Closed-loop control of inspired oxygen in premature infants

Extended CPAP or low-flow nasal cannula for intermittent hypoxaemia in preterm infants: a 24-hour randomised clinical trial

OBJECTIVE

Optimal timing of continuous positive airway pressure (CPAP) cessation in preterm infants remains undetermined. We hypothesised that CPAP extension compared with weaning to low-flow nasal cannula (NC) reduces intermittent hypoxaemia (IH) and respiratory instability in preterm infants meeting criteria to discontinue CPAP.

DESIGN

Single-centre randomised clinical trial.

SETTING

Level 4 neonatal intensive care unit.

PATIENTS

36 infants <34 weeks' gestation receiving CPAP≤5 cmH2O and fraction of inspired oxygen (FiO2) ≤0.30 and meeting respiratory stability criteria.

INTERVENTIONS

Extended CPAP was compared with weaning to low-flow NC (0.5 L/kg/min with a limit of 1.0 L/min) for 24 hours.

OUTCOMES

The primary outcome was IH (number of episodes with SpO2<85% lasting ≥10 s). Secondary outcomes included: coefficient of variability of SpO2, proportion of time in various SpO2 ranges, episodes (≥10 s) with SpO2<80%, median cerebral and renal oxygenation, median effective FiO2, median transcutaneous carbon dioxide and bradycardia (<100/min for≥10 s).

RESULTS

The median (IQR) episodes of IH per 24-hour period was 20 (6-48) in the CPAP group and 76 (18-101) in the NC group (p=0.03). Infants continued on CPAP had less bradycardia, time with SpO2 <91% and <85%, and lower FiO2 (all p<0.05). There were no statistically significant differences in IH<80%, median transcutaneous carbon dioxide or median cerebral or renal oxygenation.

CONCLUSION

In preterm infants meeting respiratory stability criteria for CPAP cessation, extended CPAP decreased IH, bradycardia and other hypoxaemia measures compared with weaning to low-flow NC during the 24-hour intervention.

TRIAL REGISTRATION NUMBER

NCT04792099.

Prolonged use of closed-loop inspired oxygen support in preterm infants: a randomised controlled trial

OBJECTIVE

This randomised study in preterm infants on non-invasive respiratory support investigated the effectiveness of automated oxygen control (A-FiO2) in keeping the oxygen saturation (SpO2) within a target range (TR) during a 28-day period compared with manual titration (M-FiO2).

DESIGN

A single-centre randomised control trial.

SETTING

A level III neonatal intensive care unit.

PATIENTS

Preterm infants (<28 weeks' gestation) on non-invasive respiratory support.

INTERVENTIONS

A-FiO2 versus M-FiO2 control.

METHODS

Main outcomes were the proportion of time spent and median area of episodes in the TR, hyperoxaemia, hypoxaemia and the trend over 28 days using a linear random intercept model.

RESULTS

23 preterm infants (median gestation 25.7 weeks; birth weight 820 g) were randomised. Compared with M-FiO2, the time spent within TR was higher in the A-FiO2 group (68.7% vs 48.0%, p<0.001). Infants in the A-FiO2 group spent less time in hyperoxaemia (13.8% vs 37.7%, p<0.001), but no difference was found in hypoxaemia. The time-based analyses showed that the A-FiO2 efficacy may differ over time, especially for hypoxaemia. Compared with the M-FiO2 group, the A-FiO2 group had a larger intercept but with an inversed slope for the daily median area below the TR (intercept 70.1 vs 36.3; estimate/day -0.70 vs 0.69, p<0.001).

CONCLUSION

A-FiO2 control was superior to manual control in keeping preterm infants on non-invasive respiratory support in a prespecified TR over a period of 28 days. This improvement may come at the expense of increased time below the TR in the first days after initiating A-FiO2 control.

TRIAL REGISTRATION NUMBER

NTR6731.

Automated oxygen delivery for preterm infants with respiratory dysfunction

BACKGROUND

Many preterm infants require respiratory support to maintain an optimal level of oxygenation, as oxygen levels both below and above the optimal range are associated with adverse outcomes. Optimal titration of oxygen therapy for these infants presents a major challenge, especially in neonatal intensive care units (NICUs) with suboptimal staffing. Devices that offer automated oxygen delivery during respiratory support of neonates have been developed since the 1970s, and individual trials have evaluated their effectiveness.

OBJECTIVES

To assess the benefits and harms of automated oxygen delivery systems, embedded within a ventilator or oxygen delivery device, for preterm infants with respiratory dysfunction who require respiratory support or supplemental oxygen therapy.

