Summary: Randomised cross-over study of automated oxygen control for preterm infants receiving nasal high flow.

Topic: Automated Oxygen Control

Reynolds PR, Miller TL, Volakis LI, et al. Randomised cross-over study of automated oxygen control for preterm infants receiving nasal high flow. Archives of Disease in Childhood – Fetal and Neonatal Edition2019;104:F366-F371

Reynolds and colleagues performed a randomized crossover study in two neonatal intensive care units (NICU) to evaluate a prototype automated controller (IntellO2) of the inspired fraction of oxygen (FiO2) in maintaining a target range of oxygen saturation (SpO2) in preterm babies receiving nasal high flow (HF). The IntellO2 works with the Vapotherm Precision Flow®, using a closed-loop control algorithm, using pulse oximetry as the primary input signal with signal averaging set at 8 seconds (Masimo, Irvine, CA, USA) to target a user-set SpO2 value. In this trial, the researchers evaluated automated versus manual control of FiO2 to maintain a target SpO2 range of 90%–95% (or 90%–100% if FiO2=21%). The authors cite avoiding both hypoxia and hyperoxia in the preterm infant as an important goal and rationale behind the investigation. They report that while additional training improves compliance, manual maintenance of the target range 90%–95% may only be achieved less than 50% of the time. 

The study was conducted in the NICU’s at St Peter’s Hospital, Surrey, UK (United Kingdom), and Oxford University Hospitals NHS Foundation Trust, Oxford, UK as a prospective two center order-randomized crossover study. The study enrolled preterm infants receiving HF at FiO2 ≥25%. Inclusion criteria was that patients would require at least 12 adjustments of FiO2 during the manual arm to ensure adequate algorithm testing. Exclusion criteria were as follows: (A) presence of major congenital abnormalities; (B) hemodynamic instability; (C) seizures; (D) ongoing sepsis; (E) meningitis; or (F) clinician’s concern regarding infant stability. The study included and analyzed data from 30 preterm infants with median gestational age of 26 weeks (24–27) weeks, study age of 29 (18–53) days and study weight 1080 (959–1443) grams. 

Babies were randomized to start on either manual or automated mode. SpO2 (alarm range 90%–95%) was continuously monitored on the NICU monitors as per normal standard of care. In manual mode, all FiO2 adjustments were made by clinical staff as needed. In automated mode, FiO2 was adjusted by the IntellO2, set to maintain a single SpO2 value of 93%. Staff could adjust all settings, including oxygen, in both modes, depending on clinical judgement. In both arms, data for FiO2, SpO2, pulse rate, flow, mode, and manual adjustments were logged by the IntellO2. Staff recorded the time and reason for all manual oxygen adjustments, and any cares or procedures which could affect SpO2. The study period in each arm was run consecutively for 24 hours. 

The primary outcome measure was percent of time spent within the target SpO2 range. Secondary outcomes included the overall proportion and durations of SpO2 within specified hyperoxic and hypoxic ranges and the number of in range episodes per hour. The results showed that babies in the automated arm spent significantly more time in the target range 80% (70–87) versus the manual arm 49% (40–57); p<0.0001). There were fewer episodes of SpO2 below 80% lasting at least 60 secs under automated control (0 (IQR 0–1.25)) compared with manual control (5 (IQR 2.75–14)). In addition, babies spent a lower proportion of time with SpO2 >95% in the automated versus manual arm (12% vs 23%; p<0.0001). There were more oversaturation episodes in the automated arm than the manual arm (37 vs 18 episodes/hour; p<0.0001) but the episodes were typically very brief and corrected back to the target range (12 vs 48 s; p<0.0001), resulting in the overall reduction in hyperoxic exposure seen in the automated arm findings. At SpO2 above 98% there were no differences in the episode frequency between the study arms.  

The authors caution that automated control of oxygen has the potential to reduce the reliability of the pulse oximetry identification of desaturation episodes as a clinically useful diagnostic indicator of the baby’s stability. Therefore, alternative indicators to inform the caregivers of clinical deterioration must be in place to prevent false reassurance provided by a stable SpO2 such as the progressive increase in oxygen requirement to maintain such stable pulse oximetry readings. 

The results showed that under automated control by the IntellO2, the babies in this study spent 31% more time in the target SpO2 range (80% vs 49%), and less time in hypoxic or hyperoxic SpO2 ranges. The findings concluded that the IntellO2 device in automated control mode maintained preterm babies’ SpO2 in the target SpO2 range significantly more effectively than manual control when receiving HF and reduced the duration of hypoxic and hyperoxic episodes. The authors note that a larger study is needed to determine if this better targeting would improve clinical outcomes. 

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