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

Objective: To explore the associations between decreased pulse oximetry values (SpO(2)) 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 SpO(2) values (≤ 95% and ≤ 92%). Results: Of 372 patients included (mean age 61.5 years, 62% women), 82 (22.0%) had SpO(2) ≤ 95%, of which 11 had SpO(2) ≤ 92%. In both asthma and COPD patients, SpO(2) ≤ 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 SpO(2) ≤ 95%. These associations were confirmed by multivariable logistic regression, where FEV(1)% predicted < 50 was the strongest predictor of SpO(2) ≤ 95% (odds ratio 6.8, 95% confidence interval 2.8–16.4). Conclusion. 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.