Exhaled breath microanalysis in veterinary medicine

Wyse, Cathy (2001) Exhaled breath microanalysis in veterinary medicine. PhD thesis, University of Glasgow.

Abstract

Breath microanalysis is an investigative method that is of considerable potential for non- invasive monitoring of health status, and early detection of disease in veterinary medicine. The aim of this thesis was to investigate the potential use of breath analysis for assessment of gastrointestinal transit and in vivo lipid peroxidation in animals. Initial studies in this thesis describe the use of the 13C-octanoic acid breath test (13C-OBT) and the 13C-lactose-ureide (13C-LUBT) for assessment of gastric emptying and oro-caecal transit time in the dog. The results revealed that collection of exhaled breath could be performed quickly, easily, and with minimal disturbance of the animal. The data produced could be fitted by simple mathematical models derived for analysis of gastric emptying breath tests, and reproducibility was comparable to previous reports of this test in humans. Furthermore, the parameters of the 13C-OBT were significantly altered by increased test meal energy density, a condition known to delay the rate of gastric emptying. In this study, the recovery of 2H2O in saliva did not occur simultaneously with the recovery of 13CO2 in breath following ingestion of 2H and 13C-octanoic acid in a dog. This finding indicates that the post-gastric processing of 13C-octanoic acid imposes a delay on the recovery of breath 13CO2, and confirms that the 13C-OBT does not provide a real-time measurement of gastric emptying in the dog. The results of these studies have shown that the 13C-OBT and the 13C-LUBT are potentially useful methods for assessment of gut transit in dog, although further validation is necessary. Lipid peroxidation is increasingly associated with many pathological processes, and the breath pentane test has been described as a non-invasive method for in vivo assessment of lipid peroxidation in humans. In order to assess the application of the breath pentane test in animals, a system for cryogenic concentration of exhaled breath samples, and analysis by gas chromatography (GC) was developed. Good specificity for discrimination of ethane and pentane from other breath hydrocarbons was demonstrated. The assay was sensitive to 0.5ppb and 5ppb pentane and ethane, respectively. Inter and intra-assay variation were comparable to previous studies. The test was sensitive enough to detect pentane in the exhaled breath of horses. Intra-subject variability in pentane exhalation in a group of 5 horses was lower than previously reported in man. The "electronic nose" is a method of analysis of gas samples that could potentially be applied for measurement of breath pentane. In these studies an array of composite polymer sensors, sample presentation system and data analysis protocol was integrated to form an "electronic nose" system. Composite polymer sensors were constructed by depositing a layer of a polymer solution with suspended carbon black particles on the surface of inter-digitated gold electrodes. Initial work demonstrated that these sensors were sensitive to alterations in temperature and humidity and that their baseline resistance was dependant on the percentage carbon black particles suspended in the polymer layer. Further work demonstrated that whilst the electronic nose was capable of discriminating between specific compounds, the specificity of this instrument was not sufficient to permit application for analysis of breath hydrocarbons. However, the unique chemical "fingerprint" measurement provided by the electronic nose could in the future be used to address problems in veterinary clinical investigation that cannot be contended using current analytical methods. The results of these studies suggest that the microanalysis of exhaled breath is a simple and potentially useful investigative method in veterinary medicine and is worthy of further investigation.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Advisers: Jon Cooper; Philippa Yam
• Keywords: Veterinary science
• Date of Award: 2001
• Depositing User: Enlighten Team
• Unique ID: glathesis:2001-72574
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 11 Jun 2019 11:06
• Last Modified: 11 Jun 2019 11:06
• URI: https://theses.gla.ac.uk/id/eprint/72574