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Implementing a Wearable Sensor for Lymphedema Garments: A Prospective Study of Training Effectiveness

Special Report

Implementing a Wearable Sensor for Lymphedema Garments: A Prospective Study of Training Effectiveness

Index: Wound Management & Prevention 2019;66(1):39–48 doi: 10.25270/wmp.2020.1.3948

Abstract

Lymphedema garments apply therapeutic pressure to maintain minimum leg volume. Practitioners and patients apply these garments and seek to achieve appropriate compression pressure “by feel.” PURPOSE: A study was conducted to assess the feasibility of applying a sensor-feedback device to train staff to accurately apply garments. METHODS: A convenience sample of wound care and rehabilitation staff volunteered for a prospective, randomized, unblinded, single-center pilot study. Participants were randomized to instruction+feedback (ie, receiving training on compression application and using the device to determine whether they achieved desired pressure) or instruction only groups (n = 6 each). Each volunteer applied hook-and-loop closures on the author’s leg pre- and post-training with a target of 35 mm Hg, or |Ppre- 35|= |Ppost- 35|=0. (|P| is absolute value of P). The feedback group used a device to measure the applied compression; the device consists of a capacitive sensor of thin polyurethane foam between conductive fabric layers and a microcomputer/Bluetooth transmitter under a vacuum seal that fits into a fabric pocket of a lymphedema garment at the posterior ankle and pairs with a mobile device. A lymphology-certified therapist coordinated training. Data were collected with a pen/paper tool and analyzed with Student’s t test. RESULTS: The instruction+feedback group was closer to target after training (|Ppre - 35|= 10 ± 12 mm Hg; |Ppost - 35|=5 ± 4 mm Hg; P <.05; paired t test) than the instruction only group (|Ppre- 35|=19 ± 11 mm Hg; |Ppost - 35|=12 ±12 mm Hg; not significant). CONCLUSION: This wearable mobile pressure sensor device assists practitioners in applying hook-and-loop lymphedema garments closer to target pressure. Larger studies with clinicians and research that involves patient application of compression are warranted.

Introduction

Lymphedema is a disfiguring condition of indurated edema in the extremities. The lymph system normally collects the overflow of interstitial fluid from capillary and venous blood. For lymphedema to occur, extravascular fluid must overwhelm the lymphatic channels. The clinical stages of lymphedema include abnormal lymphatic system flow (subclinical stage), accumulation of protein-rich fluids with swelling (reversible stage), permanent swelling (spontaneously irreversible stage), and elephantiasis (final stage).1,2  Prolonged excess lymphatic fluid can lead to excessive fat cell and collagen deposition, which leads to a characteristic clinical appearance of nonpitting brawny edema, fibrosis, lack of “pitting,” dorsal foot hump, loss of visualization of ankle landmarks, and edema.3 In advanced cases of lymphedema, verrucous skin changes and fibrous deformities are noted.3

The treatment for lymphedema usually involves complete decongestive therapy (CDT). Decongestion comprises reduction of tissue pressure, release of leukocytes, reduction of lymphatic protein, improved subfascial lymph flow, and reduction of interstitial fluid pressure.4  Commonly, CDT includes manual lymphatic drainage and compression.4 

When lymphedema decongests and the legs achieve a minimum obtainable volume, preventive measures should be taken. Stockings or garments (eg, leggings, sleeves, strapping, gloves or boots) are utilized to maintain compression. Compression stockings are graded for different uses by pressure range,  where pressure is measured at the ankle.  Clinicians in the United States use the following is the classification system: Class 1 (20 mm Hg to 30 mm Hg) is useful for varicose veins. Class 2 (30 mm Hg to 40 mm Hg) is used for lymphedema and more severe venous insufficiency. Class 3 (40 mm Hg to 50 mm Hg) is used  for lymphedema decongestion.5 In the author’s clinic,  compression is provided at the class 2 level to maintain the positive results of CDT.5,6  

Stockings are relatively inexpensive and widely available, but practitioners in a wound or lymphedema clinic will generally affirm that some patients have difficulty donning compression stockings, making compression garments a useful alternative.7,8 The garments the author most commonly uses are termed hook-and-loop closures; they are readily available and typically comprise a series of horizontal straps that are progressively applied in the distal to proximal direction. Ideally, the patient tightens each strap firmly and comfortably in an overlapping fashion. Each strap attaches anteriorly with a hook-and-loop closure to achieve the desired compression level (see Figure 1). Several types of garments are available and include ReadyWrap (Lohmann & Rauscher, Milwaukee, Wisconsin) and  Farrow Wrap (BSN Medical GmbH, Hamburg, Germany).

