Electronic device sniffs out sleep apnea syndrome

By Lucy Piper, Senior medwireNews Reporter

An electronic nose could be used to diagnose obstructive sleep apnea syndrome (OSAS), by detecting the presence of volatile organic molecules in the breath of a patient, research suggests.

Such a test is beneficial because it would avoid the need for overnight sleep tests with multichannel polysomnography, the current gold standard, which is "technically demanding, time-consuming, and labour- and cost-intensive with limited availability," say the researchers.

They used the Cyranose 320 electronic nose (Smiths Detection Group Ltd, Watford, UK) to study patterns of volatile organic molecules related to inflammation in the exhaled breath of 40 patients with confirmed OSAS and 20 healthy individuals.

Three data sets obtained by the electronic nose were averaged for each individual and the data were fed into a linear discriminant analysis and used for further analyses.

The scores of OSAS patients and healthy controls differed significantly from each and there was a significant correlation between the linear discriminant and apnea-hypopnea index scores, indicating a dose-response relationship.

With regard to accuracy in distinguishing patients with OSAS from controls, Timm Greulich (University Hospital of Gießen and Marburg, Germany) and colleagues found that the electronic nose had a sensitivity of 93% and a specificity of 70%.

Greulich and colleagues say that the electronic nose could be useful in two instances: "First, to rule out the disease in a low prevalence population, eg, in a general practitioner's office where the prevalence of OSAS is about 2% to 4%.

"Second, the device could be a decision aid on whom to conduct overnight polysomnography."

The researchers also examined the ability of the electronic nose to measure the effects of therapy with continuous positive airway pressure and found that linear discriminant analysis values differed significantly before and after treatment. Indeed, the electronic nose distinguished between pre- and post-treatment with 80% sensitivity and 65% specificity.

It also proved to be superior to other markers of inflammation - exhaled breath condensate pH and conductivity, and matrix metalloproteases, alpha-1-antitrypsin, and tissue inhibitor of matrix metalloproteases in pharyngeal washings - for predicting OSAS and changes in the condition.

However, the combination of inflammatory markers in pharyngeal washings and exhaled breath condensate pH/conductivity with the linear discriminant analysis values did increase the diagnostic accuracy to 100%, the team reports in the European Respiratory Journal.

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