SEARCH METHODS

We searched CENTRAL, MEDLINE, CINAHL, and clinical trials databases without language or publication date restrictions on 23 January 2023. We also checked the reference lists of retrieved articles for other potentially eligible trials.

SELECTION CRITERIA

We included randomised controlled trials and randomised cross-over trials that compared automated oxygen delivery versus manual oxygen delivery, or that compared different automated oxygen delivery systems head-to-head, in preterm infants (born before 37 weeks' gestation).

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our main outcomes were time (%) in desired oxygen saturation (SpO2) range, all-cause in-hospital mortality by 36 weeks' postmenstrual age, severe retinopathy of prematurity (ROP), and neurodevelopmental outcomes at approximately two years' corrected age. We expressed our results using mean difference (MD), standardised mean difference (SMD), and risk ratio (RR) with 95% confidence intervals (CIs). We used GRADE to assess the certainty of evidence.

MAIN RESULTS

We included 18 studies (27 reports, 457 infants), of which 13 (339 infants) contributed data to meta-analyses. We identified 13 ongoing studies. We evaluated three comparisons: automated oxygen delivery versus routine manual oxygen delivery (16 studies), automated oxygen delivery versus enhanced manual oxygen delivery with increased staffing (three studies), and one automated system versus another (two studies). Most studies were at low risk of bias for blinding of personnel and outcome assessment, incomplete outcome data, and selective outcome reporting; and half of studies were at low risk of bias for random sequence generation and allocation concealment. However, most were at high risk of bias in an important domain specific to cross-over trials, as only two of 16 cross-over trials provided separate outcome data for each period of the intervention (before and after cross-over). Automated oxygen delivery versus routine manual oxygen delivery Automated delivery compared with routine manual oxygen delivery probably increases time (%) in the desired SpO2 range (MD 13.54%, 95% CI 11.69 to 15.39; I2 = 80%; 11 studies, 284 infants; moderate-certainty evidence). No studies assessed in-hospital mortality. Automated oxygen delivery compared to routine manual oxygen delivery may have little or no effect on risk of severe ROP (RR 0.24, 95% CI 0.03 to 1.94; 1 study, 39 infants; low-certainty evidence). No studies assessed neurodevelopmental outcomes. Automated oxygen delivery versus enhanced manual oxygen delivery There may be no clear difference in time (%) in the desired SpO2 range between infants who receive automated oxygen delivery and infants who receive manual oxygen delivery (MD 7.28%, 95% CI -1.63 to 16.19; I2 = 0%; 2 studies, 19 infants; low-certainty evidence). No studies assessed in-hospital mortality, severe ROP, or neurodevelopmental outcomes. Revised closed-loop automatic control algorithm (CLACfast) versus original closed-loop automatic control algorithm (CLACslow) CLACfast allowed up to 120 automated adjustments per hour, whereas CLACslow allowed up to 20 automated adjustments per hour. CLACfast may result in little or no difference in time (%) in the desired SpO2 range compared to CLACslow (MD 3.00%, 95% CI -3.99 to 9.99; 1 study, 19 infants; low-certainty evidence). No studies assessed in-hospital mortality, severe ROP, or neurodevelopmental outcomes. OxyGenie compared to CLiO2 Data from a single small study were presented as medians and interquartile ranges and were not suitable for meta-analysis.

AUTHORS' CONCLUSIONS

Automated oxygen delivery compared to routine manual oxygen delivery probably increases time in desired SpO2 ranges in preterm infants on respiratory support. However, it is unclear whether this translates into important clinical benefits. The evidence on clinical outcomes such as severe retinopathy of prematurity are of low certainty, with little or no differences between groups. There is insufficient evidence to reach any firm conclusions on the effectiveness of automated oxygen delivery compared to enhanced manual oxygen delivery or CLACfast compared to CLACslow. Future studies should include important short- and long-term clinical outcomes such as mortality, severe ROP, bronchopulmonary dysplasia/chronic lung disease, intraventricular haemorrhage, periventricular leukomalacia, patent ductus arteriosus, necrotising enterocolitis, and long-term neurodevelopmental outcomes. The ideal study design for this evaluation is a parallel-group randomised controlled trial. Studies should clearly describe staffing levels, especially in the manual arm, to enable an assessment of reproducibility according to resources in various settings. The data of the 13 ongoing studies, when made available, may change our conclusions, including the implications for practice and research.

