Measurements in Wound Healing by Raj Mani Marco Romanelli & Vijay Shukla

Author:Raj Mani, Marco Romanelli & Vijay Shukla
Language: eng
Format: epub
Publisher: Springer London, London

Transcutaneous Oximetry

Transcutaneous oximetry is the partial pressure of oxygen measured with an electrode placed on the skin surface. The observation of the existence of an exchange of O2 and CO2 between skin and ambient air was first made by Gerlach in 1851 [40].

Transcutaneous oximetry is an effective technique widely used in the evaluation of local skin microcirculation, nutrition and tissue ischaemia. Several methods for non-invasive measurements of tissue O2 are available [41]. One of these is the TcPO2 technique, based on the electrochemical reduction of oxygen, which is measured on the skin surface with a calibrated Clark electrode. The TcPO2 measurement provides information about the content of tissue oxygenation in superficial skin layers. The post-heating reactive hyperaemia responses of TcPO2 can be used as relative measures of the vasodilatory capacity of skin micro-vessels. TcPO2 values depend on cutaneous circulation, arterial PO2, oxygen consumption in skin tissue and oxygen diffusiveness through the skin. The values measured represent the partial pressure of oxygen diffusing from the capillaries and provide data on the oxygenation of superficial skin layers. The TcPO2 values from undamaged skin can vary depending on the body region and it has been noticed that low values are associated with failure in wound healing [42]. In tissue with inflammatory reaction, the dramatic increase in local metabolism and the infiltration of large amount of cells requiring oxygen may increase the consumption of oxygen in the skin, leading to low TcPO2 values. The TcPO2 and TcPCO2 values have been measured in a large number of skin conditions, such as evaluation and management of leg ulcers [43], the assessment of skin involvement in patients with morphea and scleroderma [44], investigation into hypertrophic scars [45], and the understanding of the action and efficacy of vasoactive drugs such as topical nitroglycerin [46]. These values can be influenced by many local factors such as blood flow, thickness of the epidermis, metabolism of the epidermis and glands, conductivity of the gases, and the production and consumption of such gases in situ. The epidermal barrier has also to be considered in the measurement of TcPO2, since the stratum corneum represents an important resistance to oxygen diffusion; its removal (using a stripping technique or other methods) is recommended when studying the skin, for a better reproducibility of the assessment [47].

Other perfusion analyses such as arteriography, capillaroscopy, plethysmography and videomicroscopy are considered difficult to perform and too invasive.

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