Baseline Variation in Lung Point-of-Care Ultrasound Cohorts With COVID: Implications for Prognostication

Study Objectives: Lung point-of-care ultrasound (L-POCUS) is a novel, radiation-free diagnostic tool that could aid in COVID-19 prognosis in non-critically ill patients. Prognostication requires capturing presenting symptoms and outcomes that may change over time. Variations of environment, presenting symptomatology and follow up can introduce uncontrolled heterogeneity impacting outcome. The purpose of our study was to examine demographic, clinical, and 40-day follow up patterns between two national sites enrolling ambulatory COVID patients for the purpose of determining the association between hypoxia at day 40 and initial L-POCUS findings. Method(s): This was a cross sectional study design of patients at two tertiary care institutions in the Northeast (NE) and Midwest (MW) from January 1st, 2021-April 30th, 2022. We included subjects with respiratory complaints who tested positive for COVID-19 and maintained oxygen saturation >=92% for two hours after presentation to the emergency department as part of a larger project focused on describing L-POCUS prognostic characteristics in non-critically ill COVID patients. Initial vital signs and diagnostic data were collected. Blinded L-POCUS operators recorded seven lung windows (two anterior, two lateral and three posterior per lung field). We utilized a rubric that ranged from zero to six with zero being normal lung and six indicating severe lung pathology from COVID to score each image. Pleural findings included indentation, thickening (each one point), or discontinuity (two points). Parenchymal abnormalities included B lines (1-3 B lines =1 point, >3 B lines =2 points, coalescing or "waterfall" B lines=3 points). Subpleural consolidations scored an automatic six points out of a maximum of 42 per lung. Subjects received pulse oximetry use training and were followed by structured chart review or telephone interview 40-days following presentation. Telephone follow up included highest and lowest pulse oximetry at rest and on 60 second ambulatory test and a structured chart review at any health care visit documented evidence of hypoxia. Hypoxia was defined at <=92% 40 days from index visit. We present descriptive data and corresponding parametric or non-parametric statistic. Result(s): We enrolled 154 subjects (MW 122 (80%), NE 32 (21%). The NE population was more likely to be Hispanic (55% vs 18%, p=<.05) while the MW site was more likely to be African American (76% vs 42%, p<.05). There were no sex differences (NE, 63% female, MW 56% female). There were no significant differences between age (NE 40 years (IQR 31-54), MW 42 years (IQR, 30-56), or Body Mass Index (NE 29 (IQR 25-33), MW 29 (IQR, 24-35). CXR was ordered for 128 (83%) subjects and CT for 18 (12%) but there was no difference between sites (NE: CXR 27(93%), CT 5 (17%), MW: CXR 101 (83%), CT 13 (11%)). Median L-POCUS scores were 6 (IQR 5-12) and differed by site (NE 14, (IQR 13-27);MW 2 (IQR 2-10, p<.0001). Forty day telephone follow-up was 40% (59/154) and did not differ by site. We identifed 40 (26%) cases of subsequent hypoxia within 40 days of index visit. Outcome did not differ by site (NE 5/32 (16%): MW35/122 (29%), P=0.18). Conclusion(s): There were no meaningful clinical differences between cohorts at distinct geographical locations although NE subjects score higher on initial L-POCUS. Telephone follow up rates were low at both sites. Prognostication may need to account for L-POCUS scoring variability. No, authors do not have interests to disclose Copyright © 2022

Interpreter Variability Of Lung Point-of-Care Ultrasound Rubric in a Population of Non-Critically Ill COVID Patients

Study Objectives: Lung point-of-care ultrasound (L-POCUS), a novel and radiation-free diagnostic tool, could aid in COVID-19 prognosis. Early studies have yielded scoring rubrics focused heavily on hospitalized populations including the critically ill. Operator characteristics of this novel technology in non-critically ill, ambulatory COVID patients has not been described and is an important consideration for dissemination. The purpose of our study was to determine to the inter-rater reliability of an L-POCUS scoring rubric in a population of non-oxygen dependent patients. Methods: This was a cross sectional study design of patients at three academic institutions in the Northeast, Midwest, and West. We included subjects with respiratory complaints who tested positive for COVID-19 and maintained oxygen saturation ≥92% for two hours after presentation to the emergency department as part of a larger project focused on describing L-POCUS prognostic characteristics in a non-critically ill COVID pneumonia population. L-POCUS was performed on seven lung windows on each side of the chest: two anterior, two lateral, and three posterior. All clips were obtained with a curvilinear probe or a linear probe using machine settings to enhance lung findings ("nerve" or "lung"). The scoring rubric ranged from 0 to 6 for each lung field with 0 being normal lung and 6 indicating severe lung pathology from COVID. We divided lung findings into pleural and parenchymal with the score per lung field representing the sum of the two parts. Pleural findings included normal (0 points), blurring, indenting, or thickening (1 point), and discontinuity (2 points). Parenchymal findings included normal (0 points), B lines (1-3 B lines equaled 1 point, >3 B lines equaled 2 points, coalescing or “waterfall” B lines equaled 3 points), and subpleural consolidation (4 points). As discontinuous pleura necessarily accompanies subpleural consolidations per definition, lung fields with subpleural consolidations automatically scored 6 points. Clips, collected and scored at bedside by an expert sonologist, were randomly selected for scoring by other operators of differing experiences: a resident, a faculty member without ultrasound fellowship training, an ultrasound fellow, and a second expert. Scores were then analyzed using the intraclass correlation coefficient (ICC) using the R package “ICC” to determine inter-rater reliability between the initial expert rater and all other raters. Results: A total of 50 clips lasting 6 seconds each were chosen for scoring, 49 with the culvilinear probe and 1 with the linear probe. The calculated Intraclass Correlation Coefficient (ICC) for expert raters was 0.71 (0.55, 0.83, p<0.0001) 0.83). Moderate agreement between all raters was found with an ICC of 0.72 (0.62, 0.81). The faculty member without ultrasound fellowship training and the fellow disagreed the most from the group and resulted in the highest variability. A Loess graph demonstrates less variability at low scores than high scores. Conclusion: The L-POCUS rubric for scoring lungs infected with COVID in an ambulatory population revealed moderate to good agreement among a diverse group of operators. Greater variation at higher scores reveals ambiguity in definitions of lung pathology in COVID. This warrants future studies refining criteria for lung findings and correlating to clinical implications. [Formula presented]