J. Melhuish

Bandaging technique after knee replacement

Background Firm bandaging of the knee following knee replacement may prevent bleeding into the joint by a tamponade effect. We studied the pressure required to achieve tamponade, and then clinically compared the use of a compression bandage with the use of a standard crêpe bandage, with or without a drain. Method Transducers were used to measure the pressure achieved on the surface of the knee under different bandages, and within the knee following release of the tourniquet. We prospectively compared 3 series of 50 patients each: (1) with compression bandaging from toes to mid-thigh, (2) with crêpe bandage from mid-calf to mid-thigh alone, or (3) with crêpe bandage and suction drain. Results The pressure within the joint at which tamponade occurs is 52–62 mm Hg. The pressure on the skin under a properly applied compression bandage is between 28 and 32 mm Hg, and this controls bleeding within the joint. Patients treated with compression bandaging recovered more quickly from the operation, had a shorter hospital stay, and a greater range of flexion on discharge. They had no swelling of the limb, rarely suffered a tense hemarthrosis, and had fewer complications. Interpretation The use of a compression bandage incorporating the foot and calf following knee replacement surgery, without the use of drains, confers specific advantages over the use of a crêpe bandage alone.

Infrared imaging in diabetic foot ulceration

Diabetic foot ulcers present a difficult problem in clinical management because of increased risk of soft-tissue infection in diabetes plus impaired local blood supply due to diabetic vascular disease. Infection of diabetic foot ulcers has particular risk of involvement of the adjacent bone resulting in the serious complication of osteomyelitis. This needs early aggressive antibiotic therapy to avoid even more serious secondary long-term complications, but unfortunately clinical diagnosis and radiological examination may be unhelpful in early osteomyelitis, when antibiotic therapy is most effective. Furthermore the large number of patients plus the chronic nature of diabetic foot ulceration precludes routine investigation for early osteomyelitis by X-ray or isotope bone scanning in every case, for logistic, radiation protection, and cost reasons. This preliminary study has shown significantly increased temperature on infrared imaging, not only around the ulcer, but in the entire foot in patients subsequently confirmed radiologically as having early osteomyelitis.

Measurement of forces associated with compression therapy

Compression therapy is the principal treatment for leg ulcers associated with venous disease. The efficacy of compression therapy can be variable, which may in part be owing to the degree of compression applied. However, if the mechanism of action of this treatment could be better understood, it might be possible to improve its efficacy. It is not clear whether assessment of the degree of compression should be made under static or dynamic conditions, or both. A review of methods used previously suggests the need for a new method of assessment allowing continuous monitoring, even during movement. A system for continuous static and dynamic measurements of compression is described. Using an air chamber and manometer to test the system, agreement within ±3 mmHg is observed. The system is applied to investigate changes in forces, expressed as pressure, under bandages and compression stockings. Application of five bandage systems by experienced nurses to a volunteer shows a marked variation in applied pressure. During short periods of walking, rapid changes in pressure under compression stockings are observed, including some transients of less than 0.25 s. The method is simple to apply and may help to understand further the mechanism of action of compression therapy.

Measurement of the skin microcirculation through intact bandages using laser Doppler flowmetry.

The microcirculation under compression bandages has been assessed by numerous methods; however, the measurement techniques can disrupt the bandage-skin interface, affecting the measurement. In this study, a non-invasive method for measuring cutaneous blood flow using laser Doppler flowmetry (LDF) is presented. Ten volunteers had their microcirculation assessed by a laser Doppler probe being placed on their upper forearm with and without a light-transmissive gel and with a compression bandage plus light-transmissive gel. A circulatory challenge to the bandaged forearm in two of the volunteers was also undertaken. The median (95% confidence interval) perfusion (p.u.) for the skin surface was 24 (15–33) perfusion units (p.u.), and the skin plus light-transmissive gel demonstrated a higher perfusion: 66 (50–82) p.u., (p<0.012). The addition of the compression bandage, with additional gel allowed to permeate through to the underlying skin, decreased the perfusion to 27 (20–34) p.u. (p<0.007). In both volunteers, the microcirculatory flow responded to the vascular challenge, resulting in flow changes related to the cuff pressure (45-27 and 14-8 p.u.). This method demonstrated that it may be possible to assess the microcirculation through intact bandages, without the need to place any sensors at the skin-bandage interface.

