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This is a plain English summary of an original research article. The views expressed are those of the author(s) and reviewer(s) at the time of publication.

This NIHR-funded trial found that acute bronchiolitis in children can be safely managed to a slightly lower target level of oxygen saturation than currently used. Setting the level at which children might be taken off oxygen or allowed home at 90% or more led to resolution of cough in 15 days. Time to resolution of cough was no longer than if the usual higher target of 94% or more were used.

The results of this trial should be reliable and come from eight UK hospitals, so should be directly relevant to the UK context. A lowering in the threshold may save NHS resources by reducing length of stay in hospital. As guidelines on the topic vary from country to country it is likely that this research may prompt a change in advice in due course.

Why was this study needed?

Bronchiolitis is a common respiratory tract infection affecting about 1 in 3 babies. About 2% to 3% of these babies develop severe breathing difficulties needing hospital treatment. The number of hospital admissions for bronchiolitis has been increasing over the last 10 years, from 21,330 admissions in England in 2004 to 30,451 in 2011.

Children with bronchiolitis are treated with supplemental oxygen, but there are variations in the levels recommended in national guidelines in different countries. The 2006 Scottish national guidelines on bronchiolitis recommend oxygen saturation 94% or higher, while the American Academy of Pediatrics and the WHO guidelines recommend a target of 90%.

This trial, called BIDS, aimed to assess whether a target oxygen saturation of 90% would lead to faster resolution of cough in acute bronchiolitis compared to a target level of 94% or higher.

What did this study do?

This was a double-blind randomised controlled trial that included 615 babies in eight UK hospitals. The babies were allocated to two groups, one used a standard device for measuring oxygen saturation and the other used a device modified by the manufacturer to display 94% oxygen saturation when in reality it was 90%. The researchers measured the time taken to resolution of symptoms and a range of adverse events such as rates of transfer to a high-dependency unit or readmission to hospital. Expert opinion was sought to set a level at which they would consider the treatments the same (plus or minus two days). The BIDS trial included a cost analysis.

What did it find?

  • Median time to cough resolution was the same in both groups: 15.0 days in the ≥94% threshold group (range 10.0 to 42.5 days) and 15.0 days in the ≥90% threshold group (range 10.0 to 41.0 days), 95% confidence interval for difference -1.0 to 2.0 and so oxygen thresholds were equivalent.
  • There were no significant differences between the groups for serious adverse events.
  • The overall cost analysis from a NHS perspective showed a small average cost saving per child using the lower, 90% and over threshold, but this result was not statistically significant. However the longer hospital inpatient stay cost significantly more in the ≥94% threshold group, £1,055 compared to £886 in the ≥90% threshold group.

What does current guidance say on this issue?

The 2015 NICE guideline on bronchiolitis recommends that children should be given oxygen if their blood oxygen saturation is persistently less than 92%. They should be discharged only if they have maintained oxygen saturation over 92% in air for four hours, including a period of sleep.

What are the implications?

This NIHR-funded trial found that acute bronchiolitis can be managed to a lower target level of oxygen saturation of 90% or more. This is as safe and as effective as the currently used targets of 92% or 94% or more. This approach is also associated with cost savings for the NHS.


Cunningham S, Rodriguez A, Adams T, et al. Oxygen saturation targets in infants with bronchiolitis (BIDS): a double-blind, randomised, equivalence trial. The Lancet 2015;386(9998):1041-8.

Cunningham S, Rodriguez A, Boyd KA, et al. Bronchiolitis of Infancy Discharge Study (BIDS): a multicentre, parallel-group, double-blind, randomised controlled, equivalence trial with economic evaluation. Health Technol Assess. 2015;19(71):1-172.

This project was funded by the National Institute for Health Research Health Technology Assessment programme (project number 09/91/16).



NICE. Bronchiolitis in children. NG9. London: National Institute for Health and Care Excellence; 2015.

SIGN. Bronchiolitis in children. Guideline No. 91. Edinburgh: Scottish Intercollegiate Guidelines Network; 2006.

Produced by the University of Southampton and Bazian on behalf of NIHR through the NIHR Dissemination Centre


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Bronchiolitis is a common lower respiratory tract infection that affects babies and young children under two years old. The majority of cases are caused by respiratory syncytial virus. Most children get better without treatment in about two weeks, but some develop more severe symptoms that require admission to hospital and supplementary oxygen treatment. Some children may have trouble feeding and they may need to be fed using a tube.


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