Calciphylaxis is a severe complication of chronic renal failure, confined almost 
exclusively to patients on dialysis therapy. Histological characteristics of 
calciphylaxis include small-vessel calcifications of skin, subcutaneous tissue, 
and visceral organs. These vascular changes promote tissue ischemia that often 
results in tissue necrosis. In this study, we investigated the extent of skin 
ischemia in patients with calciphylaxis by means of transcutaneous oxygen 
tension (TCPO(2)) measurement, a noninvasive test that accurately assesses skin 
oxygenation. TCPO(2) levels were measured in 21 patients with calciphylaxis and 
21 age- and sex-matched patients without evidence of calciphylaxis (controls). 
TCPO(2) levels were measured bilaterally at the chest, anterior abdomen, and 
upper thigh while patients breathed room air and after a 30-minute exposure to 
100% fraction of inspired oxygen (FIO(2)). Compared with controls, patients with 
calciphylaxis showed significantly lower TCPO(2) levels at each body region. In 
both controls and patients with calciphylaxis, lower TCPO(2) levels correlated 
with increased weight and use of hemodialysis. No correlation with serum 
parathyroid hormone (PTH), serum calcium, or serum phosphorus values was 
present, although 39% of the patients with calciphylaxis had markedly elevated 
PTH values (sixfold greater than normal; >300 pg/dL). Low TCPO(2) levels in 
patients with calciphylaxis were documented in body regions with and without 
skin lesions. In patients with calciphylaxis, extremely low TCPO(2) values 
(</=30 mm Hg while patients breathed room air) were present in 62% of the body 
regions with skin lesions and 26% of the body regions without lesions. Room-air 
TCPO(2) levels </=30 mm Hg were present in only 0.8% of the body regions of 
control patients. TCPO(2) levels obtained while patients breathed 100% FIO(2) 
remained lower in patients with calciphylaxis than in controls. In conclusion, 
TCPO(2) levels are abnormally low in patients with calciphylaxis, indicating 
that severe and diffuse skin ischemia exists, even at areas free of skin 
lesions. Low TCPO(2) values did not substantially increase with 100% FIO(2) in 
many patients with calciphylaxis, suggesting a fixed insufficiency of the skin 
vessels. This study shows that TCPO(2) measurements may allow rapid and 
noninvasive screening for skin ischemia before the development of skin lesions 
in patients with calciphylaxis.