间歇式气压仪对正常腿和静脉炎腿的效果比较.doc

间歇式气压仪对正常腿和静脉炎腿的效果比较Effects of intermittent pneumatic calf compressionin normal and postphlebitic legsA. J. Salvian, M.D., F.R.C.S.(C),* and J. D. Baker, M.D.From the Vascular Surgery Sections, Sepulveda, VA Medical Centerand the UCLA School of Medicine, Los Angeles, CA, U.S.A.SUMMARY.-The changes in common femoral vein flow produced by three different intermittent pneumatic compression devices were recorded with a Doppler velocity detector in 20 normal legs and 20 with postphlebltic syndrome. Mean and peak velocity increases were measured and expressed as a percent of resting base-line values. There was no significant difference in the peak velocity increase produced by the three devices in normals and abnormals; however, there were differences in the mean velocity increases. The devices worked as well on postphlebltic legs as on normal ones. Correct cuff application was more critical than indicated by the manufacturers, suggesting that some of the failures of intermit. tent pneumatic compression may have resulted from improper cuff placement. Tile results show that different designs of intermittent pneumatic compression equipment accelerate venous flow in the leg.KEY WORDS.-Deep vein thrombosis - Prophylaxis - Intermittent compression Postphlebitic syndrome. In recent years there has been an increasing awareness of the need for prophylaxis against deep venous thrombosis and pulmonary emboli in patients at high risk for this complication. The objective of investigation in this area has been directed against one or the other of the two main components of Virchows triad, that is, (a) to pre-vent coagulation or, (b) to prevent stasis. The former method, particularly using low dose heparin, has received a great deal of attention by such eminent investigators as Kakkar,1 Nico-laides,2 and Cotton.3 However, the suggested, benefit of low dose heparin has not always been substantiated in the literature and, indeed, in the study by Borow in 1980, low dose heparin was second in efficacy to all other methods in the prevention of I 125 fibrinogen tagged thrombi.4 Also, there is a group of patients in whom anti-coagulation of any form is relatively contraindicated. Such patient groups include neurosurgical patients, orthopedic surgery patients, and patients undergoing prostatic surgery.*Current address: Department of Surgery, University of British Columbia, Vancouver, Canada. The alternative method of prophylaxis is aimed at prevention of venous stasis. Fibrinogen studies have shown that 50% of thrombi originate at the time of surgery and that 30% develop in the sub-sequent three hours. Twenty percent of these tend to remain and propagate and become significant deep venous thrombosis McLachlin et al. have showed that there is pooling of contrast in the venous valve pockets when the leg is at rest and that this can be rapidly cleared by either mechanical compression or galvanic stim-ulation.6 There have been subsequent studies showing that intermittent calf compression is a very effective method of preventing deep venous thrombosis.4 7 8 Nicolaides in 1980 studied the hemodynamic effects of calf compression therapy and showed that blood flow in the femoral vein was markedly increased with intermittent pneumatic calf compression and that a sequential device gave consistently higher flow rates than a non-sequential device. These patients were all normal volunteers studied in a semirecumbent position with their legs horizontal. The object of our study was to extend Nicolaides original work to: (1) compare the effect of the sitting and supine position on the venous hemodynamics of calf compression therapy; (2) to study the venous hemodynamic effects in the patients with abnormal deep venous systems and incompetent venous valves; (3) to compare the hemodynamic effects of a single chamber device to a multi-chamber device and to assess the value of above knee sequential compression in conjunction with calf compression. Material and methods Three compression devices were chosen and all devices are characterized by a moderate inflation pressure, and a short compression cycle followed by a long recovery period. The devices chosen were: 1. The Thrombogard (Gaymar Industries, Orchard Park, NY), a sequential compression device with four separate chambers all below the knee. These four chambers compress in sequence with a present pressure of about 45 mmHg for 16 seconds with a 60 second recovery phase of noncompression. 2. The T.E.D. sequential compression sleeve (Kendall, Boston, Mass.) a full-leg, sequential pneumatic compression device consisting of three separate chambers, one over the distal calf, one over the proximal calf, and one over the distal thigh. The maximum compression of 45 mmHg is applied for 11 seconds with 60 seconds of non-compression to allow for venous refilling. The device circulates cool air under the legging to increase comfort with prolonged use. 3. The PAS pulsatile anti-embolism system * a single chamber compression device with a 5 second inflation, a 15 second compression period, and a 60 second recovery phase. The compression chamber is incorporated into a kneehigh elastic stocking so that inflation increases the tension of the stocking on the calf. *American Hamilton, Two Rivers, Wisconsin. The patient