Comparison of oxygen supplementation in very preterm infants: Variations of oxygen saturation features and their application to hypoxemic episode based risk stratification

Background

Oxygen supplementation is commonly used to maintain oxygen saturation (SpO₂) levels in preterm infants within target ranges to reduce intermittent hypoxemic (IH) events, which are associated with short- and long-term morbidities. There is not much information available about differences in oxygenation patterns in infants undergoing such supplementations nor their relation to observed IH events. This study aimed to describe oxygenation characteristics during two types of supplementation by studying SpO₂ signal features and assess their performance in hypoxemia risk screening during NICU monitoring.

Subjects and methods

SpO₂ data from 25 infants with gestational age <32 weeks and birthweight <2,000 g who underwent a cross over trial of low-flow nasal cannula (NC) and digitally-set servo-controlled oxygen environment (OE) supplementations was considered in this secondary analysis. Features pertaining to signal distribution, variability and complexity were estimated and analyzed for differences between the supplementations. Univariate and regularized multivariate logistic regression was applied to identify relevant features and develop screening models for infants likely to experience a critically high number of IH per day of observation. Their performance was assessed using area under receiver operating curves (AUROC), accuracy, sensitivity, specificity and F1 scores.

Results

While most SpO₂ measures remained comparable during both supplementations, signal irregularity and complexity were elevated while on OE, pointing to more volatility in oxygen saturation during this supplementation mode. In addition, SpO₂ variability measures exhibited early prognostic value in discriminating infants at higher risk of critically many IH events. Poincare plot variability at lag 1 had AUROC of 0.82, 0.86, 0.89 compared to 0.63, 0.75, 0.81 for the IH number, a clinical parameter at observation times of 30 min, 1 and 2 h, respectively. Multivariate models with two features exhibited validation AUROC > 0.80, F1 score > 0.60 and specificity >0.85 at observation times ≥ 1 h. Finally, we proposed a framework for risk stratification of infants using a cumulative risk score for continuous monitoring.

Conclusion

Analysis of oxygen saturation signal routinely collected in the NICU, may have extensive applications in inferring subtle changes to cardiorespiratory dynamics under various conditions as well as in informing clinical decisions about infant care.

Preliminary study of automated oxygen titration at birth for preterm infants

OBJECTIVE

To study the feasibility of automated titration of oxygen therapy in the delivery room for preterm infants.

DESIGN

Prospective non-randomised study of oxygenation in sequential preterm cohorts in which FiO₂ was adjusted manually or by an automated control algorithm during the first 10 min of life.

SETTING

Delivery rooms of a tertiary level hospital.

PARTICIPANTS

Preterm infants <32 weeks gestation (n=20 per group).

INTERVENTION

Automated oxygen control using a purpose-built device, with SpO₂ readings input to a proportional-integral-derivative algorithm, and FiO₂ alterations actuated by a motorised blender. The algorithm was developed via in silico simulation using abstracted oxygenation data from the manual control group. For both groups, the SpO₂ target was the 25th-75th centile of the Dawson nomogram.

MAIN OUTCOME MEASURES

Proportion of time in the SpO₂ target range (25th-75th centile, or above if in room air) and other SpO₂ ranges; FiO₂ adjustment frequency; oxygen exposure.

RESULTS

Time in the SpO₂ target range was similar between groups (manual control: median 60% (IQR 48%-72%); automated control: 70 (60-84)%; p=0.31), whereas time with SpO₂ >75th centile when receiving oxygen differed (manual: 17 (7.6-26)%; automated: 10 (4.4-13)%; p=0.048). Algorithm-directed FiO₂ adjustments were frequent during automated control, but no manual adjustments were required in any infant once valid SpO₂ values were available. Oxygen exposure was greater during automated control, but final FiO₂ was equivalent.

CONCLUSION

Automated oxygen titration using a purpose-built algorithm is feasible for delivery room management of preterm infants, and warrants further evaluation.

Statistical Description of SaO2–SpO2 Relationship for Model of Oxygenation in Premature Infants

A pulse oximeter model linking arterial (SaO2) and peripheral (SpO2) oxygen saturation is the terminal part of a mathematical model of neonatal oxygen transport. Previous studies have confirmed the overestimation of oxygen saturation measured by pulse oximetry in neonates compared to arterial oxygen saturation and the large variability of measured values over time caused by measurement inaccuracies. This work aimed to determine the SpO2 measurement noise that affects the biased SpO2 value at each time point and integrate the noise description with the systematic bias between SaO2 and SpO2. The SaO2–SpO2 bias was based on previously published clinical data from pathological patients younger than 60 days requiring ventilatory support. The statistical properties of the random SpO2 measurement noise were estimated from the SpO2 continuous recordings of 21 pathological and 21 physiological neonates. The result of the work is a comprehensive characterization of the properties of a pulse oximeter model describing the transfer of the input SaO2 value to the output SpO2 value, including the bias and noise typical for the bedside monitoring of neonates. These results will help to improve a computer model of neonatal oxygen transport.

