title: The relationship of the transcutaneous oxygen tension, pulse waves and systolic pressures to the risk for limb amputation in patients with peripheral arterial disease and skin ulcers or gangrene.
abstract: OBJECTIVE
  Our aim was to determine how the risk associated with presence of low transcutaneous oxygen tension (tcPO2) for subsequent major amputation in patients with skin ulcers or gangrene and peripheral arterial disease, compares with the risks associated with low peripheral pressures and low amplitude of pulse waves. Secondly, we determined whether combination of measurements of oxygen tension with that of the pressures or pulse wave amplitude predicts amputation better than pressure, wave or oxygen tension measurements alone.
  
  
  METHODS
  Measurements were carried out to obtain foot tcPO2, ankle and toe pressures, pressure indices, and toe pulse wave amplitude in 75 limbs with skin lesions and arterial disease of 66 patients referred to the vascular laboratory. These variables were related to the risk of a subsequent major amputation during a median time of 4.2 years, using Cox proportional hazards model.
  
  
  RESULTS
  Low oxygen tension was associated with increased risk of amputation (relative risks 2.16 and 2.55 for tcPO2 < or = 10 mmHg and < or = 20 mmHg, respectively, P<0.05; relative risk 2.22 for tcPO2 < or = 30 mmHg, P=0.07). The relative risks associated with cutoff values of ankle and toe pressures and pressure indices varied from 2.53 (toe < or = 20 mmHg, P<0.05) to 5.83 (ankle < or = 50 mmHg, P<0.001) and the relative risk associated with low wave amplitude (< or = 4 mm) was 3.41, P<0.01. The cutoff values of tcPO2 became insignificant when included in the models together with each pressure variable or pulse amplitude separately. In contrast, wave amplitude remained significantly associated with increased risk of amputation after controlling for each pressure variable (P<0.05).
  
  
  CONCLUSIONS
  TcPO2 < or = 10 mmHg and < or = 20 mmHg are related significantly to increased risk of amputation in patients with skin lesions and arterial disease, but these relative risks are similar in magnitude or smaller than those associated with low cutoff values of pressures, pressure indices or pulse wave amplitude. Low wave amplitude does provide significant information in addition to peripheral pressures with respect to the risk of amputation. On the other hand, low tcPO2 does not provide significant information in addition to peripheral pressures or pulse wave amplitude.
authors.affiliation: Department of Medicine, Vascular Laboratory, University of Manitoba, Canada. sacarte@cc.umanitoba.ca
authors.forename: S A
authors.initials: SA
authors.lastname: Carter
authors.forename: R B
authors.initials: RB
authors.lastname: Tate
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000671:Amputation, Surgical; D000842:Ankle / Q000098:blood supply* / Q000473:pathology / Q000503:physiopathology; D001785:Blood Gas Monitoring, Transcutaneous; D001794:Blood Pressure; D001916:Brachial Artery / Q000473:pathology / Q000503:physiopathology; D005260:Female; D005500:Follow-Up Studies; D005734:Gangrene / Q000503:physiopathology / Q000601:surgery; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption; D016491:Peripheral Vascular Diseases / Q000453:epidemiology / Q000503:physiopathology* / Q000601:surgery; D016016:Proportional Hazards Models; D011674:Pulse; D012307:Risk Factors; D012883:Skin Ulcer / Q000453:epidemiology / Q000503:physiopathology* / Q000601:surgery; D016019:Survival Analysis; D014034:Toes / Q000098:blood supply* / Q000473:pathology / Q000503:physiopathology; D016896:Treatment Outcome
chemical_list: D010100:Oxygen