A portable system for subatmospheric pressure therapy in connection with healing a surgical wound, including a wound dressing dimensioned for positioning relative to a wound bed of a subject and a subatmospheric pressure mechanism dimensioned to be carried or worn by the subject. The subatmospheric pressure mechanism includes a housing having a control unit adapted to draw a vacuum and a canister associated with the housing. The canister has a collection bag disposed therein, which is in fluid communication with the wound dressing to receive exudates from the wound bed. The collection bag is adapted to expand upon receipt of the fluids and has means to release gas from within the collection bag in connection with operation of the control unit. With this arrangement, the canister is attitude independent, i.e., the canister may be positioned on edge, on its side or on its end etc. while still maintaining operation of the control unit. The collection bag may include a hydrophobic vent or material for releasing the gases. In another embodiment, the collection bag comprises a gas permeable material. The collection bag may include one of pleats or bellows.