Accuracy in the measurement of compartment pressures: a comparison of three commonly used devices.

BACKGROUND: In situations in which accurate physical diagnosis is inconclusive, an objective method for measuring compartment pressure can aid in the diagnosis of compartment syndrome. Previous studies have compared measurement devices with each other but not with an accurately determined gold standard. The purpose of the present study was to devise a reproducible in vitro model of compartment pressure and to compare commonly used measurement devices in order to determine their accuracy.

METHODS: With a graduated cylinder being used to generate a known pressure, freshly harvested ovine muscle was placed into a chamber for testing. The cylinder was incrementally filled with saline solution (in fifty-five steps), and measurements of tissue pressure were obtained with use of the Stryker Intracompartmental Pressure Monitor System, an arterial line manometer, and the Whitesides apparatus. Each device was tested with a straight needle, a side-port needle, and a slit catheter, for a total of nine setups in all. Five trials were done with each setup. Control pressures were calculated on the basis of the height of the saline solution column (test range, 0.13 to 10.80 kPa). Multiple regression analysis was used to compare measured tissue pressures with calculated control pressures.

RESULTS: Most methods demonstrated excellent correlation (R2> 0.95) between calculated and measured pressures. The arterial line manometer with the slit catheter showed the best correlation (R2= 0.9978), and the Whitesides apparatus with the side-port needle showed the worst (R2= 0.9115). Furthermore, the Stryker system with the side-port needle demonstrated the least constant bias (+0.06 kPa). Straight needles tended to overestimate pressure. Two of the three needle configurations involving the Whitesides apparatus overestimated pressure. The data for the Whitesides methods had the highest standard errors, showing clinically unacceptable scatter.

CONCLUSION: Side-port needles and slit catheters are more accurate than straight needles are. The arterial line manometer is the most accurate device. The Stryker device is also very accurate. The Whitesides manometer apparatus lacks the precision needed for clinical use.