A respiratory device of negative pressure type comprising a shell fastened to the user's chest and/or abdomen with minimal dead space, one or more vacuum and compressed air chambers attached to the shell； vacuum generating and compressed air generating sources connected to the vacuum and compressed air chambers respectively, one or more openings on the shell to allow exchange of the air enclosed between shell and user's body, with the vacuum and compressed air chambers； a valve shuttling between the vacuum and compressed air chambers. By having low dead space, pre-generated vacuum and compressed air close to the user, and the use of fast acting valves in some embodiments, the power requirement, weight, and size are reduced, making the device low cost and portable. In some embodiments, the vacuum and compressed air generating sources can be mounted on the shell itself, making the device ambulatory.
