Presently oxygen is titrated against saturation (SpO2) by manual adjustment. Automated or servo-control systems have been developed that result in tighter control of SpO2 and more time spent in the intended target range. These systems are already in clinical use. Automated systems produce quite large fluctuations in fraction of inspired oxygen (FiO2) in order to keep SpO2 in range. It is possible that this could result in short periods of high or low oxygen tension (PO2) that are undetectable using saturation monitoring. Studies to date have examined the effects of manual and automated (servo) oxygen targeting on SpO2 but not on transcutaneous oxygen tension (TcPO2). There are no studies directly comparing two automated systems.
There is a need to determine the achieved SpO2 and TcPO2 distributions associated with the use of different automated control systems as a first step in planning future trials. When this is measured over a small number of hours it is not anticipated that this would have an influence on clinical outcome.
This study is a prospective, single centre, randomised crossover trial of two automated (servo) control devices - IntellO2 (Vapotherm, USA) versus Leoni plus CLAC (Löwenstein Medical, Germany) - delivering nasal high flow employing automated oxygen titration. Each infant will act as their own control. Infants born at less than 30 weeks gestation, greater than 48 hour of age and receiving supplementary oxygen will be eligible for inclusion.
The study will be undertaken in the Neonatal Unit at the Simpson Centre for Reproductive Health at the Royal Infirmary of Edinburgh.
Total study time is 12 hours for each infant. Infants will be randomised to commence on either automated (servo) control using either Leoni plus CLAC or IntellO2, Vapotherm. SpO2 (range 90-95%) will be continuously monitored as per normal standard of care. A second pulse oximetry probe will be place for servo control input.
Additional monitoring will be carried out as shown below:
1. TcPO2 monitoring
2. FiO2 monitoring
3. Heart rate monitoring (used to validate SpO2 readings)
4. Arterial gas sampling (only if conducted by the direct care team as part of the routine care of the infant; no extra blood samples will be taken as part of the study)
FiO2 will be adjusted by the respiratory support devices which have integrated automated oxygen control, set to maintain a SpO2 target range of 90-95%. The IntellO2 device uses Precision Flow technology (IntellO2, Vapotherm, USA). By means of a modified closed-loop algorithm, the devise uses Masimo pulse oximetry to target a user-set SpO2 value. The Leoni plus CLAC (Closed-Loop Automated oxygen Control) ventilator (Leoni plus, Löwenstein Medical, Germany) similarly uses MasimoSET (Signal Extraction Technology) to target SpO2 and automate oxygen control. Both devices have a signal averaging time of 8 seconds (Masimo, Irvine, USA). The Leoni plus CLAC algorithm is set to a 30 seconds wait time between adjustments, allowing up to 120 automated adjustments/hour.
SpO2 readings will be downloaded directly from the multiparameter patient monitor. SpO2 will be measured using a Phillips MX500 multiparameter monitor (Phillips, Germany, CE 0366). TcPO2 will be measured using a SenTec Digital Monitoring System with OxiVent sensor (SenTec AG, Switzerland, European patent No. 1535055, CE 0120). Both monitors are routinely used in clinical practice. Transcutaneous data will be recorded contemporaneously and the site of the transcutaneous probe will be rotated on each infant every 2 hours. Control of sensor temperature and application duration are designed to meet all applicable standards and this monitoring device is use routinely in many neonatal units.
