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The measurement of dynamic compartmentpressure during exercise*

J. G. LOGAN,† B ESC, C. H. RORABECK,‡§ MD, FRCS(C), ANDG. S. P. CASTLE,† PHD, P ENG

From †the Faculty of Engineering Science, The University of Western Ontario, London, Ontario,Canada, and the ‡ Department of Orthopaedic Surgery, University Hospital,

London, Ontario, Canada

ABSTRACT

Anterior tibial compartment pressures have been ex-amined during exercise in nine healthy university stu-dents. Six male and three female subjects weighing140 to 160 pounds and between 18 and 25 years ofage were tested. A slit catheter was introduced intothe muscle belly of the subjects’ right anterior tibialcompartment and dynamic compartment pressuresmeasured using an F.M. telemetry system. Subjectswere exercised on a treadmill at speeds from 1 to 6

mph and the variations in compartment pressure duringone exercise cycle (one stride length) and over thecourse of the exercise period examined. Results haveshown that both average and peak to peak pressuresmeasured during exercise are much higher than thoserecorded at rest, and compartment pressures rose withincreasing speed.

An upward change in compartmental pressure has long beenrecognized as an indicator of the onset of an acute compart-ment syndrome as a result of fracture trauma, prolongedlimb compression, or arterial damage.2 As such, the meas-urement of compartmental pressure provides a valuableclinical tool in aiding the early detection of compartmentsyndromes.The detection and evaluation of a recurrent compartment

syndrome due to exercise is somewhat more difficult. Recur-rent compartment syndromes are usually found in athletesand military recruits who are required to perform vigorousexercises regularly. The most common method of diagnosingthese patients is to measure the pressure in the affected

compartment both before and immediately after the patienthas performed a set of exercises that cause the characteristicsymptoms to recur.3 However, tissue fluid pressure changesduring the course of exercise cannot be evaluated using thismethod. In an attempt to overcome this problem, studieshave been performed in which anterior compartment pres-sure is monitored continuously while the patient dorsiflexeshis foot against a constant load.4 However, this method doesnot allow the patient’s normal exercise activity to be usedin the evaluation.

In addition, Baumann et aLl have demonstrated thatcompartment pressures may be used to evaluate both passiveand active muscle tension during exercise. Thus, a devicefor evaluating tissue fluid pressure continuously duringphysical activity without restricting the subjects’ motionprovides a valuable research tool.

It is the purpose of this paper to present the results of an

experimental investigation performed at University Hospi-tal, London, Ontario, in which compartmental pressureswere monitored continuously during a variety of exerciseactivities using a remote telemetry system developed at theFaculty of Engineering Science, The University of WesternOntario.

MATERIALS AND METHODS

The experimental subjects were healthy asymptomatic uni-versity students weighing 140 to 160 pounds, between 18and 25 years of age, and without previous history of com-partment syndromes. Six males and three female volunteershave been tested and subjects were chosen without regardto their level of physical fitness. All subjects were requestednot to undertake any strenuous physical exercise for 48hours prior to participating in the study.A slit catheter as shown in Figure 1, was filled with sterile

saline solution. Observing sterile technique, the volunteerwas given a local anesthetic (1% Xylocaine) and then the

*Presented at the 15th Annual Meetmg of the Canadian Orthopaedic Re-search Society, Kingston, Ontano, Canada, June 11 to 13, 1982

§ Address correspondence and reprnt requests to C H Rorabeck, MD,FRCS(C), P O Box 5339, Station A, London, Ontano, Canada N6A 5A5

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Figure 1. The slit catheter.

catheter was inserted into the muscle belly of the anteriortibial compartment of the volunteers’ right leg.Compartment pressures were then measured using the

F.M. telemetry system illustrated in Figure 2. The systemconsisted of a battery-powered transmitter package which isconnected to a Micron model MP 15 miniature pressuretransducer (Micron Instruments, Inc., Los Angeles, CA) anda 17 cm long slit catheter. The use of this transducer-catheter combination provides a frequency response of over100 Hz, providing detailed pressure waveshapes for record-ing.

The pressure signal from the transducer is used to fre-

quency modulate an audio oscillator. This audio signal thenmodulates a 90 MHz F.M. transmitter. This radio frequencysignal is received using an F.M. tuner and the recoveredaudio tone decoded to an output voltage which is displayedon an oscilloscope and/or a high speed strip chart recorder.In addition, the receiver circuit contains an averaging filterand a digital display allowing average pressure values to beobtained.Each subject exercised on a fitness testing treadmill and

his/her compartmental pressure was measured while walk-ing at speeds from 1 to 6 mph. During this test, the treadmillspeed was increased in l-mph increments every 2 minutes.

After these measurements were completed, the subjectwas allowed to rest for approximately 15 minutes or untilthe resting compartmental pressure returned to preexerciselevels. Compartment pressures were then measured whilethe subject was exercised to fatigue by continued jogging at6 mph. After the onset of fatigue, the postexercise changesin compartment pressure were monitored for a period of 7minutes. All subjects were tested in bare feet to eliminateany effects that might be caused by varying footwear.

RESULTS

Anterior tibial compartment pressure waveshapes duringwalking were recorded for each subject tested.

