CPMT Journal

Introduction

Soovu Labs has published a series of papers describing the Soovu™ Pain Relief System (“Soovu”), a novel device that uses high temperature pulses of heat to reduce pain in both chronic and acute conditions [1-3]. Soovu is a Bluetooth-enabled wearable device that delivers pulsing heat to the area of pain. The system includes a companion mobile app that initiates the 10-30-minute heat treatment and allows for customization of the treatment session.

Based on the clinical response to the device, fast onset and duration of treatment effects, it was hypothesized that the mechanism of action is likely activation followed by de-functionalization of the TRPV-1 receptor on peripheral nerves [1,4,5]. Similar effects are demonstrated with heat in laboratory studies and analogous to the clinical response associated with capsaicin treatment [4,6,7].

Having demonstrated the device’s ability to reduce pain in clinical settings [3], the company was contracted by a large Pacific NW health insurance company to provide the Soovu system to employees and dependents of the health plan in a six-month realworld pilot.

The primary outcome measures included pain interference on quality of life, impact of pain on users’ ability to function, the utilization of healthcare resources such as medications and interventions, and users’ pain ratings. In addition, the observational design allowed for statistical prediction of the characteristics of those most likely to benefit from this therapy. These predictive findings support better individualization of therapy and may help program sponsors target the therapy to those most likely to respond to it.

Materials and Methods

Study Design

The current study was done in a real-world home and work environment involving mostly office workers. The study used a long-term, six-month, observational design. The device was offered to employees and their dependents as an employee fringe benefit program for those who met the clinical criteria and were free from medical conditions that contraindicated its use. Per the health plan’s requirements, up to 220 eligible individuals were to be granted access to the device without randomization. This limitation is discussed in later sections. All employees using the device agreed to regular assessments as part of the employer’s evaluation of the effectiveness of the device.

Participants who passed the screening and opted into the pilot were treated remotely via the wearable medical device and asynchronous coaching program between July 8, 2024, and January 7, 2025.

Population

Eligible participants were adult employees or spouses/partners/ other adult dependents of employees of the health plan who wished to use the device for musculoskeletal pain relief and selfreported having chronic pain for three or more months of a level 4 or greater on the numeric pain rating scale. Exclusion criteria included having any of the following conditions which are labeled contraindications for using the device: (1) neuropathy or nerve damage; (2) allergy to medical adhesives; (3) pregnant or possibly pregnant.

All participants reviewed and consented to Soovu Labs’ Terms & Conditions and the company’s Privacy Policy.

Of the 199 enrolled pilot participants, 173 participants had a baseline self-reported pain level of 4 or higher and used the device more than three times over the timeline of the study. These participants, who were included in the data analyses, were primarily women (76.7%), with 42.8% between the ages of 40 and 54 years old. Participants identified back (39.6%), neck (15.1%), shoulder/arm (13.2%), and other (32.1%; e.g., hip, legs, joints, etc.) as primary pain areas they would treat with the Soovu device. Of note, most participants (76.1%) reported suffering from pain in more than one area (Table 1).

Table 1: Participant demographics for the sample of n=159 participants who screened into the data analyses and provided demographic information. Note demographic information was missing for 14 participants.

Program Design

The Soovu^™ Pain Relief System is an FDA-registered Class II medical device indicated to provide topical heating for the purpose of elevating tissue temperature for the temporary relief of minor muscle and joint pain and stiffness; the temporary relief of joint pain associated with arthritis; the temporary relief of muscle spasms, minor sprains and strains, and minor muscular back pain; the temporary relief of menstrual discomfort; the relaxation of muscles; and the temporary increase of local circulation where applied.

The Soovu therapy consists of repetitive cycles of thermal energy applied to the area of pain where the heat cycles between 108°F (42°C) and up to 113°F (45°C) over a period of up to 30 minutes per therapy session. The wearer of the device determines the duration of the therapy (10, 20, or 30 minutes) and the maximum temperature for each session. The Soovu device is held on the body using a medical grade adhesive. The device can be worn on any flat surface of the body including back, neck, back of shoulders, abdomen, quadriceps, hamstrings, hips, glutes, calves, forearms, biceps, and triceps.

