Data elements:
(1) inhalation injury symptom score: from 0 to 7 (see previous section)
(2) percentage burns: The specification for this is a little unclear. Clark refers to the paper of Bull (1971), which does not appear to separate burn area involvement by burn depth, since this might not be known immediately. Some other burn scores use the combined area involved by second and third degree burns.
(3) age in years
(4) carboxyhemoglobin concentration at exposure. The percent carboxyhemoglobin is determined and then this is converted to a concentration using a nomogram (Clark, 1981).
Z =
= (0.034 * (age)) + (0.094 * (percent burns)) + (0.78 * (symptom score)) – 7.9
Y =
= (0.061 * (age)) + (0.18 * (percent burns)) + (0.086 * (carboxyhemoglobin concentration)) – 9.7
probability of death =
= EXP(factor) / (EXP(factor) + 1) =
= 1 / (1 + EXP((-1) * (factor)))
Interpretation:
• All patients with a probability > 0.66 died.
• All patients with a probability < 0.17 survived.
|
Probability
|
Risk Group
|
|
>= 0.66
|
high
|
|
0.33 – 0.65
|
moderate
|
|
< 0.33
|
low
|
where:
• I would be tempted to make the moderate risk category 0.17 to 0.65 and the low risk category < 0.17.
Limitations:
• The mortality from burns was higher prior to modern developments in burn care, although the risk categories probably still are applicable.
• Carboxyhemoglobin (up to 9%) may be present in smokers.
