Table 1.

Summary of the difference between early and late intubation for COVID-19 patients.

Authors	Design	N	Definition of Intubation Group	Main Results
Hyman et al. [19]	Retrospective cohort study	755	NA	Intubation increased the in-hospital mortality rate by 1.03-fold per day of delay (adjusted HR, 1.03; 95% CI, 1.01–1.05).
Papoutsi et al. [20]	Meta-Analysis	8944	Early: intubation within 24 h of admission in the ICU. Late: intubation after 24 h from ICU admission.	Mortality: early vs. late: 45.4% vs. 39.1%; RR: 1.07, 95% CI: 0.99–1.15, p = 0.08.
Baek et al. [21]	Retrospective cohort study	133	Early: intubation within 48 h of HFNC initiation. Late: intubation after 48 h from HFNC initiation.	Mortality: early vs. late: 38.0% vs. 65.0%, p = 0.041.
Candel et al. [22]	Retrospective cohort study	272	Early: intubation within 48 h of HFNC initiation. Late: intubation after 48 h from HFNC initiation.	Mortality: early vs. late: 39.3% vs. 53.2%, p = 0.18.