Magnetic Field Therapy-Does Affect Soft Tissue? *

Transcription

1 /83/ $02.00/0 THE JOURNAL OF ORTHOPAEDIC AND SPORTS PHYSICAL THERAPY Copyright O 1983 by The Orthopaedic and Sports Physical Therapy Sections of the American Physical Therapy Association Magnetic Field Therapy-Does Affect Soft Tissue? * ROBERT RAILTON, BSc, PHD, F. INST. P,t PETER NEWMAN, BSC, ARCS* It Claims that magnetic field therapy improves peripheral circulation and tissue oxygenation have been tested on normal volunteers. Transcutaneous oxygen tension measurements were made and skin temperatures measured in a double blind trial. Using recommended magnetic field configurations, no significant effects attributable to the magnetic field therapy could be demonstrated. Copyright All rights reserved. Magnetic field therapy is an old technique with claims being made for the use of lodestone (natural magnetic rock) in wound healing some 2000 years ago. In the nineteenth century, work was reported on the use of alternating magnetic fields generated electrically as an aid in clinical thera ~ y Recently,. ~ physiotherapy treatment machines have come on to the market which rely on a weak pulsating magnetic field for their effect, e.g., the ~agnetotron~ (Elec GmbH, Wiesbaden, West Germany). This consists of a solenoid wound round a drum 34.5 centimeters long with a radius of 24 centimeters connected to a variable frequency pulse generator. The manufacturer of this machine makes claims in its literature and will provide unpublished data from various experimenters which purport to show that the therapeutic action of pulsating magnetic fields on soft tissues is by the stimulation of peripheral blood flow and improved oxygenation. It is clear that any device which does this would indeed improve healing both in patients with impaired circulation and also those without evidence of underlying vascular disease. For example, increased oxygenation of the tissues by means of a hyperbaric oxygen chamber has * The Draeger Oxymeter was provided by a grant from the Scottish Home and Health Department. t Principal Physicist, Medical Physics Department, Monklands District General Hospital, Airdrie. Scotland and West of Scotland Health Boards, Department of Clinical Physics and Bio-Engineering, Glasgow, Scotland. To whom correspondence should be addressed at the Medical Physics Department, Monklands District General Hospital. Monkscourt Avenue, Airdrie, Scotland, UK ML6 0-JS. $ Senior Physicist. Medical Physics Department, Monklands District General Hospital, Airdrie, Scotland and West of Scotland Health Boards, Department of Clinical Physics and Bio-Engineering, Glasgow, Scotland. been demonstrated4 and this technique has been used in the treatment of gangrene.' It is stated in the manufacturer's literature that the Magnetotron can be used for the treatment of sport injuries, i.e., trauma in presumably healthy individuals. Indeed the majority of Magnetotron units sold in Scotland have been to football clubs. In the quoted trials, no distinction is made between patients and normal volunteers; it would thus appear that any effects on blood supply should be demonstrable on normal subjects. The methods described by the experimenters to measure tissue oxygen tension and peripheral blood flow include the measurement of oxygen perfusion through the skin and also thermography. In order to test the validity of these claims we have used a transcutaneous oxygen monitor to measure tissue oxygen tensions in normal subjects using the magnetic field configurations described by the manufacturer's agent. Skin temperature changes were also measured. No attempt has been made to assess the effects of magnetic fields on bone healing. This trial was designed to study soft tissue effects only and unlike the trials quoted by the manufacturer it was performed double blind, i.e., neither subject nor experimenter knew at the time of measurement whether the magnetic field was off or on. METHODS Transcutaneous oxygen tension (TcP02) measurements were made with a dual channel Oxymetera (Draeger Medical Limited) at electrode temperatures of 45 and 37" C. With the electrode temperature at 45' C, maximum vaso-

2 242 RAILTON AND NEWMAN JOSPT Vol. 4, No. 4 Copyright All rights reserved. dilatation is produced and a correlation between TcPO, and arterial PO2 has been demonstrated in normal subject^.^ With the electrode temperature at 37OC the TcPO, is related to skin blood flow.3 Before recordings were made, the TcP02 monitor was calibrated in air and the zero level checked using sodium dithionite solution. Skin temperatures were measured by means of an Elab DU3 precision thermocouple thermometer. Twenty-two normal subjects were studied with a mean age of SD years. All had refrained from smoking for over 1 hour before the test and all had no known circulation defects. All tests were done double blind, i.e., neither the experimenter making the measurements nor the patient knew whether the magnetic field was on or off. The magnetic field used was that recommended by the manufacturer's agent for the maximum effect, i.e., 100 gauss at a repetition frequency of 25 hertz and this field was either on for the first 15 minutes of the test and then off for the second 15 minutes or vice versa. Whether the machine was on or off for the first 15 minutes was decided on the toss of a coin by a second experimenter. The switching of the machine was done by the second experimenter who recorded this information and placed it in a sealed envelope. This information was not disclosed until the end of the experimental phase of the trial. Two configurations of magnetic field and oxygen sensor were used as follows. 1) One electrode was attached to the dorsum of the foot of the subject and the other electrode to the flexor aspect of the forearm approximately midway between the wrist and elbow. Both these electrodes were operated at 45" C. The subject lay within the drum of the device so that the torso was enveloped with the arms outside (Fig. 1). Twelve subjects were studied with this configuration. 2) Both electrodes were attached to the flexor aspects of each forearm. One electrode was operated at 45O C as in configuration 1, whereas the other electrode was operated at 37O C. The subject lay with his head within the magnetic field (Fig. 2). Twelve subjects were studied with Fig. 1. Experimental layout for configuration 1 (see text). During the trial, the control unit for the Magnetotron was located in another room.

