A dressing for covering a wound of a patient, comprising a sheet member adapted to be adhered to the patient's skin in use to provide an airtight seal around the wound, the sheet member being adapted to be spaced apart from the skin in the region of the wound to define in use a space above the wound, and a plurality of mutually spaced-apart flutter valves being provided permitting one-way air, blood and/ or other fluid flow communication from the space above the wound to the exterior of the dressing, the sheet member comprising: a first layer constituted by a skin-adhesive layer and provided with an aperture, which in use would encircle the wound, the first layer having a surface directed away from the patient's skin in use, a surface being directed away from the wound in use being termed an upper surface, wherein overlain over the total upper surface of the skin-adhesive layer, and also provided with a corresponding aperture where the wound will be in use, is a second layer, which is a layer of backing material, which provides mechanical support to the skin-adhesive layer and prevents the upper surface of the skin adhesive layer sticking to external objects in use, and overlain over the upper surface of the backing material layer is a third layer that provides an anchor for sealing a fourth layer that forms parts of the flutter valves, the third layer also having an aperture generally corresponding to the apertures of the first and second layers where the wound will be in use; and the fourth layer is overlain on the upper surface of the third layer, and is formed of a thin film having sufficient flexibility to serve as the moveable portions of the plurality of flutter valves, this fourth layer having no aperture corresponding to the apertures of the first to third layers, but instead a plurality of holes near its periphery, these holes being dimensioned and arranged to serve in use as the flutter valves, this fourth layer being non-adhesive on both major faces, and is sealed to the upper surface of the third layer in a seal line around its periphery, ensuring that the holes are free to open and close in use in flutter valve manner, cooperating with the underlying portion of the upper surface of the third layer.. a first layer constituted by a skin-adhesive layer and provided with an aperture, which in use would encircle the wound, the first layer having a surface directed away from the patient's skin in use, a surface being directed away from the wound in use being termed an upper surface, wherein overlain over the total upper surface of the skin-adhesive layer, and also provided with a corresponding aperture where the wound will be in use, is a second layer, which is a layer of backing material, which provides mechanical support to the skin-adhesive layer and prevents the upper surface of the skin adhesive layer sticking to external objects in use, and overlain over the upper surface of the backing material layer is a third layer that provides an anchor for sealing a fourth layer that forms parts of the flutter valves, the third layer also having an aperture generally corresponding to the apertures of the first and second layers where the wound will be in use; and the fourth layer is overlain on the upper surface of the third layer, and is formed of a thin film having sufficient flexibility to serve as the moveable portions of the plurality of flutter valves, this fourth layer having no aperture corresponding to the apertures of the first to third layers, but instead a plurality of holes near its periphery, these holes being dimensioned and arranged to serve in use as the flutter valves, this fourth layer being non-adhesive on both major faces, and is sealed to the upper surface of the third layer in a seal line around its periphery, ensuring that the holes are free to open and close in use in flutter valve manner, cooperating with the underlying portion of the upper surface of the third layer..