Throughout the six-month pilot, participants used the Soovu System at home and work as needed to manage pain. The device is controlled by the Soovu Mobile App which participants installed on their personal phones. Participants received guidance via the mobile app on how to place the device on the body and adjust the therapy settings. Participants received a printed Quick Start Guide and an electronic copy of the full owner’s manual.

The intervention also included asynchronous educational and Cognitive Behavioral Therapy (CBT) emails and text messages from customer care of approximately three messages per month. Participants were encouraged to ask questions and engage in messaging with the customer care team as needed.

Outcome Measures

Data was collected at baseline, 6 weeks (about 1 and a half months), 12 weeks (about 3 months), 18 weeks (about 4 months), and 26 weeks (about 6 months).

Pain intensity

Pain intensity was measured by the 11-point Numerical Pain Rating Scale (NPRS) for the participant’s primary reported pain area [8-10]. The following question was asked: “For your primary pain area (the location that typically bothers you the most), how do you rate your pain level over the last 7 days? (0=no pain at all; 5=moderate pain; 10=worst pain imaginable).

Responders to the Soovu treatment were those who decreased their pain rating by 2 points or 30%. The IMMPACT guidelines for clinical trials on pain treatment state that pain reduction of 2 points or 30% were associated with patient ratings of “much improved [11,12].”

Pain Interference on Quality of Life

Pain interference was measured with this question: “In the past 7 days, how much did pain interfere with each of the following?” The question was asked for: Enjoyment of life; Ability to concentrate: Day-to-day activities; Enjoyment of recreational activities; Outside of home tasks (e.g. getting groceries, running errands, etc.); Socializing with others; Sleep [13].

Anxiety

Anxiety was assessed with this question: “Over the past 7 days, how do you rate your level of anxiety? Select a number between 0 and 100 where 0 is no anxiety at all and 100 is anxiety at the highest level.”

Nervousness

Nervousness was assessed with this question: “Over the past 7 days, how do you rate how nervous you’ve been? Select a number between 0 and 100 where 0 is not nervous at all and 100 is nervous

at the highest level.”

Tension

Tension was assessed with this question: “Over the past 7 days, how do you rate how tense you’ve been? Select a number between 0 and 100 where 0 is not tense at all and 100 is tense at the highest level.”

Productivity

Productivity was assessed with this question: “During the past 7 days, how much did your pain affect your productivity while you were working? Think about days you were limited in the amount or kind of work you could do, days you accomplished less than you would like, or days you could not do your work as carefully as usual. If pain affected your work only a little, choose a low number. Choose a high number if pain affected your work a great deal.”

Healthcare utilization

Changes in healthcare utilization for pain management was assessed with this question: “Have you eliminated or reduced your use of therapeutic services such as chiropractor, physical therapist or massage since using Soovu?”

Medication utilization

Changes in medication utilization for pain management was assessed with this question: “Have you eliminated or reduced your use of pain medications (either prescription or over the counter) since using Soovu?

Engagement

Engagement with the Soovu System was assessed with the following measures: 1) number of weeks wherein participant completed 1 or more Soovu therapy sessions; 2) total number of Soovu therapy sessions completed.

Safety and Adverse Events

Patients were instructed to report any adverse events when they occurred to Soovu Customer Care and to their manager at the sponsoring health plan.

There was one adverse event reported to Soovu Customer Care during the six-month period in which an individual failed to operate the Soovu device according to the use instructions resulting in minor skin damage. The individual acknowledged ignoring several layers of safety warnings when using the device.

Statistical Analysis

For simplicity, we report statistical models fitted using mixedeffects models with the lmer function from the lmerTest package for R. This approach enables us to assess the treatment effect while accounting for the repeated measures on participants. We used the emmeans package for R to compare outcomes across baseline, 12 weeks, and 26 weeks. We note here that several outcomes are on the ordinal scale: Self-Reported Pain Intensity (0-10), Pain Interference on Quality of Life (0-10), Anxiety (0-100), Nervous Feelings (0-100), Tension (0-100). Parallel analyses using cumulative link mixed models, fitted with the clmm function from the ordinal package in R, yielded consistent significance results and interpretation with those reported below.

To formally evaluate whether treatment reduced outcome measures through reduction in Self-Reported Pain Intensity, we fit mediation models using the mediate function from the mediation package in R. These models enable us to untangle a total treatment effect into an average causal indirect effect, which quantifies the effect of the treatment on each outcome measure through reductions in Self-Reported Pain intensity, and an average causal direct effect, representing the effect of the treatment on each outcome measure.

