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garment for venous leg ulcer treatment
Journal of Tissue Viability (2008) 17, 82e94
www.elsevier.com/locate/jtv
Basic research
Pressure mapping and performance of the compression bandage/garment for venous leg ulcer treatment S. Ghosh, A. Mukhopadhyay*, M. Sikka, K.S. Nagla National Institute of Technology, Jalandhar-144011, India
KEYWORDS Compression bandages; Compression garment; Creep; Interface friction; Laplace equation; Mannequin leg; Venous leg ulcers
Abstract A study has been conducted on the commercially available compression bandages as regards their performance with time. Pressure mapping of these bandages has been done using a fabricated pressure-measuring device on a mannequin leg to see the effect on pressure due to creep, fabric friction and angle of bandaging. The results show that the creep behavior, frictional behavior and the angle of bandaging have a significant effect on the pressure profile generated by the bandages during application. The regression analysis shows that the surface friction restricts the slippage in a multilayer system. Also the diameters of the limb and the amount of stretch given to the bandage during application have definite impact on the bandage pressure. In case of compression garments, washing improves the pressure generated but not to the extent of the pressure of a virgin garment. Comparing the two compression materials i.e. bandage and garment, it is found that the presence of higher percentage of elastomeric material and a highly close construction in case of garment provides better holding power and a more homogeneous pressure distribution. ª 2007 Tissue Viability Society. Published by Elsevier Ltd. All rights reserved.
Introduction The worldwide chronic venous insufficiency is characterized by a combination of symptoms like varicose veins, deep vein thrombosis, oedema, * Corresponding author. Tel.: þ91 2690302/453x253 (O), 2690052 (R); fax: þ91 181 2690320. E - m a i l a d d r e s s : a r u n a n g s h u _ r e c j @ r e d i f f ma i l . c o m (A. Mukhopadhyay).
lymphoedema and finally ulcers on the legs [1]. The recurrence rates of the ulcers are also high, with two third of the patients experiencing one or more recurrence [2]. Graduated compression hosiery is accepted as an integral part for both as an active treatment for healing ulcers [3,4] and having an essential role in the prevention of venous ulcer reoccurrence. The compression bandage form a major category among different bandage types that are used for the application
0268-0009/$34 ª 2007 Tissue Viability Society. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.jtv.2007.09.013
Constructional parameters of compression material
S. no. Type
Constituent fiber
Warp
1
2
3
4
5
6
7 8
Warp knitted
Polyester with rubber in core Warp knitted Polyester with rubber in core Warp knitted Polyester with rubber in core Warp knitted Polyester with rubber in core Warp knitted Polyester with rubber in core Warp knitted Polyester with rubber in core Crepe, leno Cotton/ fabric wool Weft knitted garment e
Fibre proportion
Yarn linear density (tex)
Polyester Cotton Viscose Elastomeric Wool Warp Weft/ (%) (%) (%) material mislapped (%) (%) yarn
Weft
Thread density (per cm)
Fabric Fabric thickness weight (mm) (GSM)
Wales/ Course/ Loops ends picks
Polyester
85.3
e
e
14.7 (rubber)
e
66
63
3
9
9
1.01
195
Cotton (3 Ply)
26
61
63
6.7 (rubber)
e
66
46
3
8
8
0.78
231
Cotton (4 Ply)
39.7
22.7
28.5
9.1 (rubber)
e
66
27
3
8
8
0.62
206
Cotton (2 Ply)
40.8
44
4.6
10.6 (rubber)
e
66
119
3
6
6
0.80
210
10.6 (rubber)
e
66
66 30
3
7
7
0.68
200
6.9 (rubber)
e
66
66 55
3
7
7
0.72
202
54 29
66
24
27
e
0.89
259
35
30
70
30
1.16
510
Polyester: 48.6 cotton (1:2)
40.8
Polyester: 50.2 cotton (1:2)
39.3
Cotton
e
90.8
e
e
9.2
Cotton: lycra (2:1)
e
82
e
18 (lycra)
e
e
3.6
Performance of the compression bandage
Table 1
83
84
S. Ghosh et al.
Figure 1
Scanned images of the compression materials.
of clinically effective levels of pressure, applied to modify or assist the physiological process of blood flow [5]. The working mechanism of compression therapy is a result of the pressure exerted on the leg, through which the varicose veins become narrower and the insufficient perforating veins become closed and the retrograde bloodstream will diminish. The venous blood volume will diminish as well as calf muscle pumps can work better, thus resulting in higher tissue oxygenation and better microcirculation [1]. These bandages need to give good holding capacity during use and also be suitable for repeated use. Furthermore these properties can be improved if the creep behavior, the frictional behavior and the constructional parameters of the bandage material are optimized to give the required levels of pressure for a specific ailment.
In the present work an attempt has been made to study the effect of the creep, friction and angle of bandaging on the pressure profile of the compression bandages. The effect of creep and washing is also seen on the pressure profile of the compression garment, using fabricated prototype pressure-measuring device (mannequin leg) in both the cases. The performance of these bandage fabrics differing in constructional parameters is studied to adjudge their utility for specific end uses.
Materials and methods Eight different samples of commercially available compression bandages were analyzed in the laboratory for their constructional parameters as given in Table 1. It was observed that the samples 1e6 can be broadly classified as warp knitted fabrics with rubber being inlaid as an elastomeric component. Sample 7 was a woven leno structure and sample 8 is a weft knitted garment with fine lycra
3.5 Compression bandage
3
Crepe bandage
Force (kgf)
2.5
Compression garment
2 1.5 1 0.5 0 1
2
3
4
5
6
7
8
9
10
11
Elongation (mm)
Figure 2
Prototype pressure-measuring device.
Figure 3 Tensile behavior of the compression bandaging material.
Instantaneous extension and primary creep of compression bandages at different load
S. Instant. no. extension at 80 gf/cm (mm) 1 2 3 4 5 6 7
93 70 59 60 53.5 51 35
Table 3
Creep at 80 gf/cm (mm) Time series (min) 100
101
102
103
0.3 0 0 0 0 0 0
1.7 0.7 0.7 0.7 1.3 0.7 0.7
2.3 1.7 1.7 2.3 3 2.3 1.3
4 3 3 3.7 4.3 3.7 2.3
Total extension 80 gf/cm (mm)
97 73 62 63.7 57.8 54.7 37.3
Instant. extension at 120 gf/cm (mm) 112 79 64 65 57 53 42
Creep at 120 gf/cm (mm) Time series (min) 100 101 102 103 0.7 0 0 0 0 0 0
2.3 0 1 1.3 1 0.7 0.7
3.7 0.7 2.3 3 2.3 1.7 1.3
Total extension 120 gf/cm (mm)
5.7 117.7 4 83 3 67 4.3 67.3 3.3 60.3 3 56 2.3 44.3
Instant. extension at 160 gf/cm (mm) 121 85 70 68 58 57 45
Creep at 160 gf/cm (mm) Time series (min)
Total extension 160 gf/cm (mm)
100 101 102 103 0 0 0 0 0 0 0
1.7 1 1 1 2 1 1
2 1.7 1.3 1.7 3.3 2.3 1.3
3.3 124.3 3.3 88.3 2.3 72.3 2 70 5 63 3 60 2 47
Instant. extension at 200 gf/cm (mm) 130 91 72 72 62 61 50
Creep at 200 gf/cm (mm) Time series (min) 100 101 102 103 0 0 0 0 0 0 0
0.7 0.7 0.7 1 1.3 0.7 1.3
2 1.3 2 2 2.3 1.3 2.3
Total extension 200 gf/cm (mm)
3 133 3 94 2.3 74.3 3.7 75.7 3 65 3 64 2.7 52.7
Performance of the compression bandage
Table 2
Recovery of compression bandages initially stretched at different loads
S. Instant. Delayed recovery Permanent Instant. Delayed recovery Permanent Instant. Delayed recovery Permanent Instant. Delayed recovery Permanent set (mm) set (mm) recovery for 200 gf/cm set (mm) recovery for 160 gf/cm set (mm) recovery for 120 gf/cm no. recovery for 80 gf/cm for 200 loading (mm) for 160 loading (mm) for 120 loading (mm) for 80 loading (mm) gf/cm Time series (min) gf/cm Time series (min) gf/cm Time series (min) gf/cm Time series (min) loading loading loading loading 0 1 2 3 0 1 2 3 0 1 2 3 10 10 10 10 10 10 10 10 10 10 10 10 100 101 102 103 (mm) (mm) (mm) (mm) 1 2 3 4 5 6 7
93 67 56 58 53.2 50.5 25
0 0 0 0 0 0 0
1.3 1.3 2 1.3 1 1 1
2 2.3 2.7 2.3 2.3 2 2
3.3 0.7 3.7 2.3 3.3 2.7 3.3 2.4 4 0.6 3.3 0.9 2.3 10
112 76 60 63 56 52 31
0 0 0 0 0 0 0
1.3 1.7 1.3 1 1 1 1
2.7 3.3 2.3 1.7 2 2 1.7
4.3 1.4 4.7 2.3 4.3 3.7 3 3.3 2.3 2 2 2 2 11.3
118 82 64 63 57 55 33
0 0 0.7 0 0 0 0
1.3 1 2.3 1 1 1 0.7
2.3 2.3 3.7 2.3 2 1 1
4 2.3 3.3 3 4.3 4 3 4 3.7 2.3 2.3 2.7 2 12
126 86 66 67 60 58 38
0 0 0 0 0 0 0
1.3 1 1.7 1.3 1 1 0.7
2.7 3.3 3.3 3 2 2 1.7
4.3 2.7 4.3 3.7 4 4.6 4 4.4 2.3 2.7 3 3 2 12.7
85
86
S. Ghosh et al. Sample 4
Sample 2
Sample 5
Sample 3
Sample 6
3000 Sample 7 2500
Frictional force (gf)
140
Sample 1
Extension (mm)
120
100
80
2000
Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Sample 7
1500
1000 60 500 80 40
120
160
200
Load (gf/cm)
Figure 6
20 80
120
160
Variation of frictional force with load.