Regardless of the type of dressing or garment, Laplace’s Law holds.9,10 According to this law, the pressure exerted on the lower extremity by compression increases as a function of the tension of the bandage or strap and the curvature of the underlying surface. Although limitations exist on the applicability of Laplace’s Law in predicting compression on the leg, this law helps explain how variations in stretching and overlapping pressure within a lymphedema garment vary widely from person to person.9,10 Therefore, although it is not difficult for the practitioner (or the patient) to learn how to apply a compression garment, it is often unclear whether the desired therapeutic pressure is achieved.11 One can reasonably make the argument that if the garments are too loose, the risk for shear injury or the return of lymph fluid into interstitial spaces increases, leading to lymphedema exacerbation, skin breakdown, cellulitis, or sepsis. If the garments are too tight, pressure necrosis may occur, especially in people with diabetes or peripheral arterial disease.  However, because subbandage and subgarment pressure are not typically measured in practice, the rates of injury in response to too little or too much pressure is unknown. Such scenarios are underscored by the gap between the literature and clinical practice. Although subgarment pressure is important to measure accurately, the literature does not provide direct guidance as to how to teach a patient or practitioner to achieve therapeutic pressure, and outside the research laboratory or a few specialized centers, tools for clinicians to learn, teach, or monitor subgarment pressure are not readily available.9,12-17

For this purpose, a sensor beneath the closure next to the skin may be therapeutically advantageous. Such a product should be inexpensive and easy to use. 

The purpose of this study was to determine if receiving pressure feedback helps practitioners more accurately apply pressure through lymphedema garments to achieve a target pressure of 35 mm Hg on the lower third of the leg.6,18 

Methods

apacitive sensor constructed of thin polyurethane foam between conductive silver fabric. A 2-inch by 2-inch, 0.4-cm thick sensor was developed to measure pressure between the lymphedema garment and the skin (see Figure 2). The polyurethane foam has negligible “memory”: it has been found in mechanical engineering testing to retain 98% of its original thickness after 22 hours of 30% compression at room temperature.19,20 Hence, it retains its initial capacity to store charge after prolonged compression. The sensor is not yet commercially available.19

The sensor was incorporated within a  Bluetooth peripheral device (LightBlue Bean; Punchthrough Technologies, San Francisco, California) that communicates with a small microcomputer/Bluetooth low energy (BLE) transmitter/receiver. The peripheral device uses the ATmega328 microprocessor (Atmel Corp, San Jose, California), with software based on Arduino architecture.21 An Arduino C++ sketch reads the capacitance, finds a running average, and transforms the capacitance into pressure in mm Hg.

The sensor, microprocessor, and Bluetooth transmitter/receiver were wrapped in polyethylene under vacuum packaging.22 The advantages of using this technique include its strength and compactness, ability to measure pressure (rather than force), and inertness (polyethylene wrap is used for food storage) (see Figure 2). 

A smartphone (with either an iOS Phone or Android OS operating system) served as the central Bluetooth device. The Bluefruit LE Connect Version 3.3.121 (Adafruit Industries; New York, NY)23 is available for both devices. The Bean Console, Version 1.0.0 (Punch Through Design, San Francisco, California), which is not longer sold or supported, is iOS only.24 Pressure readings on these apps scroll up from the bottom of an emulated serial terminal screen at a rate of 1 per second (see Figure 3).   

Calibration. Before the pilot study, the author calibrated each device. The device was placed in a small pneumatic pressure chamber, the air pressure was increased from 0 mm Hg to 100 mm Hg in 20 mm Hg increments over a period of less than 3 minutes, and pressure measurements were recorded at approximately 10-second intervals. The sensor output was measured against the output of a commercially available pressure monitor (Thermo Fisher Scientific, Hampton, New Hampshire.  A traceability certificate for the Thermo Fisher Scientific monitor has been filed in compliance with the National Institute of Standards and Technology).25 The published accuracy of the Thermo Fisher Scientific  monitor is ± 2.3 mm Hg. The study device calibration data were analyzed as follows:  a typical calibration curve is a second-order polynomial. This polynomial takes the form Ax2+Bx+C. For the calibration curve illustrated (see Figure 4) A = -0.00004, B = 0.2075 and C = 0.8399. For a representative sample of calibration curves (n=10), the coefficient of variation R2 ranges from 0.9992 to 0.9999.

