Abstract
Background:
Pulse oximetry is commonly used to measure oxygen saturations (SpO2) in assessment of patients with stable COPD. This is considered to be equivalent to oxygen saturations measured on a blood gas analyser (SaO2). The ATS, ERS and GOLD guidelines for COPD define suitability for long term oxygen therapy with PaO2 less than 7.3kPa or SaO2 of less than 88%.
Aim:
To confirm if SpO2 correlates to SaO2 in stable COPD patients.
Methods:
Retrospective study of patients with stable COPD attending oxygen clinics in an acute teaching hospital.
Results:
N=73, Male 29 %, Mean Age70 (range 53 - 93), Mean FEV1 0.89 L, current smokers 29%, 26% on oxygen, mean MRC grade 4, mean BORG score at rest 2 and mean hematocrit (HCT) 0.41.
On't' paired testing in all patients, no statistically significant difference was noted between SpO2 and SaO2 (p value: 0.972), the mean SpO2- SaO2 is -0.012% (95% CI of -0.71 to 0.69).
However, in current smokers subgroup (N=21) high variation between these values was noted, with the mean SpO2- SaO2 1.067%. There was a tendency for SpO2 to be higher than SaO2 (95% CI of -1.038 to 3.171).
There is no statistically significant relationship between SpO2 and SaO2 in COPD patients in relation to sex, age, severity of COPD, smoking status, MRC grade, BORG score, and HCT levels.
Conclusions:
As the difference between SpO2 and SaO2 is high in current smokers, SpO2 reading using pulse oximetry might not be reliable. Further studies with larger sample size are needed to evaluate this further.
- © 2012 ERS