200
Load (gf/cm)
Figure 4
Effect of load on instantaneous extension.
yarn being knitted into the structure (Fig. 1). The compression bandage samples (1e6) have warp component as polyester but vary in the mislapping threads which act similar to the weft counterpart. It is either polyester or plied cotton yarn or a combination of polyester and cotton in different ratios. The different test methods such as pressure mapping of the bandage material, creep and friction measurement, all were performed in standard testing atmosphere.
Experimental set up A prototype electronic device was used to investigate the pressure mapping of the bandage systems as shown in Fig. 2. Three resistance foil
70
Pressure (mm Hg)
60 50 40 30 20 10
Sample 1 Sample 2 Sample 3 Sample 4
Sample 5 Sample 6 Sample 7
0 20
30
40
50
Angle (degree)
Figure 5 Effect of angle of bandaging on the pressure profile of the bandages.
strain gauges were fitted on the mannequin leg. The leg was used to simulate a real lower limb and has a definable tibia, calf and ankle region so that compression bandage pressure profiles are obtained. The inner dimensions of the leg made it possible to insert the strain gauges at strategic points so that pressure measurements could be made at the back of the leg. Compression bandage pressures were detected by means of pressure pins which were connected to each strain gauge device and protrude from the inside of the leg to the outer surface. The strain gauge consisted of a grid that was cemented to carrier (base) which was a thin sheet of bakelite. The gauge was calibrated using dead weight system and it follows both the tensile and compression strain of the specimen. The spreading of foil permitted a uniform distribution of strain over the grid. The bandage was then applied around the mannequin leg at a stretch as practiced by the medical practitioners to determine the pressure mapping of each sample with time. The calculation of the actual pressure values were based on the pressure exerted by the bandage on the projected annular ring portion of the sensor used. For creep testing a dead weight system of loading was used on the fabric with two wooden clamps, one fixed and the other movable. Test specimen length to width ratio was kept as 1:2 (5 cm:10 cm). The displacement of the lower clamp was noted down at different intervals of time at four different load values (80 gf/cm, 120 gf/cm, 160 gf/cm, 200 gf/cm) as recommended by the doctors to observe the extension and the recovery behavior of both the bandage and the garment.
19.04 16.75 16.66 14.58 15.08 12.3 14.76 13.30 11.68 10.69 12.12 11.30 10.36 6.14 19.21 16.93 16.84 14.76 15.34 12.56 15.02 13.56 11.86 10.95 12.38 11.57 10.62 6.4 19.3 17.1 17.02 14.85 15.43 13 15.2 13.74 12.03 11.04 12.56 11.74 10.71 6.66 19.3 17.1 17.02 14.85 15.43 13 15.2 13.82 12.03 11.04 12.56 11.74 10.71 6.66 24.79 21.92 22.27 19.28 19.80 16.82 20.55 16.64 17.58 14.24 16.76 14.35 14.98 09.60 25.15 22.18 22.62 19.55 20.16 17.08 20.89 17.99 17.94 14.77 17.2 14.79 15.32 10.04 7
6
5
4
3
2
1
1st 2nd 1st 2nd 1st 2nd 1st 2nd 1st 2nd 1st 2nd 1st 2nd
36.34 34.14 33.97 30.36 31.95 27.98 31.32 27.63 28.6 25.35 28.42 25 25.25 19.38
36.43 34.23 34.06 30.45 32.03 28.95 31.42 27.72 28.78 25.69 28.51 25.08 24.98 19.12
36.61 34.49 34.14 30.62 32.21 29.3 31.68 27.89 28.86 25.79 28.69 25.25 24.81 18.77
36.96 34.67 34.32 30.81 32.38 29.48 31.86 28.07 28.95 25.96 28.95 25.34 24.28 18.42
35.38 33.08 32.56 29.48 30.8 28.6 29.92 26.49 27.46 24.29 27.28 23.76 24.10 17.80
25.15 22.18 22.62 19.55 20.16 17.08 20.89 17.99 17.94 14.77 17.2 14.79 15.32 10.04
25.15 22.18 22.62 19.55 20.16 17.08 20.89 17.99 17.94 14.77 17.2 14.79 15.32 10.04
24.97 22.09 22.45 19.46 19.98 16.99 20.72 16.90 17.85 14.6 17.11 14.7 15.06 09.95
19.3 17.1 17.02 14.85 15.43 13 15.2 13.82 12.03 11.04 12.56 11.74 10.71 6.66
102 101 100 Instant.
Time series (min)
103 102 101 100 Instant.
Time series (min)
87
103 102 101 100 Instant.
Time series (min)
Pressure profile at ankle (mmHg) Sample
Table 4
Pressure profile of compression bandages
Pressure profile at calf (mmHg)
Pressure profile at knee (mmHg)
103
Performance of the compression bandage
The fabric surface frictional force was calculated from the trace generated by the universal testing machine (Zwick). A sample of 10 cm length was cut from the roll and put on the flat wooden board, with a dead weight system of loading attached to one end of the clamped sample, as pretension. Another 10 cm length of the same sample stretched under the same load was clamped on to the smaller wooden block and connected to the top jaw of the machine through an inextensible string moving over a frictionless pulley. It moved on the fabric laid on flat wooden surface. The values of stretching load used were 80 gf/cm, 120 gf/cm, 160 gf/cm and 200 gf/cm and the normal load put on the wooden block was estimated by using the Laplace equation [6].
Results and discussion All the structures except crepe bandage have elastomeric material in different ratios as is given in Table 1. Further, the placement of the elastomeric yarn in the fabric also varies in each type of structure. It was found that the stress strain curve of compression garment is stiffer in nature as compared to the compression bandages (Fig. 3) which are flatter in nature even at high elongation. This indicates very slow or gradual build up of pressure on extension of bandage fabric. Moreover, the higher the stiffness/slope, the more capable the compression material will be as regards preventing oedema, but the more difficult it will be to put on the material [1].
