Should pulse oximetry be included in GPs’ assessment of patients with obstructive lung disease?

Abstract

Objective: To explore the associations between decreased pulse oximetry values (SpO₂) and clinical, laboratory, and demographic variables in general practice patients diagnosed with asthma or chronic obstructive pulmonary disease (COPD), including those with both COPD and asthma in combination.

Design/setting: A cross-sectional study in seven Norwegian general practices of patients aged 40 years or over who were diagnosed by their general practitioner (GP) with asthma and/or COPD. The patients were examined during a stable phase of their disease. Patients diagnosed with COPD (including those with combined COPD/asthma) and those diagnosed with asthma only were analysed separately.

Main outcome measures: Decreased SpO₂ values (≤ 95% and ≤ 92%).

Results: Of 372 patients included (mean age 61.5 years, 62% women), 82 (22.0%) had SpO₂ ≤ 95%, of which 11 had SpO₂ ≤ 92%. In both asthma and COPD patients, SpO₂ ≤ 95% was significantly associated with reduced lung function (spirometry), a diagnosis of coronary heart disease and older age (≥ 65 years). In the COPD group, haemoglobin above normal was associated with SpO₂ ≤ 95%. These associations were confirmed by multivariable logistic regression, where FEV₁% predicted < 50 was the strongest predictor of SpO₂ ≤ 95% (odds ratio 6.8, 95% confidence interval 2.8–16.4).

Conclusion. Pulse oximetry represents a useful diagnostic adjunct for assessing the severity of obstructive pulmonary disease. Decreased pulse oximetry values in stable-phase patients with asthma and/or COPD should prompt the GP to consider revising the diagnosis and treatment and to look for co-morbidities.

Key Points

• Despite its common use in general practice, the diagnostic benefits of pulse oximetry remain to be established.

• Decreased pulse oximetry values are associated with both reduced lung function (spirometry) and with a diagnosis of coronary heart disease.

• Decreased pulse oximetry values may reflect suboptimal treatment and/or undiagnosed comorbidity.

• Pulse oximetry may therefore be a useful measure in the follow-up of asthma and COPD patients in general practice.

KeyWords:

• Asthma
• chronic obstructive pulmonary disease
• comorbidity
• general practice
• Norway
• oximetry

Acknowledgements

The authors would like to thank all patients, GPs, and health secretaries who participated in the study.

Ethical approval

Participating patients signed a written consent form and the study was approved by the Regional Committee for Medical and Health Research Ethics in North Norway.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

LGD were supported by a grant from the Norwegian Research Fund for General Practice.