Predictive Intelligent Control of Oxygenation (PRICO) in preterm infants on high flow nasal cannula support: a randomised cross-over study

OBJECTIVE

To investigate the efficacy of automated control of inspired oxygen (FiO2) by Predictive Intelligent Control of Oxygenation (PRICO) on the Fabian ventilator in maintaining oxygen saturation (SpO2) in preterm infants on high flow nasal cannula (HFNC) support.

DESIGN

Single-centre randomised two-period crossover study.

SETTING

Tertiary neonatal intensive care unit.

PATIENTS

27 preterm infants (gestational age (GA) <30 weeks) on HFNC support with FiO2 >0.25.

INTERVENTION

A 24-hour period on automated FiO2-control with PRICO compared with a 24-hour period on routine manual control (RMC) to maintain a SpO2 level within target range of 88%-95% measured at 30 s intervals.

MAIN OUTCOME MEASURES

Primary outcome: time spent within target range (88%-95%).

SECONDARY OUTCOMES

time spent above and below target range, in severe hypoxia (SpO2 <80%) and hyperoxia (SpO2 >98%), mean SpO2 and FiO2 and manual FiO2 adjustments.

RESULTS

15 patients received PRICO-RMC and 12 RMC-PRICO. The mean time within the target range increased with PRICO: 10.8% (95% CI 7.6 to 13.9). There was a decrease in time below target range: 7.6% (95% CI 4.2 to 11.0), above target range: 3.1% (95% CI 2.9 to 6.2) and in severe hypoxia: 0.9% (95% CI 1.5 to 0.2). We found no difference in time spent in severe hyperoxia. Mean FiO2 was higher during PRICO: 0.019 (95% CI 0.006 to 0.030). With PRICO there was a reduction of manual adjustments: 9/24 hours (95% CI 6 to 12).

CONCLUSION

In preterm infants on HFNC support, automated FiO2-control by PRICO is superior to RMC in maintaining SpO2 within target range. Further validation studies with a higher sample frequency and different ventilation modes are needed.

Effects of Perinatal Hyperoxia on Breathing

Air-breathing animals do not experience hyperoxia (inspired O₂ > 21%) in nature, but preterm and full-term infants often experience hyperoxia/hyperoxemia in clinical settings. This article focuses on the effects of normobaric hyperoxia during the perinatal period on breathing in humans and other mammals, with an emphasis on the neural control of breathing during hyperoxia, after return to normoxia, and in response to subsequent hypoxic and hypercapnic challenges. Acute hyperoxia typically evokes an immediate ventilatory depression that is often, but not always, followed by hyperpnea. The hypoxic ventilatory response (HVR) is enhanced by brief periods of hyperoxia in adult mammals, but the limited data available suggest that this may not be the case for newborns. Chronic exposure to mild-to-moderate levels of hyperoxia (e.g., 30-60% O₂ for several days to a few weeks) elicits several changes in breathing in nonhuman animals, some of which are unique to perinatal exposures (i.e., developmental plasticity). Examples of this developmental plasticity include hypoventilation after return to normoxia and long-lasting attenuation of the HVR. Although both peripheral and CNS mechanisms are implicated in hyperoxia-induced plasticity, it is particularly clear that perinatal hyperoxia affects carotid body development. Some of these effects may be transient (e.g., decreased O₂ sensitivity of carotid body glomus cells) while others may be permanent (e.g., carotid body hypoplasia, loss of chemoafferent neurons). Whether the hyperoxic exposures routinely experienced by human infants in clinical settings are sufficient to alter respiratory control development remains an open question and requires further research. © 2020 American Physiological Society. Compr Physiol 10:597-636, 2020.