High compression bandages Effect of creep Tables 2 and 3, show the extension and recovery characteristics of the compression bandages. It is observed from Table 2 and Fig. 4 that as the load on the bandage material is varied from 80 gf/cm to 200 gf/cm, extension of the material increases steadily. However, in case of recovery, the total recovery may or may not be higher for the samples stretched at higher load (Table 3). This is because all the samples followed different patterns of delayed recovery and permanent set due to their inherent characteristics. It is observed that the delayed recovery and permanent set are always high for the samples initially stretched at higher load. The instantaneous recovery is lowest for the bandage initially stretched at 80 gf/cm load (i.e. 800 gf loads on a 10 cm width
88
S. Ghosh et al. 38
Pressure (mm Hg)
37.5
(a)
37 36.5 36 35.5 35 34.5 34 1
10
100
1000
Time series (min) 29
27
28.5
26
Pressure (mm Hg)
Pressure (mm Hg)
26.5
(b)
25.5 25 24.5 24
(c)
28 27.5 27 26.5 26 25.5
23.5 23
25 1
10
100
1000
Time (min)
1
10
100
1000
Time (min)
Figure 7 Change in pressure at the ankle with time for (a) compression bandage (b) crepe bandage and (c) compression garment.
bandage). Different sample behave differently with the change in time. It is observed that the instantaneous extension is higher for samples 1 and 2, but lowest in case of sample no 7. In bandage fabric greater importance should be laid on delayed extension as higher value of delayed extension reduces the holding power of bandage on the affected body part. Sample 7 which possesses higher fabric weight shows high value of delayed extension. Therefore, it can be inferred that the bandage fabric of higher weight does not necessarily perform the best as far as the holding power of the fabric on the affected body part is concerned over a longer period of time. This is in agreement with the earlier findings by Mukhopadhyay and Ghosh [7]. It may be added that the cost factor is also high for the fabric of higher weight. It is observed from Table 3 that instantaneous recovery and delayed recovery are lowest for sample no. 7. However, the permanent set is a relevant parameter which indicates the suitability of the fabric for reuse. Although sample no. 5 shows the moderate value of instantaneous
recovery and delayed recovery, it still has a low value of permanent set. Effect of angle of bandaging It is observed from Fig. 5 that as the angle of bandaging is increased, the pressure generated at the surface of the leg drops thus affecting the healing process. This drop in the generated pressure at higher angle is due to decrease in the number of layers of the fabric at a particular point. For treatment of leg ulcers, the angle of bandaging is found to be around 40 for typical stretch level of 80 gf/cm which provides nearly 35 mmHg pressure as recommended by doctors. Further 40 angle of bandaging provides overlapping of two layers of bandage as practiced by the doctors while applying them for treatment of the ulcer patients. Effect of frictional properties Fig. 6 indicates that the frictional behavior of all the samples varies with the change in the
Performance of the compression bandage
89
Table 5 Comparison of the Laplace, regression and actual values of pressure (mmHg) S. no.
Position of the limb
Actual value
Laplace value of pressure
Regression value
1
Ankle Calf Knee Ankle Calf Knee Ankle Calf Knee Ankle Calf Knee Ankle Calf Knee Ankle Calf Knee Ankle Calf Knee
36.34 25.15 19.3 33.97 22.62 17.02 31.95 20.16 15.43 31.31 20.89 15.2 28.6 17.94 12.03 28.42 17.2 12.56 25.28 15.32 10.71
37.5 21.8 24 37.5 21.8 24 37.5 21.8 24 37.5 21.8 24 37.5 21.8 24 37.5 21.8 24 37.5 21.8 24
36.98 26.06 20.56 33.17 22.24 16.95 31.07 20.14 14.85 31.27 20.34 15.05 30.03 19.1 13.81 29.39 18.46 13.71 25 14.71 9.42
2
3
4
5
6
7
Pressure mapping of bandage Table 4 shows that the pressure profile of the bandages (at 80 gf/cm stretching load) at three critical points on the surface of the leg varies with the time. As expected the pressure reduces with time because of the creep which in turn is counteracted by frictional behavior of the bandage fabric. A slight fall in pressure is observed at the calf and knee position but at the ankle substantial change is observed (Fig. 7a). The typical geometry at the ankle position may be responsible for layer slippage. But this observation is not true for crepe bandage since the frictional force between layers in case of crepe bandage is higher restricting the slippage effect. The change in pressure at the calf and knee position is not so significant due to more or less flat circular profile at these points. Further the pressure falls for the repeated wearing of the bandage due to the permanent set generated in them (Table 4). Based on the data in Tables 2 and 4, a polynomial regression equation relating bandaging pressure with diameter of the limb and instantaneous extension is developed. Y ¼180:85 39:440X1 þ 0:322X2 þ 2:130X12 0:001X22 ; R2 ¼ 0:988
stretching load. Actually at different stretching loads, the normal reaction and surface of the fabric changes with the amount of extension given to it and this affects the frictional force value which further restricts the recovery of the material.
where X1 ¼ diameter of the limb (cm), X2 ¼ instantaneous extension at 80 gf/cm (mm), and Y ¼ bandage pressure (mmHg). The equation shows that both the parameters viz. diameter and instantaneous extension have significant influence on the bandaging pressure.
40 Laplace S1-actual S1-regression S2-actual
Pressure in mm Hg
35
30
S2-regression S3-actual
25
S3-regression S4-actual
20
S4-regression S5-actual S5-regression S6-actual
15
S6-regression S7-actual S7-regression
10
5
Ankle
Calf
Knee
Position on the limb
Figure 8
Comparison of actual, the Laplace and regression values of pressure at different position of limb.
90
S. Ghosh et al.
Table 6 Position Ankle
Calf
Impact of creep and frictional force on decay of pressure Time series (min) 10 103 102 103
Knee
102 103
R2
S.E.
Y ¼ 2:53 0:550X1 0:002X2 þ 0:125X12
0.970
0.088
Y ¼ 0:046 þ 0:376X1 0:001X2 0:007X12
0.972
0.04
Y ¼ 0:038 þ 0:297X1 0:001X2 0:014X12
0.919
0.057
Y ¼ 0:002 þ 0:331X1 0:001X2 þ 0:003X12
0.973
0.04
Y ¼ 0:161 þ 0:295X1 0:01X2 0:024X12
0.929
0.05
For 102 min at the ankle position the decay in pressure is negative.
Compression garment Effect of creep It is observed from Tables 7 and 8 that the value of instantaneous extension and delayed extension do not vary much at the three positions (ankle, calf
and knee) although the recovery behavior shows a slight difference. The permanent set value at the ankle position is higher than the knee and calf which may be due to the typical geometry of the ankle which causes more stretch in fabric (Fig. 10). Effect of position on the pressure mapping The pressure profile of the virgin garment at three different positions indicate an initial increase and then decrease at ankle and slight decrease in
pressure decay (mm Hg)
(mm
)
4.2 4.0 3.8 3.6 3.4 3.2 3.0 2.8 2.6 2.4
1400 1300
ep
Based on the regression equation, it can be stated as the instantaneous extension increases the bandage pressure increases. However, the effect of instantaneous extension at constant stretching load is smaller than the effect of diameter. Also the instantaneous extension is directly proportional to the pressure generated in the bandage. It is further noticed that the pressure profile of the compression bandage calculated theoretically using the Laplace equation varies from the actual as can be seen in Table 5. According to the data calculated by using the Laplace equation, as the diameter increases the pressure should decrease but the reverse is true in actual measurement at calf and knee positions. This may be due to noncircular geometry at the knee position where the sensor is fitted. The deviation of pressure values at the calf and the knee position can be seen in Fig. 8. The above findings were earlier pointed out by Lisa Macintyre et al. [8]. Another set of regression analysis is done for the assessment of pressure decay with creep and the frictional force at different positions of the limb. The regression equations at all positions are given in Table 6. It can be seen that as the creep increases over time the decay in pressure also increases but the frictional force acts as a restriction in the process of decay (Fig. 9). As the frictional force increases it inhibits the decay in pressure in a multilayer bandage system.
1200 1100
friction
Cre
a
Regression equation
2a
1000 900
al forc e
(gf)
600 700
800
Figure 9 Effect of creep and frictional force on pressure for ankle at 103 min.
