Exhaled breath microanalysis in veterinary medicine

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

Stable isotope tracer studies for the measurement of equine gastrointestinal motility

Abdominal disorders are a major cause of morbidity and mortality in horses, and abnormal gastrointestinal motility may be a significant factor in the aetiopathogenesis of many equine colic syndromes. The understanding of such conditions is hampered by the lack of suitable noninvasive tests for the quantitative measurement of intestinal transit. The overall objective of this work was to investigate the potential value of stable 13C-isotope breath tests for the assessment of specific parameters of equine gastrointestinal motility. A new method developed for the collection of equine expiratory breath and measurement of its ratio was shown to have excellent repeatability. Assessment of peripheral blood tracer content was also performed and correlated significantly to that of concurrent breath samples. In the first study, the 13C-octanoic acid breath test (13C-OABT) was evaluated for the measurement of solid phase gastric emptying rate in 12 healthy horses by direct comparison with the predicate method of gastric scintigraphy. Having shown that the 13C-OABT was a reliable diagnostic procedure for use in healthy horses, a further study was performed against scintigraphy in subjects with atropine-induced gastroparesis (n = 8) to determine whether the test remained accurate when emptying rate was markedly prolonged. In study 3, the 13C-OABT was applied to measure the relative and dose-related effects of common sedative agents on solid phase gastric emptying in 8 horses. The study results may have clinical significance for case selection when these agents are used for purposes of sedation and/or analgesia. The 13C-bicarbonate and sodium 13C-acetate breath tests were investigated in study 4 for the assessment of equine liquid phase gastric emptying, and elucidation of the pattern of 13CO2 recovery from the body bicarbonate pool. The lactose 13C-ureide breath test (13C-LUBT) was investigated in study 5 for estimation of orocaecal transit time (OCTT), and concurrent comparison made to the hydrogen breath test (H2BT). In study 6 the induced 13C-LUBT was evaluated in vivo for the measurement of OCTT and a mean (+/- s.d.) time of 3.24 (+/- 0.65) h was gained. In order to examine the relationship between gastric emptying of solid ingesta, small bowel transit and its arrival in the caecum, a combined test was developed and applied in study 7, incorporating both 13C-OA and 13C-LU. Mathematical modelling of 13C recovery after ingestion of the dual test meal allowed calculation of small bowel half transit time, in addition to gastric and caecal parameters. Finally, minimised test protocols were developed for the 13C-OABT and 13C-LUBT in order to increase their clinical utility. The effects of decreasing the duration or frequency of breath collection on generation of intestinal transit parameters were assessed and linear regression models produced for each test based on the collection of 5 breath samples. Gastric t1/2, tlag and OCTT estimates from the reduced model and the full sampling protocols were highly correlated. However, in each case the reduced models were likely to underestimate these parameters when significantly prolonged, decreasing their sensitivity for the detection of delayed intestinal transit. The stable isotope breath tests offer a novel means of investigating features of intestinal motility and physiology in the horse and have potential value as both diagnostic modalities and humane research tools in this species. As the tests are non-invasive, simple to perform and do not require extensive equipment, they may be performed on site and the samples then submitted for isotopic analysis. Unlike other techniques for assessment of equine gastrointestinal motility, the stable isotope breath tests also provide an indirect measure of the transit rate of ingesta itself, which is directly relevant to the clinical situation. (Abstract shortened by ProQuest.)

Comparison of Radionuclide Scan and Conventional Contrast Study in Detection of Esophageal Anastomotic Leaks: A Prospective Study

