Quantifying Oxygen Demand by Patients Hospitalized with COVID-19 at a Large Safety-Net Hospital Using Multiple Methodologies

Abstract

Background: During the COVID-19 pandemic, many facilities worldwide struggled to forecast oxygen demand, which often exceeded oxygen supply to the detriment of patient care. Accurate estimates of oxygen demand by patients with COVID-19 are scarce, and proposed estimation methods have not been fully evaluated or implemented. To address this knowledge gap, oxygen demand by COVID-19 patients was calculated at a large safety-net hospital in the United States using patient consumption (demand) data, oxygen procurement (supply) data, and modeled data with a novel calculator tool. Methods: Data were extracted from electronic medical records of patients admitted with COVID-19 to Zuckerberg San Francisco General Hospital (ZSFG) from March 2020 to March 2022, including every recorded peripheral oxygen saturation (SpO2) measurement as well as oxygen delivery device(s) and settings. Total patient oxygen consumption was calculated as the sum of oxygen delivery amounts for each recorded time interval during hospitalization. Oxygen delivery amounts were calculated using delivery device-specific formulas. Patient and treatment-specific factors which may impact oxygen demand were also reported. For comparison, oxygen procurement logs from the study period were reviewed to estimate supply consumed, and the Oxygencalculator.com tool was used to model oxygen demand using an experimental patient population of the same size. Results: In total, 282,095 time points from 1,076 patients were analyzed. Two-thirds of patients received oxygen, of which 24.3% received high-flow oxygen (HFO) therapy and 16.0% received invasive mechanical ventilation (IMV) at some point. In-hospital mortality was 7.5% overall, 10.8% for patients who received oxygen, and 28.3% for patients who received IMV. The median (IQR) duration of oxygen therapy was 3.1 (0.8-8.9) days, mean (SD) oxygen flow was 5.6 (5.0) liters per minute (LPM), and mean (SD) total volume of oxygen delivered was 180,115 (510,330) liters (L) per hospitalization. Both the supply- and model-based methods overestimated oxygen consumption compared to demand estimated from patient data. Conclusions: This study represents one of the largest cohorts of patients with COVID-19 for which oxygen demand has been calculated, including patient clinical characteristics which may help explain variations in oxygen demand. Moreover, oxygen demand was quantified using a methodology that could be applied in any setting.