Clinical Characteristics of COVID-19: Risk Factors for Early Oxygen Requirement after Hospitalization

Background: Some coronavirus disease 2019 (COVID-19) patients initially present with early oxygen demand, requiring more medical resources, and some develop severe conditions, while others worsen later in their clinical course. Whether the nature of the two groups is the same but in the spectrum of different diagnostic time points is not certain. Methods: Hospitalized COVID-19 patients who needed oxygen therapy from February to November 2020 were included in the study. The patients were divided into early and late groups based on the time when the oxygen requirement occurred. Basic and epidemiologic characteristics were compared. Clinical variables were analyzed in both groups. Results: A total of 164 patients needed oxygen therapy, 94 of whom were in the early group and 70 of whom were in the late group. The early and late groups had similar baseline characteristics except age (median age, 73 vs. 67 years), uncertain exposure history (50% vs. 31.4%) and the time from the onset of illness to admission (median, 5 vs. 2 days). Multivariate analysis showed that age > 65 years (OR, 4.65), symptom onset > 5 days (OR, 9.13) and several clinical manifestations, such as febrile sensation (OR, 6.01), dyspnea (OR, 30.0), C-reactive protein > 1 mg/dL (OR, 7.87) and chest X-ray abnormality (OR, 8.15), were predictive factors in the early group. The early group required more intensive care such as mechanical ventilation care, extracorporeal membrane oxygenation and death (29.8% vs. 14.3%, P = 0.002). Conclusion: Older age, especially > 65 years, and a delay of over 5 days from the onset of illness to admission were associated with early oxygen demand in COVID-19 patients. Interventions for earlier diagnosis of elderly people may benefit clinical outcomes.