3 JOSPT Spring 1983 MAGNETIC FIELD THERAPY 243 Copyright All rights reserved. Fig. 2. Experimental layout for configuration 2 (see text). During the trial, the control unit for the Magnetotron was located in another room. this configuration including two who had been studied in configuration 1. Skin temperatures were measured close to the electrode sites just before the change in field status and just before the end of the test. TcPO, chart recordings were taken throughout the entire period of the test and the mean values of the TcP02 were estimated over the 4 minutes before the change of field status (a) and for the 4 minutes before the end of the test (b). The changes in these parameters (b - a) were then calculated. Similarly, changes in the skin temperatures were calculated. Once all measurements and calculations had been made, the envelopes were opened and the magnetic field sequence was then established. The results were compared in terms of whether the magnetic field was initially on or initially off. RESULTS A typical recording is shown in Figure 3a. For comparison, Fig. 3b shows the effect on TcPO, (45' C) of a subject breathing oxygen-enriched air (40% oxygen). 1) Configuration 1. The mean change in foot TcPO, for the sequence magnetic field on-off is kpa and for the sequence magnetic field off-on is kpa. These values are not significantly different. The mean foot TcPO, at 45" C with the magnetic field off was kpa. The mean change in arm TcP02 was for the sequence magnetic field on-off and kpa for the sequence magnetic field off-on. These are not significantly different. The mean arm TcP02 at 45" C with the magnetic field off was kpa. 2) Configuration 2. The mean change in TcP02 for the electrode operated at 45" C on the arm was kpa for the sequence magnetic field -on-off and kpa for the sequence magnetic field off-on. These are not significantly different. The mean arm TcP02 at 45" C with the magnetic field off was kpa.

4 RAILTON AND NEWMAN JOSPT Vol. 4, No. 4 A MAG. FIELD OFF MAG. FIELD ON Copyright All rights reserved. b I, *I I I, * Fig. 3. a, typical recording of TcPO, measured at 45' C (dotted line) and TcP02 measured at 37" C (solid line). Average values were taken over the periods indicated by the double arrows. The magnetic field status was changed at 15 minutes. b, recording of TcPO2 measured at 45' C on a normal subject. The subject breathed oxygen-enriched air (40% oxygen) during 'the period indicated by the arrows. MINS. MINS The mean change in TcP02 for the electrode operated at 37" C on the arm was 0.35 & 0.38 kpa for the sequence magnetic field on-off and 0.35 & 0.22 kpa for the sequence magnetic field off-on. These are not significantly different. The mean TcP02 at 37" C with the magnetic field off was kpa. Grouping all the results on the electrode op- erated at 45" C on the foot and arm of the subjects, the mean change in TcP02 is k 0.63 kpa for the sequence magnetic field on-off and 0.47 & 0.66 for the sequence magnetic field off-on. These are not significantly different. The mean TcP02 at 45" C for the 22 subjects was 9.57 k 1.73 kpa. The mean change in temperature in the arm

