Index of Modesti et al for Identifying a Patient at Risk for Acute Mountain Sickness (AMS)

The evaluation is performed at an intermediate altitude (3,400 to 3,650 meters) just prior to ascent to the final altitude (> 4,500 meters).

Acute mountain sickness was defined as headache and a Lake Louise Score (LLS) >= 4.

Parameters:

(1) percent oxygen saturation

(2) hematocrit in percent

(3) day of the expedition

(4) maximum velocity of clot formation in mm per minute (peal of the first derivative of the thromboelastographic clotting curve)

predictive index =

= 100 / X

X =

= (0.174 * (percent oxygen saturation)) + (0.050 * (hematocrit in percent)) + (0.074 * (day of expedition)) - (0.077 * (maximum velocity of clot formation in mm per min))

Interpretation:

• In the Italian Alps an index >= 5.92 had an odds ratio of 8 for onset of AMS within 48 hours of reaching high altitude.

• The 2 parameters associated with AMS was the increased index and an oxygen saturation < 91.5%.

Performance:

• The sensitivity of the index in the study group was 85% and specificity 59%.