Continuous vital sign analysis for predicting and preventing neonatal diseases in the twenty-first century: big data to the forefront

In the neonatal intensive care unit (NICU), heart rate, respiratory rate, and oxygen saturation are vital signs (VS) that are continuously monitored in infants, while blood pressure is often monitored continuously immediately after birth, or during critical illness. Although changes in VS can reflect infant physiology or circadian rhythms, persistent deviations in absolute values or complex changes in variability can indicate acute or chronic pathology. Recent studies demonstrate that analysis of continuous VS trends can predict sepsis, necrotizing enterocolitis, brain injury, bronchopulmonary dysplasia, cardiorespiratory decompensation, and mortality. Subtle changes in continuous VS patterns may not be discerned even by experienced clinicians reviewing spot VS data or VS trends captured in the monitor. In contrast, objective analysis of continuous VS data can improve neonatal outcomes by allowing heightened vigilance or preemptive interventions. In this review, we provide an overview of the studies that have used continuous analysis of single or multiple VS, their interactions, and combined VS and clinical analytic tools, to predict or detect neonatal pathophysiology. We make the case that big-data analytics are promising, and with continued improvements, can become a powerful tool to mitigate neonatal diseases in the twenty-first century.

Intermittent hypoxia and bronchial hyperreactivity

The premature neonate is at high risk for childhood airway hyperreactivity and episodes of wheezing. Intermittent hypoxic events are frequently observed during the first weeks and months of life in these infants. Intermittent hypoxemia has been associated with adverse outcomes in extremely premature infants; including the diagnosis of bronchopulmonary dysplasia, reported wheezing, and use of prescription asthma medications. We review the incidence of intermittent hypoxia, their potential role in short and longer term respiratory morbidity, and the translational newborn models now being used to investigate common pathways by which intermittent hypoxia contributes to respiratory disease.

Physiological instability after respiratory pauses in preterm infants

BACKGROUND

The factors influencing the severity of apnea-related hypoxemia and bradycardia are incompletely characterized, especially in infants receiving noninvasive respiratory support.

OBJECTIVES

To identify the frequency and predictors of physiological instability (hypoxemia-oxygen saturation (SpO₂ ) <80%, or bradycardia-heart rate (HR) < 100 bpm) following respiratory pauses in infants receiving noninvasive respiratory support.

METHODS

Respiratory pause duration, derived from capsule pneumography, was measured in 30 preterm infants of gestation 30 (24-32) weeks [median (interquartile range)] receiving noninvasive respiratory support and supplemental oxygen. For identified pauses of 5 to 29 seconds duration, we measured the magnitude and duration of SpO₂ and HR reductions over a period starting at the pause onset and ending 60 seconds after resumption of breathing. Temporally clustered pauses (<60 seconds separation) were analyzed separately. The relative contribution of respiratory pauses to overall physiological instability was determined, and predictors of instability were sought in regression analysis, including demographic, clinical and situational variables as inputs.

RESULTS

In total, 17 105 isolated and 9180 clustered pauses were identified. Hypoxemia and bradycardia were more likely after longer duration and temporally-clustered pauses. However, the majority of such episodes occurred after 5 to 9 second pauses given their numerical preponderance, and short-lived pauses made a substantial contribution to physiological instability overall. Birth gestation, hemoglobin concentration, form of respiratory support, caffeine treatment, respiratory pause duration and temporal clustering were identified as predictors of instability.

CONCLUSIONS

Brief respiratory pauses, especially when clustered, contribute substantially to hypoxemia and bradycardia in preterm infants.

New Methods for Noninvasive Oxygen Administration

Oxygen therapy is an essential part of neonatal care. Targeting oxygen saturations and preventing hypoxemia and hyperoxemia is difficult, particularly in preterm infants. The mode of oxygen delivery directly affects the stability of oxygen saturations, hypoxemia, and hyperoxemia. This stability has important clinical implications. New methods of noninvasive oxygen administration, including closed-loop automated control and servo-controlled oxygen environments, have been developed to improve oxygen saturation targeting and decrease episodes of hyperoxemia and hypoxemia.

Achieved Oxygenation Saturations and Outcome in Extremely Preterm Infants

Infants in the Neonatal Oxygenation Prospective Meta-analysis trials were randomized to SpO₂ targets of 85% to 89% or 91% to 95%. Group allocation was masked. Different outcomes are likely partially attributable to differences in achieved SpO₂. Infants randomized to the lower range had higher than intended readings. SpO₂ distributions of infants in the low-range group of the Benefits of Oxygen Saturation Targeting II UK trial who died or developed necrotizing enterocolitis were centered around 90% to 92%. These achieved SpO₂ distributions caution against using lower SpO₂ target ranges early or throughout the clinical course in extremely preterm infants.

Adherence to oxygen saturation targets increased in preterm infants when a higher target range and tighter alarm limits were introduced

AIM

European consensus guidelines published in May 2013 recommended a target peripheral capillary oxygen saturation (SpO₂ ) range of 90-95% for preterm infants. These were incorporated into guidelines at the Karolinska University Hospital, Sweden, in November 2013. This study compared clinical practice before and after those local guidelines.