The global error of calculation was defined as the average |(P-Pref)/Pref|. At a given capacitance, Pref is the reference pressure on the calibration curve, and P is the measured pressure. For 50 determinations over 10 sensors using the same reference pressure monitor, the global error was 2.2%.15,26

Calibration constants A and B of this equation were entered into a program in the computer language C++ to yield a digital output pressure. The constant C (typically less than 1 mm Hg) was neglected. The pressure was verified within 24 hours of device fabrication. When verified, the unit typically displays pressures ±2 mm Hg. At the present level of development of this device, the author (not a manufacturer or testing laboratory) calibrated the sensor.

Procedure. Figure 5, Figure 6, and Figure 7 illustrate device performance in practice once the calibration constants are entered. The investigator inserted the sensor/peripheral device into the lowest pocket on the posterior side of the hook-and-loop closure with the sensor visible (see Figure 5). As the practitioner affixed straps distally to proximally, the display on the mobile device (on the right of the figures) scrolled up from the bottom of the screen at 1 reading per second. Midway through the process, the display showed that the pressure on the sensor was 17 mm Hg (see Figure 6). The pressure reached a maximum of 44 mm Hg as the practitioner secured all the straps (see Figure 7). It should be noted that 44 mm Hg is higher that the study target of 35 mm Hg.  These illustrations are from a video created before the start of the current study.

Study protocol. Study participants comprised staff and personnel of the Hyperbaric Wound and Edema Center, Fort HealthCare and Fort HealthCare Therapy and Fitness Physical Therapy Center (Fort HealthCare, Fort Atkinson, Wisconsin). The author verbally invited staff to participate; additionally, he invited employees with rehabilitation experience to participate. Participation was voluntary, and staff incurred no repercussions if they chose not to participate. 

The author collected data in real time with pen and notebook. The participants’ professional and/or work title was recorded as a measure of experience. This was a low-risk, noninvasive, supervised trial on healthy employees at a community hospital without an Institutional Review Board. Therefore, IRB approval was deferred, and no formal informed consent documents were provided.  Participants were divided into 2 groups: the instruction+feedback group and instruction only group. The selection process utilized the Excel random number generator function (Excel version 15.19.1; Microsoft Corporation, Redmond, Washington). Once randomized, participants were informed of their assigned group. 

A hook-and-loop garment (medium ReadyWrap; see Figure 1) was applied on the right leg of the author, referred to herein as “the model.” All practitioners that applied a hook-and-loop pressure garment on the model received instructions from a trained and certified lymphedema specialist. The author (as the model) provided some information during training, which was limited to subjective levels of tightness (for the instruction group) or the pressure from the sensor (for the instruction+feedback group). The model was seated during training and measurement. Table 1 summarizes the teaching sequence.

At several points in the process, the practitioner applied the hook-and-loop closure to the model. For both groups, the first step in measuring the pressure on the model was to determine the zero pressure. First, the author inserted the sensor into the posterior pocket of the first strap of the garment (see Figure 5). Thee practitioner then affixed the most distal strap to the corresponding section of the loop. At this point, the author’s hand positioned the garment in place lightly against the skin on the surface of the posterior leg. In this position, the sensor was contiguous with the skin and garment. The investigator “zeroed” the sensor with a command on the mobile device. Next, the practitioner applied the remaining 4 straps distally to proximally, attempting to reach the correct tension.

For the pretraining session, the practitioner was asked to affix the hook-and-loop closure garment without specific direction. The only words stated were “try to reach 35 mm Hg.” The pressure was recorded but not shared with the practitioner.

The next step was a 10-minute hands-on training session during which the practitioner applied the garment on the model’s leg and tightened the straps. During these training sessions, the practitioners received verbal instructions from the lymphedema therapist. Practitioners in the instruction+feedback group received feedback on the actual pressure of the garment they were applying to the model. Feedback was subjective or subjective/objective, depending on the treatment arm. The after-training session was identical to the before-training session. The practitioners decided themselves when they had enough training.

