A hyperbaric wound treatment control apparatus comprising: a hyperbaric wound treatment device providing a treatment chamber, wherein the treatment chamber has an open end and an inflatable sleeve (112, 240) for sealing against a limb of a patient at the open end of the chamber, and wherein a controller is operable for controlling supply means (36, 38, 40) for selectively conveying gas into and out of the treatment chamber and the sleeve and for supplying a treatment gas from a gas supply under pressure to the treatment chamber, and wherein the device comprises a collapsible bag including inflatable ribs extending at least partially along sides of the device or a plurality of interconnected pockets formed between sheets (224, 226); negative pressure means for creating a negative pressure by removing existing ambient air from within the treatment chamber; wherein the controller is coupled to and operable for controlling the negative pressure means and the supply means (36, 38, 40) for inflating the ribs or the plurality of interconnected pockets for retaining the bag in a rigid state; providing that the negative pressure means and the supply means (36, 38, 40) are in fluid communication with the treatment chamber; creating a negative pressure within the portion of the treatment chamber by at least partially evacuating existing ambient air from within the treatment chamber by the negative pressure means; and then supplying a treatment gas to the treatment chamber by the supply means (36, 38 40) following evacuating existing ambient air at least partially from within the treatment chamber by the negative pressure means. a hyperbaric wound treatment device providing a treatment chamber, wherein the treatment chamber has an open end and an inflatable sleeve (112, 240) for sealing against a limb of a patient at the open end of the chamber, and wherein a controller is operable for controlling supply means (36, 38, 40) for selectively conveying gas into and out of the treatment chamber and the sleeve and for supplying a treatment gas from a gas supply under pressure to the treatment chamber, and wherein the device comprises a collapsible bag including inflatable ribs extending at least partially along sides of the device or a plurality of interconnected pockets formed between sheets (224, 226); negative pressure means for creating a negative pressure by removing existing ambient air from within the treatment chamber; wherein the controller is coupled to and operable for controlling the negative pressure means and the supply means (36, 38, 40) for inflating the ribs or the plurality of interconnected pockets for retaining the bag in a rigid state; providing that the negative pressure means and the supply means (36, 38, 40) are in fluid communication with the treatment chamber; creating a negative pressure within the portion of the treatment chamber by at least partially evacuating existing ambient air from within the treatment chamber by the negative pressure means; and then supplying a treatment gas to the treatment chamber by the supply means (36, 38 40) following evacuating existing ambient air at least partially from within the treatment chamber by the negative pressure means.