Other experimental data were analysed to study the rela-tionship of compartment pressure and walking speed,changes in compartment pressure during continued running,and postexercise changes in compartmental pressure. Figure3 shows a typical anterior compartment pressure waveshapeobtained for a 160 pound male walking at 3 mph. Both theaverage and peak to peak pressures were used in evaluatingthe data obtained. Pressure data for each subject were nor-malized by dividing the patients’ compartment pressuremeasured at any given speed by their compartment pressureat natural walking speed. The normalized values for all thesubjects were then averaged to obtain mean and SD values.For the nine asymptomatic subjects tested, the anteriortibial compartment pressure measured with subject supine

Figure 2. The 90 MHz F.M. telemetry system.

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Figure 3. Right anterior tibial compartment (ATC) pressure during natural gait for a 160 pound male subject.

Figure 4. Right anterior tibial compartment pressure as afunction of walking speed.

was 13.2 ± 6.7 mm Hg. The large SD is indicative of thevariation in compartmental pressures that may be observedeven in asymptomatic subjects.

Figure 4 shows the relationship between anterior tibialcompartment pressure and walking speed. The average pres-sures were normalized with respect to the subjects’ averagepressure at natural walking speed and peak to peak pressuresnormalized with respect to the corresponding value meas-ured at natural walking speed. The nine subjects tested hadnatural walking speeds between 2.6 and 3.1 mph, with anaverage natural walking speed of 2.8 mph. The mean valueof average pressure at a natural walking speed for the ninesubjects was 26 ± 12 mm Hg and the mean peak to peakpressure was 40 ± 18 mm Hg. Variations caused by thesubjects having considerably different compartment pres-sure values at natural walking speed were eliminated byusing normalized pressure values in the analysis of the data.Note the large increases in both average and peak to peakpressure as velocity increases.Compartment pressures also rise slightly at speeds below

natural gait, indicating that minimum pressures occur at ornear natural walking speed.

Figure 5 illustrates the changes in compartmental pressureobserved during continued jogging at 6 mph. Again, both

Figure 5. Right anterior tibial compartment pressure duringcontinued jogging at 6 mph.

Figure 6. Postexercise right anterior tibial compartment pres-sure, subject standing.

average and peak to peak pressures have been normalizedwith respect to the values obtained at natural walking speed.Due to the variation in the levels of physical fitness observedin the subjects, the length of time required for the subjectto become fatigued varied from 8 to 25 minutes. Despite thelack of a quantitative measure of fatigue, there was goodcorrespondence between the pressure trends observed foreach subject. For ease of evaluation, the results are presentedas measured as &dquo;percent of time to fatigue&dquo; rather thanabsolute time values.

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The average pressure values show an initial increase, buttend to decline as exercise is continued. The measured valuesof peak to peak pressure also tend to decline with time.These trends are consistent with those observed by otherauthors using dorsiflexion against a constant load for com-partmental pressure evaluation during exercise.5

Studies of postexercise pressures indicate that the anteriorcompartment pressures in asymptomatic subjects return tovalues below preexercise levels within the one-minute periodrequired to slow the treadmill from 6 mph to a stop (referto Fig. 6). This postexercise recovery is more rapid than thatobserved by Hargens and Mubarak2 when testing asympto-matic subjects using the repeated dorsiflexion method ofexercise. This difference may be due to subjects on thetreadmill slowly reducing their pace to a stop at the end ofexercise rather than coming to an immediate halt as theywould be able to do if a treadmill were not used.

DISCUSSION

A relationship between compartment pressure and walkingspeed has been demonstrated. Compartment pressures havebeen found to be proportional to walking speed, indicatinga possible reason why recurrent compartment syndromesufferers can continue to exercise at a reduced pace after theonset of compartment syndrome symptoms.6The changes in compartment pressure as exercise is con-

tinued have been measured and compare well with thoseobserved by other authors using the technique of dorsiflexionagainst a constant load. On the other hand, the postexercisepressure tests indicate a more rapid return to preexercisevalues. However, this difference may be due to the fact that

the volunteers on the treadmill slowly reduce their pace toa stop as the treadmill slows down rather than coming to animmediate halt.

CONCLUSIONS

The new apparatus for measuring compartment pressuresduring exercise has been shown to be effective. Several

relationships between compartment pressure and exercisefactors have been studied and the potential value of furtherresearch in these areas demonstrated.

ACKNOWLEDGMENTS

The authors would like to thank Mr. R. Hardie and Ms.Anne Toman for their valuable technical assistance withthis project. In addition, special thanks to all those whovolunteered to participate in the gait studies and to theNatural Sciences and Engineering Research Council fortheir financial support provided to Mr. Logan.

REFERENCES

1 Bauman JU, et al Intramuscular pressure during walking An experimentalstudy using the wick catheter Clin Orthop 145 292-299, 1979

2 Hargens AR, Mubarak SJ Compartment Syndromes and Volkmanns Con-tractures Philadelphia, WB Saunders Co , 1981, p 49

3 Matsen FA Compartment Syndromes New York, Grune and Stratton,1980, p 135

4 Matsen FA Compartment Syndromes New York, Grune and Stratton,1980, p 136

5 Matsen FA Compartment Syndromes New York, Grune and Stratton1980, p 137-140

6 Reneman RS The anterior and the lateral compartmental syndrome of theleg due to intensive use of muscles Clin Orthop 113 69-80, 1975