population consisted of 20 normal limbs in 11 healthy patients, with a mean age of 46.6 years with a range of 25-63 years. There were 20 abnormal limbs in 16 patients, with a mean age of 60.4 years, with a range of 48-87 years (the normal limbs from these patients were not included in the legs studied for normal controls).The patients in the abnormal limb group all suffered from postphlebitic syndrome and were being treated for active stasis ulceration or were on long-term Coumadin therapy for recurrent deep venous thrombosis. All patients had patent deep venous systems with free reflux on Doppler examination. None had evidence of venous out-flow obstruction. Full informed consent was obtained from each patient prior to entry into the study. To study the blood flow in the femoral vein a Parks, model 806, directional Doppler ultra-sound velocity detector was connected to a single channel recorder. An adjustable clamp held the probe over the femoral vein at a constant angle of 45 degrees to the axis of the vessel. For each device three separate recordings of the change in venous velocity signals were made in each position: (a) supine, and (b) sitting with head of a hospital bed elevated to a 45 degree angle. Before each recording a baseline tracing of femoral vein flow was made which showed the normal phasic variation with respiration. The recordings were very consistent for each device. The mean velocity for the precompression and the compression segments were determined by measuring the area under the baseline tracing and under the curve from beginning to end of compression; the results expressed as the percent increase. Similarly, the percentage increase in peak velocity can be determined by comparing the peak of the precompression curve to the peak of the compression curve. The baseline velocities varied substantially from patient to patient, due in part to differences in limb size and in femoral vein diameter. Therefore, we chose to use the percent change in velocities in order to permit comparisons among patients. No attempt was made to estimate volume flow, for this determination requires knowing the diameter of the femoral vein, which can be affected by flow rate as well as by the phase of the respiratory cycle.Fig. 1.-(1) Changes in femoral vein Doppler signal produced by the Thrombogard. Note the fourdistinct peaks produced by the separate compression chambers. (2) Doppler signal produced bythe TED device. Note the distinct fluctuations in the baseline produced by respiration. (3) Doppler signal produced by the PAS device. Results Each device was found to produce its own typical pattern of increased femoral vein flow. The Thrombogard produced four separate peaks for each chamber compression, reflecting the sequential inflation of the four chambers (Fig. 1-1). For the TED device there were three peaks over a shorter period (Fig. 1-2), and with the PAS device there was a single peak (Fig. 1-3). All the devices had a period of slow flow after maximum compression suggesting that the calf veins had been emptied by the compression and were gradually refilling until the precompression baseline tracing returned. The patients found all of the devices to be comfortable with no complaints of pain or undue heat. The compression chambers were all quite simple to apply, but the TED and Thrombogard devices required special attention to insure the proper compression pressure. Both these devices Were secured with velcro straps, and these straps must be applied very carefully. If they are too loose there is virtually no compression achieved and therefore no subsequent increase in venous flow. There were no specific instructions with the devices as to how tightly to apply these, and we found that they should be snugged up tightly and uniformly on the leg. The PAS apparatus, of course, does not have, this problem since it is applied as a stocking. Tables 1 and 2 show the increases in peak and mean flow to be between 30% and 80% throughout. When this data was analyzed there was no statistically significant difference in flow between the sitting or the supine position for any of the devices in either the normal or abnormal limbs. When one looked at peak flows, there was no difference between the three devices in normal or abnormal limbs, either in the supine or sitting positions. However, mean flows in the normal limbs in both the sitting and supine positions were significantly greater with both the TED and PAS devices when compared to the Gaymar de-vice (P0.05). In the abnormal limbs, sitting, the TED and PAS devices had mean flows that were significantly higher than the Thrombogard (P-0.05). Mean flows in the abnormal limbs, supine, showed that the TED had a significant increase over the other two, with P0.005 for the Thrombogard and P0.05 for the PAS. The peak and mean flows for all devices were not significantly different when comparing abnormal to normal limbs.Table l.-Patients with normal veins % increase inflow. Venous thrombosis.KENDALL GAYMOR PASSitting Lying Sitting Lying Sitting LyingPeak Mean Peak Mean Peak Mean Peak Mea Peak Mean Peak MeanX 79 74 61 60 62 28 53 26 71 54 64 46SD 63 60 36 30 36 13 40 27 57 41 45 37Table 2.