Compartment pressure is measured to assist in diagnosing compartment syndrome. Measurement of compartment pressure is a hospital-based procedure that requires considerable technical skill; an orthopedic or general surgeon is typically consulted.
Compartment pressures can be measured in the 3 compartments of the forearm (volar, dorsal, and mobile wad).
The Stryker® system, a commercially available instrument, is used here. Follow all instrument instructions. Know what equipment is available at your particular institution.
(See also Compartment Syndrome.)
Indications for Measuring Forearm Compartment Pressure
Suspected compartment syndrome
Compartment syndrome is suggested by worsening pain of the involved compartment that is disproportionate to the apparent severity of the injury and exacerbated by passive stretching of compartment muscles. On palpation, the compartment may be swollen and tense, but these findings may not always be present.
Contraindications to Measuring Forearm Compartment Pressure
Absolute contraindications
None
Relative contraindications
Infection of skin or deeper tissues at the anticipated site of needle insertion: If possible, use an alternate, uninfected site.
Bleeding diathesis, which may need to be corrected before compartment pressure measurement
Complications of Measuring Forearm Compartment Pressure
Erroneously high or low pressure measurements that may be due to poorly placed or obstructed needles, faulty or inaccurately calibrated devices, patient agitation, or excess test saline injected into the compartment. These measurement errors can lead to incorrect treatment.
Infection, bleeding, or tissue damage resulting from needle insertion may occur.
Equipment for Measuring Forearm Compartment Pressure
Sterile gowns, gloves, and drapes
Sterile gauze
The Stryker® system, containing a needle, tubing, and transducer
25- to 27-gauge needle
About a 3- to 5-mL syringe for local anesthetic injection
Sterile dressings
Additional Considerations for Measuring Forearm Compartment Pressure
Sterile technique is required to prevent microbial contamination of the compartment tissues.
Maintain a low threshold for measuring compartment pressure in at-risk patients because deep compartments may not have palpable tenseness or swelling, pain is nonspecific, and, in obtunded patients, symptoms and signs can be absent or nonspecific.
Diagnosis must be made and treatment started before pallor or pulselessness develops.
Relevant Anatomy for Measuring Forearm Compartment Pressure
The forearm has 3 compartments:
Volar compartment: Includes the flexor carpi ulnaris, flexor pollicis longus, flexor digitorum profundus, flexor digitorum superficialis, palmaris longus, and flexor carpi radialis muscles and also the ulnar, superficial radial, and median nerves and the radial, ulnar, and anterior interosseus arteries
Dorsal compartment: Includes the extensor pollicis longus, abductor pollicis longus, extensor digitorum, extensor digiti minimi, and the extensor carpi ulnaris muscles and also the posterior interosseus nerve and posterior interosseus artery
Mobile wad compartment: Includes the brachioradialis, the extensor carpi radialis brevis, and the extensor carpi radialis longus muscles
The volar compartment is most commonly affected by compartment syndrome.
Positioning for Measuring Forearm Compartment Pressure
Position the patient with the affected arm at heart level and so that the needle can enter the skin at an angle perpendicular to the compartment being measured.
Step-by-Step Description for Measuring Forearm Compartment Pressure
Prepare the equipment
Open the Stryker® system and remove the contents onto a sterile field.
Place the needle firmly onto the tapered stem of the diaphragm chamber. Remove the cap on the pre-filled syringe and attach it to the stem on the opposite side.
Open the cover of the monitor and place the chamber into the pressure monitor with the black surface down. Carefully push it until it is seated in place. Snap the cover of the monitor closed.
Hold the needle at a 45° angle upward and depress the plunger to purge the system of air. Do not allow saline to trickle down the needle into the transducer well.
Turn on the monitor and check for a numeric reading to appear in the display window.
Calibrate the device: Hold the device at the intended angle of insertion. Press the "zero" button and ensure that, after a few seconds, the display reads “00.” The display must read “00” before continuing. For each additional measurement, the unit must be recalibrated to “00.”
General steps for all compartments
Do a pre-procedure neurovascular examination of the affected forearm.
Using a 25- to 27-gauge needle, place a wheal of local anesthetic over the needle entry site. Avoid injecting anesthetic into the deeper tissues of the muscle and fascia. Doing so may falsely elevate the compartment pressure measurement.
Hold the assembled and calibrated pressure monitor perpendicular to the compartment being measured and insert the needle as gently as possible through the skin to a depth appropriate for the target compartment.
Slowly inject 0.3 mL of saline into the compartment.
Wait for the display window to show equilibrium has been reached and record the resultant pressure.
For each additional measurement, recalibrate the unit to "00" and repeat the process.
A measured pressure of more than about 30 mm Hg or within about 30 mm Hg of diastolic blood pressure supports the diagnosis of compartment syndrome and indicates consideration for immediate fasciotomy.
Compartment syndrome is possible even if compartment pressure is not elevated; if suspected based on clinical findings, the diagnosis should be presumed and compartment pressures should be measured serially.
Specific steps for the volar compartment
Position the patient supine with the forearm supinated.
Identify the palmaris longus tendon and its proximal course.
Insert the needle just medial to the palmaris longus at the junction of the proximal and middle thirds of the forearm.
Advance the needle perpendicularly and direct it toward the posterior border of the ulna to a depth of 1 to 2 cm.
Confirm proper needle placement by observing a rise in pressure when you press with your finger over the volar compartment just proximal or distal to the needle insertion site and with extension of the fingers and wrist.
Specific steps for the dorsal compartment
Position the patient supine with the forearm pronated.
Palpate the posterior aspect of the ulna at the level of the junction of the proximal and middle thirds of the forearm.
Insert the needle at this level, 1 to 2 cm lateral to the posterior aspect of the ulna.
Advance the needle perpendicularly to a depth of 1 to 2 cm.
Confirm proper needle placement by observing a rise in pressure when you press with your finger over the dorsal compartment just proximal or distal to the needle insertion site and with flexion of the wrist or fingers.
Specific steps for the mobile wad compartment
Position the patient supine with the arm supinated.
Identify the most lateral portions of the forearm at the junction of its proximal and middle thirds.
Insert the needle at this level and lateral to the radius.
Advance the needle perpendicularly to a depth of 1 to 1.5 cm.
Confirm proper needle placement by observing a rise in pressure when you press with your finger over the mobile wad just proximal or distal to the needle entry site and with ulnar deviation of the wrist.
Aftercare for Measuring Compartment Pressure in a Forearm
Apply sterile dressings to all needle entry sites.
Repeat the neurovascular examination of the arm.
Warnings and Common Errors for Measuring Forearm Compartment Pressure
Compartment syndrome is a clinical, often difficult, diagnosis to make. Early consultation with an orthopedist or general surgeon is recommended.
Presence of distal pulses and capillary refill and even normal compartment pressures do not rule out compartment syndrome.
Measure pressures for all possibly affected compartments in the involved extremity.
Tips and Tricks for Measuring Forearm Compartment Pressure
To maximize accuracy, measure pressure at sites of trauma or maximum palpable tension.