Evaluation of Compression under an Elastic Tubular Bandage Utilised as an Introduction to Compression Therapy in the Treatment of Venous Leg Ulcers

Objective: To investigate the physical parameters of an elasticated tubular bandage (Tubigrip) on the leg and in durability studies. Design and setting: Cohort studies. Participants: Six healthy volunteers and 16 patients. Main outcome measure: Sub-bandage pressure. Results: Median pressures recorded under the Tubigrip bandage system at the lower, middle and upper calf muscle in 6 healthy volunteers, while sitting were 26, 25 and 12.5 mmHg, and for standing were 32, 40 and 16 mmHg. The median pressures recorded at the lower, middle and upper calf muscle in 16 venous leg ulcer patients while sitting were 18, 20 and 14 mmHg, and for standing were 32.5, 29.5 and 18 mmHg. Tubigrip durability studies demonstrated no decrease in sub-bandage compression over 8 days when applied to a model leg and volunteer leg. However, sub-bandage pressure decreased by more than 29% when the bandage was subjected to four wash-dry cycles. Conclusions: The pressures measured under Tubigrip were consistent with the ranges seen in other compression therapies. Laundering reduced the applied sub-bandage pressure.

Infrared imaging in the long-term follow-up of osteomyelitis complicating diabetic foot ulceration

Diabetic foot ulcers are susceptible to secondary infection; when this occurs, there is risk of spread of the infection to adjacent bone, resulting in the serious complication of osteomyelitis, which may be clinically silent in this group of patients. Prompt, aggressive treatment with appropriate antibiotics is indicated to prevent even more serious complications ranging from loss of the foot or limb to death. A previous study has shown that infrared imaging is useful in identifying those patients with diabetic foot ulceration at particular risk of developing clinically silent osteomyelitis. This long-term follow-up study has used infrared imaging to trace the progress of these patients.

An integrated instrumentation approach to the study of wound healing

The authors have developed a system for monitoring pressure and skin temperature associated with compression therapy. The system was applied to investigate forces and skin surface temperature under the 4 layer bandage system in 5 healthy volunteers. At a position about 8 cm above the medial malleolus the authors observed a median pressure of 32 mmHg (range 27 to 40 mmHg), in the sitting position, and 40 mmHg (range 25 to 47 mmHg) in the standing position. Twelve minutes after bandage application there was an increase in temperature on the bandaged legs, median=+1.9/spl deg/C (range+1.5 to +4.3 /spl deg/C) and a decrease on the unbandaged legs, median=-0.7/spl deg/C (range -0.2 to 1.4/spl deg/C). The range in applied pressure and the variation observed with posture suggests that the mode of action of compression therapy may not be solely the result of the degree of compression applied. The increase in skin surface temperature may suggest a temperature related increase in skin blood flow. This study illustrates the advantage of combining results of the different investigations of pressure and skin surface temperature.

MEASUREMENT OF PERIPHERAL VENOUS OXYGEN SATURATION IN THE LEG USING NEAR-INFRARED SPECTROSCOPY

Background: It has been suggested that poor healing of wounds may be associated with reduced tissue oxygenation. A non-invasive method of assessing peripheral venous oxygenation has been investigated. Method: Changes in oxyhaemoglobin (O2Hb), deoxyhaemoglobin (HHb), oxidized cytochrome aa3 (cyt aa3) and total haemoglobin (tHb) were monitored in the left lower leg of seven healthy volunteers. A short period of venous occlusion was achieved by rapidly inflating a sphygmomanometer cuff placed around the leg to 60 mmHg. The changes in O2Hb and tHb, with respect to the baseline readings, were evaluated. PSvO2 was calculated from (ΔO2Hb/ΔtHb) × 100%. Results: From 17 sets of readings on the seven volunteers the median PSvO2 calculated was 64% (range 50–86%). Conclusion: This method appears to be a simple means of evaluating PSvO2. A change in cyt aa3 was often seen associated with the venous occlusion.

Ultrasound imaging of the leg in patients with chronic wounds

A non‐invasive method of studying the extent of tissue changes may be of use in evaluating healing therapies for chronic wounds. The aim of this study was to investigate the use of ultrasound imaging to study the appearance of tissue in the vicinity of lesions in the lower limb.

Assessment of forces associated with compression therapy under static and dynamic conditions

Compression therapy has been used for centuries to treat venous leg ulcers. However the efficacy of this therapy is variable, which may in part be due to variations in compression applied. However it is not clear whether this should be measured under static or dynamic conditions or both. In order to further investigate the degree of compression applied the authors developed a system for continuous direct measurement that is also capable of measuring during movement. The system is being applied to investigate forces under compression bandages and compression stockings. The forces monitored are expressed as pressure. In accordance with previous studies the authors observed clear variations in recorded pressure under compression bandages applied by experienced nurses to a healthy volunteer. Studies of forces under compression stockings during movement indicated variations in pressure that were position dependent and of variable duration.