917918

letter2020
IJLXXX10.1177/1534734620917918The International Journal of Lower Extremity WoundsRamar et al

Article
The International Journal of Lower

Regular Use of FlowAid FA100 SCCD

Extremity Wounds
1­–6
© The Author(s) 2020
Reduces Pain While Increasing Perfusion Article reuse guidelines:
sagepub.com/journals-permissions

and Tissue Oxygenation in Contralateral DOI: 10.1177/1534734620917918

https://doi.org/10.1177/1534734620917918
journals.sagepub.com/home/ijl

Limbs of Amputees With Diabetic

Neuropathy and Peripheral Arterial Disease:
Results of an Open, Pre-Post Intervention,
Single-Center Study

Suganya Ramar, MPH1, Seena Rajsekar, MSc2, Bamila Selvaraj, MPT2,

Vijay Viswanathan, MD, PhD, FRCP1,2 ,
and Raj Mani, DSc, PhD, FACA, FIPEM, CSci3

Abstract
Patients with diabetic neuropathy and peripheral arterial disease often suffer pain, develop foot wounds, and go on
to lose limbs leaving them with a painful limb. Electrical stimulation is one possibility open to physicians. In this study,
the effects of the FlowAid FA100 SCCD, a sequential contraction compression device, were tested. The FA100 device
is noninvasive; it uses 4 electrodes to sequentially stimulate the calf muscles in a modified intermittent pneumatic
compression manner. A total of 14 patients with diabetic neuropathy, peripheral arterial disease, unilateral amputation,
and a painful limb were treated with FlowAid FA100 (FlowAid Medical Technologies Corporation, New York, NY)
with prior ethical approval. The study design was open, pre-post intervention comparison, and nonrandomized. Pain
perceived was measured using Visual Analogue Scale (VAS) scores. Assessments of ankle brachial index (ABI), ultrasound
color Duplex, and tissue oxygen using the transcutaneous oxygen technique were done at baseline and 2 successive
follow-ups 4 weeks apart. Three out of 14 patients dropped out on account of distances involved in traveling to the
clinic. Eleven out of 14 patients experienced statistically significant reduction in pain mean VAS scores (7.5 ± 0.93 to
5.8 ± 1.47, P = .002) associated with increase in ABI (0.64 ± 0.06 to 0.69 ± 0.04, P < .001) and transcutaneous oxygen
tension measured on the dorsum (29.4 ± 4.03 to 33.2 ± 5.26 in mm Hg, P = .005). When pain scores were regressed
against ABI and transcutaneous oxygen tension values, there was a significant association between these (r = 0.8, P =
.002). The reduction in pain following regular use of FlowAid was accompanied by beneficial and statistically significant
increases in perfusion and oxygenation.

Keywords
FlowAid, tissue oxygenation, diabetic neuropathy, amputation, pain assessment, VAS scores, wound assessment

Impaired perfusion is a major factor implicated in the patho- is an integral part of this treatment paradigm.4 FlowAid
genesis of diabetic foot ulceration, the others being poor FA100 (FlowAid Medical Technologies Corporation, New
glycemic control, neuropathy, and trauma.1,2 Clinical man-
1
agement of the complications of the diabetic foot is based Prof. M. Viswanathan Diabetic Research Centre, Chennai, Tamil Nadu,
India
on treating infection, improving local skin perfusion and 2
M.V. Hospital for Diabetes, Chennai, Tamil Nadu, India
oxygenation, while persisting with bettering glycemic con- 3
Shanghai Jiao Tong University, Shanghai, China
trol. A significant part of wound healing is neoangiogenesis,
Corresponding Author:
whereby new blood vessels are induced to grow in the new
Vijay Viswanathan, M.V. Hospital for Diabetes, No. 4, West Madha
tissue, enabling better oxygenation and metabolism within Church Road, Royapuram, Chennai 600013, Tamil Nadu, India.
the wound.3 When ischemia is significant, revascularization Email: drvijay@mvdiabetes.com
2 The International Journal of Lower Extremity Wounds 00(0)

York, NY) is a relatively new sequential contraction com-

pression device that enhances blood flow, reduces edema,
and decreases pain5 approved by the US Food and Drug
Administration as well as the CE. This report presents a
pilot study done on painful limbs of subjects with painful
diabetic neuropathy, peripheral arterial disease, and an
amputated limb to better understand its effect on tissue per-
fusion and oxygenation.

Materials and Methods

Study Design
A prospective pre- to postinterventional, nonrandomized,
open, pilot study was done in the M.V. Hospital for Diabetes,
Chennai.

