Can You ID this Seldom-Needed, but Essential EM Tool?


1) Name that tool. This device goes by the name “Compass.” It is similar to a model manufactured by Stryker, which is also highly distributed, but tends to have less accurate readings than the Compass.

2) Why do you need it?

It’s most critical function is for measurement of compartment pressures (it has other uses, as well, such as measurement of opening pressure for LP). Although compartment syndrome is really a clinical diagnosis (remember your “6 P’s”), you or your consultants may want to use this device for diagnostic confirmation before fasciotomy.

3) How does it work?

Your Compass will likely come in a kit containing the necessary accessories for its use. The kit stocked in our ED looks like this:

Ready to confirm your diagnosis? Prep skin and find your sterile gloves. Remove the caps from the ports on both ends of the Compass monitor. Attach an 18 G needle to the longer port. Attach a syringe with sterile water to the other and inject ~ 0.5 cc to remove air in the monitor. Hold down the red button on the side of the monitor until the reading “00” appears. Now you’re set to go.


For a review of how and where to check compartments, check out this video by EM:RAP (which gives instructions for the Stryker model, but the same principles apply for both devices).


Finally, remember the number 30.

For the diagnosis of compartment syndrome:

Delta Pressure (= diastolic BP - compartment pressure) < 30

Or an absolute compartment pressure > 30


Want to learn more?