Table 7
Instantaneous extension and primary creep of compression garment at different load
Position Instant. on the extension at 80 leg gf/cm (mm) Ankle Calf Knee
Table 8
7 7.3 6.7
Creep at 80 gf/cm (mm) Time series (min) 100 101 102 103 0 0 0
Total extension at 80 gf/cm (mm)
0.3 1.7 3 10 0.3 1.3 2.7 10 0.3 1.3 2.3 9
Instant. extension at 120 gf/cm (mm) 14 14 15
Creep at 120 gf/cm (mm) Time series (min) 100 101 102 103 0 0 0
Total extension at 120 gf/cm (mm)
1 2 3.3 17.3 0.7 1.7 3 17 0.7 1.7 3.3 18.3
Instant. extension at 160 gf/cm (mm) 20 16 18
Creep at 160 gf/cm (mm) Time series (min) 100 101 102 103 0 0 0
Total extension at 160 gf/cm (mm)
0.3 1.3 2.7 22.7 0.3 1.7 3.3 19.3 0.7 1.7 3.3 21.3
Instant. extension at 200 gf/cm (mm) 25.3 25.6 28
Creep at 200 gf/cm (mm) Time series (min) 100 101 102 103 0 0 0
Total extension at 200 gf/cm (mm)
1.3 2.7 4.3 29.6 0.3 2.7 4.3 29.9 1.3 2.7 4.3 32.3
Recovery of compression garment initially stretched at different loads
Permanent Instant. Delayed recovery for Permanent Instant. Delayed recovery Permanent Position Instant. Delayed recovery Permanent Instant. Delayed set (mm) recovery for 200 gf/cm set set (mm) recovery 160 gf/cm loading set (mm) recovery recovery on the recovery for 80 gf/cm for 200 loading (mm) (mm) for 160 (mm) for 120 for 120 gf/cm for 80 loading (mm) leg gf/cm gf/cm gf/cm loading (mm) gf/cm loading Time series (min) loading Time series (min) loading Time series (min) loading Time series (min) (mm) (mm) (mm) (mm) 100 101 102 103 100 101 102 103 100 101 102 103 100 101 102 103 Ankle Calf Knee
6.7 7.1 5.7
0 0 0
0.7 1.7 2.7 0.6 0.3 1.3 2.7 0.2 0.7 1.7 2.7 0.6
13 12.7 13.7
0 0 0
1 1.7 3.3 1.3 1.7 2.3 3.7 0.6 1.7 2.3 3.3 1.3
18.3 14 15.7
0.3 0.3 0.3
1.3 1.3 1.7
2.3 3 3
2.7 4.3 4
1.7 1 1.6
23.6 23.9 25.3
0 0 0
1 1 1
2.3 3.7 2.3 2.3 4 2 2.3 4.7 2.3
92
S. Ghosh et al. 17.64 14.74 17.64 14.74 17.73 14.87 17.73 14.87 17.73 14.87 16.92 14.10 16.92 14.10 17 14.28 17 14.28 17 14.28 21.12 18.48 21.70 19 21.60 18.96 21.47 18.83
21.52 18.88
21.29 19.84 17.60 14.69 21.2 19.84 17.60 14.69 21.38 19.93 17.69 14.78 21.38 19.93 17.69 14.78 21.38 19.93 17.69 14.78 20.10 19.56 17.18 14.28 20.10 19.56 17.18 14.28 20.19 19.65 17.27 14.40 20.19 19.65 17.27 14.40 20.19 19.65 17.27 14.40 25.52 23.85 21.47 19 25.96 24.38 22 19.58
10 10 10 Instant. 10 10 10 10
25.91 24.33 21.91 19.54
101 10 2 1 0 3 2 1 0
Instant.
After wash Initial wear 2nd wear
Compression garment apart from being comfortable and easily wearable tailor made product shows some additional advantages of better holding power and suitability for repeated use. This may be attributed to lower value of delayed extension and permanent set in case of the compression garment as compared to the bandages (Figs. 13 and 14).
Pressure profile of compression garment
Comparison of compression bandage and garment
Table 9
Effect of washing Fig. 12 shows the effect of washing the garment after use which results in a drop in pressure value at all the three critical positions. This indicates that opposing to the common claim; washing does not bring the performance of the garments near to a new one. Actually improvement after washing takes place only with respect to the value of pressure that is generated after 2nd or 3rd wearing of the garment before wash. This range of pressure may not be the desired pressure range for the treatment of the disease.
3
pressure at calf and knee (Table 9). It is also observed that the change in pressure over time is not so significant in case of the garment as compared to the bandages (Fig. 7). This is due to the low value of delayed extension in case of the garment. It is also observed from Tables 4 and 9, that during repeated wearing, the drop in the pressure generation in case of the garment is less as compared to bandage. This may be because of the lower values of permanent set for the garment. Further this insignificant drop in pressure at the ankle is followed by marginal drop in pressure at the calf and knee positions (Fig. 11).
25.82 24.29 21.82 19.49
Figure 10 Effect of position of the limb on permanent set of the compression garment.
25.74 24.20 21.78 19.36
200
Time series (min)
160
Load (gf/cm)
Pressure profile at calf (mmHg)
120
Time series (min)
80
Before wash Initial wear 2nd wear 3rd wear 4th wear
0
100
0.5
Instant.
1
Time series (min)
Pressure profile at knee (mmHg)
1.5
102
103
Ankle Calf Knee
Pressure profile at ankle (mmHg)
2
State of the sample
Permanent set (mm)
2.5
Performance of the compression bandage
93
27
Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Sample 7 Sample 8
40
26 35
24
Ankle
23
Calf
Pressure (mm Hg)
Pressure (mm Hg)
25
Knee
22 21 20 19
30 25 20 15 10
18 5
17
0
16 1
10
100
1000
ankle
calf
knee
Position on the limb
Time (min)
Figure 11 Pressure profile of the garment on different position of the limb.
Figure 14 Effect of position of the limb on the pressure profile of the compression material at 80 gf/cm.
Conclusions Initial wear before wash 2nd wear
30
3rd wear 4th wear
25
Initial wear after wash
Pressure (mm Hg)
2nd wear after wash
20
15
10
5
0
ankle
calf Position on the limb
knee
Figure 12 Effect of washing on the pressure profile of the garment at different position of the limb.
14
Permanent set (mm)
12
Sample Sample Sample Sample
1 2 3 4
Sample Sample Sample Sample
5 6 7 8
10 8 6 4 2 0 80
120
160
200
Load (gf/cm)
Figure 13 Effect of load on the permanent set value of the compression material.
Compression bandage used for the similar application exhibit a lot of variability regarding the material used, constructional parameters of the yarn and fabric set. As regards holding capacity with time, the fabric of higher weight may not perform the best. Furthermore, in the existing bandage material, the bandage that is most suitable for repeated use may not be very suitable to offer good holding during use and vice-versa. In compression bandages the level of initial pressure on the pressure point at the mannequin leg for a particular level of stretching force is primarily influenced by the instantaneous extension and the diameter of the limb. The value of pressure shows some deviation from the Laplace equation at the knee which can be attributed to the non-circular geometry at that position. At the other points the values are nearly same as calculated by the Laplace equation. The general relationship of pressure decay (at the pressure point of the mannequin leg) with material creep and friction shows that the decay parameter is largely governed by the creep and frictional force. Pressure decay increases with higher value of creep and lower value of friction among the layers. The angle of bandaging is inversely related to the pressure at the pressure point in the mannequin leg and the angle which results in two layers overlapping and generates the 35 mmHg pressure recommended by the doctors for the treatment of leg ulcers at about 40 degrees. Compression garments give a lower value of delayed extension and permanent set and thus are better than bandages for repeated usage and better holding. But it cannot act as a substitute because of higher cost, its unsuitable for use at night or during rest and high working pressure. So the
94 suggestion of the doctors that the complete therapy for the treatment of the ailment lies in rotation between bandage and garment may be true to a large extent.
