Comparison of effects of 95% and 90% oxygen saturations in respiratory distress syndrome

Effects of targeting lower versus higher arterial oxygen saturations on death or disability in preterm infants

BACKGROUND

The use of supplemental oxygen in the care of extremely preterm infants has been common practice since the 1940s. Despite this, there is little agreement regarding which oxygen saturation (SpO₂) ranges to target to maximise short- or long-term growth and development, while minimising harms. There are two opposing concerns. Lower oxygen levels (targeting SpO₂ at 90% or less) may impair neurodevelopment or result in death. Higher oxygen levels (targeting SpO₂ greater than 90%) may increase severe retinopathy of prematurity or chronic lung disease.The use of pulse oximetry to non-invasively assess neonatal SpO₂ levels has been widespread since the 1990s. Until recently there were no randomised controlled trials (RCTs) that had assessed whether it is better to target higher or lower oxygen saturation levels in extremely preterm infants, from birth or soon thereafter. As a result, there is significant international practice variation and uncertainty remains as to the most appropriate range to target oxygen saturation levels in preterm and low birth weight infants.

OBJECTIVES

1. What are the effects of targeting lower versus higher oxygen saturation ranges on death or major neonatal and infant morbidities, or both, in extremely preterm infants?2. Do these effects differ in different types of infants, including those born at a very early gestational age, or in those who are outborn, without antenatal corticosteroid coverage, of male sex, small for gestational age or of multiple birth, or by mode of delivery?

SEARCH METHODS

We used the standard search strategy of Cochrane Neonatal to search the Cochrane Central Register of Controlled Trials (CENTRAL 2016, Issue 4), MEDLINE via PubMed (1966 to 11 April 2016), Embase (1980 to 11 April 2016) and CINAHL (1982 to 11 April 2016). We also searched clinical trials databases, conference proceedings and the reference lists of retrieved articles for randomised controlled trials.

SELECTION CRITERIA

Randomised controlled trials that enrolled babies born at less than 28 weeks' gestation, at birth or soon thereafter, and targeted SpO₂ ranges of either 90% or below or above 90% via pulse oximetry, with the intention of maintaining such targets for at least the first two weeks of life.

DATA COLLECTION AND ANALYSIS

We used the standard methods of Cochrane Neonatal to extract data from the published reports of the included studies. We sought some additional aggregate data from the original investigators in order to align the definitions of two key outcomes. We conducted the meta-analyses with Review Manager 5 software, using the Mantel-Haenszel method for estimates of typical risk ratio (RR) and risk difference (RD) and a fixed-effect model. We assessed the included studies using the Cochrane 'Risk of bias' and GRADE criteria in order to establish the quality of the evidence. We investigated heterogeneity of effects via pre-specified subgroup and sensitivity analyses.

MAIN RESULTS

Five trials, which together enrolled 4965 infants, were eligible for inclusion. The investigators of these five trials had prospectively planned to combine their data as part of the NeOProM (Neonatal Oxygen Prospective Meta-analysis) Collaboration. We graded the quality of evidence as high for the key outcomes of death, major disability, the composite of death or major disability, and necrotising enterocolitis; and as moderate for blindness and retinopathy of prematurity requiring treatment.When an aligned definition of major disability was used, there was no significant difference in the composite primary outcome of death or major disability in extremely preterm infants when targeting a lower (SpO₂ 85% to 89%) versus a higher (SpO₂ 91% to 95%) oxygen saturation range (typical RR 1.04, 95% confidence interval (CI) 0.98 to 1.10; typical RD 0.02, 95% CI -0.01 to 0.05; 5 trials, 4754 infants) (high-quality evidence). Compared with a higher target range, a lower target range significantly increased the incidence of death at 18 to 24 months corrected age (typical RR 1.16, 95% CI 1.03 to 1.31; typical RD 0.03, 95% CI 0.01 to 0.05; 5 trials, 4873 infants) (high-quality evidence) and necrotising enterocolitis (typical RR 1.24, 95% 1.05 to 1.47; typical RD 0.02, 95% CI 0.01 to 0.04; 5 trials, 4929 infants; I² = 0%) (high-quality evidence). Targeting the lower range significantly decreased the incidence of retinopathy of prematurity requiring treatment (typical RR 0.72, 95% CI 0.61 to 0.85; typical RD -0.04, 95% CI -0.06 to -0.02; 5 trials, 4089 infants; I² = 69%) (moderate-quality evidence). There were no significant differences between the two treatment groups for major disability including blindness, severe hearing loss, cerebral palsy, or other important neonatal morbidities.A subgroup analysis of major outcomes by type of oximeter calibration software (original versus revised) found a significant difference in the treatment effect between the two software types for death (interaction P = 0.03), with a significantly larger treatment effect seen for those infants using the revised algorithm (typical RR 1.38, 95% CI 1.13 to 1.68; typical RD 0.06, 95% CI 0.01 to 0.10; 3 trials, 1716 infants). There were no other important differences in treatment effect shown by the subgroup analyses using the currently available data.

