In vitro evaluation of delays in the adjustment of the fraction of inspired oxygen during CPAP: effect of flow and volume

Reducing the time delay of oxygen transport to the neonate on continuous positive airway pressure support: A bench study

Background

Premature newborns often require oxygen support as part of their therapy. Systems for oxygen administration are developed to assure adequate oxygenation of newborns. Several factors were identified in the systems that contribute to the time delay between the change in the set inspiratory oxygen fraction and its actual delivery to tissues. In this study, we aimed to reduce the physical delay in oxygen delivery to newborns.

Methods

We developed an O₂ Flush System (O₂-FS) that brings the source of oxygen as close to a patient as possible to make oxygen available for rapid delivery that compensates for the physical delay in the ventilator circuit. The O₂-FS system is built around an electromechanical on/off valve. We validated the O₂-FS concept in experiments with non-invasive Continuous Positive Airways Pressure (CPAP) ventilators.

Results

The O₂-FS accelerated oxygen delivery with all the tested systems and arrangements, typically by 5-15 s. We also observed that the application of supplemental oxygen increased the pressure in the ventilator circuit by 3-4 cmH₂O which may mitigate the apneic pauses that are common in premature newborns.

Conclusions

The O₂-FS system may work as a universal accessory of the CPAP lung ventilator and shorten the distribution of oxygen to the patient during oxygen desaturation events, possibly eliminating or interrupting apneic pauses in neonates, for whom oxygen therapy is an essential treatment. In clinical practice, the O₂-FS could help maintain normoxemic saturation values through adequate oxygen dosing in preterm neonates, thus reducing morbidity and mortality.

Randomised crossover trial comparing algorithms and averaging times for automatic oxygen control in preterm infants

OBJECTIVE

Automatic control (SPOC) of the fraction of inspired oxygen (FiO₂), based on continuous analysis of pulse oximeter saturation (SpO₂), improves the proportion of time preterm infants spend within a specified SpO₂-target range (Target%). We evaluated if a revised SPOC algorithm (SPOC_new, including an upper limit for FiO₂) compared to both routine manual control (RMC) and the previously tested algorithm (SPOC_old, unrestricted maximum FiO₂) increases Target%, and evaluated the effect of the pulse oximeter's averaging time on controlling the SpO₂ signal during SPOC periods.

DESIGN

Unblinded, randomised controlled crossover study comparing 2 SPOC algorithms and 2 SpO₂ averaging times in random order: 12 hours SPOC_new and 12 hours SPOC_old (averaging time 2 s or 8 s for 6 hours each) were compared with 6-hour RMC. A generated list of random numbers was used for allocation sequence.

SETTING

University-affiliated tertiary neonatal intensive care unit, Germany PATIENTS: Twenty-four infants on non-invasive respiratory support with FiO₂ >0.21 were analysed (median gestational age at birth, birth weight and age at randomisation were 25.3 weeks, 585 g and 30 days).

MAIN OUTCOME MEASURE

Target%.

RESULTS

Mean (SD) [95% CI] Target% was 56% (9) [52, 59] for RMC versus 69% (9) [65, 72] for SPOC_old__2s, 70% (7) [67, 73] for SPOC_new__2s, 71% (8) [68, 74] for SPOC_old__8s and 72% (8) [69, 75] for SPOC_new__8s.

CONCLUSIONS

Irrespective of SpO₂-averaging time, Target% was higher with both SPOC algorithms compared to RMC. Despite limiting the maximum FiO₂, SPOC_new remained significantly better at maintaining SpO₂ within target range compared to RMC.

TRIAL REGISTRATION

NCT03785899.

Comparison of two devices for automated oxygen control in preterm infants: a randomised crossover trial

OBJECTIVE

To compare the effect of two different automated oxygen control devices on target range (TR) time and occurrence of hypoxaemic and hyperoxaemic episodes.

DESIGN

Randomised cross-over study.

SETTING

Tertiary level neonatal unit in the Netherlands.

PATIENTS

Preterm infants (n=15) born between 24+0 and 29+6 days of gestation, receiving invasive or non-invasive respiratory support with oxygen saturation (SpO₂) TR of 91%-95%. Median gestational age 26 weeks and 4 days (IQR 25 weeks 3 days-27 weeks 6 days) and postnatal age 19 (IQR 17-24) days.

INTERVENTIONS

Inspired oxygen concentration was titrated by the OxyGenie controller (SLE6000 ventilator) and the CLiO₂ controller (AVEA ventilator) for 24 hours each, in a random sequence, with the respiratory support mode kept constant.

MAIN OUTCOME MEASURES

Time spent within set SpO₂ TR (91%-95% with supplemental oxygen and 91%-100% without supplemental oxygen).

RESULTS

Time spent within the SpO₂ TR was higher during OxyGenie control (80.2 (72.6-82.4)% vs 68.5 (56.7-79.3)%, p<0.005). Less time was spent above TR while in supplemental oxygen (6.3 (5.1-9.9)% vs 15.9 (11.5-30.7)%, p<0.005) but more time spent below TR during OxyGenie control (14.7 (11.8%-17.2%) vs 9.3 (8.2-12.6)%, p<0.05). There was no significant difference in time with SpO₂ <80% (0.5 (0.1-1.0)% vs 0.2 (0.1-0.4)%, p=0.061). Long-lasting SpO₂ deviations occurred less frequently during OxyGenie control.

CONCLUSIONS

The OxyGenie control algorithm was more effective in keeping the oxygen saturation within TR and preventing hyperoxaemia and equally effective in preventing hypoxaemia (SpO₂ <80%), although at the cost of a small increase in mild hypoxaemia.

TRIAL REGISTRY NUMBER

NCT03877198.

Automation of oxygen titration in preterm infants: Current evidence and future challenges

For the preterm infant with respiratory insufficiency requiring supplemental oxygen, tight control of oxygen saturation (SpO₂) is advocated, but difficult to achieve in practice. Automated control of oxygen delivery has emerged as a potential solution, with six control algorithms currently embedded in commercially-available respiratory support devices. To date, most clinical evaluations of these algorithms have been short-lived crossover studies, in which a benefit of automated over manual control of oxygen titration has been uniformly noted, along with a reduction in severe SpO₂ deviations and need for manual FiO₂ adjustments. A single non-randomised study has examined the effect of implementation of automated oxygen control with the CLiO₂ algorithm as standard care for preterm infants; no clear benefits in relation to clinical outcomes were noted, although duration of mechanical ventilation was lessened. The results of randomised controlled trials are awaited. Beyond the gathering of evidence regarding a treatment effect, we contend that there is a need for a better understanding of the function of contemporary control algorithms under a range of clinical conditions, further exploration of techniques of adaptation to individualise algorithm performance, and a concerted effort to apply this technology in low resource settings in which the majority of preterm infants receive care. Attainment of these goals will be paramount in optimisation of oxygen therapy for preterm infants globally.