S. Ghosh et al.
[3]
[4]
Conflict of interest
[5]
The authors have no conflict of interest. [6]
References [1] Van Geest AJ, Franken CPM, Neumann HAM. Medical elastic compression stockings in the treatment of venous insufficiency. In: Elsner P, Hatch K, Wigger-Alberti W, editors. Textiles and the skin, vol. 31. p. 98e107. [2] Anand SC, Rajendran S. Design and characterization of novel medical devices for venous leg treatment. In:
[7]
[8]
Jassal M, Aggarwal A, editors. International conference on emerging trends in polymers and textile 2005. p. 155e67. Judith R, Casley S. Compression bandages in the treatment of lymphoedema. Available from,; 2002 (L.A.A., University of Adelaide). Juidth R, Casley S. Compression garments for the treatment of lymphoedema. Available from, ; 2002. Johnson S. Compression hosiery in the prevention and treatment of venous leg ulcer. Journal of Tissue Viability 2002; 12(No. 2):67e74. Thomas S. The use of the lap lace equation in the calculation of sub bandage pressure. Available from: ; 2003. Mukhopadhyay A, Ghosh S. Creep performance of short stretch bandages. Indian Journal of Fibre and Textile Research 2005;30:331e4. Macintyre L, Baird M, Weedall P. The study of pressure delivery for hypertrophic scar treatment. In: Anand S, Kennedy JF, Miraftab M, Rajendran S, editors. Medical textiles and biomaterials for healthcare. Woodhead Publishing Limited; 2003. p. 221e34.
www.elsevier.com/locate/jtv
Basic research
Pressure mapping and performance of the compression bandage/garment for venous leg ulcer treatment S. Ghosh, A. Mukhopadhyay*, M. Sikka, K.S. Nagla National Institute of Technology, Jalandhar-144011, India
KEYWORDS Compression bandages; Compression garment; Creep; Interface friction; Laplace equation; Mannequin leg; Venous leg ulcers
Abstract A study has been conducted on the commercially available compression bandages as regards their performance with time. Pressure mapping of these bandages has been done using a fabricated pressure-measuring device on a mannequin leg to see the effect on pressure due to creep, fabric friction and angle of bandaging. The results show that the creep behavior, frictional behavior and the angle of bandaging have a significant effect on the pressure profile generated by the bandages during application. The regression analysis shows that the surface friction restricts the slippage in a multilayer system. Also the diameters of the limb and the amount of stretch given to the bandage during application have definite impact on the bandage pressure. In case of compression garments, washing improves the pressure generated but not to the extent of the pressure of a virgin garment. Comparing the two compression materials i.e. bandage and garment, it is found that the presence of higher percentage of elastomeric material and a highly close construction in case of garment provides better holding power and a more homogeneous pressure distribution. ª 2007 Tissue Viability Society. Published by Elsevier Ltd. All rights reserved.
Introduction The worldwide chronic venous insufficiency is characterized by a combination of symptoms like varicose veins, deep vein thrombosis, oedema, * Corresponding author. Tel.: þ91 2690302/453x253 (O), 2690052 (R); fax: þ91 181 2690320. E - m a i l a d d r e s s : a r u n a n g s h u _ r e c j @ r e d i f f ma i l . c o m (A. Mukhopadhyay).
lymphoedema and finally ulcers on the legs [1]. The recurrence rates of the ulcers are also high, with two third of the patients experiencing one or more recurrence [2]. Graduated compression hosiery is accepted as an integral part for both as an active treatment for healing ulcers [3,4] and having an essential role in the prevention of venous ulcer reoccurrence. The compression bandage form a major category among different bandage types that are used for the application
0268-0009/$34 ª 2007 Tissue Viability Society. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.jtv.2007.09.013
Constructional parameters of compression material
S. no. Type
Constituent fiber
Warp
1
2
3
4
5
6
7 8
Warp knitted
Polyester with rubber in core Warp knitted Polyester with rubber in core Warp knitted Polyester with rubber in core Warp knitted Polyester with rubber in core Warp knitted Polyester with rubber in core Warp knitted Polyester with rubber in core Crepe, leno Cotton/ fabric wool Weft knitted garment e
Fibre proportion
Yarn linear density (tex)
Polyester Cotton Viscose Elastomeric Wool Warp Weft/ (%) (%) (%) material mislapped (%) (%) yarn
Weft
Thread density (per cm)
Fabric Fabric thickness weight (mm) (GSM)
Wales/ Course/ Loops ends picks
Polyester
85.3
e
e
14.7 (rubber)
e
66
63
3
9
9
1.01
195
Cotton (3 Ply)
26
61
63
6.7 (rubber)
e
66
46
3
8
8
0.78
231
Cotton (4 Ply)
39.7
22.7
28.5
9.1 (rubber)
e
66
27
3
8
8
0.62
206
Cotton (2 Ply)
40.8
44
4.6
10.6 (rubber)
e
66
119
3
6
6
0.80
210
10.6 (rubber)
e
66
66 30
3
7
7
0.68
200
6.9 (rubber)
e
66
66 55
3
7
7
0.72
202
54 29
66
24
27
e
0.89
259
35
30
70
30
1.16
510
Polyester: 48.6 cotton (1:2)
40.8
Polyester: 50.2 cotton (1:2)
39.3
Cotton
e
90.8
e
e
9.2
Cotton: lycra (2:1)
e
82
e
18 (lycra)
e
e
3.6
Performance of the compression bandage
Table 1
83
84
S. Ghosh et al.
Figure 1
Scanned images of the compression materials.
of clinically effective levels of pressure, applied to modify or assist the physiological process of blood flow [5]. The working mechanism of compression therapy is a result of the pressure exerted on the leg, through which the varicose veins become narrower and the insufficient perforating veins become closed and the retrograde bloodstream will diminish. The venous blood volume will diminish as well as calf muscle pumps can work better, thus resulting in higher tissue oxygenation and better microcirculation [1]. These bandages need to give good holding capacity during use and also be suitable for repeated use. Furthermore these properties can be improved if the creep behavior, the frictional behavior and the constructional parameters of the bandage material are optimized to give the required levels of pressure for a specific ailment.
In the present work an attempt has been made to study the effect of the creep, friction and angle of bandaging on the pressure profile of the compression bandages. The effect of creep and washing is also seen on the pressure profile of the compression garment, using fabricated prototype pressure-measuring device (mannequin leg) in both the cases. The performance of these bandage fabrics differing in constructional parameters is studied to adjudge their utility for specific end uses.
Materials and methods Eight different samples of commercially available compression bandages were analyzed in the laboratory for their constructional parameters as given in Table 1. It was observed that the samples 1e6 can be broadly classified as warp knitted fabrics with rubber being inlaid as an elastomeric component. Sample 7 was a woven leno structure and sample 8 is a weft knitted garment with fine lycra
3.5 Compression bandage
3
Crepe bandage
Force (kgf)
2.5
Compression garment
2 1.5 1 0.5 0 1
2
3
4
5
6
7
8
9
10
11
Elongation (mm)
Figure 2
Prototype pressure-measuring device.
Figure 3 Tensile behavior of the compression bandaging material.
Instantaneous extension and primary creep of compression bandages at different load
S. Instant. no. extension at 80 gf/cm (mm) 1 2 3 4 5 6 7
93 70 59 60 53.5 51 35
Table 3
Creep at 80 gf/cm (mm) Time series (min) 100
101
102
103
0.3 0 0 0 0 0 0
1.7 0.7 0.7 0.7 1.3 0.7 0.7
2.3 1.7 1.7 2.3 3 2.3 1.3
4 3 3 3.7 4.3 3.7 2.3
Total extension 80 gf/cm (mm)
97 73 62 63.7 57.8 54.7 37.3
Instant. extension at 120 gf/cm (mm) 112 79 64 65 57 53 42
Creep at 120 gf/cm (mm) Time series (min) 100 101 102 103 0.7 0 0 0 0 0 0
2.3 0 1 1.3 1 0.7 0.7
3.7 0.7 2.3 3 2.3 1.7 1.3
Total extension 120 gf/cm (mm)
5.7 117.7 4 83 3 67 4.3 67.3 3.3 60.3 3 56 2.3 44.3
Instant. extension at 160 gf/cm (mm) 121 85 70 68 58 57 45
Creep at 160 gf/cm (mm) Time series (min)
Total extension 160 gf/cm (mm)
100 101 102 103 0 0 0 0 0 0 0
1.7 1 1 1 2 1 1
2 1.7 1.3 1.7 3.3 2.3 1.3
3.3 124.3 3.3 88.3 2.3 72.3 2 70 5 63 3 60 2 47
Instant. extension at 200 gf/cm (mm) 130 91 72 72 62 61 50
Creep at 200 gf/cm (mm) Time series (min) 100 101 102 103 0 0 0 0 0 0 0
0.7 0.7 0.7 1 1.3 0.7 1.3
2 1.3 2 2 2.3 1.3 2.3
Total extension 200 gf/cm (mm)
3 133 3 94 2.3 74.3 3.7 75.7 3 65 3 64 2.7 52.7
Performance of the compression bandage
Table 2
Recovery of compression bandages initially stretched at different loads
S. Instant. Delayed recovery Permanent Instant. Delayed recovery Permanent Instant. Delayed recovery Permanent Instant. Delayed recovery Permanent set (mm) set (mm) recovery for 200 gf/cm set (mm) recovery for 160 gf/cm set (mm) recovery for 120 gf/cm no. recovery for 80 gf/cm for 200 loading (mm) for 160 loading (mm) for 120 loading (mm) for 80 loading (mm) gf/cm Time series (min) gf/cm Time series (min) gf/cm Time series (min) gf/cm Time series (min) loading loading loading loading 0 1 2 3 0 1 2 3 0 1 2 3 10 10 10 10 10 10 10 10 10 10 10 10 100 101 102 103 (mm) (mm) (mm) (mm) 1 2 3 4 5 6 7
93 67 56 58 53.2 50.5 25
0 0 0 0 0 0 0
1.3 1.3 2 1.3 1 1 1
2 2.3 2.7 2.3 2.3 2 2
3.3 0.7 3.7 2.3 3.3 2.7 3.3 2.4 4 0.6 3.3 0.9 2.3 10
112 76 60 63 56 52 31
0 0 0 0 0 0 0
1.3 1.7 1.3 1 1 1 1
2.7 3.3 2.3 1.7 2 2 1.7
4.3 1.4 4.7 2.3 4.3 3.7 3 3.3 2.3 2 2 2 2 11.3
118 82 64 63 57 55 33
0 0 0.7 0 0 0 0
1.3 1 2.3 1 1 1 0.7
2.3 2.3 3.7 2.3 2 1 1
4 2.3 3.3 3 4.3 4 3 4 3.7 2.3 2.3 2.7 2 12
126 86 66 67 60 58 38
0 0 0 0 0 0 0
1.3 1 1.7 1.3 1 1 0.7
2.7 3.3 3.3 3 2 2 1.7
4.3 2.7 4.3 3.7 4 4.6 4 4.4 2.3 2.7 3 3 2 12.7
85
86
S. Ghosh et al. Sample 4
Sample 2
Sample 5
Sample 3
Sample 6
3000 Sample 7 2500
Frictional force (gf)
140
Sample 1
Extension (mm)
120
100
80
2000
Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Sample 7
1500
1000 60 500 80 40
120
160
200
Load (gf/cm)
Figure 6
20 80
120
160
Variation of frictional force with load.