Patients
The study enrolled 14 patients with a diagnosis of diabetic
neuropathy, peripheral arterial disease, and a history of
major amputation in one leg. The study received Ethics
approval from the authors’ institution starting from July 26,
2018. All patients gave informed oral consent prior to the
study. Patients with a history of neuropathy as well as
peripheral arterial disease were included after standardized Figure 1. FlowAid treatment showing patient in the supine
assessments.6 Patients awaiting revascularization or with a position.
history of back pain or who were pregnant or who were on
analgesics for the past 12 weeks were excluded. placed on clean dry skin. Each electrode set consists of
Three patients after completing baseline investigations four 50 mm by 50 mm electrode pads. Each pad is marked
were unwilling to continue the study on account of the dis- with a specific number, 1 through 4. With the patient
tances involved in traveling to this center. rested, his/her calf skin was cleaned and dried using gauze
pad. FlowAid electrodes were placed on the calf muscle
with the proximal electrodes to the outer edge of the gas-
Outcome Measures trocnemius muscles. The distal electrodes were posi-
The primary outcome measure was pain measured using a tioned at least 5 cm distal and inferior to those above as
10-cm scale to record Visual Analogue Scale (VAS) scores. shown in Figure 2, following the instruction manual
Secondary outcome measures were the following: supplied.
The intensity of stimulation was gently raised till the
1. Ankle brachial index (ABI) patient perceived the stimulation after which it was raised
2. Transcutaneous oxygen (TcPO2) expressed as marginally and left at that level for the duration of the
Regional Perfusion Index (RPI = test site/control respective treatment event. Patients were asked to inform
site) and/or TcPO2 about their perception of the vibrations. FlowAid FA100
3. Arterial color Doppler ultrasound examination of was administered for at least 60 minutes on the test limb
the lower limb arteries. All tests were done using twice daily following directions for use supplied with the
standardized protocols described in the consensus device and our experiences with other stimulation devices.
guideline.6 The investigator instructed patients to use the FlowAid,
how to disconnect, and to store the device.
Intervention
Assessments
All patients were treated with FlowAid FA100 Sequential
Contraction Compression Therapy Device (SCCD) using Pain was assessed using a VAS score system by the same
the AA (arterial) mode. Patients were asked to lie supine investigator at all visits when the following questions were
(see Figure 1) during the procedure and electrodes were asked of patients:
Ramar et al 3

Figure 3. Positioning of transcutaneous oxygen tension

sensors.

Figure 2. Location of FlowAid (FA100) electrodes on the test

limb: an amputated stump is seen on the right.

•• How severe is the pain on the scale of 0 (minimum)

to 10 (maximum)?
•• Where is the pain located?
•• What does it feel like?
•• Is it sharp, dull, stabling, burning, crushing, throb-
bing, nauseating, shooting, twisting, or stretching?

Transcutaneous oxygen (TcPO2).7 TcPO2 is a noninvasive

measure of the partial pressure of oxygen or oxygen tension
using skin surface sensors and the TCM monitor (Radiom-
eter, Copenhagen, Denmark). Its operating principles and Figure 4. Duplex imaging of lower limb arteries.
use have been reported.7 Patients lay in a supine position in
a room free from draughts, and the temperature was con- exclusion of arterial disease; when ABI is ≤0.5, this is con-
trolled. The test and control sites were cleaned with injec- sistent with the presence of significant arterial disease.6
tion swabs. The electrodes were positioned on the mid
clavicular line in the fourth/fifth rib space on the chest (as Michigan Neuropathy Screening Instrument (MNSI).8 The
control site) and lower limb (mid dorsum of the foot) as MNSI is an instrument including 2 parts, a questionnaire
figuratively shown in Figure 3. A period of 15 minutes was with 15 questions and a foot examination. The maximum
permitted for the measuring site to be heated and results score of the foot examination is 8 points, and each limb is
recorded. Both absolute values of TcPO2 dorsum (test site) independently scored. An MNSI examination score of ≥2 is
and RPI (test site/control site) were noted. positive for diabetic peripheral neuropathy.

The Ankle Brachial Index. This is a simple noninvasive test Duplex Scanning of Arterial Color Doppler. Blood vessels may
that compares the blood pressure in upper and lower limbs be visualized and imaged using Duplex ultrasound imaging.
to diagnose peripheral arterial disease; the thresholds of Blood flow is displayed on the screen as a picture, as shown
significance are defined.6 ABI ≥0.9 and ≤1.2 permits figuratively in Figure 4.
4 The International Journal of Lower Extremity Wounds 00(0)

Table 1. Visual Analogue Scale Scores for Pain at Baseline to

Visit 2 for Each Patient.

No. Baseline Visit 1 Visit 2 Mean ± 1 SD

1 7 6 6 6.3 ± 0.4
2 9 7 6 7.3 ± 1.2
3 7 7 4 6.0 ± 1.4
4 8 7 6 7.0 ± 0.8
5 7 6 6 6.3 ± 0.4
6 6 5 5 5.3 ± 0.4
7 9 7 8 8.0 ± 0.8
8 7 8 8 7.6 ± 0.4
9 8 6 4 6.0 ± 1.6
10 8 7 7 7.3 ± 0.4
11 7 4 4 5.0 ± 1.4
Figure 5. Changes in the pain scores of Visual Analogue Scale
(VAS) from baseline to visit 2 for individual patient.

