• Lene G Dalbak, Jørund Straand, and Hasse Melbye.
• a General Practice Research Unit, Department of Community Medicine , University of Tromsø , Norway ;
• Scand J Prim Health Care. 2015 Jan 1; 33 (4): 305-10.

ObjectiveTo 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/SettingA 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 MeasuresDecreased SpO2 values (≤ 95% and ≤ 92%).ResultsOf 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).ConclusionPulse 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.

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