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Simple Needle | Wick Catheter | Slit Catheter | Side-ported Needle | Transducer-tipped Catheters Several needle and catheter types exist for use of measurement of intracompartmental pressures. Below we discuss each of the types and present the advantages and disadvantages associated with each.
Early compartmental measurement techniques employed a simple 18 gauge needle inserted into the compartment to be measured. 37,38 The needle was then connected to a mercury pressure manometer for pressure recording. Although the needles are readily available, several studies have shown that they yield the least reliable and least reproducible data. 26,39 Because there is a single entry port for interstitial fluid, pressures are falsely elevated or depressed if the needle becomes plugged with tissue or is inadvertently inserted into tendon or fibrous tissue.
The wick catheter technique was introduced in 1976 to provide an improved method for pressure monitoring 20,40 . The catheter contains multiple fibers at its tip which are introduced into a compartment with an introducer needle. The fibers act by capillary action to improve rapid equilibration with intracompartmental interstitial pressures, while preventing ball-valve obstruction at the tip. Furthermore, the catheter may be left in place for up to 8 hours for serial recordings. Disadvantages include the possibility of coagulation and occlusion around the tip, as well as the possibility for fibers to break off and remain within the tissues. Furthermore, wick catheters may only be used to measure a single compartment and cannot be reused.
The slit catheter was introduced in 1981 39 . It is a polyethelene catheter with 5 six-millimeter axially cut slits at the tip to provide a greater open surface area of the catheter for equilibration with interstitial fluid 41 . As with the wick catheter, it may be left in place for serial pressure recordings, but is also susceptible to clotting. Additionally, it may only be used for measurement of a single compartment.
 The side-ported needle was introduced in 1988 42 . These needles are inserted into intramuscular compartments perpendicular to the surface, and therefore side ports have low risk of occlusion. This allows for improved accuracy (compared with simple needles) of interstitial pressure measurements along with the additional advantage of being capable of measuring several compartments in the same patient 43 . They have been shown to have similar accuracy to slit catheters 26 . The Stryker Pressure Monitor utilizes this needle type.
These are open-ended catheters that have a built-in transducer tip 44-46 . The advantage is that no saline needs to be injected into the measured compartment (which would have the potential to further increase compartmental pressures). There is no needed external manometer or pressure transducer, and the catheter is directly connected to the display. Catheters are relatively expensive, but may be sterilized and reused. They are not yet widely available.
Stryker Pressure Monitor | Mercury Manometer | Infusion Technique | CVP Monitors and IV Pumps
 The Stryker pressure monitor is a solid-state hand-held transducer that has gained popularity in the rapid measurement of compartment pressures. It was first introduced in 1988 and has been shown to yield accurate and reproducible results 42 . The Stryker monitor is designed specifically for use with the side-ported needle, although simple needles, wick or slit catheters could theoretically be used. Disposable Stryker "Quick Monitor Packs" purchased separately contain the side ported needle and diaphragm chamber. Additionally, a Stryker pre-filled 3 cc saline syringe is also commercially available. When assembled, the pressure monitor may be re-zeroed and used for multiple compartment pressure measurements in the same patient (up to 10 if 0.3 cc saline is used for each measurement). Please see the Procedure section for full description of its use.
One of the earlier techniques described to measure compartment pressures was described in 1975 by Whiteside and his colleagues 37 . As many hospitals have phased out the use of mercury containing devices, this method has become antiquated. A simple needle is connected to IV tubing and saline is aspirated to fill half of the length of the tube. This is connected to a three way stopcock and on the opposite side, IV tubing filled with air is attached to a mercury manometer. The needle is inserted into the compartment to be measured. The third opening on the three-way stopcock is connected to a 20 cc air-filled syringe. The stopcock is positioned such that all openings are in free communication and the plunger is slowly depressed to increase pressure in the system. The mercury column will rise until the pressure in the tubing connected to the manometer is equal to the pressure in the muscle compartment. At this point, the mercury stops rising, and fluid will begin to move into the muscle compartment. Just as this begins to occur, the manometer pressure is recorded.
This method is similar to the above mercury manometer technique, but utilizes a pressure transducer and calibrated monitor 47 . An IV catheter, wick or slit catheter is connected to a pressure transducer dome with IV tubing. The dome is then connected to a small continuous infusion pump and syringe. The system is flushed with saline, and the catheter is inserted into the compartment. The transducer dome is connected to the trasducer which is then attached to the calibrated monitor. The suggested infusion rate is 0.7 cc saline per 24 hours to maintain catheter patency, and thus may be used for continuous pressure recordings up to three days. This set-up is somewhat more complicated than the aforementioned above and requires specialized equipment. Although the total infusion volume is very small, there is a theoretical risk of further elevating compartment pressures using this technique 3 .
Variations on this technique involve the use of directly connected CVP monitors 48 or IV pumps with pressure sensing capabilities (available in many ICUs) 49 . These replace the use of the transducer/monitor and offer the advantage of not needing a continuous infusion of saline. |
Multiple methods exist to determine intra-compartmental pressures. These methods use different various types of needles and cathter assemblies that are introduced into the compartment in question. Here we provide a review of several of the available methods, with emphasis on the Stryker Pressure Monitor. 