The primary outcome was treatment failure ( composite outcome of early treatment failure defined as -LSB- @ -RSB- clinical deterioration indicated by development of shock , -LSB- @ -RSB- need for invasive mechanical ventilation not present at baseline , or -LSB- @ -RSB- death within @ hours of treatment ; or composite outcome of late treatment failure defined as -LSB- @ -RSB- radiographic progression , -LSB- @ -RSB- persistence of severe respiratory failure , -LSB- @ -RSB- development of shock , -LSB- @ -RSB- need for invasive mechanical ventilation not present at baseline , or -LSB- @ -RSB- death between @ hours and @ hours after treatment initiation ; or both early and late treatment failure ) .