Movement-related variation in forces under compression stockings

iWRAP: A Theranostic Wearable Device With Real-Time Vital Monitoring and Auto-Adjustable Compression Level for Venous Thromboembolism

OBJECTIVE

Venous Thromboembolism (VTE) is a commonly underdiagnosed disease with severe consequences and an exceedingly high mortality rate. Conventional compression wraps are devised for therapeutic purpose but lack diagnostic capacity. Recent advances in flexible electronics and wearable technologies offer many possibilities for chronic disease management. In particular, vital signs have been studied to show a strong correlation with the risk of VTE patients. In this study, we aim to develop an intelligent theranostic compression device, referred to as iWRAP, with the built-in capacity of real-time vital sign monitoring together with auto-adjustable compression level.

METHODS

An instantaneous pneumatic feedback control with a high-resolution pressure sensor is integrated to provide a highly stabilized compression level at the prescribed interface pressure for an improved therapeutic outcome. Meanwhile, arterial pulse waveforms extracted from the pressure readings from the smart compression device can be utilized to derive the body vital signs, including heart rate (HR), respiratory rate (RR) and blood pressure (BP).

RESULTS

A reliable delivery of the targeted compression level within ±5% accuracy in the range of 20-60 mmHg has been achieved through the feedback of the interface pressure. Both HR and RR have been measured within clinical-grade accuracies. Moreover, BP estimated using an ALA model has been achieved at low compression levels, which is also within a clinical-acceptable accuracy. The acquired vital information has been instantaneously fit into the clinically acceptable criteria for life-threatening PE risk with timely assessments.

CONCLUSION

The iWRAP has shown the potential to become the first theranostic wearable device with both continuous delivery of accurate and effective compression therapy and real-time monitoring of life-threatening conditions for VTE patients.

The Haemodynamic Efficacy of Six Different Compression Stockings from Compression Class 2 in Patients Suffering from Chronic Venous Insufficiency

Objective:

To describe the efficacy of six different compression stockings from compression class 2 on venous haemodynamics in patients with chronic venous insufficiency (CVI).

Design:

An open, randomised, prospective study.

Setting:

University Department of Dermatology, Tübigen, Germany.

Patients:

Twenty-two patients (11 women, 11 men; mean age 55.1 years, SD 10.3 years) suffering from chronic venous insufficiency (CVI) at clinical stages C14EpAs, A14, Ap, PR.

Interventions:

The acute effect of six different compresion stockings from compression class 2 (CEN) on venous haemodynamics were measured using dynamic mercury strain gauge plethysmography. At the same time as venous function, the pressure exerted by the compression hosiery was determined under resting conditions and during exercise.

Main outcome measures:

Resting pressure exerted in the supine position was equivalent in all compression hosiery to the data defined in textile technology for compression class 2 (25–35 mmHg at the ankle). Compression hosiery produced a statistically significant improvement in venous refilling time t 0. The differing improvement in venous function could be explained by the quotient for maximum active pressure/resting pressure on standing (r = 0.98, p <0.01).

Conclusion:

Compression stockings from the same compression class possess differing acute effects on venous haemodynamics. The efficacy of the various compression devices derives to an exceptional degree from the elasticity of the material, and can be characterised in vivo by the ratio between maximum pressure exerted during exercise and the resting pressure on standing.

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.

Skin pressure profiles and variations with body postural changes beneath medical elastic compression stockings

BACKGROUND

Medical elastic compression stockings (GCSs) are one of the most widely used mechanical compression approaches to relieve venous disorders of the lower limb. The skin pressure profiles applied by compression stockings may be altered with body postural changes, thus exerting influences on their therapeutic efficiency.

OBJECTIVES

To examine and quantify objectively the skin pressure distribution and magnitude beneath GCSs with body postural changes, and to analyze the possible reasons for skin pressure variations.

METHODS

The pressure levels of four different kinds of commonly used GCS were measured using piezoelectric sensors and a multichannel measuring system in six female healthy volunteers in 10 different body positions.

RESULTS

Body postural changes significantly influenced the skin pressure profiles (P < 0.001). Skin pressures at the ankle and on the anterior side of the leg were always highest when tested in all positions. Extension and flexion of the knee joint significantly influenced the skin pressure at the anterior and posterior aspects of the leg, especially when tested in the sitting position with the knee flexed at 90 degrees and in the supine position with the knee flexed at more than 90 degrees (P < 0.001). Plantar flexion of the ankle joint, such as up-heel standing and heel-off walking, significantly increased the skin pressure in the ankle region. Contraction, extension, and relaxation of the calf muscle did not produce large fluctuations in skin pressure when tested in positions with full knee extension.

CONCLUSIONS

Body postures may be one of the most important factors influencing the skin pressure profiles applied by compression stockings. The anatomic structure of individual legs, the special design of compression stockings, and the physical properties of stocking materials also influence skin pressure variations at different tested locations in different body positions. Appropriate leg postural changes and exercise may improve the therapeutic effectiveness of GCSs.

Objective Evaluation of Skin Pressure Distribution of Graduated Elastic Compression Stockings

BACKGROUND

The beneficial effects of graduated elastic compression stockings (GCSs) have been demonstrated. However, their pressure performances are variable and unstable in practical applications owing to many influencing factors. Comprehensive assessment of skin pressure profiles may help elucidate the mechanisms of action of compression stockings.