Data collection and analysis. Each practitioner’s before-training and after-training performance was logged in a laboratory notebook and entered into Excel. The statistical paradigm stipulated practitioners with hands-on training with a pressure biofeedback device would be closer to the target than those who received hands-on training alone (between-group significance) and that compression approached the target in each group (within-group significance). The specific endpoint was the response to the question of how close each practitioner came to achieving the target pressure of 35 mm Hg before and after training. The “difference from target” was the absolute value of the following quantity: measured pressure minus 35 mm Hg. For each group, the pretraining pressure (Ppre) and post-training pressure (Ppost) were measured. The hypothesis was that the instruction+feedback group would be closer to the target post training than the instruction only group (ie, the mean |Ppost – 35| would approach zero for the instruction+feedback group but not for the instruction group). A paired t test was used to analyze within-group performance improvements; an unpaired t test was used assess between-group performance.

Results

Participants (6 in each group) were relatively evenly distributed among physical therapists (PTs), registered nurses (RNs), certified nursing assistant/hyperbaric technologist (CNA/CHT), and administrative staff between the instruction+feedback and instruction only groups (see Table 2). For the instruction+feedback group the participation was 3 PTs , 1 RN, 1 CNA/CHT, and 3 administrative staff. For the instruction group, the numbers were 2, 1, 1, and 2, respectively. For the most highly trained staff, there appeared to be a slight trend in favor of the instruction+feedback group. Most practitioners decided not to take the full 10 minutes; in fact, the instruction+feedback group received 8 ± 1 minutes of instruction, and the instruction group received 5 ± 2 minutes. This difference approached significance according to an unpaired t test (P = .05).

Using raw pretraining and post-training pressures, no difference was noted between groups. However, a difference was noted between |Ppre – 35| and |Ppost – 35|; after training, the 6 participants in the instruction+feedback group approached the target (before training 10 ± 12 mm Hg; after training 5 ± 4 mm Hg; P <.05) (see Figure 8). The within instruction group performance did not approach the target (before training 19 ± 11 mm Hg; after training 12 ± 12 mm Hg). 

After training, a nonstatistically significant trend toward improvement was noted in the instruction+feedback group relative to the instruction only group (5 ± 4 mm Hg vs 12 ± 11 mm Hg). 

Discussion

A new wearable sensor that displays the pressure (as mm Hg) directly applied by the hook-and-loop garments may increase the accuracy of desired pressure applied in compression dressings. To the best of the author’s knowledge, this is the first study that demonstrates that this information regarding pressure, provided as a direct, real-time variable, may improve training effectiveness. The results are different than information provided by indirect measures of pressure from products with lines or shapes that guide the amount of stretching.26 This study device provides a direct pressure measurement. 

This study showed that compression wrap pressure was applied more accurately when specific pressure feedback during training was provided — that is, within-group performance improved significantly. However, a direct comparison between groups did not yield significant differences.

Although no studies on devices that directly display compression pressure for hook-and-loop garments have been performed, studies for other types of compression have been conducted. Almost all of these devices have a tube, wires, or contacts from the sensor to an electronic box to display subbandage pressure. 

Specifically, the Oxford pressure monitor (Tally Group Ltd, Romsey, UK)  is an electropneumatic sensor.28 It is approximately 3 cm in diameter and 2 mm thick. The device measures the pressure needed to fill a hollow plastic disk as the opposite walls separate (the disk has contacts that disconnect when the pressure exceeds the external pressure) and features a tube emerging from the bandage and a dedicated box to display the pressure.12 In a prospective, cohort study12 (N = 20) measuring the effectiveness of compression dressings used to heal venous ulcers, the device was placed 4 cm above the medial malleolus. The device provided stable readings over a week of compression. Compression reached >40 mm Hg, and 70% of these patients healed in 12 weeks or less. However, to the best of the author’s knowledge, this sensor is no longer commercially available.

Another device is the PicoPress® (Microlab, Padua, Italy). This pneumatic system has a pressure balloon measuring 5 cm in diameter, and when deflated, is less than 1 mm thick. It is filled with 2 mL of air during the measurements. A tube extends from the sensor to a dedicated electronics box. A prospective, randomized controlled trial13 reported the tubular bandage ranged from 25 mm Hg to 40 mm Hg (interquartile range), and the short-stretch bandage ranged from 40 mm Hg to 60 mm Hg (interquartile range). An uncontrolled study9 of 5 women included a computer-simulated pressure map of the leg partially derived from Laplace’s Law. The theoretical pressure was compared to the pressure measured by the PicoPress (the gold standard for this study) at 4 locations on the leg. The measurements were in close agreement. 

