Mattress bladder boosting during chair egress

A patient support apparatus comprising

• a lower frame,
• an upper frame movable relative to the lower frame,
• a deck supported on the upper frame, the deck including at least a head deck section, a seat deck section, and a foot deck section,
• a horizontal bed position for supporting a patient in a lying position in which the head deck section is lowered and the foot deck section is raised,
• a chair egress position for supporting the patient in a sitting position in which the head deck section is raised and the foot deck section is lowered,
• an inflatable support structure supported on the deck, the inflatable support structure including at least a head support section, a lumbar support section, a seat support section, and a foot support section, each of the head support section, the lumbar support section, seat support section, and foot support section each including an inflatable bladder, the inflatable bladders in the lumbar support section and seat support section operable to be inflated from a support pressure when the deck is positioned in the horizontal bed position to an egress pressure when the deck is positioned in the chair egress position, wherein in the horizontal bed position the lumbar support section and the seat support section bladders are configured to provide substantially planar support surfaces at a support pressure and in the chair egress position the lumbar support section and seat support section bladders are inflated to an egress pressure that is greater than the support pressure so that the lumbar support section and seat support section bladders are expanded to provide a convex support surface,
• an air system including a source of pressurized air, an air distribution assembly, and a controller to control the flow of air from the source of pressurized air through the air distribution system to the inflatable support structure, and
• a control system coupled to the deck, the control system including a circuit having an output for controlling movement of the deck to vary the position of the deck between the horizontal bed position and the chair egress position and for controlling the air system to control the inflation and deflation of the inflatable bladders, a processor in electrical communication with the circuit and operable to vary an output of the circuit, a memory device including instructions that when executed by the processor, cause the processor to control the circuit to vary the movement of the deck to vary the position of the deck between the horizontal bed position and the chair egress position, the control system coordinating the inflation of the inflatable bladders with movement of the deck between the horizontal bed position and chair egress position so that the inflatable bladders of the lumbar support section and seat support section inflate to the egress pressure as the patient support apparatus transitions to the chair egress position, and the inflatable bladder of the foot support section deflates to the egress pressure as the patient support apparatus transitions to the chair egress position.