Follow-up
Follow-up visits were done at 4 weekly intervals. During
visits 2 and 3, all the patients had repeat assessments of
pain, ABI, transcutaneous oxygen tension, and color Duplex
ultrasound.

Data Analysis
SPSS 20.0 statistical package was used. For the analysis of
quantitative descriptive variables, group means were Figure 6. Changes in the Ankle Brachial Index from baseline to
tested. In order to determine the effect of the intervention visit 2 for individual patient.
(FA100) on the chosen parameters, repeated measures of
analysis of variance (ANOVA) was done. Both Wilcoxon Table 2. Ankle Brachial Index at Baseline to Visit 2 for Each
sign rank test and paired student t test were used for test for Patient.
significance. The level of significance for confidence was
set at 95% (P < .005). No. Baseline Visit 1 Visit 2 Mean ± 1 SD
1 0.72 0.75 0.78 0.75 ± 0.02
Results 2 0.64 0.62 0.7 0.60 ± 0.03
3 0.7 0.7 0.72 0.70 ± 0.09
All patients used FA100 for at least 1 hour twice daily as 4 0.6 0.63 0.67 0.63 ± 0.02
required by the study protocol; none of the patients com- 5 0.6 0.66 0.66 0.64 ± 0.02
plained of any issues such as discomfort or pain with using 6 0.7 0.7 0.76 0.72 ± 0.02
the device. 7 0.7 0.7 0.7 0.70 ± 1.1
8 0.7 0.7 0.7 0.70 ± 1.1
9 0.61 0.67 0.68 0.65 ± 0.03
Pain Scores
10 0.6 0.6 0.64 0.61 ± 0.01
Visual Analogue Scale data for all patients at all visits are 11 0.5 0.6 0.66 0.58 ± 0.06
presented graphically in Figure 5. A decreasing trend in
VAS pain scores was detected in all patients; the range of
change was marked. On the final visit, mean VAS was sta- usually consistent with improved blood flow to the distal
tistically significantly reduced (P = .002) compared with aspect of the legs.
baseline values (Table 1). TcPO2 data at test site and RPI values (defined as test
Ankle brachial index data for all visits are presented in site TcPO2/control site TcPO2) for all patients at all visits
Figure 6. Mean ABI increased statistically significantly are presented in tabular form (Tables 3 and 4) and graphi-
through the study (P < .001; Table 2). Increased ABI is cally in Figures 7 and 8. TcPO2 measured on the dorsum
Ramar et al 5

Table 3. Transcutaneous Oxygen (TcPO2) = Regional

Perfusion Index (RPI; Test Site/Control Site) at Baseline to Visit
2 for Each Patient.