Another sensor is the Kikuhime pressure monitoring device (Medi-iGroup, Melbourne, Australia), a pneumatic sensor that operates similarly to the PicoPress. In a cross-sectional, operational study (N = 10,) Parsch5 determined the resting pressure of inelastic garments was 50 mm Hg in the sitting position at the B1 location (ie, where the Achilles tendon emerges from gastrocnemius muscle) using a Kikuhime probe. This matches the pressure determined by Weller et al.29

Brophy-Williams et al15 determined the validity and reliability of the Kikuhime sensor on a thigh-high sports compression garment. The gold standard for validity was a cylinder of deionized water of a known temperature at a range of depths. Among 3 sensors and 30 individual measurements, the global error was 2.97%. In comparison, the capacitive sensor described in the current study has a global error of 2.2%.

The same study14 measured 6 points on the leg and thigh using the Kikuhime instrument. Two (2) researchers each applied 6 sensors to predetermined points 5 times. The pressure at all points ranged from 17 mm Hg to 30 mm Hg. As a measure of reliability, the mean error of measurement was 1.3 mm Hg for a single tester and 1.8 mm Hg between testers.

Several studies have assessed force-sensitive resistors (FSRs). These elements have electrical resistance that decreases as pressure increases. They are quite thin and flexible and have been evaluated as pressure monitors with a direct connection to a graphic interface. In their in vitro study on simulated human legs, Parmar et al16 tested 5 different types of FSRs with known static weights and found that only 1 had an accuracy greater than 80% at 30 mm Hg, 50 mm Hg, and 70 mm Hg. Mahmood et al17 developed a telemetry system for an FSR. The 4 cm by 8 cm transmitter was limited by inaccuracy for pressures less than 30 mm Hg. Additionally, FSRs measure pressure indirectly; they measure force, which translates to pressure only if the force is reasonably constant over a known area.

The Smart Sleeve (Carolon, Rural Hall, NC) includes an FSR.30 This FSR is connected by tape to an underlining sleeve that extends from the ankle to the knee. This sleeve has parallel electrically conductive fabric lines extending from the ankle to the knee. Proximally, these 2 conductive lines connect to removable conductive clips. From these clips, wires extend to a dedicated electronics box that displays pressure in 5-mm Hg increments. After assembly, a practitioner applies a compression dressing. This dressing applies pressure to the FSR, and the device displays the pressure. The advantage of this device is that it is unobtrusive at the level of the skin-bandage interface. The disadvantage is the need to attach wires to the sleeve and the need for a dedicated liner under the compression dressing.

Many resistive, capacitive, and other types of sensors that display pressure gradients are available for measuring plantar pressure31 and buttocks pressure28,32 to help develop shoes or seating systems. The advantage is that these convey impressive 3-D maps of pressure across a surface. The disadvantages are that these pressure map systems tend to be fragile and expensive, require bulky packages, and interface via cables to computer monitors. Saenz et al31 proposed a novel resistive textile array that interfaces to a local area network to a laptop or mobile device without cables. However, the transmitter is a bulky microcontroller board, and a second layer is necessary for an analog connection to the digital conversion device. To the best of the author’s knowledge, sensor arrays are not available for compression stockings or garments.

In comparison to these published methods and devices, the Bluetooth pressure sensor has the potential to be completely contained within the garment to measure pressure. It requires no dedicated electronics box, wires, tubes, or dressings. No pump, reservoir, or pressure transducer is required for pressurized air. 

Limitations

One (1) limitation was that the sample size was small and that the study was carried out at a single center. A direct comparison between groups requires a larger study with more participants. A power analysis33 indicated that 11 participants per group would be necessary to establish a significant difference at the P <.05 level with 80% certainty (for this study, there were 6 persons per group).

A related limitation was that the results were reported for the Lohmann-Rausher Ready Wrap device but not for other products. This was because the pockets of the Ready Wrap garment fit the peripheral device well. A body of data collected for the BSN Farrow Wrap garment (unpublished) had similar findings.

Another limitation was that the author was the model on whose right leg the hook and loop garment was applied. He provided subjective feedback of how loose or tight the garment felt. Additionally, as an investigator, the author zeroed the sensor. There is always a risk of unintentional bias when the author/inventor is involved in the collection of data.