Results

Completion Rates

We obtained responses from 199 participants at baseline. Six participants who reported a pain level of 4 or greater at prescreening but then reported a pain level of 3 or lower at the baseline survey were excluded from analysis. Further, twenty participants who used the device fewer than 3 times over the timeline of the study were also excluded from analysis. Of the 173 participants included, we obtained 159 (91.9%) at the six-week follow-up, 147 (85%) at the 12-week follow-up, 151 (87.3%) at the 18-week follow-up, and 150 (86.7%) at the 26-week follow-up.

Pain Intensity

Self-Reported Pain Intensity was significantly lower at 12 Weeks, and lowest by 26 Weeks compared to baseline (Tables 2-3, Figure 1). Patients experienced an initial statistically significant decrease in self-reported pain intensity at 12 weeks (t=5.99, p<0.001) and a smaller subsequent statistically significant decrease at 26 weeks (t=2.77, p=0.0163). Of note, 39.3% of the 150 participants providing self-reported pain intensity at baseline and 26 weeks showed a clinically meaningful reduction in pain intensity, defined as ≥30% reduction in pain intensity. By baseline pain intensity, 37.6% of 93 patients with moderate pain intensity (4-6), and 42.1% of 57 participants with severe pain intensity (7-10) experienced a clinically meaningful reduction in pain intensity (Figure 2).

Table 2: Linear mixed effects model for self-reported pain.

Table 3: Contrasts of estimated marginal means comparing Self-Reported Pain Intensity at baseline, 12 weeks and 26 weeks.

Figure 1: Estimated marginal mean self-reported pain intensity at baseline, 12 weeks, and 26 weeks.

Figure 2: The proportion of participants who experienced a clinically meaningful reduction in pain intensity (a ≥30% reduction; orange), reduced (grey), same or reduced (light grey). Estimated marginal mean self-reported pain intensity at baseline, 12 weeks, and 26 weeks.

Pain Interference with Activities and Quality of Life

The causal mediation model results in Table 4 demonstrate that treatment had statistically significant direct, mediated, and total effects decreasing pain interference with Enjoyment of Life, Day to Day Activities, Recreational Activities, Outside of Home Tasks, Sleep, as well as Anxiety and Tension by 26 weeks. Additionally, treatment had a statistically significant total and mediated effects decreasing pain interference with the Ability to Concentrate, Socializing with Others, and Productivity. Finally, we observed statistically significant total and direct effects decreasing Nervous Feelings.

Table 4: Causal mediation model results assessing the total treatment effect, direct treatment effect, and mediated effect through reduction in Self-Reported Pain Intensity on Pain Interference on Quality of Life, Anxiety, Nervousness, Tension, and Productivity from baseline to 26 weeks. Note an asterisk indicates the scale is 0-100 instead of 0-10.

Medication and Healthcare Usage

At the end of the pilot, 32.4% of participants reported reducing or eliminating services that help manage pain. Services that were reduced or eliminated included: massage; physical therapy; chiropractic work; acupuncture; and injections. Three participants reported cancelling scheduled medical procedures because of the relief they received from the Soovu device. The procedures canceled were: 1 hysterectomy; 1 back surgery; and 1 round of injections.

Additionally, 46.8% of subjects who had been using medication to manage pain either reduced or stopped using medication to manage pain. Among the medication users, 80% of the subjects were using over-the-counter medication while 5% used prescription medication and 15% were using a combination of over-the-counter medication and prescription medication to manage pain.

Engagement with Soovu System

Study participants were instructed to use the Soovu System on an as-needed basis whenever pain arose or was anticipated. In general, the Soovu System was used more in the first months of the pilot (nearly 1000 times in week 2) and declined over time (just under 100 times at week 26) (Figure 3). Approximately 12.7% of participants remained consistently engaged (at least one session per week) at 6 months (Figure 3). All participants were asked if they felt Soovu helped manage their pain; 90.7% responded in the affirmative. While some fall off in device usage is expected with all medical wearables, it can be hypothesized that Soovu helps users reduce pain, and in some cases, resolve pain to a low enough level that ongoing use of the device is not necessary.

Figure 3: The Number of Soovu users (grey) and treatments (orange) conducted per week through week 26.