AUTHORS' CONCLUSIONS

In extremely preterm infants, targeting lower (85% to 89%) SpO₂ compared to higher (91% to 95%) SpO₂ had no significant effect on the composite outcome of death or major disability or on major disability alone, including blindness, but increased the average risk of mortality by 28 per 1000 infants treated. The trade-offs between the benefits and harms of the different oxygen saturation target ranges may need to be assessed within local settings (e.g. alarm limit settings, staffing, baseline outcome risks) when deciding on oxygen saturation targeting policies.

Restricted versus liberal oxygen exposure for preventing morbidity and mortality in preterm or low birth weight infants

BACKGROUND

While the use of supplemental oxygen has a long history in neonatal care, resulting in both significant health care benefits and harms, uncertainty remains as to the most appropriate range to target blood oxygen levels in preterm and low birth weight infants. Potential benefits of higher oxygen targeting may include more stable sleep patterns and improved long-term growth and development. However, there may be significant deleterious pulmonary effects and health service use implications resulting from such a policy.

OBJECTIVES

To determine whether targeting ambient oxygen concentration to achieve a lower vs. higher blood oxygen range, or administering restricted vs. liberal supplemental oxygen, effects mortality, retinopathy of prematurity, lung function, growth or development in preterm or low birth weight infants.

SEARCH STRATEGY

The standard search strategy of the Neonatal Review Group was used. An additional literature search was conducted of the MEDLINE and CINAHL databases in order to locate any trials in addition to those provided by the Cochrane Controlled Trials Register (CENTRAL/CCTR). Search updated to week two July 2008.

SELECTION CRITERIA

All trials in preterm or low birth weight infants utilising random or quasi-random patient allocation in which ambient oxygen concentrations were targeted to achieve a lower vs. higher blood oxygen range, or restricted vs. liberal oxygen was administered were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

The methodological quality of the eligible trials was assessed independently by each review author for the degree of selection, performance, attrition and detection bias. Data were extracted and reviewed independently by the each author. Data analysis was conducted according to the standards of the Cochrane Neonatal Review Group.

MAIN RESULTS

In the meta-analysis of the five trials included in this review, the restriction of oxygen significantly reduced the incidence and severity of retinopathy of prematurity without unduly increasing death rates The one prospective, multicenter, double-blind, randomized trial investigating lower vs. higher blood oxygen levels from 32 weeks postmenstrual age showed no significant differences in the rates of ROP, mortality or growth and development between the two groups. However, this study did show increased rates of chronic lung disease and home oxygen use.

AUTHORS' CONCLUSIONS

The results of this systematic review confirm that (the now historical) policy of unrestricted, unmonitored oxygen therapy has potential harms without clear benefits. However, the question of what is the optimal target range for maintaining blood oxygen levels in preterm/LBW infants was not answered by the data available for inclusion in this review.

A rational approach to home oxygen use in infants and children

The provision of supplemental oxygen for infants and children with hypoxaemia is expensive but advantageous because it facilitates earlier discharge from hospital and enhances quality of life in the home setting. It is seen as potentially cost effective and family friendly. However, the prescription of supplemental oxygen varies greatly between neonatologists, paediatric respiratory physicians and paediatric cardiologists. There is a lack of consensus on appropriate indications for prescribing oxygen, desirable oxygen targets and clinically significant immediate and longer-term outcome measures. Of the limited studies available, most are small studies reporting the treatment of infants with chronic neonatal lung disease with inconsistent outcome measures. Such data are not readily extrapolated to older children, who are also poorly served by existing data in adult studies. Further delineation of the indications for home oxygen therapy is required together with appropriately designed and funded multicentre trials to provide evidence for optimal oxygen therapy.

