Inability of Laplace's law to estimate sub-bandage pressures after applying a compressive bandage: a clinical study

Validation of a compression pressure measuring device and its clinical impact

OBJECTIVE

Compression pressure (CP) measurement is necessary as it represents the dosage of compression therapy (CT). It is almost always neglected, leading to a poor understanding of compression outcomes, especially when applying bandages or wraps. This work aims to present a measuring compression device validation system and underline the clinical impact of CP measurement.

METHOD

The tested device was submitted to validation tests to assess its accuracy, linearity and repeatability. The tests included measuring the pressure under a known weight, along and on the bottom of a water column, in parallel with a sphygmomanometer and under a sphygmomanometer applied to a plastic tube, as well as to a human leg.

RESULTS

The tested device showed good concordance with the theoretical pressure exerted by a known weight, water, a sphygmomanometer cuff, and when paralleled to a sphygmomanometer.

CONCLUSION

The tested device provided accurate, linear and repeatable data in all tested conditions. Its use is recommended to improve healthcare providers' skills in applying the correct pressure and to increase the scientific value of studies on CT.

Interface Pressures Derived from a Calibrated Bandage Applied for Compression Therapy

Objectives: We sought to clarify the interface pressure (IP) and its variation by applying Biflex16, a calibrated bandage, to the lower leg. Methods: In Study I, 50 participants applied a bandage to the lower leg of a single subject in two ways: first, with 50% overlap, while the calibration rectangle became a square (Application 1), and then with 50% overlap without intentional stretch (Application 2) which served as a control. In Study II, another 51 participants applied the bandage to their lower leg via Application 1. The IP was measured at the level of the transposition of the medial gastrocnemius muscle into the Achilles tendon (B1). Results: In Study I, the median IP (37 mmHg) and interquartile range (IQR; 9 mmHg) in the standing position were the same for Applications 1 and 2. In Study II, the obtained IP and IQR values were 38 and 12 mmHg, respectively, in the sitting position. This IP was similar to that obtained in Study I, and no correlation was found between IP and leg circumference. Conclusions: The variation in the IP obtained by the calibrated bandage was reasonably small when applied via Application 1. The obtained IPs did not correlate with the leg circumference.

Comparing the Energy-Stretch Properties of Two Compression Bandage Systems in a Laboratory-Based Test under Controlled Conditions

OBJECTIVE

To compare the characteristics of two commercially available compression systems, a dual-compression bandage system (DCS) and a traditional two-layer bandage (TLB), using a laboratory bench test.

METHODS

The compression systems were evaluated in a computer-controlled tensile test to generate force-deflection curves for each sample. The compressive work and the theoretical pressure applied to the limb by the respective compression bandages were calculated at the maximum stretch and a stretch instructed by the manufacturers. The manufacturer of the DCS provides reference points on how much the bandage should be stretched to provide the desired pressure, and the TLB stretch was calculated from the product’s datasheet.

RESULTS

The combined results of layers 1 and 2 for the DCS showed greater load and work than the TLB at both the maximum and recommended stretch. The recommended stretch for DCS and TLB was less than 50% of the deflection up to the breaking point.

CONCLUSIONS

The high work provided by the two layers of the DCS suggests a wider range of performance than the TLB when applied to the lower limb, especially after the limb volume is initially reduced by compression. Moreover, using the tensile test and the guide of the reference points on layers 1 and 2 from DCS, the calculated pressure achieved the expected values stated by the manufacturer. Human studies should be conducted to determine whether the reference points provided by DCS are beneficial for obtaining repeatable values.

Fibre Bragg Grating Based Interface Pressure Sensor for Compression Therapy

Compression therapy is widely used as the gold standard for management of chronic venous insufficiency and venous leg ulcers, and the amount of pressure applied during the compression therapy is crucial in supporting healing. A fibre optic pressure sensor using Fibre Bragg Gratings (FBGs) is developed in this paper to measure sub-bandage pressure whilst removing cross-sensitivity due to strain in the fibre and temperature. The interface pressure is measured by an FBG encapsulated in a polymer and housed in a textile to minimise discomfort for the patient. The repeatability of a manual fabrication process is investigated by fabricating and calibrating ten sensors. A customized calibration setup consisting of a programmable translation stage and a weighing scale gives sensitivities in the range 0.4–1.5 pm/mmHg (2.6–11.3 pm/kPa). An alternative calibration method using a rigid plastic cylinder and a blood pressure cuff is also demonstrated. Investigations are performed with the sensor under a compression bandage on a phantom leg to test the response of the sensor to changing pressures in static situations. Measurements are taken on a human subject to demonstrate changes in interface pressure under a compression bandage during motion to mimic a clinical application. These results are compared to the current gold standard medical sensor using a Bland–Altman analysis, with a median bias ranging from −4.6 to −20.4 mmHg, upper limit of agreement (LOA) from −13.5 to 2.7 mmHg and lower LOA from −32.4 to −7.7 mmHg. The sensor has the potential to be used as a training tool for nurses and can be left in situ to monitor bandage pressure during compression therapy.