200
Load (gf/cm)
Figure 4
Effect of load on instantaneous extension.
yarn being knitted into the structure (Fig. 1). The compression bandage samples (1e6) have warp component as polyester but vary in the mislapping threads which act similar to the weft counterpart. It is either polyester or plied cotton yarn or a combination of polyester and cotton in different ratios. The different test methods such as pressure mapping of the bandage material, creep and friction measurement, all were performed in standard testing atmosphere.
Experimental set up A prototype electronic device was used to investigate the pressure mapping of the bandage systems as shown in Fig. 2. Three resistance foil
70
Pressure (mm Hg)
60 50 40 30 20 10
Sample 1 Sample 2 Sample 3 Sample 4
Sample 5 Sample 6 Sample 7
0 20
30
40
50
Angle (degree)
Figure 5 Effect of angle of bandaging on the pressure profile of the bandages.
strain gauges were fitted on the mannequin leg. The leg was used to simulate a real lower limb and has a definable tibia, calf and ankle region so that compression bandage pressure profiles are obtained. The inner dimensions of the leg made it possible to insert the strain gauges at strategic points so that pressure measurements could be made at the back of the leg. Compression bandage pressures were detected by means of pressure pins which were connected to each strain gauge device and protrude from the inside of the leg to the outer surface. The strain gauge consisted of a grid that was cemented to carrier (base) which was a thin sheet of bakelite. The gauge was calibrated using dead weight system and it follows both the tensile and compression strain of the specimen. The spreading of foil permitted a uniform distribution of strain over the grid. The bandage was then applied around the mannequin leg at a stretch as practiced by the medical practitioners to determine the pressure mapping of each sample with time. The calculation of the actual pressure values were based on the pressure exerted by the bandage on the projected annular ring portion of the sensor used. For creep testing a dead weight system of loading was used on the fabric with two wooden clamps, one fixed and the other movable. Test specimen length to width ratio was kept as 1:2 (5 cm:10 cm). The displacement of the lower clamp was noted down at different intervals of time at four different load values (80 gf/cm, 120 gf/cm, 160 gf/cm, 200 gf/cm) as recommended by the doctors to observe the extension and the recovery behavior of both the bandage and the garment.
19.04 16.75 16.66 14.58 15.08 12.3 14.76 13.30 11.68 10.69 12.12 11.30 10.36 6.14 19.21 16.93 16.84 14.76 15.34 12.56 15.02 13.56 11.86 10.95 12.38 11.57 10.62 6.4 19.3 17.1 17.02 14.85 15.43 13 15.2 13.74 12.03 11.04 12.56 11.74 10.71 6.66 19.3 17.1 17.02 14.85 15.43 13 15.2 13.82 12.03 11.04 12.56 11.74 10.71 6.66 24.79 21.92 22.27 19.28 19.80 16.82 20.55 16.64 17.58 14.24 16.76 14.35 14.98 09.60 25.15 22.18 22.62 19.55 20.16 17.08 20.89 17.99 17.94 14.77 17.2 14.79 15.32 10.04 7
6
5
4
3
2
1
1st 2nd 1st 2nd 1st 2nd 1st 2nd 1st 2nd 1st 2nd 1st 2nd
36.34 34.14 33.97 30.36 31.95 27.98 31.32 27.63 28.6 25.35 28.42 25 25.25 19.38
36.43 34.23 34.06 30.45 32.03 28.95 31.42 27.72 28.78 25.69 28.51 25.08 24.98 19.12
36.61 34.49 34.14 30.62 32.21 29.3 31.68 27.89 28.86 25.79 28.69 25.25 24.81 18.77
36.96 34.67 34.32 30.81 32.38 29.48 31.86 28.07 28.95 25.96 28.95 25.34 24.28 18.42
35.38 33.08 32.56 29.48 30.8 28.6 29.92 26.49 27.46 24.29 27.28 23.76 24.10 17.80
25.15 22.18 22.62 19.55 20.16 17.08 20.89 17.99 17.94 14.77 17.2 14.79 15.32 10.04
25.15 22.18 22.62 19.55 20.16 17.08 20.89 17.99 17.94 14.77 17.2 14.79 15.32 10.04
24.97 22.09 22.45 19.46 19.98 16.99 20.72 16.90 17.85 14.6 17.11 14.7 15.06 09.95
19.3 17.1 17.02 14.85 15.43 13 15.2 13.82 12.03 11.04 12.56 11.74 10.71 6.66
102 101 100 Instant.
Time series (min)
103 102 101 100 Instant.
Time series (min)
87
103 102 101 100 Instant.
Time series (min)
Pressure profile at ankle (mmHg) Sample
Table 4
Pressure profile of compression bandages
Pressure profile at calf (mmHg)
Pressure profile at knee (mmHg)
103
Performance of the compression bandage
The fabric surface frictional force was calculated from the trace generated by the universal testing machine (Zwick). A sample of 10 cm length was cut from the roll and put on the flat wooden board, with a dead weight system of loading attached to one end of the clamped sample, as pretension. Another 10 cm length of the same sample stretched under the same load was clamped on to the smaller wooden block and connected to the top jaw of the machine through an inextensible string moving over a frictionless pulley. It moved on the fabric laid on flat wooden surface. The values of stretching load used were 80 gf/cm, 120 gf/cm, 160 gf/cm and 200 gf/cm and the normal load put on the wooden block was estimated by using the Laplace equation [6].
Results and discussion All the structures except crepe bandage have elastomeric material in different ratios as is given in Table 1. Further, the placement of the elastomeric yarn in the fabric also varies in each type of structure. It was found that the stress strain curve of compression garment is stiffer in nature as compared to the compression bandages (Fig. 3) which are flatter in nature even at high elongation. This indicates very slow or gradual build up of pressure on extension of bandage fabric. Moreover, the higher the stiffness/slope, the more capable the compression material will be as regards preventing oedema, but the more difficult it will be to put on the material [1].
