Supplemental oxygen: More isn’t always better

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A recent study says that in certain populations, supplemental oxygen above certain levels can increase mortality.


Do not use liberal oxygen therapy (SpO2 > 96%) in acutely ill adults, as it is associated with increased all-cause mortality.1


A: Based on a systematic review and meta-analysis of 25 randomized controlled trials.

Chu DK, Kim LH, Young PJ, et al. Mortality and morbidity in acutely ill adults treated with liberal versus conservative oxygen therapy (IOTA): a systematic review and meta-analysis. Lancet. 2018;391:1693-1705.




A 60-year-old woman who is generally healthy except for a history of recurrent urinary tract infections presents to the emergency department with fever, hypotension, and altered mental status, meeting criteria for septic shock. During her resuscitation, supplemental oxygen is administered. Standard treatment calls for a minimum SpO2 (saturation of peripheral oxygen) > 90%. What should your SpO2 goal be?

Use of supplemental oxygen in the acute care of the critically ill adult is a common practice in pre-hospital, emergency department (ED), and hospitalized settings.2,3 Despite their prevalence, guidelines about appropriate oxygen concentration and target SpO2 levels are often conflicting or vague.3-5

Excessive oxygen supplementation in acute illness may be harmful and cause increased risk of hypercapnic respiratory failure, delayed recognition of clinical deterioration, and oxygen toxicity.2,6 The perception of oxygen safety persists despite these findings, and it likely contributes to the ongoing practice of liberal oxygen supplementation in the acutely ill adult.2,7,8


Liberal supplemental O2 linked to increased mortality

The Improving Oxygen Therapy in Acute illness (IOTA) study was a systematic review and meta-analysis of 25 randomized controlled trials (RCTs) that compared liberal vs conservative oxygen strategies for acutely ill adults (N = 16,037; median age = 64 years; range = 28-76 years). Patients with sepsis, critical illness, stroke, trauma, myocardial infarction, or cardiac arrest, and patients who had emergency surgery were included. Studies were excluded if they involved patients who had chronic respiratory illness or psychiatric diseases, were receiving extracorporeal membrane oxygenation, were undergoing elective surgeries, were being treated with hyperbaric oxygen therapy, or were pregnant.

The outcomes studied were mortality (in-hospital, at 30 days, and at the longest ­follow-up) and morbidity (disability measured by the modified Rankin Scale at longest follow-up, risk of hospital-acquired pneumonia, risk of any hospital-acquired infection, and hospital length of stay).

Liberal supplemental oxygen, above an SpO2 range of 94% to 96%, increased mortality during inpatient stays (relative risk [RR] = 1.21; 95% confidence interval [CI], 1.03-1.43; N = 15,071), at 30 days (RR = 1.14; 95% CI, 1.01-1.29; N = 15,053), and at longest follow-up (RR = 1.10; 95% CI, 1.00-1.20; N = 15,754; median = 90 days; range = 14,365 days). There was no difference in morbidity outcomes between groups.

While it’s difficult to define a specific target SpO2 range, the number needed to harm when using a liberal oxygen approach (SpO2 > 96%) resulting in 1 death was 71 (95% CI, 37-1000).

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