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Oxygen

Question 1:


What is the prognostic ability of SpO2 values for guiding treatment of children with acute asthma in the ED?

 

Asthma team recommendation: We recommend using supplemental O2 to keep SpO2 90-92%. We value reducing hospital admissions for children with asthma exacerbation. Data from Boychuk (2006), Mehta (2004), and (Keahey (2002) show increase in admission rates when initial SaO2 is ≤ 93%. All three studies are moderate quality studies (cohort studies) but they are strong studies that utilized robust methods. Biases of all types were limited.

Literature synthesized by: N Allen, MS, MLS, RD, LD, CNSC

Clinical Bottom Line developed by The Asthma ED team.

Date created:  2/2011 Revised,3/2011 12/ 2011 11/2013

Synthesis of relevant studies:


Author, date, country, and industry of funding

Patient Group

Level of Evidence (Oxford)

Research design

Significant results

Limitations

Boychuk, R. B., Yamamoto, L.G., DeMesa, C.J., & Kiyabu, K.M. (2006). Correlation of initial emergency department pulse oximetry values in asthma severity classes (steps) with the risk of hospitalization

1219 encounters of 1008 unique children with acute asthma in 5 EDs/clinics, including urban, suburban and rural settings.

Children were> 12 months and < 18 years, presenting with wheezing or bronchospasm. Convenience enrollment

 

Prospective cohort study.

 

Asthma severity was determined by NIH severity class groups.

 

Phase 1 subjects received usual care.

Phase 2 subjects received an educational video, and a written asthma action plan

 

Phase 1 and Phase 2 groups were similar except phase two subjects were older. (Phase 1 mean age was 3.6+2.3 and Phase 2 mean age was 4.3+3.4 (p< 0.0001)).

The overall hospitalization rate was 15%,

The greater the severity class, the higher the hospitalization rate.

The lowest severity group was least likely to have an asthma action plan. Hospitalization rates by presenting oxygen saturation

Presenting O2 Sat

Admission

 rate

98% or >

6%

95%-97%

12%

93%-94%

28%

90%-92%

45%

85%-89%

65%

80%-84$

100%

The mean O2 saturation across severity scores ranged from 96.0 +3.0 to 96.8+2.5. There was no significance among initial O2 Sat and severity score. Severity score was not related to admission rate.

Severity Score is a global score of asthma, not a measure of the event that brought the child to the ED. It is easy to confuse the term "severity score" in relation to the acute event vs the burden of the disease which the score measures.

 

The age difference between Phase 1 and Phase 2 subjects is a concern for bias.

 

Some of the initial O2 sat measures may have been obtained with the subject getting O2.

Carruthers, D.M., & Harrison, B.D.W. (1995). Arterial blood gas analysis or oxygen saturation in the assessment of acute asthma?

89 consecutive patients with asthma (adults) of which 29 had a smoking history. 

Prospective surveillance study- descriptive

Blood gas determination in 89 patients

The mean age(years) of subjects with SaO2> 92%(n=72) was 32 (range 13-79) and the mean age of subjects with SaO2 < 92% (n=17) was 43 (range 16-65)

Inspired O2 was not consistently recorded when blood gases were obtained. Nor was the time since last nebulized treatment.

 

Presence of anemia not reported

Keahey, L., Bulloch, B., Becker, A.B., Pollack, C.V.,Clark, S., & Camargo, C.A.(2002). Initial oxygen saturation as a predictor of admission in children presenting to the emergency department with acute asthma. Annals of Emergency Medicine, 40, 300-307.

Children 2-17 years presenting to the ED with acute asthma.

N= 1040 children who had a SaO2 measured of 1184 children who presented.

Mean age 8+4 years

Children with missing data were not different from those who had initial SaO2 measurement.

Prospective multicenter 1997-98 at 44 North American EDs.

SaO2 measured with on room air

Pulmonary Index score was calculated using respiratory rate, accessory muscle use, wheezing and inspiratory/expiratory ratio up to 3 points each, max score 12.

The mean initial SaO2 was 95%+4.

The mean initial SaO2 of children admitted to the hospital was 93%+5.

The mean initial SzO2 of children not admitted to the hospital was 96%+5.

 

Presenting O2 Sat

Admission

rate

98% or >

8%

95%-97%

4%

93%-94%

30%

90%-92%

44%

<89%

27%

 

 

SaO2 of < 88% has a LR of 12 in determining need for admission.

88% of children had a SaO2 of 91% or greater, so this does not add much.

When values for Pulmonary Index were missing, values were imputed, only is patients had at least 3 of the other factors to create the score recorded. Statistical software imputed the score.

Although they say subjects who did not enroll were not different, 7% (n=83) of the total who presented to the EDs were "too sick" to be enrolled.

Likelihood ratios:

  • LR> 10 generates a large and often conclusive change in pretest to post test probability.
  • LR of 5-10 generates a moderate shift in pre test to post probability. 
  • LR of 2-5 generates a small, although occasionally important change in probability
  • LR of 1-2 alters probability to a small and rarely important value.

