Methods for facilitated non-invasive oxygen monitoring

A method for non-invasive monitoring of a characteristic of the blood of a patient, comprising: (i) providing a transdermal delivery device (10) comprising: (a) a backing member (20) that is substantially impermeable to a vaso-dilating agent; (b) a first adhesive layer (26) adjacent to one surface of the backing member; (c) a reservoir (22) adjacent to another surface of the backing member, the reservoir comprising sufficient vaso-dilating agent to induce local vaso-dilation in the skin of the patient to which the device may be attached; (d) a rate-controlling membrane (24) adjacent to a backing layer distal surface of the reservoir, (ii) attaching one exposed surface of the delivery device to a predetermined site on the patient's skin; (iii) mating an electro-optical sensor (40) to the first adhesive layer (26) of the transdermal delivery device, either before or after step (ii); (iv) thereafter permitting transdermal delivery of the vaso-dilating agent through the skin site at a rate dependent on the composition and thickness of the rate-controlling membrane (24) and on the diffusion co-efficient of the vaso-dilating agent within the rate-controlling membrane (24); and (v) concurrently monitoring a characteristic of the patient's blood with the sensor.