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Analysing exhaled breath during endovenous laser ablation of varicose veins using an electronic nose and gas chromatography-mass spectrometry

During the last two decades, several minimally invasive techniques have been developed to treat the incompetent great saphenous vein (GSV). In the late 1990s, various endovenous laser treatments were generally used. During this procedure the temperature of the venous wall tissue and blood remaining in the vein can reach temperatures of over 8008C. This causes carbonization and a release of steam bubbles and gases. During and after the endovenous laser ablation (EVLA) procedure patients often report a barbeque-like taste. Even the treating surgeon can sometimes smell an indistinct odour. The sensation of flavour is due to three main chemoreceptor systems: olfaction (sense of smell by nose), gustation (sense of taste by tongue) and trigeminal (sense of irritation of trigeminal receptors). The sense of smell is used to detect patterns of volatile compounds, while the sense of taste is used to detect non-volatile chemicals. Electronic noses (e-noses) have been developed as a simplified ‘electronic’ model of the human olfactory system and were used in the present study to analyse the breath produced during EVLA. In our centre EVLA 980 nm bare tip is being used for the treatment of the GSV and small saphenous vein, using tumescent anaesthesia only. In this study we hypothesized that e-nose assessment can detect changes in exhaled breath molecular profiles during the EVLA procedure. We also hypothesized that non-physiological and elevated volatile organic compounds (VOCs) can be identified and quantified by gas chromatography-mass spectrometry (GC-MS) during EVLA. We aimed to associate these observations with the subjective tastes and odours as reported by the subjects. This is an experimental study in patients eligible for EVLA, and agreed to have local tumescent anaesthesia. Inclusion and exclusion criteria for surgery and method of treatment have been fully described in a previous publication. The study was approved by the medical ethical committee Noord-Holland, The Netherlands, and a written informed consent was signed by all patients. Exhaled breath of 12 patients was analysed using the Cyranose 320 e-nose (Smiths Detection, Pasadena, CA, USA), a hand-held portable chemical vapour analyser, containing a 32-polymer nanocomposite sensor array. Patients needed to be sober and non-smoking for at least three hours, in order to avoid confounding factors for breath analysis. Fifteen minutes before the EVLA, they breathed for five minutes through a nonrebreathing valve (Hans Rudolph, Kansas City, MO, USA) using an inspiratory VOC filter (A2, North Safety, Middelburg, The Netherlands) to avoid contamination by environmental VOCs. An expiratory silica reservoir was used to dry the expired air and a nose clip was used to prevent nasal air leakage. One single vital capacity manoeuvre was done while the expiratory port was connected to a 10-L Tedlar bag. The subject exhaled the full expiratory vital capacity into the bag with an expiratory resistance of 20 cm H2O. 12 The same procedure was repeated during the actual EVLA procedure 3–5 minutes after the start of the heating of the laser wire. Then a second Tedlar bag was filled with a single vital capacity volume. Within ten minutes the Tedlar bag was connected to the e-nose for analysis. Patients recorded whether they did have (yes 1⁄4 1) or did not have (no 1⁄4 0) a ‘barbeque-like’ taste and/or smell during the procedure. The breathprints were analysed using SPSS software (version 18). A paired t-test was assessed to calculate the difference in breathprint measured at both timetables. Then correlation coefficients of these results and changes in perceived taste and smell were calculated. As an explorative procedure, in two out of 12 patients, GC-MS was introduced to perform specific compound analysis.