Feasibility of Noninvasive Trigeminal Nerve Stimulation During Exercise

Arm1 - Healthy Volunteers Inclusion Criteria: * Adults aged 18-50 years * BMI 18-30 kg/m² * Ability to provide informed consent and complete study procedures in English Exclusion Criteria: * Current daytime respiratory impairment such as uncontrolled asthma, uncontrolled COPD, pneumonia, or interstitial lung disease * Use of supplemental oxygen * Pregnancy or breastfeeding * Current use of acetazolamide, Sodium-glucose cotransporter-2 (SGLT2) inhibitors, or daily opioids * History of claustrophobia or panic disorder * Metallic implants in the craniofacial or cervical region that may interfere with electrode placement or electrical stimulation * Implanted cardiac or neuroelectric device (e.g., pacemaker, implantable cardioverter-defibrillator (ICD), deep brain stimulator, vagus nerve stimulator, implanted drug pump) * Open, broken, inflamed, infected, or healing skin lesions at or near facial electrode placement sites * Resting heart rate \<60 Beats Per Minute * History of seizure disorder or epilepsy Arm 2 -COPD Inclusion Criteria: * Adults aged 40-75 years * Confirmed diagnosis of COPD by spirometry (post-bronchodilator Forced Expiratory Volume (FEV1) /Forced Vital Capacity (FVC) \<0.70) or provider documentation in medical records * Modified Medical Research Council (mMRC) dyspnea grade ≥2 * Stable COPD (no exacerbation requiring hospitalization, systemic corticosteroids, or antibiotic therapy within the preceding 6 weeks) * On stable COPD therapy for at least 4 week…