Healthy Volunteers  Inclusion Criteria:  Participant is Aged 18 or above Participant has capacity to understand written English Participant is not on regular prescription medicines Participant has an RSI score of 0 Participant has a body mass index (BMI) of 18.5 - 34.9 kg/m2 (bounds included)  Exclusion Criteria:  Participant has experienced any symptoms of LPR or GORD symptoms in the past year Participant has taken any medication for GORD/LPR in the past year (e.g. proton pump inhibitors, h2 antagonists, over the counter antacids) Participant has active oral disease Participant has a significant medical diagnosis  Patients with symptoms of LPR  Inclusion Criteria:  Participant is Aged 18 or above Participant has capacity to understand written English Participant has an RSI score of >13 Participant has a body mass index (BMI) of 18.5 - 34.9 kg/m2 (bounds included Participant has been referred for 24hr ambulatory pH-impedance monitoring  Exclusion Criteria:  Participant has active oral disease Participant has other ongoing health problems that could account for their LPR symptoms. Participant has NOT undergone nasoendoscopy within last 6 months OR does not have one scheduled within next 6 weeks Previous antireflux surgery (e.g. fundoplication or magnetic sphincter augmentation) Previous bariatric surgery (e.g. gastric bypass or sleeve gastrectomy)