Bioimpedance measurement device for chronic wound healing monitoring

A chronic wound is loosely defined as a wound that fails to heal within a time period of a few months. Elderly bedridden people and people suffering from certain underlying medical conditions, such as vascular diseases and type 2 diabetes, are particularly prone to develop chronic wound. The group of people exposed is increasing in numbers. Treatment of a chronic ulceration is very costly and the monitoring of healing is often based on visual inspection by medical professionals. There exists a need for objective and non-intrusive method for assessment of chronic wound healing. In this Master of Science Thesis a prototype of a bioimpedance device for monitoring of chronic wound healing was designed, constructed and tested. The device works from an indicator basis and measures the changes in the tissue impedance. The direction of the change correlates with the change in the volume and in the conductivity of the tissue, consequently in the swelling around the inflamed wound. Decrease in extracellular fluid can be detected as increasing low frequency impedance. The device measures impedance at 5kHz and 100kHz frequency by using triangular excitation. The emphasis of the design was on the simplicity of the device to provide a possibility for downscaling in the future. Ultimately the device would be integrated on a patch type platform together with a drug delivery system. The test measurements with the bioimpedance device were fairly extensive. The measurements were performed with a purely resistive load and a 2R-1C circuit. For 5kHz excitation the results for both load circuits did show only a slight mean error with a fairly small standard deviation. For 100kHz excitation the results did show larger mean error with a small standard deviation. Small standard deviation points to a systematic error. However, the 100kHz results are somewhat controversial since the difference between mean error for the purely resistive load and for the 2R-1C is fairly large. Restricted in vivo measurements were also performed. The in-vivo measurements did show large error compared to the reference measurements. Due to the limited nature of the measurements solid conclusions from these measurements cannot be made. All in all, the test measurements indicate the potential of simplified design. The accuracy of the device can be increased remarkably with certain improvements made to the design

Bioimpedance method for monitoring venous ulcers: Clinical proof-of-concept study

Evaluation of wound status is typically based on means which require the removal of dressings. These procedures are often also subjective and prone to inter-observer bias. To overcome aforementioned issues a bioimpedance measurement-based method and measurement system has been developed to evaluate the state of wound healing. The measurement system incorporated a purpose-built bioimpedance device, a measurement software and a screen-printed electrode array. The feasibility and the performance of the system and method were assessed in an open non-randomized follow-up study of seven venous ulcers. Healing of ulcers was monitored until the complete re-epithelialization was achieved. The duration of follow-up was from 19 to 106 days (mean 55.8 +/- 25.2 days). A variable designated as the Wound Status Index (WSI), derived from the bioimpedance data, was used for describing the state of wound healing. The wound surface area was measured using acetate tracing for the reference. A strong correlation was found between the WSI and the acetate tracing data, r(93) = 0.84, p < 0.001. The results indicate that the bioimpedance measurement-based method is a promising quantitative tool for the evaluation of the status of venous ulcers

Bioimpedance measurement device for chronic wound healing monitoring

A chronic wound is loosely defined as a wound that fails to heal within a time period of a few months. Elderly bedridden people and people suffering from certain underlying medical conditions, such as vascular diseases and type 2 diabetes, are particularly prone to develop chronic wound. The group of people exposed is increasing in numbers. Treatment of a chronic ulceration is very costly and the monitoring of healing is often based on visual inspection by medical professionals. There exists a need for objective and non-intrusive method for assessment of chronic wound healing. In this Master of Science Thesis a prototype of a bioimpedance device for monitoring of chronic wound healing was designed, constructed and tested. The device works from an indicator basis and measures the changes in the tissue impedance. The direction of the change correlates with the change in the volume and in the conductivity of the tissue, consequently in the swelling around the inflamed wound. Decrease in extracellular fluid can be detected as increasing low frequency impedance. The device measures impedance at 5kHz and 100kHz frequency by using triangular excitation. The emphasis of the design was on the simplicity of the device to provide a possibility for downscaling in the future. Ultimately the device would be integrated on a patch type platform together with a drug delivery system. The test measurements with the bioimpedance device were fairly extensive. The measurements were performed with a purely resistive load and a 2R-1C circuit. For 5kHz excitation the results for both load circuits did show only a slight mean error with a fairly small standard deviation. For 100kHz excitation the results did show larger mean error with a small standard deviation. Small standard deviation points to a systematic error. However, the 100kHz results are somewhat controversial since the difference between mean error for the purely resistive load and for the 2R-1C is fairly large. Restricted in vivo measurements were also performed. The in-vivo measurements did show large error compared to the reference measurements. Due to the limited nature of the measurements solid conclusions from these measurements cannot be made. All in all, the test measurements indicate the potential of simplified design. The accuracy of the device can be increased remarkably with certain improvements made to the design

Bioimpedance Sensor Array for Long-Term Monitoring of Wound Healing from Beneath the Primary Dressings and Controlled Formation of H2O2 Using Low-Intensity Direct Current

Chronic wounds impose a significant financial burden for the healthcare system. Currently, assessment and monitoring of hard-to-heal wounds are often based on visual means and measuring the size of the wound. The primary wound dressings must be removed before assessment can be done. We have developed a quasi-monopolar bioimpedance-measurement-based method and a measurement system to determine the status of wound healing. The objective of this study was to demonstrate that with an appropriate setup, long-term monitoring of wound healing from beneath the primary dressings is feasible. The developed multielectrode sensor array was applied on the wound area and left under the primary dressings for 142 h. The impedance of the wounds and the surrounding intact skin area was measured regularly during the study at 150 Hz, 300 Hz, 1 kHz, and 5 kHz frequencies. At the end of the follow-up period, the wound impedance had reached the impedance of the intact skin at the higher frequencies and increased significantly at the lowest frequencies. The measurement frequency affected the measurement sensitivity in wound monitoring. The skin impedance remained stable over the measurement period. The sensor array also enabled the administration of periodical low-intensity direct current (LIDC) stimulation in order to create an antimicrobial environment across the wound area via the controlled formation of hydrogen peroxide (H2O2).publishedVersionPeer reviewe

Bioimpedance method for monitoring venous ulcers

Evaluation of wound status is typically based on means which require the removal of dressings. These procedures are often also subjective and prone to inter-observer bias. To overcome aforementioned issues a bioimpedance measurement-based method and measurement system has been developed to evaluate the state of wound healing. The measurement system incorporated a purpose-built bioimpedance device, a measurement software and a screen-printed electrode array. The feasibility and the performance of the system and method were assessed in an open non-randomized follow-up study of seven venous ulcers. Healing of ulcers was monitored until the complete re-epithelialization was achieved. The duration of follow-up was from 19 to 106 days (mean 55.8 ± 25.2 days). A variable designated as the Wound Status Index (WSI), derived from the bioimpedance data, was used for describing the state of wound healing. The wound surface area was measured using acetate tracing for the reference. A strong correlation was found between the WSI and the acetate tracing data, r(93) = - 0.84, p < 0.001. The results indicate that the bioimpedance measurement-based method is a promising quantitative tool for the evaluation of the status of venous ulcers.Peer reviewe