No. Baseline Visit 1 Visit 2 Mean ± 1 SD

1 0.6 0.7 0.7 0.6 ± 0.04
2 0.6 0.6 0.7 0.63 ± 0.04
3 0.7 0.7 0.7 0.7 ± 1.1
4 0.5 0.5 0.6 0.53 ± 0.04
5 0.6 0.7 0.7 0.66 ± 0.04
6 0.6 0.6 0.6 0.60 ± 0.0
7 0.5 0.6 0.7 0.6 ± 0.08
Figure 8. Transcutaneous oxygen (TcPO2) dorsum (test site)
8 0.5 0.5 0.5 0.50 ± 0.0 at baseline to visit 2 for individual patient.
9 0.6 0.7 0.7 0.66 ± 0.04
10 0.4 0.5 0.6 0.50 ± 0.08
11 0.5 0.5 0.6 0.53 ± 0.04 through the study (P = .003). This is consistent with the
increased test site values but may also reflect some
decrease in control site values though all these were
Table 4. Transcutaneous Oxygen (TcPO2) Dorsum (Test Site) within the normal range. These changes are presented in
at Baseline to Visit 2 for Each Patient.
tabular form in Table 4.
No. Baseline Visit 1 Visit 2 Mean ± 1 SD The mean age of the sample was 62.09 ± 7.2 years that
included (N = 9 males, 81.8%; and N = 2 females, 18.2%).
1 29 34 38 33.6 ± 3.68
The change in mean of the pain score for the group was 7.5
2 34 32 32 32.6 ± 0.94
3 33 35 43 37 ± 4.32 ± 0.93 to 5.8 ± 1.47; this reduction is statistically signifi-
4 32 33 34 33 ± 0.81 cant (P = .002; Table 1 and Figure 5). ABI increased sig-
5 29 30 32 30.3 ± 1.24 nificantly from 0.64 ± 0.06 to 0.69 ± 0.04 (P < .001). RPI
6 29 30 36 31.6 ± 3.09 (test/control site) was significantly elevated from 0.55 ±
7 32 30 30 30.6 ± 0.94 0.08 to 0.66 ± 0.06 (P < .003), and TcPO2 dorsum (test
8 22 25 25 24 ± 1.41 site) was significantly elevated from 29.4 ± 4.03 to 33.2 ±
9 31 30 35 32 ± 2.16 5.26 (P = .005; Table 4).
10 23 23 27 24.3 ± 1.88
11 22 23 25 23.3 ± 1.24
Discussion
The purpose of this study was to test the effects of FlowAid
FA100 on pain, perfusion, and oxygenation in the skin over
the foot since this site is a predilection for diabetic foot
wounds. Pain perceived, expressed as VAS scores, reduced
statistically significantly in all patients over the period of the
study (P = .002). ANOVA test showed that all measured vari-
ables were significantly related to the outcome, that is, pain
(r = .8, P = .002) as presented in tabular form in Table 5 and
graphically in Figure 9. These data suggest that regular use of
the FlowAid FA100 benefits pain while increasing perfusion
and oxygenation.
The findings of the study beg the question how long
Figure 7. Changes in transcutaneous oxygen (TcPO2) = the FlowAid FA100 should be used by cohorts in this
Regional Perfusion Index (RPI; test site/control site) at baseline study to obtain lasting benefits. Only an appropriately
to visit 2 for individual patient. designed future study can answer this question with
confidence.
increased statistically significantly through the study This study has limitations: the sample size was small,
(P = .005), which suggests improved microcirculation on placebo control was lacking, and selection was not random-
the skin over the dorsum. RPI values also increased ized. All these arguments are addressable and should be
6 The International Journal of Lower Extremity Wounds 00(0)

Table 5. Changes in Outcome Measures After Intervention of FlowAid and Follow-up (N = 11).

Outcome Measures Baseline Visit 1 Visit 2 P

Pain (graded from 0 to 10), mean ± 1 SD 7.5 ± 0.93 6.3 ± 1.12 5.8 ± 1.47 .002
Ankle brachial index, mean ± 1 SD 0.64 ± 0.06 0.66 ± 0.04 0.69 ± 0.04 .001
TcPO2
RPI (test site/control site), mean ± 1 SD 0.55 ± 0.08 0.62 ± 0.08 0.66 ± 0.06 .003
Dorsum (test site), mean ± 1 SD 29.4 ± 4.03 30.2 ± 3.76 33.2 ± 5.26 .005

Abbreviations: SD, standard deviation, TcPO2, transcutaneous oxygen; RPI, Regional Perfusion Index.

ORCID iD
Vijay Viswanathan https://orcid.org/0000-0001-9116-3937

References
1. Tomita M, Kabeya Y, Okisugi M, et al. Diabetic microangi-
opathy is an independent predictor of incident diabetic foot
ulcer. J Diabetes Res. 2016;2016:5938540.
2. Alexiadou K, Doupis J. Management of diabetic foot ulcers.
Diabetes Ther. 2012;3:4.
3. de Medeiros ML, Araújo-Filho I, da Silva EM, et al. Effect of
low-level laser therapy on angiogenesis and matrix metallo-
proteinase-2 immunoexpression in wound repair. Lasers Med
Sci. 2016;32:35-43.
Figure 9. Changes in outcome measures after intervention of 4. Akbari CM, LoGerfo FW. Diabetes and peripheral vascular
FlowAid and follow-up (N = 11). disease. J Vasc Surg. 1999;30:373-384.
5. Rosenblum J, Gimmelreich D, Rosenblum S. Sequential
built into the design of future studies. This study permits the contraction compression therapy raises foot temperatures in
observation that FlowAid FA100 has a place in the manage- patients with peripheral arterial disease. J Vasc Diagn Interv.
ment and prevention of diabetic foot disease. 2016;2016:39-43.
6. Mani R, Margolis D, Shukla VK, et al. Optimal use of tech-
Declaration of Conflicting Interests nology in wound management. Int J Low Extrem Wounds.
2016;15:102-119.
The author(s) declared no potential conflicts of interest with respect 7. Thomsen AM. The TcpCO2 Handbook. Brønshøj, Denmark:
to the research, authorship, and/or publication of this article. Radiometer Medical ApS; 2011.
8. Feldman EL, Stevens MJ, Thomas PK, Brown MB, Canal
Funding N, Greene DA. A practical two-step quantitative clinical and
The author(s) received no financial support for the research, electrophysiological assessment for the diagnosis and staging
authorship, and/or publication of this article. of diabetic neuropathy. Diabetes Care. 1994;17:1281-1289.