A elderly gravida (G6P5) became disoriented, lightheaded, breathless, and cyanotic 20 minutes after an uncomplicated spontaneous vaginal term delivery. Her blood pressure is 80/40 mm Hg, pulse is 110/min, and respiratory rate is 30/min. O2 saturation is 75% on face mask.A generalized purpuric rash and bleeding from the I.V line site are seen. Which of the following is the most appropriate next step in management of this patient?