Evaluating a Wearable Bronchodilator Device in People with Asthma

Participants will complete all three intervention conditions, participants will be randomly assigned to the order of conditions: • TENS wearable device • Inhaled SABA only (current standard of care), • TENS wearable device and SABA Study setting This study will be conducted at the University of Auckland’s Newmarket Campus, within the Department of Exercise Science. The department is equipped with the necessary exercise and medical equipment to safely conduct spirometry testing and standardised exercise challenges. Participants will be recruited from previous research cohorts, across the Auckland region, and through the researchers’ professional networks. All study visits—including screening, and intervention—will take place at the Newmarket Campus, which provides a controlled environment for consistent data collection and participant safety. Transcutaneous Electrical Nerve Stimulation (TENS) TENS will be applied to participants using electrodes attached to a CE marked TENS device (NeuroTrac TENS, Verity Medical Ltd., United Kingdom). A (previously defined) research nurse will deliver the interventions. All study procedures will be explained to eligible participants by a member of the study team. Informed written consent will be obtained from participants directly following written information and a verbal explanation of the study during the first study visit (screening visit). Procedure Only participants who provide informed consent and meet the criteria for exercise-induced bronchoconstriction (EIB) during the screening visit (Visit 1) will proceed to the three study visits . Participants will be asked to refrain from undertaking any physical exercise in the 24 hours prior to your visit. Participants needs to avoid eating large meals 2 hours prior to visit and avoid consuming caffeine within 6 hours prior to visit. Participants will also need to avoid use of SABA e.g. Ventolin, Bricanyl for 6–8 hours before the test and withhold LABA e.g. Serevent, Symbicort, Seretide for 12 hours for twice-daily dosed LABA inhalers. Each clinic visit will follow the same procedure, with the intervention varying by arm: 1. Baseline assessment: • Lung function (spirometry) • Respiratory monitoring (Capnography) (baseline, during and post-treadmill) 2. Continuous sensory monitoring (baseline and post-treadmill): • ECG and wearable heart rate monitor • Capnograph (Expired CO2 monitorization), • Electrical impedance sensor, • Microphone acoustically coupled to the body, • IMU (inertial measurement unit including 3 axis acceleration and 3 axis gyroscope) • Nasal cannula 3. Intervention (if applicable to the allocated arm) • Administration of salbutamol and /or (participants will be required to bring and use their own salbutamol inhaler throughout the study) • Application of the transcutaneous electrical nerve stimulation (TENS) with CE certified device for 6 minutes For this current study TENS will be delivered at 200Hz. Two electrodes (32mm diameter) will be placed bilaterally on the back within the T-3 dermatome (5cm lateral to the lower border of the T-3 spinous process) immediately post-exercise and stimulation will occur for 6 minutes. The TENS current will be adjusted to obtain a sense of tingling and visible localized rhomboid muscle contractions. All stimulation currents will be kept at a comfortable range for the participants; prior studies show that there were no subjective perceptions of pain reported. The strength of the TENS (milliamperes; mA), will be between 9mA and 14mA, and the pulse bandwidth 175 mS width bipolar square waveform. 4. Exercise challenge: • 8 min exercise task . 5. Post exercise assessment: a. Capnography b. Lung function (Spirometry) completed at 5, 10, 15, 30 minute post exercise. Exercise challenge: An exercise protocol previously validated in an Exercise Induced Bronchoconstriction (EIB) Albuterol/budesonide asthma study will be used in all four study visits. On all four visits, the participants will be asked to exercise on an off-the-shelf treadmill for eight minutes. Similar to the EIB diagnostic test used by Leff et al. (1998), the first two minutes will be used as a warmup to reach 80 to 90% of maximum Heart Rate(HR) and the speed adjusted throughout the remaining six minutes to maintain HR between these limits. HR will be monitored which will primarily be used within the first two minutes to ensure the participant reaches the target intensity. Every effort will be made to perform the exercise challenge at roughly the same time of day, ideally 72 hours apart for each participant. Participants will be continuously monitored by trained health professionals with over 25 years of clinical experience and a safety plan has been generated in the case of any adverse event arising in any of the visits. Patient reported measures (e.g. wellbeing, asthma control) will be collected at each of the four study visits (assessed by the Asthma Control Test (ACT))25 and wellbeing (assessed by WHO-5)26. Asthma control and wellbeing will be assessed via longer validated questionnaires (ACT and WHO-5) every study visit based on their previous 2 weeks. Participant acceptability of the devices used in the study will be assessed using an adapted version of the System Usability Scale27 and questionnaire informed by the Technology Acceptance Model.