Oxygen Saturation Targets in Bronchiolitis – Magic Numbers?


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Where can I find this paper?

http://www.ncbi.nlm.nih.gov/pubmed/26382998 – this paper is currently open access

What is this paper about (what is the research question)?

Is a target oxygen saturation of 90% or higher equivalent to 94% or higher for resolution of illness in acute viral bronchiolitis?

Summary of the Paper

Design: multicentre, parallel group, randomised controlled equivalence trial with allocation concealment.

Objective: to determine whether accepting a reduced lower limit target oxygen saturation in infants with viral bronchiolitis affected time to resolution of illness

Primary outcome measure: time to resolution of cough (parental reporting)

Intervention: subjects were randomised following decision to admit, to either standard SpO2 monitoring or a modified oximeter which skewed the reading such that SpO2 90% read as 94%. All other care was standard.

Participants: 615 subjects randomised between 03/10/2011-30/03/2012 and 01/10/2012-29/03/2013. 308 randomised to standard group, 307 to modified oximeter group

  • Inclusions: infants aged 6 weeks to 12 months (corrected gestational age) with clinically diagnosed bronchiolitis admitted to hospital for supportive care following presentation to the Emergency Department or Acute Assessment Area
  • Exclusions: preterm (<37 weeks) who had received oxygen in past 4 weeks; cyanotic or haemodynamically significant heart disease; CF or interstitial lung disease; documented immunodeficiency; direct admission to HDU/ICU; previously randomised

Results: Median time to cough resolution was 15.0 days in both groups with a median difference of 1.0 days (95% CI -1 to 2). This fell between the prespecified equivalence limits of plus and minus two days.

 

Authors’  conclusions

In children with acute viral bronchiolitis, the time taken for symptoms to resolve was the same whether they were managed to a target oxygen saturation of 90% or 94%.

On the study design

 

This study used eight centres to recruit a sample with 80% power to detect non-equivalence of greater than two days in time to resolution of cough. Cough resolution was determined by parents at pre-determined follow-up phonecalls (7, 14, 28 days and 6 months). Some allowances were made for inaccurate recording of this data using random selection of a date between the last time the cough was known to be present and the first date it was noted to be absent (if available). This method of reporting does still leave the outcome open to some parental bias and accuracy of reporting cannot be guaranteed.

Allocation to a group was concealed until definite enrolment, and the allocation was masked to study staff, hospital staff and parents. It’s not clear why the authors have chosen to use the work “masking” rather than “blinding”.

Several interesting secondary outcomes were also recorded although it is always worth remembering that studies are designed and powered to detect differences in the primary outcome and may be underpowered to detect differences in secondary outcome. The authors decided in advance to statistically analyse time until “fit for discharge” and actual discharge date for both groups, along with parental anxiety scores and whether the child was fit to attend daycare.

What were the results and what does this mean?

 

Following some loss to follow-up and protocol violations, 293 subjects were analysed in the standard group at 6 months and 291 in the modified oximeter group. This still reflects a study population greater than that determined by the power calculation. There was no difference in the median time to cough resolution which was 15.0 days in both groups.

The authors addressed both intention to treat analysis (analysing those subjects with protocol violations – being given the wrong oximeter probe – according to their original allocated group) and per-protocol analysis (analysing them only if they fulfilled the allocation from start to finish) and found this did not affect the results.

The modified group also had quicker return to adequate feeding and “back to normal” time. Patients in the modified group, predictably, received supplemental oxygen in fewer cases, for a shorter period, were considered fit for discharge sooner and were discharged sooner. There were fewer serious adverse events and adverse events in the modified group (35 SAEs in 32 infants in the standard group vs 25 SAEs in 24 infants in the modified group). The modified group had increased HDU admissions (13 episodes in the modified group vs 8 in the standard group) but fewer reattendances (26 in the standard group vs 12 in the modified group).

The authors postulate that having a higher target oxygen saturation influences decisions about fitness for discharge and that the increased use of oxygen in the standard group might have adversely affected feeding through drying of nasal passages, reflected in the time to adequate feeding. They also suggest that increased time in hospital in the standard group might expose these infants to nosocomial infection, causing the increased readmission rate – but of course this is all speculation 🙂

What can we take from this paper into clinical practice?

It seems that infants subjectively recover from bronchiolitis at the same rate even if we target SpO2 90% or above instead of 94% or above. However this was a population for whom a need for admission to hospital had already been identified and the extrapolation of this to the Emergency Department population is not wholly appropriate. We can be reasonably relaxed about SpO2 90-94% in these patients but until further work is done to reflect our undifferentiated population we should probably be careful about assuming we can safely discharge these infants.

More questions to ask

  • Would we see the same resolution and patterns of return to normal behaviour/complications in the undifferentiated ED population of infants with bronchiolitis?

See Also:

Don’t Forget the Bubbles – Tessa Davis reviews a JAMA paper on oxygen saturations in admission decision-making in patients with bronchiolitis – http://dontforgetthebubbles.com/effect-oximetry-hospital-admission-bronchiolitis/

 

Follow us on twitter: @PEMLit

2 thoughts on “Oxygen Saturation Targets in Bronchiolitis – Magic Numbers?

  1. Pingback: What I learnt this week: If you can’t trust oxygen what can you depend on? #WILTW | The Rolobot Rambles

  2. Pingback: PEM in Review - PEMLit at #IAEM15 - St.Emlyn's

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