Neonatal automated oxygen titration algorithms: response characteristics and performance.

OBJECTIVE: Neonatal respiratory support devices now have algorithms for automated adjustment of oxygen concentration (fraction of inspired oxygen (FiO2)) in response to oxygen saturation (SpO2) disturbances, but their performance has not been systematically examined. We investigated the response of six available devices and algorithms to standardised and simulated SpO2 disturbances. DESIGN: Bench-top study in neonatal centres. METHODS: Devices under study received SpO2 input from a vital signs simulator at 1 Hz; device response was recorded as measured FiO2 in the respiratory circuit. Response to protracted hypoxaemia (SpO2=80%) and hyperoxaemia (SpO2=98%) was examined in several test conditions. In closed-loop testing, measured FiO2 was combined with abstracted patient data in an oxygenation simulator, generating novel SpO2 values input to the device. Device capability in keeping simulated SpO2 in target range (91-95%) was examined, as was FiO2 adjustment frequency and propensity for FiO2 oscillation. RESULTS: The FiO2 trajectories in response to SpO2 disturbances differed considerably between devices. Maximum rate of sustained FiO2 escalation (ΔFiO2/min) during hypoxaemia was Avea: 0.30; Fabian: 0.20; Leoni: 0.20; SLE: 0.10; Sophie: 0.062; Vapotherm: 0.30. Corresponding values for FiO2 reduction during hyperoxaemia were 1.20, 0.20, 0.20, 0.13, 0.53 and 1.32. In closed-loop testing, average SpO2 target range time proportion was 51%, 52%, 55%, 77%, 64% and 53% for the six devices, respectively, with 1.9-5.1 automated FiO2 adjustments/min, in some cases with a prominent oscillatory pattern. CONCLUSIONS: Automated oxygen control devices exhibit considerable variation in their FiO2 response to SpO2 disturbances, with important consequences for SpO2 targeting potential and the pattern of FiO2 adjustment.