This study is designed to investigate whether non-invasive ultrasound (US) that is optimized for stimulation and can elicit an anti-inflammatory response in people with Inflammatory Arthritis as compared to a sham intervention. The primary endpoint is the change in pro-inflammatory cytokines in blood drawn before and after US. Each participant receives 4 experimental US sessions, one of which is randomly assigned to be placebo.

The CAP has demonstrated potential as a treatment for various autoimmune and inflammatory disorders, including inflammatory arthritis (Rheumatoid Arthritis, Psoriatic Arthritis, Ankylosing Spondylitis) and Inflammatory Bowel Disease (Ulcerative Colitis and Crohn's Disease).

The target populations for this study include healthy volunteers and individuals aged 22-75 years diagnosed with Rheumatoid Arthritis (RA), Psoriatic Arthritis (PsA) or Ankylosing Spondylitis (AS) by a board-certified rheumatologist.

Up to 20 healthy volunteers and 40 individuals with RA or PsA will be enrolled. After an initial blood draw, participants will receive either active or sham ultrasound during each visit. There will be a total of 5 visits involving ultrasound, with 2 being a sham and 3 being active. The visit in which the sham is administered will be determined according to the Randomization Table. To ensure participant safety, the ultrasound parameters used for the active sessions will not exceed the FDA's limits.

After the US is completed, participants should be asked to wait in the clinic for a few hours following the completion of the US intervention, after which they will have a second blood draw. Once the second blood draw is completed, participants may leave and resume their regular diet. Participants will be asked to return after 24 hours of their intervention for their third blood draw.

Healthy Volunteer Population

Inclusion Criteria:

• 22-75 years of age
• Weigh at least 40 kg

Exclusion Criteria:

• Any physical disabilities, conditions, or diseases that limit the capacity to participate in study procedures or increase the risk of harm as determined by the study PI
• Unable to provide informed consent
• Active bacterial or viral infection
• Class II obesity with a BMI of 35 or higher
• Pregnant women or those trying to become pregnant
• Active use of tobacco/nicotine products
• History of substance use disorder or active regular use of substances (nicotine, marijuana, cocaine, psychedelics, stimulants, etc.)
• Splenomegaly, asplenia, or splenectomy

Inflammatory Arthritis Population

Inclusion Criteria:

• 22-75 years of age
• Weigh at least 40 kg
• Diagnosis of Rheumatoid Arthritis, Psoriatic Arthritis, or Axial Spondyloarthritis of at least 6 months duration as defined by ACR guidelines
• Able to continue the same stable dose of immunomodulatory medication(s) while participating in the study

Exclusion Criteria:

• Unable to provide informed consent
• Took a JAK inhibitor within the last 4 weeks, or likely to start one while participating in this study
• Started a conventional synthetic DMARD (csDMARD) within the last 8 weeks or had a change in prescription within the last 4 week
• Started a Tumor Necrosis Factor (TNF) inhibitor within the last 5 months or had a change in prescription within the last 3 months
• Started any other biologic or targeted synthetic DMARD within the last 3 months, or likely to start one while participating in the study
• Started a corticosteroid, had a change in prescription, or on a stable dose = or > 10 mg of prednisone daily within the last 4 weeks
• Regular use of epinephrine like medications (cold, cough, congestion, or sinus medications, bronchodilators, appetite suppressants)
• Active use of tobacco/nicotine products
• History of substance use disorder or likely use of substances during the study period (marijuana, opioids/heroin, cocaine, psychedelics, methamphetamine, etc.)
• Active bacterial or viral infection
• Receiving chemotherapy or immunotherapy to treat malignancy
• Significant immunodeficiency due to underlying illness
• Class II obesity with a BMI of 35 or higher
• Pregnant women or those trying to become pregnant
• Wound, rash, infection, or traumatic injury over the target area
• Vagal nerve injury or vagotomy
• Surgery or major traumatic injury in the past 90 days
• Chronically-implanted medical devices (i.e. pacemaker, AICD, vagus nerve stimulator, spinal cord stimulator)
• Clinically significant cardiovascular disease
• CKD Stage 3 or higher
• Uncontrolled fibromyalgia or other diffuse pain syndromes