Transcutaneous Oxygen and Nasal High Flow in healthy adults

Absence or presence of a transcutaneous oxygen partial pressure (TcO2) plateau. A transcutaneous oxygen monitor will be used to continuously record in TcO2 measurements for the entire duration of the study.

Transcutaneous oxygen partial pressure (TcO2) is a non-invasive method to measure oxygen partial pressure in participants. TcO2 may also be a useful method to measure the effectiveness of oxygenation in humans, particularly of use in future clinical studies involving healthy volunteers assessing the performance of novel extensions to the NHF system. However, the reliability of TcO2 to measure the effectiveness of oxygenation via NHF has not been previously investigated. The study is a two arm, randomised controlled, crossover feasibility study to explore transcutaneous oxygen partial pressure (TcO2) as a potential measure for the effectiveness of oxygenation using NHF. Participants will be given NHF at the following flow rates with the standard mechanical flow meter: - Treatment A: 100% O2 at 10 L/min - Treatment B: 100% O2 at 70 L/min Participants will be randomised (1:1) to the sequence of treatment (A-B or B-A). Participants will be instructed to breath normally for the duration of the study, maintaining a respiratory rate of approximately 10-12 breaths per minute. Participants will be given the first flow rate for 30 minutes or until TcO2 reaches a plateau, whichever occurs first. A plateau is defined as when TcO2 increases no more than 1 kPa over 5 minute. Nasal high flow will then be stopped and TcO2 will be monitored for 1 hour or until TcO2 returns to baseline (+/- 1kPa), whichever occurs first. Then the process will be repeated with the second flow rate. We will include 6 participants randomised at a 1:1 ratio, 3 participants per crossover sequence. The feasibility endpoints for this study will be: ability to achieve TcO2 plateau, time to TcO2 plateau (if present), time from TcO2 plateau (if present) to baseline, and inter- and intra- participant variability of TcO2. Adverse events will also be collected. We are conducting this study to confirm whether these endpoints are obtainable and useful for a future non-inferiority study. Data from this study will also be used to calculate the sample size needed for the proposed future study.