What are normal oxygen saturation levels?

SpO2 values in acute medical admissions breathing air—Implications for the British Thoracic Society guideline for emergency oxygen use in adult patients?

Resuscitation,Volume 83, Issue 10, October 2012, Pages 1201–1205

Oxygen saturations (SpO2) are routinely used to assess the well-being of patients, but it is difficult to find an evidence-based description of its normal range. In 2008 the British Thoracic Society (BTS) published guidance for oxygen administration and recommended a target SpO2 of 94–98% for most adult patients. These recommendations rely on consensus opinion and small studies using arterial blood gas measurements of saturation (SaO2). The authors used large datasets of routinely collected vital signs from four hospitals and analysed the SpO2 range of 37,593 acute general medical inpatients (males: 47%) observed to be breathing room air. Age at admission ranged from 16 to 105 years with a mean (SD) of 64 (21) years. 19,642 admissions (52%) were aged <70 years.

The authors found that SpO2 levels ranged from 70% to 100% with a median (IQR) of 97% (95–98%). SpO2 values for males and females were similar. In-hospital mortality for the study patients was 5.27% (range 4.80–6.27%). Mortality (95% CI) for patients with initial SpO2 values of 97%, 96% and 95% was 3.65% (3.22–4.13); 4.47% (3.99–5.00); and 5.67% (5.03–6.38), respectively. Additional analyses of SpO2 values for 37,299 medical admissions aged ≥18 years provided results that the authors believe are distinctly different to those upon which the current BTS guidelines based their definition of normality.

The authors suggest that the BTS should consider changing its target saturation for actively treated patients not at risk of hypercapnic respiratory failure to 96–98%. The update to the British Thoracic Society Guidelines, due for publication in 2013, should make interesting reading, as it could reflect five years worth of research on titrated oxygen delivery, rather than just routine administration of medium of high concentrations of oxygen, regardless of the patient’s oxygen levels.

http://www.sciencedirect.com/science/article/pii/S0300957212002973

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