High compression bandages Effect of creep Tables 2 and 3, show the extension and recovery characteristics of the compression bandages. It is observed from Table 2 and Fig. 4 that as the load on the bandage material is varied from 80 gf/cm to 200 gf/cm, extension of the material increases steadily. However, in case of recovery, the total recovery may or may not be higher for the samples stretched at higher load (Table 3). This is because all the samples followed different patterns of delayed recovery and permanent set due to their inherent characteristics. It is observed that the delayed recovery and permanent set are always high for the samples initially stretched at higher load. The instantaneous recovery is lowest for the bandage initially stretched at 80 gf/cm load (i.e. 800 gf loads on a 10 cm width
88
S. Ghosh et al. 38
Pressure (mm Hg)
37.5
(a)
37 36.5 36 35.5 35 34.5 34 1
10
100
1000
Time series (min) 29
27
28.5
26
Pressure (mm Hg)
Pressure (mm Hg)
26.5
(b)
25.5 25 24.5 24
(c)
28 27.5 27 26.5 26 25.5
23.5 23
25 1
10
100
1000
Time (min)
1
10
100
1000
Time (min)
Figure 7 Change in pressure at the ankle with time for (a) compression bandage (b) crepe bandage and (c) compression garment.
bandage). Different sample behave differently with the change in time. It is observed that the instantaneous extension is higher for samples 1 and 2, but lowest in case of sample no 7. In bandage fabric greater importance should be laid on delayed extension as higher value of delayed extension reduces the holding power of bandage on the affected body part. Sample 7 which possesses higher fabric weight shows high value of delayed extension. Therefore, it can be inferred that the bandage fabric of higher weight does not necessarily perform the best as far as the holding power of the fabric on the affected body part is concerned over a longer period of time. This is in agreement with the earlier findings by Mukhopadhyay and Ghosh [7]. It may be added that the cost factor is also high for the fabric of higher weight. It is observed from Table 3 that instantaneous recovery and delayed recovery are lowest for sample no. 7. However, the permanent set is a relevant parameter which indicates the suitability of the fabric for reuse. Although sample no. 5 shows the moderate value of instantaneous
recovery and delayed recovery, it still has a low value of permanent set. Effect of angle of bandaging It is observed from Fig. 5 that as the angle of bandaging is increased, the pressure generated at the surface of the leg drops thus affecting the healing process. This drop in the generated pressure at higher angle is due to decrease in the number of layers of the fabric at a particular point. For treatment of leg ulcers, the angle of bandaging is found to be around 40 for typical stretch level of 80 gf/cm which provides nearly 35 mmHg pressure as recommended by doctors. Further 40 angle of bandaging provides overlapping of two layers of bandage as practiced by the doctors while applying them for treatment of the ulcer patients. Effect of frictional properties Fig. 6 indicates that the frictional behavior of all the samples varies with the change in the
Performance of the compression bandage
89
Table 5 Comparison of the Laplace, regression and actual values of pressure (mmHg) S. no.
Position of the limb
Actual value
Laplace value of pressure
Regression value
1
Ankle Calf Knee Ankle Calf Knee Ankle Calf Knee Ankle Calf Knee Ankle Calf Knee Ankle Calf Knee Ankle Calf Knee
36.34 25.15 19.3 33.97 22.62 17.02 31.95 20.16 15.43 31.31 20.89 15.2 28.6 17.94 12.03 28.42 17.2 12.56 25.28 15.32 10.71
37.5 21.8 24 37.5 21.8 24 37.5 21.8 24 37.5 21.8 24 37.5 21.8 24 37.5 21.8 24 37.5 21.8 24
36.98 26.06 20.56 33.17 22.24 16.95 31.07 20.14 14.85 31.27 20.34 15.05 30.03 19.1 13.81 29.39 18.46 13.71 25 14.71 9.42
2
3
4
5
6
7
Pressure mapping of bandage Table 4 shows that the pressure profile of the bandages (at 80 gf/cm stretching load) at three critical points on the surface of the leg varies with the time. As expected the pressure reduces with time because of the creep which in turn is counteracted by frictional behavior of the bandage fabric. A slight fall in pressure is observed at the calf and knee position but at the ankle substantial change is observed (Fig. 7a). The typical geometry at the ankle position may be responsible for layer slippage. But this observation is not true for crepe bandage since the frictional force between layers in case of crepe bandage is higher restricting the slippage effect. The change in pressure at the calf and knee position is not so significant due to more or less flat circular profile at these points. Further the pressure falls for the repeated wearing of the bandage due to the permanent set generated in them (Table 4). Based on the data in Tables 2 and 4, a polynomial regression equation relating bandaging pressure with diameter of the limb and instantaneous extension is developed. Y ¼180:85 39:440X1 þ 0:322X2 þ 2:130X12 0:001X22 ; R2 ¼ 0:988
stretching load. Actually at different stretching loads, the normal reaction and surface of the fabric changes with the amount of extension given to it and this affects the frictional force value which further restricts the recovery of the material.
where X1 ¼ diameter of the limb (cm), X2 ¼ instantaneous extension at 80 gf/cm (mm), and Y ¼ bandage pressure (mmHg). The equation shows that both the parameters viz. diameter and instantaneous extension have significant influence on the bandaging pressure.
40 Laplace S1-actual S1-regression S2-actual
Pressure in mm Hg
35
30
S2-regression S3-actual
25
S3-regression S4-actual
20
S4-regression S5-actual S5-regression S6-actual
15
S6-regression S7-actual S7-regression
10
5
Ankle
Calf
Knee
Position on the limb
Figure 8
Comparison of actual, the Laplace and regression values of pressure at different position of limb.
90
S. Ghosh et al.
Table 6 Position Ankle
Calf
Impact of creep and frictional force on decay of pressure Time series (min) 10 103 102 103
Knee
102 103
R2
S.E.
Y ¼ 2:53 0:550X1 0:002X2 þ 0:125X12
0.970
0.088
Y ¼ 0:046 þ 0:376X1 0:001X2 0:007X12
0.972
0.04
Y ¼ 0:038 þ 0:297X1 0:001X2 0:014X12
0.919
0.057
Y ¼ 0:002 þ 0:331X1 0:001X2 þ 0:003X12
0.973
0.04
Y ¼ 0:161 þ 0:295X1 0:01X2 0:024X12
0.929
0.05
For 102 min at the ankle position the decay in pressure is negative.
Compression garment Effect of creep It is observed from Tables 7 and 8 that the value of instantaneous extension and delayed extension do not vary much at the three positions (ankle, calf
and knee) although the recovery behavior shows a slight difference. The permanent set value at the ankle position is higher than the knee and calf which may be due to the typical geometry of the ankle which causes more stretch in fabric (Fig. 10). Effect of position on the pressure mapping The pressure profile of the virgin garment at three different positions indicate an initial increase and then decrease at ankle and slight decrease in
pressure decay (mm Hg)
(mm
)
4.2 4.0 3.8 3.6 3.4 3.2 3.0 2.8 2.6 2.4
1400 1300
ep
Based on the regression equation, it can be stated as the instantaneous extension increases the bandage pressure increases. However, the effect of instantaneous extension at constant stretching load is smaller than the effect of diameter. Also the instantaneous extension is directly proportional to the pressure generated in the bandage. It is further noticed that the pressure profile of the compression bandage calculated theoretically using the Laplace equation varies from the actual as can be seen in Table 5. According to the data calculated by using the Laplace equation, as the diameter increases the pressure should decrease but the reverse is true in actual measurement at calf and knee positions. This may be due to noncircular geometry at the knee position where the sensor is fitted. The deviation of pressure values at the calf and the knee position can be seen in Fig. 8. The above findings were earlier pointed out by Lisa Macintyre et al. [8]. Another set of regression analysis is done for the assessment of pressure decay with creep and the frictional force at different positions of the limb. The regression equations at all positions are given in Table 6. It can be seen that as the creep increases over time the decay in pressure also increases but the frictional force acts as a restriction in the process of decay (Fig. 9). As the frictional force increases it inhibits the decay in pressure in a multilayer bandage system.
1200 1100
friction
Cre
a
Regression equation
2a
1000 900
al forc e
(gf)
600 700
800
Figure 9 Effect of creep and frictional force on pressure for ankle at 103 min.