METHODS

We included infants who were born between 23 + 0 and 30 + 6 weeks from January 1, 2013 to December, 31 2015 and received intensive care in two Karolinska units. The lower saturation target of 88-92% and alarm limits of 85-95% used before November 2013 were compared to the new higher saturation target of 90-95% and alarm limits of 89-96%.

RESULTS

Data from 399 infants were analysed. The mean SpO₂ was 92.4% with the higher target (n = 301) and 91.1% with the lower target (n = 98). Using the higher instead of lower target meant that the SpO₂ was within the prescribed target range more frequently (51% versus 30%) and the proportion of time with SpO₂ >95% was increased by 9% (95% confidence interval 7-11%, p < 0.001).

CONCLUSION

The higher saturation target and tighter alarm limits led to higher mean oxygen saturation, increased adherence to the target and increased time with hyperoxaemia.

Hypoxemic and hyperoxemic likelihood in pulse oximetry ranges: NICU observational study

OBJECTIVE

Describe the likelihood of hypoxemia and hyperoxemia across ranges of oxygen saturation (SpO₂), during mechanical ventilation with supplemental oxygenation.

DESIGN

Retrospective observational study.

SETTING

University affiliated tertiary care neonatal intensive care unit.

PATIENTS

Two groups of neonates based on postmenstrual age (PMA): <32 weeks (n=104) and >36 weeks (n=709).

MAIN MEASURES

Hypoxemia was defined as a PaO₂ <40 mm Hg, hyperoxemia as a PaO₂ of >99 mm Hg and normoxemia as a PaO₂ of 50-80 mm Hg. Twenty-five per cent was defined as marked likelihood of hypoxemia or hyperoxemia.

RESULTS

From these infants, 18 034 SpO₂-PaO₂ pairs were evaluated of which 10% were preterm. The PMA (median and IQR) of the two groups were: 28 weeks (27-30) and 40 weeks (38-41). With SpO₂ levels between 90% and 95%, the likelihoods of hypoxemia and hyperoxemia were low and balanced. With increasing levels of SpO₂, the likelihood of hyperoxemia increased. It became marked in the preterm group when SpO₂ was 99%-100% (95% CI 29% to 41%) and in the term group with SpO₂ levels of 96%-98% (95% CI 29% to 32%). The likelihood of hypoxemia increased as SpO₂ decreased. It became marked in both with SpO₂ levels of 80%-85% (95% CI 20% to 31%, 24% to 28%, respectively).

CONCLUSIONS

The likelihood of a PaO₂ <40 mm Hg is marked with SpO₂ below 86%. The likelihood of a PaO₂ >99 mm Hg is marked in term infants with SpO₂ above 95% and above 98% in preterm infants. SpO₂ levels between 90% and 95% are appropriate targets for term and preterm infants.

Comparison of Automated and Manual Peripheral Oxygen Saturation Control Applied to One Human Subject at a High Target Range

Newborn infants, mainly those born prematurely, often require respiratory support with a varying concentration of the fraction of inspired oxygen (FiO$_{\mathbf {2}}$) to keep the peripheral oxygen saturation (SpO$_{\mathbf {2}}$) within the desired range to prevent adverse health effects due to both high and low SpO$_{\mathbf {2}}$. Manual adjustment, by nurses, is the common practice. However, the efficacy of the manual control is questionable. A novel automatic controller is evaluated clinically with application to one human subject at a high target SpO$_{\mathbf {2}}$. The automatic controller demonstrated the ability to improve oxygen saturation control over the everyday routine manual control by increasing the proportion of time where SpO$_{\mathbf {2}}\textbf{v}$alues were within the desired range.

Environmental or Nasal Cannula Supplemental Oxygen for Preterm Infants: A Randomized Cross-Over Trial

OBJECTIVE

To test the hypothesis that environmental compared with nasal cannula oxygen decreases episodes of intermittent hypoxemia (oxygen saturations <85% for ≥10 seconds) in preterm infants on supplemental oxygen by providing a more stable hypopharyngeal oxygen concentration.

STUDY DESIGN

This was a single center randomized crossover trial with a 1:1 parallel allocation to order of testing. Preterm infants on supplemental oxygen via oxygen environment maintained by a servo-controlled system or nasal cannula with flow rates ≤1.0 L per kg per minute were crossed over every 24 hours for 96 hours. Data were collected electronically to capture real time numeric and waveform data from patient monitors.

