Are we giving too much oxygen to patients at risk of hypercapnia? Real world data from a large teaching hospital

Introduction

Oxygen guidelines recommend a target saturation range (SpO₂ range) of 88–92 % for patients at risk of hypercapnia. Saturations <88 % and saturations >92 % whilst using supplemental oxygen are associated with increased mortality.

Methods

We audited SpO₂ observations of all patients with a prescribed target range of 88–92 % at one hospital over a four-year period.

Results

Of 1,045,958 observations from patients with an oxygen prescription, 107,724 (10.3 %) had a target range of 88–92 % (at risk of hypercapnia). 26,668 of these observations (24.8 %) involved oxygen use. 89.6 % of the SpO₂ observations with target SpO₂ range 88–92 % were satisfactory with SpO₂ ≥88 % breathing air or SpO₂ 88–92 % breathing oxygen. However, 1.2 % of SpO₂ observations for these patients were too low (<88 %). This was commoner in observations involving use of supplemental oxygen (2.2 %) compared with observations on air (0.9 %).

Of the SpO₂ observations with target SpO₂ range 88–92 % which were recorded whilst the patient was receiving supplemental oxygen therapy, 9870 had SpO₂ >92 % (over-oxygenated). This represented 9.2 % of all observations for patients with a target range of 88–92 % and 37.0 % of the 26,668 observations involving use of oxygen for these patients. Compared with nasal cannulae, SpO₂ observations involving use of simple masks, Venturi masks and humidified oxygen were more commonly outside of the target range.

Summary

We found that excessive oxygen administration was much commoner than insufficient oxygen therapy for hospital patients at risk of hypercapnia. Excessive oxygen use implies an increased risk of harm to these patients, increased cost, and potentially delayed discharges.