Table 7
Instantaneous extension and primary creep of compression garment at different load
Position Instant. on the extension at 80 leg gf/cm (mm) Ankle Calf Knee
Table 8
7 7.3 6.7
Creep at 80 gf/cm (mm) Time series (min) 100 101 102 103 0 0 0
Total extension at 80 gf/cm (mm)
0.3 1.7 3 10 0.3 1.3 2.7 10 0.3 1.3 2.3 9
Instant. extension at 120 gf/cm (mm) 14 14 15
Creep at 120 gf/cm (mm) Time series (min) 100 101 102 103 0 0 0
Total extension at 120 gf/cm (mm)
1 2 3.3 17.3 0.7 1.7 3 17 0.7 1.7 3.3 18.3
Instant. extension at 160 gf/cm (mm) 20 16 18
Creep at 160 gf/cm (mm) Time series (min) 100 101 102 103 0 0 0
Total extension at 160 gf/cm (mm)
0.3 1.3 2.7 22.7 0.3 1.7 3.3 19.3 0.7 1.7 3.3 21.3
Instant. extension at 200 gf/cm (mm) 25.3 25.6 28
Creep at 200 gf/cm (mm) Time series (min) 100 101 102 103 0 0 0
Total extension at 200 gf/cm (mm)
1.3 2.7 4.3 29.6 0.3 2.7 4.3 29.9 1.3 2.7 4.3 32.3
Recovery of compression garment initially stretched at different loads
Permanent Instant. Delayed recovery for Permanent Instant. Delayed recovery Permanent Position Instant. Delayed recovery Permanent Instant. Delayed set (mm) recovery for 200 gf/cm set set (mm) recovery 160 gf/cm loading set (mm) recovery recovery on the recovery for 80 gf/cm for 200 loading (mm) (mm) for 160 (mm) for 120 for 120 gf/cm for 80 loading (mm) leg gf/cm gf/cm gf/cm loading (mm) gf/cm loading Time series (min) loading Time series (min) loading Time series (min) loading Time series (min) (mm) (mm) (mm) (mm) 100 101 102 103 100 101 102 103 100 101 102 103 100 101 102 103 Ankle Calf Knee
6.7 7.1 5.7
0 0 0
0.7 1.7 2.7 0.6 0.3 1.3 2.7 0.2 0.7 1.7 2.7 0.6
13 12.7 13.7
0 0 0
1 1.7 3.3 1.3 1.7 2.3 3.7 0.6 1.7 2.3 3.3 1.3
18.3 14 15.7
0.3 0.3 0.3
1.3 1.3 1.7
2.3 3 3
2.7 4.3 4
1.7 1 1.6
23.6 23.9 25.3
0 0 0
1 1 1
2.3 3.7 2.3 2.3 4 2 2.3 4.7 2.3
92
S. Ghosh et al. 17.64 14.74 17.64 14.74 17.73 14.87 17.73 14.87 17.73 14.87 16.92 14.10 16.92 14.10 17 14.28 17 14.28 17 14.28 21.12 18.48 21.70 19 21.60 18.96 21.47 18.83
21.52 18.88
21.29 19.84 17.60 14.69 21.2 19.84 17.60 14.69 21.38 19.93 17.69 14.78 21.38 19.93 17.69 14.78 21.38 19.93 17.69 14.78 20.10 19.56 17.18 14.28 20.10 19.56 17.18 14.28 20.19 19.65 17.27 14.40 20.19 19.65 17.27 14.40 20.19 19.65 17.27 14.40 25.52 23.85 21.47 19 25.96 24.38 22 19.58
10 10 10 Instant. 10 10 10 10
25.91 24.33 21.91 19.54
101 10 2 1 0 3 2 1 0
Instant.
After wash Initial wear 2nd wear
Compression garment apart from being comfortable and easily wearable tailor made product shows some additional advantages of better holding power and suitability for repeated use. This may be attributed to lower value of delayed extension and permanent set in case of the compression garment as compared to the bandages (Figs. 13 and 14).
Pressure profile of compression garment
Comparison of compression bandage and garment
Table 9
Effect of washing Fig. 12 shows the effect of washing the garment after use which results in a drop in pressure value at all the three critical positions. This indicates that opposing to the common claim; washing does not bring the performance of the garments near to a new one. Actually improvement after washing takes place only with respect to the value of pressure that is generated after 2nd or 3rd wearing of the garment before wash. This range of pressure may not be the desired pressure range for the treatment of the disease.
3
pressure at calf and knee (Table 9). It is also observed that the change in pressure over time is not so significant in case of the garment as compared to the bandages (Fig. 7). This is due to the low value of delayed extension in case of the garment. It is also observed from Tables 4 and 9, that during repeated wearing, the drop in the pressure generation in case of the garment is less as compared to bandage. This may be because of the lower values of permanent set for the garment. Further this insignificant drop in pressure at the ankle is followed by marginal drop in pressure at the calf and knee positions (Fig. 11).
25.82 24.29 21.82 19.49
Figure 10 Effect of position of the limb on permanent set of the compression garment.
25.74 24.20 21.78 19.36
200
Time series (min)
160
Load (gf/cm)
Pressure profile at calf (mmHg)
120
Time series (min)
80
Before wash Initial wear 2nd wear 3rd wear 4th wear
0
100
0.5
Instant.
1
Time series (min)
Pressure profile at knee (mmHg)
1.5
102
103
Ankle Calf Knee
Pressure profile at ankle (mmHg)
2
State of the sample
Permanent set (mm)
2.5
Performance of the compression bandage
93
27
Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Sample 7 Sample 8
40
26 35
24
Ankle
23
Calf
Pressure (mm Hg)
Pressure (mm Hg)
25
Knee
22 21 20 19
30 25 20 15 10
18 5
17
0
16 1
10
100
1000
ankle
calf
knee
Position on the limb
Time (min)
Figure 11 Pressure profile of the garment on different position of the limb.
Figure 14 Effect of position of the limb on the pressure profile of the compression material at 80 gf/cm.
Conclusions Initial wear before wash 2nd wear
30
3rd wear 4th wear
25
Initial wear after wash
Pressure (mm Hg)
2nd wear after wash
20
15
10
5
0
ankle
calf Position on the limb
knee
Figure 12 Effect of washing on the pressure profile of the garment at different position of the limb.
14
Permanent set (mm)
12
Sample Sample Sample Sample
1 2 3 4
Sample Sample Sample Sample
5 6 7 8
10 8 6 4 2 0 80
120
160
200
Load (gf/cm)
Figure 13 Effect of load on the permanent set value of the compression material.
Compression bandage used for the similar application exhibit a lot of variability regarding the material used, constructional parameters of the yarn and fabric set. As regards holding capacity with time, the fabric of higher weight may not perform the best. Furthermore, in the existing bandage material, the bandage that is most suitable for repeated use may not be very suitable to offer good holding during use and vice-versa. In compression bandages the level of initial pressure on the pressure point at the mannequin leg for a particular level of stretching force is primarily influenced by the instantaneous extension and the diameter of the limb. The value of pressure shows some deviation from the Laplace equation at the knee which can be attributed to the non-circular geometry at that position. At the other points the values are nearly same as calculated by the Laplace equation. The general relationship of pressure decay (at the pressure point of the mannequin leg) with material creep and friction shows that the decay parameter is largely governed by the creep and frictional force. Pressure decay increases with higher value of creep and lower value of friction among the layers. The angle of bandaging is inversely related to the pressure at the pressure point in the mannequin leg and the angle which results in two layers overlapping and generates the 35 mmHg pressure recommended by the doctors for the treatment of leg ulcers at about 40 degrees. Compression garments give a lower value of delayed extension and permanent set and thus are better than bandages for repeated usage and better holding. But it cannot act as a substitute because of higher cost, its unsuitable for use at night or during rest and high working pressure. So the
94 suggestion of the doctors that the complete therapy for the treatment of the ailment lies in rotation between bandage and garment may be true to a large extent.
S. Ghosh et al.
[3]
[4]
Conflict of interest
[5]
The authors have no conflict of interest. [6]
References [1] Van Geest AJ, Franken CPM, Neumann HAM. Medical elastic compression stockings in the treatment of venous insufficiency. In: Elsner P, Hatch K, Wigger-Alberti W, editors. Textiles and the skin, vol. 31. p. 98e107. [2] Anand SC, Rajendran S. Design and characterization of novel medical devices for venous leg treatment. In:
[7]
[8]
Jassal M, Aggarwal A, editors. International conference on emerging trends in polymers and textile 2005. p. 155e67. Judith R, Casley S. Compression bandages in the treatment of lymphoedema. Available from,