RESULTS

Twenty-five infants with gestational age of 27 ± 2 weeks (mean ± SD) and a birth weight of 933 ± 328 g were studied at postnatal day 36 ± 26. The number of episodes of intermittent hypoxemia per 24 hours was 117 ± 77 (median, 98; range, 4-335) with oxygen environment vs 130 ± 63 (median, 136; range, 16-252) with nasal cannula (P = .002). Infants on oxygen environment compared with nasal cannula also had decreased episodes of severe intermittent hypoxemia (P = .005). Infants on oxygen environment compared with nasal cannula had a lower proportion of time with oxygen saturations <85% (.05 ± .03 vs .06 ± .03, P < .001), and a lower coefficient of variation of oxygen saturation (P = .02).

CONCLUSIONS

In preterm infants receiving supplemental oxygen, servo-controlled oxygen environment decreases hypoxemia compared with nasal cannula.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT02794662.

Engineering Evaluation of the Performance of an Automatic Peripheral Oxygen Controller Using a Neonatal Respiratory Model

Premature infants often require respiratory support with a varying concentration of the fraction of inspired oxygen FiO2 to keep the arterial oxygen saturation typically measured using a peripheral sensor (SpO2) within the desired range to avoid both hypoxia and hyperoxia. The widespread practice for controlling the fraction of inspired oxygen is by manual adjustment. Automatic control of the oxygen to assist care providers is desired. A novel closed-loop respiratory support device with dynamic adaptability is evaluated nonclinically by using a neonatal respiratory response model. The device demonstrated the ability to improve oxygen saturation control over manual control by increasing the proportion of time where SpO2 is within the desired range while minimizing the episodes and periods where SpO2 of the neonatal respiratory model is out of the target range.

Optimal Target Range of Closed-Loop Inspired Oxygen Support in Preterm Infants: A Randomized Cross-Over Study

OBJECTIVE

To investigate the effect of different pulse oximetry (SpO₂) target range settings during automated fraction of inspired oxygen control (A-FiO₂) on time spent within a clinically set SpO₂ alarm range in oxygen-dependent infants on noninvasive respiratory support.

STUDY DESIGN

Forty-one preterm infants (gestational age [median] 26 weeks, age [median] 21 days) on FiO₂ >0.21 receiving noninvasive respiratory support were subjected to A-FiO₂ using 3 SpO₂ target ranges (86%-94%, 88%-92%, or 89%-91%) in random order for 24 hours each. Before switching to the next target range, SpO₂ was manually controlled for 24 hours (washout period). The primary outcome was the time spent within the clinically set alarm limits of 86%-94%.

RESULTS

The percent time within the 86%-94% SpO₂ alarm range was similar for all 3 A-FiO₂ target ranges (74%). Time spent in hyperoxemia was not significantly different between target ranges. However, the time spent in severe hypoxemia (SpO₂ <80%) was significantly reduced during the narrowed target ranges of A-FiO₂ (88%-92%; 1.9%, 89%-91%; 1.7%) compared with the wide target range (86%-94%; 3.4%, P < .001). There were no differences between the 88%-92% and 89-91% target range.

CONCLUSIONS

Narrowing the target range of A-FiO₂ to the desired median ±2% is effective in reducing the time spent in hypoxemia, without increasing the risk of hyperoxemia.

TRIAL REGISTRATION

www.trialregister.nl: NTR4368.

Cost-effectiveness of FreeO2 in patients with chronic obstructive pulmonary disease hospitalised for acute exacerbations: analysis of a pilot study in Quebec

OBJECTIVE

Conduct a cost-effectiveness analysis of FreeO2 technology versus manual oxygen-titration technology for patients with chronic obstructive pulmonary disease (COPD) hospitalised for acute exacerbations.

SETTING

Tertiary acute care hospital in Quebec, Canada.

PARTICIPANTS

47 patients with COPD hospitalised for acute exacerbations.

INTERVENTION

An automated oxygen-titration and oxygen-weaning technology.

METHODS AND OUTCOMES

The costs for hospitalisation and follow-up for 180 days were calculated using a microcosting approach and included the cost of FreeO2 technology. Incremental cost-effectiveness ratios (ICERs) were calculated using bootstrap resampling with 5000 replications. The main effect variable was the percentage of time spent at the target oxygen saturation (SpO2). The other two effect variables were the time spent in hyperoxia (target SpO2+5%) and in severe hypoxaemia (SpO2 <85%). The resamplings were based on data from a randomised controlled trial with 47 patients with COPD hospitalised for acute exacerbations.