-Patients with abnormal venous reflux % increase inflow. Venous thrombosis.KENDALL GAYMOR PASSitting Lying Sitting Lying Sitting LyingPeak Mean Peak Mean Peak Mean Peak Mea Peak Mean Peak MeanX 83 57 66 52 65 32 50 30 69 55 38 36SD 69 31 41 29 34 16 29 19 41 38 22 29Discussion The risk factors of deep venous thrombosis and subsequent pulmonary emboli have been shown to be obesity, age greater than 40, previous deep venous thrombosis, malignancy, estrogen therapy, paraplegia, stasis, major abdominal and orthopedic surgery, major trauma, and certain hematologic disorders, such as antithrombin deficiency. Patients at high risk of deep venous thrombosis require some method of prophylaxis and the choice at present is between one of the forms of anticoagulation and mechanical prevention of stasis. Extensive investigation has been carried out with respect to low dose heparin, oral anticoagulants, aspirin and dextran. Although most of the studies have shown these To be effective methods of prophylaxis, this is not always the case in certain patient populations, such as patients undergoing prostatic surgery or orthopedic procedures, and it has been associated with a small complication rate.9 Many patients are denied prophylactic therapy because of the concern about intra- and post-operative bleeding, particularly in orthopedic and neurosurgical procedures. Intermittent pneumatic compression devices have been well shown to be one of the better forms of prophylaxis and one which is free from side effects. A variety of commercially available pneumatic compression machines are now obtainable. One of the main differences between the devices is the configuration of the leg cuffs; i.e., single versus multiple chambers and calf versus multiple chambers and calf versus calf plus thigh compression. In this study all three machines tested caused a comparable increase in peak femoral vein velocity, however, one of the three caused a lower increase in mean velocity. We do not know whether this difference in mean flow is clinically significant; it is likely that the peak velocity increase plays the predominant role in counteracting stasis and reducing the pooling in the venous valve pockets. Most of the previous studies on pneumatic compression devices were carried out in supine subjects. Since many nonambulatory patients spend long periods of time in the sitting position we were concerned that the method might not provide consistent protection to all patients. Our results showed no difference in the acceleration of venous flow in the two positions tested.Another concern of the investigation was whether the technique worked well on patients with venous valvular insufficiency from previous deep vein thrombosis, however, our study has shown that the hemodynamic flow at the femoral vein is not significantly altered in this group. It is possible that the effectiveness of compression may be decreased in patients with massive reflux at the femoral vein level, but our study did not include anyone in this subset. We were interested to find that application of the leg units for the TED and the Thrombogard units was more critical than had been indicated by the manufacturers. This problem was detected by finding no change in femoral vein velocity during the compression cycle. Reapplying the leg unit more snugly always produced the acceleration in femoral vein flow. In reviewing the problem cases we did not find any particular leg size or configuration associated with ineffective compression. We were impressed that in most cases only a small change in the tightness of the cuff was required to change from ineffective to effective compression of the leg. It is possible that some of the failures of intermittent compression to prevent venous thrombosis may have been caused by ineffectual compression resulting from improper cuff adjustment. The growing interest in intermittent pneumatic compression of the legs for prophylaxis against deep venous thrombosis has led to the development of a variety of commercial products. The three devices examined in this study were all found to be effective in accelerating venous blood flow in the leg. A major area for further investigation is the proper application of the leg cuffs to insure effective compression in ever3, case without having to check the femoral vein Doppler signal. Since the leg cuff for each product is a different shape, it is likely that the same guidelines will not be suitable for all. Conclusions With the growing interest in prophylaxis for post-operative deep vein thrombosis and the recognition of the value of intermittent pneumatic compression, there has been an increase in the number of devices for this purpose. In spite of the fact that there are substantial differences in design of the different products, most of the clinical studies have been limited to trials of a single machine. We evaluated the effects produced by three different intermittent compression devices by measuring the changes in common femoral vein velocity as detected with a Doppler ultrasound detector. Examinations were carried out on 20 normal legs and 20 legs with postphlebitic syndrome, with each patient studied in both supine and sitting positions. Although there was no significant difference in the peak velocity produced by the three devices, there were differences in mean velocity increases. The acceleration of venous flow was comparable in normal and p