Mehta, S.V., Parkin, P.C., Stephens, D., & Schuh, S. (2004). Oxygen saturation as a predictor of prolonged, frequent bronchodilator therapy in children with acute asthma. Journal of Pediatrics, 145, 641-645.

Children 1 to 17 years of age.

N= 273

All required corticosteroids.

 

4 groups, subjects can be in more than one group

 

  1. needing Frequent Bronchodilator therapy(FBT) < 4 hours. N=107
  2. needing FBT > 4 hours N= 166
  3. needing FBT < 12 hours N=194
  4. needing FBT > 12 hours  N=79

 

They used the data from a previously published prospective cohort study.

All subjects were treated with 2 mg/kg po prednisone 0.3 mg/kg po dexamethasone or 5 mg/kg/ hydrocortisone, as well as 3 consecutive doses of albuterol and 250 microgram/dose of ipratropium in the first hour.

The mean baseline SaO2 in the < 4 hour group was 95.5%.

The mean baseline SaO2 in the > 4 hour group was 93.3%.

The mean baseline SaO2 in the <12 hour group was 95.0%.

The mean baseline SaO2 in the > 12 hours  group was 92.1%

Nice study- They did look at data collected for a different purpose to do this analysis.

 

There is a small number of subjects with low SaO2, which increases the variability around the odds ratio

 

What is level of SaO2 was use as a cutoff for subjects in studies of asthma exacerbtions?

First Author and Year

SaO2 Values

Locations

Kelly 2004

Mild >94%; Moderate 94-90% and Severe < 90%

36 Australian centers

Keogh 2001

used a SaO2 of £92%  to administer supplemental oxygen

Toronto CANADA alt. 105 m. (347 ft)

Solé 1999

92% was the cut off  predicting the necessity to repeat treatment

Sao Paulo Brazil alt 637 ft above sea level.

Wright 1997

pretreatment SaO2£91% was not useful in predicting admission/relapse (sen. 0.24, Specificity 0.86 likelihood ration of 1.77 and Post treatment SaO2 £ 91% had a sensitivity of 0.34 and a specificity of 0.98 and a likelihood ration of 16.43 to predict admission/relapse.

Providence RI alt 50 ft

Keahey 2002

The mean SaO2 of children admitted was 93+ 5% and the mean SaO2 of children not admitted was 96% + 3%

44 Emergencies 18 in US states and 4 Canadian provinces.

Carruthers 1995

adults 32% smokers used a SaO2 of <92> for differentiation

Norwich UK, alt 30 m (28 ft)

Mehta 2004

In the group (n= 107)  that needed < 4hours of frequent bronchodilator treatment (FBT) presenting SaO2 was 95.5 + 2. In the group (n=166) that needed > 4 hours of FBT, presenting  SaO2 was 93.3 + 3.8

Toronto CANADA alt. 105 m. (347 ft)

Boychuk 2006

presenting SaO2 < 90 related to increased hospitalization

Honolulu HI, alt 4 m. (9 ft)

Connett 1993

Inpatients 75 children. All children required neb therapy with salbutamol 5 mg. Only those who required hospitalization were included in the study. SaO2 measures taken preneb and 10 minutes post neb. Children were awake. All received oral pred 2 mg/kg. To me it appears he is supporting using the post neb assessment to make the decision to admit. A post neb O2 sat was < 91% best predicted the need for IV treatment( IV aminophylline and hydrocortisone)

Brighton, altitude 0 ft

Geelhoed 1994

Subjects:280 children who were enrolled when the primary investigator was working. 198 were receiving episodic treatment and 82 were receiving regular treatment, including 11 who were on regular oral steroids. Treated in the ED with nebulized salbutamol. A minority (No number given) were given oral steroids.

Perth, Western Australia, Australia alt 66 ft

 

Search strategy implemented:

PubMed performed Sept 16, 2010

("Asthma"[Mesh] AND ("Emergency Service, Hospital"[Mesh] OR "Emergency Nursing"[Mesh] OR "Emergency Medical Services"[Mesh] OR "Emergency Medicine"[Mesh] OR "Acute Disease"[Mesh] OR exacerbation[All Fields] OR attack[All Fields])) AND ("Oximetry"[Mesh] OR "permissive hypoxia"[All Fields]) AND ((Meta-Analysis[ptyp] OR Practice Guideline[ptyp] OR Randomized Controlled Trial[ptyp] OR Guideline[ptyp]) OR ("Cohort Studies"[Mesh] OR "Epidemiologic Studies"[Mesh] OR systematic[sb])) AND English[lang] AND ("infant"[MeSH Terms] OR "child"[MeSH Terms] OR "adolescent"[MeSH Terms])

CINAHL performed Sept 16 2010

S1 (MH "Acute Disease") Limiters - Exclude MEDLINE records Search modes - Boolean/Phrase

