Evening and morning exhaled volatile compound patterns are different in obstructive sleep apnoea assessed with electronic nose

Electronic noses represent a technique for the measurement of exhaled breath volatile compound pattern which can discriminate patients with obstructive sleep apnoea (OSA) from control subjects. Although overnight changes in circulating biomarkers were reported, this effect on the exhaled volatile compound pattern has not been studied before. We aimed to compare breath patterns in the evening and in the morning in patients with OSA and to study the ability of the electronic nose to distinguish patients from controls based on these exhaled volatile patterns. Exhaled breath volatile compound pattern was measured before and after night in 26 patients with suspected sleep-disordered breathing (53 +/- 15 years) who underwent polysomnography and in ten control subjects (37 +/- 15 years), by whom sleep-disordered breathing was excluded with a home apnoea screening device. Breath measurements were also performed in the morning in 26 healthy, non-smoking age-matched controls (48 +/- 10 years) with no complaints about disturbed sleep. Exhaled volatile compound pattern was processed with a Cyranose 320 electronic nose, and principal component analysis was used for statistical analysis. Exhaled volatile compound patterns recorded in the evening and in the morning were different in patients with OSA (p = 0.01) but not in non-OSA habitual snorers (p = 0.49) or in control subjects (p = 0.23). The electronic nose distinguished patients with OSA from control subjects based on the breath samples collected in the morning (p < 0.001, classification accuracy 77 %) but not in the evening (p > 0.05). Evening and morning exhaled volatile compound patterns are different in OSA. This might affect the ability of electronic noses to identify this disorder. Overnight alterations in volatile substances need to be taken into account during exhaled breath measurements in OSA.