Effect of changes in inspired oxygen tension on indexes of oxygenation in ventilated neonates

OBJECTIVE

Several indexes are used to quantify the severity of hypoxemia, including the arterial to alveolar oxygen ratio (a/APO(2)), the alveolar-arterial difference P(a-a)o(2), the ratio Pao(2)/Fio(2), and the oxygenation index (OI = mean airway pressure x Pao(2)/Fio(2)). This study was carried out to test how stable these indexes are when small changes in Fio(2) are made in ventilated neonates.

DESIGN

Open prospective clinical study.

SETTING

Level III neonatal intensive care unit of a teaching hospital.

PATIENTS

Forty studies were performed in 31 clinically stable ventilated neonates (median birth weight, 1450 g; median gestation, 30.6 wks), monitored by transcutaneous Pao(2)-oxygen saturation (Sao(2)).

INTERVENTIONS

If hyper- or hypoxemia without derangements of Paco(2) or pH were detected in a blood sample taken from an indwelling arterial catheter, Fio(2) was changed (median change, 0.05; range, -0.3 to 0.25) and another arterial blood sample was obtained 26-83 mins (median, 42) after. The indexes were calculated in the two blood samples, and for each index the changes between baseline and the value after Fio(2) change were analyzed.

MEASUREMENTS AND MAIN RESULTS

Median baseline P(a-a)o(2) was 211.7 torr, median a/APO(2) was 0.24, median Pao(2)/Fio(2) was 161 torr, and median OI was 6.14. After the Fio(2) change, the coefficients of variation (sd/mean) were calculated, and they were 27.5%, 23.8%, 24.5%, and 31.6% for P(a-a)o(2), a/APO(2), Pao(2)/Fio(2), and OI, respectively. Changes in the value of each index were correlated to changes in Fio(2), indicating a dependency on Fio(2). When data were analyzed as "high Fio(2)" (approximate Sao(2) 95%) vs. "low Fio(2)" (approximate Sao(2) 90%), differences were statistically significant for all indexes except for a/APO(2).

CONCLUSIONS

All the indexes tested showed a dependency on the value of Fio(2): increasing Fio(2) spuriously made neonates appear less hypoxemic. The a/APO(2) appeared to perform better than other indexes in this study, with a lower variability and a lower oxygen dependency.

Restricted versus liberal oxygen exposure for preventing morbidity and mortality in preterm or low birth weight infants

BACKGROUND

This section is under preparation and will be included in the next issue.

OBJECTIVES

In preterm or low birth weight infants, does targeting ambient oxygen concentration to achieve a lower versus higher blood oxygen range, or administering restricted versus liberal supplemental oxygen, influence mortality, retinopathy of prematurity, lung function, growth or development?

SEARCH STRATEGY

The standard search strategy of the Neonatal Review Group was used. An additional literature search was conducted of the MEDLINE, EMBASE, and CINAHL databases in order to locate any trials in addition to those provided by the Cochrane Controlled Trials Register (CENTRAL/CCTR).

SELECTION CRITERIA

All trials in preterm or low birth weight infants utilising random or quasi-random patient allocation, in which ambient oxygen concentrations were targeted to achieve a lower versus higher blood oxygen range, or restricted versus liberal oxygen was administered, were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

The methodological quality of the eligible trials was assessed independently by each author for the degree selection, performance, attrition and detection bias. Data were extracted and reviewed independently by the each author. Data analysis was conducted according to the standards of the Cochrane Neonatal Review Group.

MAIN RESULTS

The restriction of oxygen significantly reduced the incidence and severity of retinopathy of prematurity without unduly increasing death rates in the meta-analysis of the five trials included in this review. The one trial that specifically addressed the question of lower versus higher PaO2 found no effect on death, but did not report (in sufficient detail to warrant inclusion) the effect of this intervention on eye or other outcomes. The effects of either of these oxygen administration policies on other clinically meaningful outcomes including chronic lung disease and long term growth, neurodevelopment, lung or visual function were not reported in any of the available trials.

REVIEWER'S CONCLUSIONS

The results of this meta-analysis confirm the commonly held view of today's clinicians that a policy of unrestricted, unmonitored oxygen therapy has potential harms, without clear benefits. However, the question of what is the optimal target range for maintaining blood oxygen levels in preterm/LBW infants was not answered by the data available for inclusion in this review.