S2 (MH "Emergency Medical Services+") OR (MH "Emergency Service+") OR (MH "Emergency Nursing+") OR (MH "Emergency Medicine") Limiters - Exclude MEDLINE recordsSearch modes - Boolean/Phrase

S3 (MH "Asthma+") Limiters - Exclude MEDLINE records Search modes - Boolean/Phrase

S4 (MH "Disease Exacerbation") Search modes - Boolean/Phrase

S5 S1 or S2 or S4 Search modes - Boolean/Phrase

S6 S3 and S5 Search modes - Boolean/Phrase

S7 (MH "Oximetry+") Limiters - Exclude MEDLINE records

Search modes - Boolean/Phrase

S8 permissive hypoxia Limiters - Exclude MEDLINE records Search modes - Boolean/Phrase

Search modes - Boolean/Phrase

S9 S6 and S7 Search modes - Boolean/Phrase

S10 S6 and S7 Limiters - English Language; Human; Age Groups: All Child

Studies from EPR-3 (2007) that were used to inform statements on SaO2 monitoring were reviewed to synthesize a statement on a SaO2 percent to guide treatment at Children's Mercy Hospital.

Search outcome:

14 results were obtained from the literature PubMed and CINAHL searches. There were ten studies identified from the EPR-3, 2007 that addressed the use of SaO2 to guide treatment of asthma exacerbation.

References:

Boychuk, R. B., Yamamoto, L.G., DeMesa, C.J., & Kiyabu, K.M. (2006). Correlation of initial emergency department pulse oximetry values in asthma severity classes (steps) with the risk of hospitalization, American Journal of Emergency Medicine, 24, 48-52.

Carruthers, D.M., & Harrison, B.D.W. (1995). Arterial blood gas analysis or oxygen saturation in the assessment of acute asthma? Thorax, 50, 186-188.

Keahey, L., Bulloch, B., Becker, A.B., Pollack, C.V.,Clark, S., & Camargo, C.A.(2002). Initial oxygen saturation as a predictor of admission in children presenting to the emergency department with acute asthma. Annals of Emergency Medicine, 40, 300-307.

Mehta, S.V., Parkin, P.C., Stephens, D., & Schuh, S. (2004). Oxygen saturation as a predictor of prolonged, frequent bronchodilator therapy in children with acute asthma. Journal of Pediatrics, 145, 641-645.

Kelly, A. M., Kerr, D., & Powell, C. (2004). Is severity assessment after one hour of treatment better for predicting the need for admission in acute asthma. Respiratory Medicine, 98, 777-781.

Keogh, K. A., Macarthur, C., Parkin, P. C., Stephens, D., Arseneault, R., Tennis, O. Bacal, L., & Schuh, S. (2001). Predictors of hospitalization in children with acute asthma. J. Pediatr, 139, 273-277.

Sole, D., Komatsu, M. K., Carvalho, K. V. T., & Naspitz, C.K. (1999). Pulse oximetry in the evaluation of the severity of acute asthma and /or wheezing children. Journal of Asthma, 36, 4, 327-333.

Wright, R. O., Santucci, K. A., Jay, G. D., & Steele, D. W. (1997). Evaluation of pre and posttreatment pulse oximetry in acute childhood asthma. Academic Emergency Medicine, 4, 2, 114-117.

Connett, G. J., & Lenney, W. (1993). Use of pulse oximetry in the hospital management of acute asthma in childhood. Pediatric Pulmonology, 15, 345-349.

 

Question 2:

 

What level of oxygen saturation was used as a cutoff for initiation of supplemental oxygen for subjects in studies of asthma exacerbations?


Asthma team recommendation:
 The Asthma ED Team strongly recommends using supplemental oxygen to maintain an oxygen saturation ≥ 92%. EPR-3 (2007) states supplemental oxygen should be used to maintain an oxygen saturation of > 90% and continue oxygen therapy until a "clear response to bronchodilator therapy has occurred." The studies below were read to support a higher oxygen saturation level to guide therapy. The studies are of variable quality; most of them are observational studies with methodological flaws. This recommendation may change when higher quality evidence becomes available. Further research (if performed) is likely to have an important influence on our confidence in the estimate of effect and is likely to change the estimate.

Literature supporting this recommendation  
Literature was searched since the publication of EPR-3. (2007). Ten of the 14 citations included for Question 1 were read to establish the oxygen saturation level utilized to guide therapy. The citations were reviewed for the oxygen saturation levels that differentiated subjects in any way (i.e. those admitted to the hospital, those who required increased therapy, or those who were readmitted to the ED or hospital). The table below reports the oxygen saturation level used the context of its use, and altitude of the study location.

These guidelines do not establish a standard of care to be followed in every case. It is recognized that each case is different and those individuals involved in providing health care are expected to use their judgment in determining what is in the best interests of the patient based on the circumstances existing at the time. It is impossible to anticipate all possible situations that may exist and to prepare guidelines for each. Accordingly these guidelines should guide care with the understanding that departures from them may be required at times.