Transcutaneous oximetry (PtcO2) is finding increasing application as a diagnostic tool to assess the peri-wound oxygen tension of wounds, ulcers, and skin flaps. It must be remembered that PtcO2 measures the oxygen partial pressure in adjacent areas of a wound and does not represent the actual partial pressure of oxygen within the wound, which is extremely difficult to perform.
To provide clinical practice guidelines, an expert panel was convened with participants drawn from the transcutaneous oximetry workshop held on June 13, 2007, in Maui, Hawaii. Important consensus statements were
- (a) tissue hypoxia is defined as a PtcO2 <40 mm Hg
- (b) in patients without vascular disease, PtcO2 values on the extremity increase to a value >100 mm Hg when breathing 100% oxygen under normobaric pressures
- (c) patients with critical limb ischemia (ankle systolic pressure of < or =50 mm Hg or toe systolic pressure of < or =30 mm Hg) breathing air will usually have a PtcO2 <30 mm Hg
- (d) low PtcO2 values obtained while breathing normobaric air can be caused by a diffusion barrier
- (e) a PtcO2 <40 mm Hg obtained while breathing normobaric air is associated with a reduced likelihood of amputation healing
- (f) if the baseline PtcO2 increases <10 mm Hg while breathing 100% normobaric oxygen, this is at least 68% accurate in predicting failure of healing post-amputation
- (g) an increase in PtcO2 to >40 mm Hg during normobaric air breathing after revascularization is usually associated with subsequent healing, although the increase in PtcO2 may be delayed
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