OBJECTIVE

The objective of this study was to quantify and objectively evaluate the magnitude and distribution of skin pressure applied by different GCSs and to analyze the possible reasons influencing the stocking pressure performances.

METHODS

Six healthy females were required to wear eight kinds of GCSs with different pressure levels while standing upright. The skin pressures of 16 different positions located in four heights and four directions of the lower limb were measured and recorded by FlexiForce interface pressure sensors (Tekscan, Inc., Boston, MA, USA) and a multichannel measuring system.

RESULTS

The pressure gradients, pressure levels, and testing locations significantly influenced skin pressure (p < .001). All tested GCSs exerted the highest pressure at the ankle region, and the pressure gradually decreased toward the thigh, which follows the gradient design of GCSs. However, many of them failed to produce the perfect pressure gradients from the ankle region to the calf region. Obviously, reversed pressure gradients occurred in the medial side of the leg, where the pressure at the ankle region was lower than that on the prominent part of the calf by 36% on average. GCSs with higher pressure levels applied higher skin pressure on the lower limb. The pressure at the anterior side was far higher than that in the medial and lateral directions. The distribution patterns of skin pressure at transverse sections were similar to the anatomic outlines of cross sections of the leg. The measured average ankle pressure of all tested GCSs did not reach the pressures specified by the manufacturers.

CONCLUSION

Skin pressure distributions and magnitudes applied by GCSs were significantly influenced by the locations of testing points in terms of height and direction, which are determined by the specific anatomic structure and body shape of individual human legs and potentially influenced by the pressure sensor and testing methods.

Measurement of Lower Leg Compression In Vivo: Recommendations for the Performance of Measurements of Interface Pressure and Stiffness

BACKGROUND

Interface pressure and stiffness characterizing the elastic properties of the material are the parameters determining the dosage of compression treatment and should therefore be measured in future clinical trials.

OBJECTIVE

To provide some recommendations regarding the use of suitable methods for this indication.

METHOD

This article was formulated based on the results of an international consensus meeting between a group of medical experts and representatives from the industry held in January 2005 in Vienna, Austria.

RESULTS

Proposals are made concerning methods for measuring the interface pressure and for assessing the stiffness of a compression device in an individual patient.

CONCLUSIONS

In vivo measurement of interface pressure is encouraged when clinical and experimental outcomes of compression treatment are to be evaluated.

The Use of Pressure Change on Standing as a Surrogate Measure of the Stiffness of a Compression Bandage

OBJECTIVES

To measure interface pressure and stiffness of short-stretch and long-stretch bandages applied with variable strength. These parameters have a deciding influence on the efficacy of compression therapy in chronic venous disease.

DESIGN

Prospective experimental study.

MATERIALS AND METHODS

Compression bandages constructed of different materials were applied with light, moderate and high pressure. Interface pressure was measured over the medial aspect of leg in 12 healthy individuals. Long-stretch bandages were compared to short-stretch bandages. The difference between standing and supine pressure was used to characterise stiffness.

RESULTS

In the low pressure range the median pressure of the final bandage in the supine position was between 18 and 30 mmHg for the long-stretch and 25-33.5 mmHg for the short-stretch bandages (p<0.01, Mann-Whitney U-test). The median differences between standing and supine pressure were between 2.0 and 8.5 for the long-stretch and 6.0-10.5 mmHg for the short-stretch material. In the group of moderate pressure the median values in the supine position were in a range 33.0-58.0 mmHg, for long-stretch and 39.0-49.5 mmHg for short-stretch bandages, with an increase after standing of 6.0-7.0 mmHg with long-stretch, and 14.0-21.0 mmHg with short-stretch bandages (p<0.01, Mann-Whitney U-test). The median supine pressure values in the high pressure group were between 52.0 and 67.0 mmHg for long-stretch and 59.5-67.0 mmHg for short-stretch material. The median increase during standing ranged between 8.5 and 14.5 mmHg in the elastic group and 23.0-33.0 in the inelastic group (p<0.01, Mann-Whitney U-test).

CONCLUSION

A bandage applied with light pressure corresponds to the moderate pressure category of stockings. The difference between the sub-bandage pressure from supine to standing can be used to characterise the stiffness of a bandage.

Venous haemodynamics and the effects of compression stockings

Over the years, graduated compression stockings exerting varying ankle pressures have been used with differing degrees of effectiveness in the prevention of deep venous thrombosis and ulcer recurrence, and the treatment of venous ulceration (Stemmer et al, 1980; Partsch and Horakova, 1994; Veraart et al, 1997). Whether in the hospital or community setting, nurses often have the responsibility of measuring the limb and fitting the compression stocking on the patient and it is he/she who often influences the patient on the type of stocking and level of compression required. Understanding the influence of graduated compression on the venous haemodynamics of the lower limb and having a good working knowledge of the claims of the manufacturers as to expected levels of compression from each garment will aid the nurse and patient in decision making. An awareness of the hazards of inappropriate use of compression therapy should ensure that the nurse is a safe practitioner.