5 JOSPT Spring 1983 MAGNETIC FIELD THERAPY 245 Copyright All rights reserved. was " C for the sequence magnetic field on-off and " C for the sequence magnetic field off-on. The mean change in temperature of the foot was " C for the sequence magnetic field on-off and " C for the sequence magnetic field off-on. None of these values are significantly different. The mean arm temperature was " C and the mean foot temperature was t 1.2' C. The performance of the electrodes did not appear to be affected by the magnetic field either when the electrodes were exposed to air (high value) or attached to a saline bag (low value). DISCUSSION The effects of pulsating magnetic fields on peripheral circulation have been assessed by means of TcP02 measurements in normal volunteers. The measurements were made without subjects or the principal experimenter knowing whether the magnetic field was off or on. Electrode temperatures of 45 and 37' C were used. It has been established that the capillaries of normal subjects are maximally dilated at electrode temperatures of 45" C At this temperature, although rapid dilatation takes place, it may take a considerable time for equilibrium to be established (215 minutes). At a temperature of 37" C, the electrode only detects oxygen in the superficial skin layer and the measurement is related to skin blood flow.3 The precision of TcP02 measurements is set by how well the equilibrium can be maintained and the degree of drift in the oxymeter calibration. We estimate that at 45' C the precision is of the order of a few percent. The precision of the electrode at 37' C is considerably less. At intermediate temperatures where capillaries are being maintained partially dilated, considerable variation in the readings will result due to the inherent instability of this arrangement. We have found that TcP02 values measured at 45' C tended to increase throughout the duration of the experiment whether the electrode was attached to the foot or the arm. An increase of approximately 2% between the reading at 15 minutes and the reading at 30 minutes was found with the magnetic field initially on for 15 minutes. This increase was approximately 5% when the magnetic field was switched on for the latter 15 minutes but the difference in these two values did not achieve statistical significance so that caution must be exercised in assuming that the magnetic field produced any enhancement. Similarly, TcP02 measured at 37" C tended to increase throughout the experiment and typically, a 30% increase between the 15-minute value and the 30-minute value was found. In this case, there was no difference whether the magnetic field was on initially or latterly and the changes can be explained by minor variations in the dilation of the capillary bed (the percentages are higher in this case since very low TcP02 values are being measured.) No significant changes in skin temperature were observed. Thermometry was used in preference to thermography because most thermographs are susceptible to drifting.6 The lack of increased skin blood flow (TcP02 values at 37' C) and no change in skin temperature suggest that magnetic fields with the characteristics described here have no effect on peripheral circulation. Any improvement in tissue oxygenation would have to come from increased oxygen tension in the blood and at the most optimistic this might be about 3% in healthy subjects. Increases of this magnitude (if validated) would be most unlikely to have any beneficial effect in these individuals. In the literature supplied by the manufacturer, claims are made by both Warnke (Saarlandes University, West Germany) and Lau (Loma Linda University, California) that up to 400% increases in the transcutaneous oxygen partial pressure have been produced by the action of magnetic fields. Warnke's technique appears to involve placing a cuff around the limb of the subject. This must perturb the blood flow which is being measured. 'Lau's technique is very similar to that described in this paper except that measurements were performed at an electrode temperature of 43' C. This is not sufficient to maximally dilate capillaries and, not surprisingly, baseline values in the range 2 to 6 kpa are quoted, compared with the value of 9.6 kpa measured by us at 45" C. Clearly with low values being detected, large increases are possible due to small increases in the capillary dilatation which may take place some time after the electrode has been applied-lau states that the increase reached a peak minutes after the magnetic field was switched on. Capillary dilatation is critically dependent on the emotional state of the subject. Thus if the subject is told that the magnetic field is being switched on, some capillary dilatation is to be expected. For this reason, a double blind trial is essential. The mean arterial oxygen tension for subjects

6 246 RAILTON AND NEWMAN JOSPT Vol. 4, No. 4 Copyright All rights reserved. in the age range studied here is about 12 kpa.2 The mean value for TcP02 (45" C) in the group of normals studied here was 9.6 kpa and this is consistent with the findings of other^.^^^ The TcP02 values are lower than the arterial oxygen tension due to oxygen consumption in the tissues before reaching the electrode. Since we believe that peripheral circulation is unaffected by the magnetic fields used, increases in the measured TcP02 would only seem possible if either tissue oxygen consumption was reduced or the arterial oxygen tension was increased. If magnetic field therapy can be demonstrated to significantly alter the TcP02 then it must work in either of these ways. To have a beneficial effect it would seem that increasing arterial oxygen tension would be more desirable. However, this can be achieved very much more easily and to far greater magnitude by breathing oxygen-enriched air (Fig. 36). The authors wish to thank Mr. Bill Clezy, Consultant. Elec Scotland (UK) for the loan of the Magnetotron and for specifying the magnetic field parameters used in the trial. We also wish to thank Mr. A. Faller, Superintendent Physiotherapist, and the staff of the Physiotherapy Department, Monklands District General Hospital. REFERENCES 1. Buerema I. Brummelkamh WH, Meijne NG: Clinical application of hyperbaric oxygen. Amsterdam: Elsev~er, Diem K, Lentner C (eds): Scientific Tables, p 570. Basle: Ciba- Geigy, Ewald U, Rooth G, Tubemo T: Postischaemic hyperaemia studied with transcutaneous oxygen electrode used at 33-37' C. Scand J Clin Lab Invest Huch A, Huch R, Hollmann G, Hockerts T. Keller HP, Seiler D, Sadzek J, Lubbers DW: Transcutaneous PO2 of volunteers during hyperbaric oxygenation. Biotelemetry 4: Huch A, Huch R. Schneider H. Pesbody J: Experience with transcutaneous PO2 (TcP02) monitoring of mother, fetus and newborn. J Perinat Med 8: Newman P. Davison M, James WB: A prototype inexpensive thermograph for routine hospital use. Acta Thermographica 4: Rooth G, Hedstrand U. Tyden H, Ogren C: The validity of the transcutaneous oxygen tension method in adults. Crit Care Med 4: , Smith E: Magnetic field therapy device, British Patent Application No , 1869