A group at MIT got together to design and develop an Emergency Ventilator toolkit. Please read more about it here and also look at the video in comments (at 36:00 min) section wherein during a discussion, ventilation experts are critiquing designs such as this for missing out on key technical aspects related to maintaining a positive pressure across the tube that goes from filter to the patient that prevents the patient from re-breathing the air he/she just exhaled.
