory failure Helmet continuous positive airway pressure vs oxygen therapy to improve oxygenation in community-acquired pneumonia: a randomized, controlled trial Predicting success of high-flow nasal cannula in pneumonia patients with hypoxemic respiratory failure: the utility of the ROX index An index combining respiratory rate and oxygenation to predict outcome of nasal high-flow therapy Monitoring of high-flow nasal cannula for SARS-CoV-2 severe pneumonia: less is more, better look at respiratory rate Prediction of outcome of nasal high flow use during COVID-19-related acute hypoxemic respiratory failure National Institute for Health and Care Excellence. Overview COVID-19 rapid guideline: critical care in adults Understanding pathways to death in patients with COVID-19 The Relation between Persistent Poor Health after COVID-19 and Respiratory Complications or Initial Disease SeverityTo the Editor:We read with interest the recent article by Townsend and colleagues that described respiratory recovery and self-reported health at the time of outpatient attendance after coronavirus disease (COVID-19) infection (1) . The authors graded participants into three groups by initial severity (not requiring admission, requiring hospital admission, and requiring intensive care unit [ICU] care) by an analysis of chest radiography, a 6-minute walk test (6MWT), fatigue, frailty, subjective return to health, and some inflammatory markers (1) . The authors concluded that none of the measures of persistent respiratory disease were associated with initial disease severity (1).Because self-reported health and symptoms such as fatigue have an essentially subjective basis, the study is limited by its analysis of only a chest radiograph. This study should be complemented with computed tomography (CT) or lung function, as the follow-up protocols of scientific societies include lung function among their main evaluations (2) . This takes on particular importance because, in Townsend and colleagues' study,persistentchestradiographabnormalitiesattributabletoCOVID-19 were seen in only 4% of patients (5/115) (1), but other authors have shown approximately 70% persistence of altered CT at 3-month follow-up (3).This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (https:// creativecommons.org/licenses/by-nc-nd/4.0/). For commercial usage and reprints, please contact Diane Gern (dgern@thoracic.org).