RESULTS

FreeO2 generated savings of 20.7% of the per-patient costs at 180 days (ie, -$C2959.71). This decrease is nevertheless not significant at the 95% threshold (P=0.13), but the effect variables all improved (P<0.001). The improvement in the time spent at the target SpO2 was 56.3%. The ICERs indicate that FreeO2 technology is more cost-effective than manual oxygen titration with a savings of -$C96.91 per percentage point of time spent at the target SpO2 (95% CI -301.26 to 116.96).

CONCLUSION

FreeO2 technology could significantly enhance the efficiency of the health system by reducing per-patient costs at 180 days. A study with a larger patient sample needs to be carried out to confirm these preliminary results.

TRIAL REGISTRATION NUMBER

NCT01393015; Post-results.

Oxygenation of the Immature Infant: A Commentary and Recommendations for Oxygen Saturation Targets and Alarm Limits

BACKGROUND

For 70 years, there has been a search for the optimal oxygenation of premature infants. In spite of the lack of evidence, guidelines have successively reduced oxygenation targets during these years.

OBJECTIVES

(1) To present a summary of previously published meta-analyses of 5 randomized studies (NeOProM) which tested a low (85-89%) versus a high (91-95%) oxygen saturation target the first weeks after birth on outcome of immature newborn infants. (2) To present international recommendations for oxygenation the first weeks after birth.

METHODS

Data were retrieved from meta-analyses and reviews of these studies.

RESULTS

Mortality and necrotizing enterocolitis (NEC) are significantly higher in patients with a low saturation target (relative risk, RR 1.16 and 1.24, respectively), while severe retinopathy of prematurity (ROP) is reduced (RR 0.74), fortunately without a change in the rate of blindness. Severe intraventricular hemorrhage, patent ductus arteriosus, and bronchopulmonary dysplasia (defined physiologically) were not significantly affected by the oxygen targets in the range of these studies. Based on these data, it is recommended that SpO2 targets from birth to 36 weeks postconceptional age for infants < 28 weeks gestational age (GA) should be between 90 and 94% (with alarm limits of 89 and 95%), respectively. It is recommended to keep infants small for GA well oxygenated within the suggested targets avoiding fluctuations.

CONCLUSIONS

The ideal oxygen saturation targets for infants < 28 weeks GA are not known. Mortality, ROP, and NEC seem to be particularly oxygen-sensitive outcome variables. The optimal oxygen saturation for premature infants > 28 weeks GA has not been carefully studied.

Physiological closed-loop control in intelligent oxygen therapy: A review

BACKGROUND AND OBJECTIVE

Oxygen therapy has become a standard care for the treatment of patients with chronic obstructive pulmonary disease and other hypoxemic chronic lung diseases. In current systems, manually continuous adjustment of O₂ flow rate is a time-consuming task, often unsuccessful, that requires experienced staff. The primary aim of this systematic review is to collate and report on the principles, algorithms and accuracy of autonomous physiological close-loop controlled oxygen devices as well to present recommendations for future research and studies in this area.

METHODS

A literature search was performed on medical database MEDLINE, engineering database IEEE-Xplore and wide-raging scientific databases Scopus and Web of Science. A narrative synthesis of the results was carried out.

RESULTS

A summary of the findings of this review suggests that when compared to the conventional manual practice, the closed-loop controllers maintain higher saturation levels, spend less time below the target saturation, and save oxygen resources. Nonetheless, despite of their potential, autonomous oxygen therapy devices are scarce in real clinical applications.

CONCLUSIONS

Robustness of control algorithms, fail-safe mechanisms, limited reliability of sensors, usability issues and the need for standardized evaluating methods of assessing risks can be among the reasons for this lack of matureness and need to be addressed before the wide spreading of a new generation of automatic oxygen devices.

Can the preterm lung recover from perinatal stress?

After birth, adequate lung function is necessary for the successful adaptation of a preterm baby. Both prenatal and postnatal insults and therapeutic interventions have an immediate effect on lung function and gas exchange but also interfere with fetal and neonatal lung development. Prenatal insults like chorioamnionitis and prenatal interventions like maternal glucocorticosteroids interact but might also determine the preterm baby's lung response to postnatal interventions ("second hit") like supplementation of oxygen and drug therapy. We review current experimental and clinical findings on the influence of different perinatal factors on preterm lung development and discuss how well-established interventions in neonatal care might be adapted to attenuate postnatal lung injury.