An additional limitation was that training times were longer for the instruction+feedback group than for the instruction only group (P =.05; see Table 2). Feedback appeared to improve the practitioners’ motivation. Two (2) explanations are possible: 1) the instructors were biased to pay more attention to the instruction+feedback group, and 2) the mean training times were not accurate. In this regard, the training time was not recorded for practitioner 1 of the instruction+feedback groups. However, even if it was assumed that the practitioner took only 3 minutes to train each group (the shortest duration for any participant), the instruction+feedback group still would have trained for 2 minutes longer than the instruction only group (7 vs 5 minutes).

Another limitation of this study was that it did not address validity. One example of how to determine validity would be to compare pressure measured to a “gold standard” sensor to pressure measured by the wearable sensor on a model of a human leg. This effort was beyond the scope of this study.  

Additional limitations were technical in nature: As currently constructed, sensor electronics have a considerable thickness relative to FSRs and balloon sensors. The electronics package is approximately 1.5 cm by 0.6 cm by 0.8 cm. For lymphedema garments with pockets and for training purposes, this sensor fits completely within the garment on the posterior aspect of the closure. If the education process for patients is supervised by practitioners and because of the ample padding and short time need for application, the risk for pressure or skin injury is minimal.

Another limitation was the thickness of the sensor itself: the sensor has a finite thickness (4 mm), which itself alters the pressure measured. This error has been measured to be as high as 15% for the PicoPress sensor.9 As a first approximation, the “thickness error” of the PicoPress sensor and capacitive sensor are similar.

Another limitation was the  inaccuracy due to the body’s own electrical charge (stray capacitance). Stray capacitance is the basis for how one’s finger “trips” touch screens on phones and other devices. However, stray capacitance was negligible in this case because the electrical connections were kept short and the sensor capacitance was many-fold higher than the body’s stray capacitance. Additionally, the device was “zeroed” out or contiguous with the skin, which canceled out the body’s stray capacitance. However, at this stage of development, “zeroing” is more involved process for this capacitive sensor than for the PicoPress or Kikuhime devices.

Another limitation was that the calibration technique did not reproduce the exact working environment — for instance, the effect of curvatures. In this regard, the sensor has not yet been validated against established pressure sensors such as the PicoPress and Kikuhime on simulated extremities. Other important sensor parameters such as drift and hysteresis26 should be determined. Hysteresis measures the memory of a pressure sensor. Because a sensor might retain the memory of a previous compression as it decompresses, reporting a pressure higher than the actual reading.

Another limitation was that pressure was not applied to a precise location on the leg. Pressure was applied approximately at the level of connection of the gastrocnemius to the Achilles, but not exactly.13 This is because the garments do not fit exactly the same on all people and therefore becomes part of the variability in the findings between subjects.

Another limitation was the assumption that the results will carry over from staff training to patient training. Patients may not be as “tech-savvy” and therefore be more resistant to training than the staff.

The final limitation was the potential difference in skill set between participants in the instruction+feedback and the instruction groups. There were 4 RNs and PTs, who have the highest level of training, in the instruction+feedback group and 3 in the instruction group. This suggests the possibility of bias in favor of the instruction+feedback participants.

Conclusion

A wearable pressure sensor, wirelessly connected to a mobile device, that displays the pressure under a lymphedema garment, was developed and pilot-tested tested to assess whether it can help clinicians achieve a desired level of compression pressure. Despite the stated limitations, the potential exists for this mobile device to help train clinicians and patients to accurately apply compression garments. Further research involving larger studies and real-life scenarios is warranted. 

Acknowledgements

The author thanks the following persons for their help in various capacities: Angela Adler, OTR, Lymphology Association of North America (LANA) certified; the Staff of Fort HealthCare Hyperbaric, Wound and Edema Center, Johnson Creek; the Staff of Fort HealthCare Therapy and Sports Center; Fort HealthCare Outpatient Services (Johnson Creek); and Nicholas Stephen Keuler, MS (University of Wisconsin, Department of Statistics).

Affiliations

Dr. Goldman is the Medical Director, Fort Healthcare Hyperbaric, Wound and Edema Center, Johnson Creek, WI.  Please address correspondence to: Robert J Goldman, MD, 756 Schuster Road, Sun Prairie, WI, 53590; email: robertgoldmanMD@gmail.com.

Potential Conflicts of Interest

Dr. Goldman is the sole proprietor of Wound Care and Rehabilitation Medicine, which owns the intellectual property on which the technology described in this manuscript is based. In the event of a successful product launch, Dr. Goldman stands to benefit financially.  

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