A wound dressing has a reservoir between a not-permeable upper layer, and a lower permeable layer, an adhesion layer facing in the direction of the permeable layer, to be pressed to skin of a patient around a wound, sealing the dressing to the patient, and one or the other of an oxygen-level indicator containing a material exhibiting color change with varying concentration of oxygen, the indicator placed to be visible to a person viewing the dressing through an interface not permeable to oxygen, and to be open to oxygen through a second interface in intimate contact with oxygen in the reservoir, or a self-sealing opening through which a hollow tube may pass without allowing oxygen to escape, the self-sealing opening useful for charging the reservoir with oxygen at pressure, or for sampling oxygen in the reservoir by an external probe.