INTRODUCTION: Esophageal resection and reconstruction remain a major therapeutic challenge for surgeons involved in the care of patients with benign and malignant disease of esophagus. Despite major advances in postoperative care, operative mortality rates worldwide remain high. Much of the operative mortality is related to complications of anastomotic leak. In a majority of esophageal surgeries, the anastomosis involves another segment of the esophagus, stomach, jejunum or colon. Anastomoses in operations of the stomach like total gastrectomy or proximal gastrectomy also involve the esophagus. One of the commonest complications encountered in patients after the above operations are an anastomotic leak. These leaks can lead to severe morbidity, increased hospital stay and cost and increased mortality. The crucial factors in the management of anastomotic leak are to recognize it earlier even at a sub clinical stage and act accordingly. Conservative management like delaying oral feeds and drainage techniques can be employed. However, rapidly progressing clinical scenario mandates aggressive approach. Contrast esophagography is the investigation of choice for detecting sub clinical anastomotic leaks when done from 7th to 10th postoperative days. Barium or water soluble contrasts are being used for the same. Our institution routinely performs thin barium contrast studies between the 7th to 10th postoperative day. Due to its hygroscopic property, water soluble contrast agents causes dilution of the contrast, thereby decreasing its sensitivity and specificity. Barium is more sensitive than water soluble contrast agents but is known to cause complications such as barium peritonitis and can interfere with repeat scans. Moreover, various studies show that the numbers of false negatives are high. Technetium scans are being used for diagnosis and evaluation of esophageal motility disorders and gastroesophageal reflux disease. There is no data of its use in detection of sub clinical anastomotic leaks in current literature. This study is to evaluate the diagnostic efficacy of technetium scans in detecting sub clinical leaks in comparison to barium contrast studies. It also aims at evaluating the reliability, limitations, disadvantages and complications of a Technetium sulphocolloid scan. AIMS OF THE STUDY: To evaluate the diagnostic efficacy and feasibility of Technetium sulphocolloid scans in comparison to esophageal contrast studies in diagnosis of sub clinical anastomotic leaks following esophageal anastomosis. OBJECTIVES: 1. To prospectively evaluate the feasibility of technetium sulphocolloid studies in the diagnosis of sub clinical anastomotic leaks. 2. To quantify the agreement that technetium sulphocolloid scans have with contrast studies in diagnosis of sub clinical anastomotic leaks. 3. To evaluate advantages and disadvantages of technetium sulphocolloid studies in terms of reliability, patient acceptance and cost in comparison to contrast studies. 4. To characterize Tc-99m sulphocolloid scan findings that would describe a sub clinical anastomotic leak. 5. To correlate patient dependant surgical factors with development of anastomotic leaks. This study aimed at exploring the diagnostic feasibility and efficacy of nuclear images in the detection of postoperative sub clinical anastomotic leak. METHODOLOGY: Patients; Cases for the study were selected according to a set of inclusion and exclusion criteria. They were as follows: Inclusion criteria: All patients undergoing the following operations, irrespective of age or sex, were included for the study. 1. Esophagectomy with reconstruction – Transhiatal, transthoracic (Ivor- Lewis, McKeown’s), en bloc esophagectomy. 2. Substernal colon bypass with or without esophageal resection, 3. Total gastrectomy, 4. Proximal gastrectomy. Exclusion criteria: 1. All patients who are clinically unstable and may not be able to tolerate both the studies as according to the surgeon’s judgment. 2. Patients with clinically obvious leaks. 3. Patients in whom both the studies could not done to completion. All patients who underwent the operations listed in the inclusion criteria were selected for the study after obtaining informed consent. Selected preoperative, intraoperative and postoperative data as mentioned in the proforma were collected for each patient. Patients who satisfied the exclusion criteria during the course of the study were taken off the study. PATIENT PROFILE: 51 cases were enrolled into the study of which 13 cases were excluded from the study due to the various exclusion criteria. The reasons for exclusion form the study were as follows. 1. Patients who were clinically unstable during the time of the tests – 4 patients. 2. Patients who developed clinically detectable leaks prior to the imaging – 5 patients. 3. Patients who could not complete either one of the study due to patient related factors -1 patient (Barium induced vomiting). 4. Patients who could not complete either one of the study due to technical reasons- 2 patients. CONCLUSION: 1. Technetium sulphocolloid esophageal scintigraphy have a good agreement with barium contrast studies in detecting sub clinical anastomotic leaks. 2. The sensitivity of technetium scans could not be assessed due to lack of a proper gold standard. 3. Technetium scintigraphy was found to have detected more sub clinical anastomotic leaks than barium. 4. Technetium sulphocolloid scans are more economical than barium contrast studies. 5. Technetium sulphocolloid imaging does not cause any of the complications of barium such as barium peritonitis or barium inspissation. 6. The amount of radiation exposure to the patient as well as his/her attendants is negligible. 7. Technetium is excreted from the body rapidly and so repeat scans are not confounded by the old technetium

Studies examining the pathophysiology of acid-induced distal oesophageal squamous mucosal damage

• Gastro-oesophageal reflux disease (GORD) is the commonest chronic disease in Western countries. Symptomatic GORD is the strongest risk factor for the development of oesophageal adenocarcinoma with obesity and male sex also linked to the development of neoplasia at this site. Recent decades have seen a significant increase in the incidence of this highly lethal cancer among Western populations with Scotland having the highest recorded incidence worldwide. • Human saliva has a high nitrite content derived from the entero-salivary recirculation of nitrate in our diet which has resulted from the increased use of nitrogenous fertilisers over the past 50-60 years. • The luminal chemistry produced at the gastro-oesophageal junction (GOJ) when swallowed salivary nitrite reacts with gastric acid, and most notably the production of nitric oxide (NO), may explain most of the physiological abnormalities that contribute to the pathogenesis of GORD. NO has been shown to reduce lower oesophageal sphincter (LOS) pressure, impair oesophageal clearance, delay gastric emptying and may be the final mediator of transient lower oesophageal sphincter relaxations (TLOSRs). Previous studies to investigate the role of this luminal chemistry in the pathogenesis of GORD show conflicting results. • In addition to the distal oesophageal acidification produced by traditional trans-sphincteric reflux, previous studies suggest ‘splaying open’ of the distal lower oesophageal sphincter following a meal may expose the gastric cardia and the most distal oesophageal squamous mucosa to the noxious effects of gastric acid. • Although the gastric cardia is an important site of pathology in the upper gastrointestinal tract, it is a complex and poorly understood area. It has been proposed, from autopsy studies, that cardia mucosa itself may be pathological and in fact an ‘acquired cardia’ due to metaplasia of the most distal oesophageal squamous mucosa. • A series of studies were designed to examine the effect of salivary nitrite on post-prandial GORD, gastro-oesophageal function and GOJ morphology in 20 healthy, asymptomatic adult volunteers using high-resolution pH manometry, an isotope gastric emptying breath testing and X-ray localisation of the squamo-columnar junction (SCJ). • Despite an excellent range of salivary nitrite concentrations extending over and above the normal physiological range no effect of salivary nitrite on gastro-oesophageal reflux, function or morphology was demonstrated. However, the studies did confirm, for the first time using high-resolution manometry, that distal opening of the LOS occurs after a meal. • The relationship of age and obesity to the SCJ position relative to the proximal border of the gastro-oesophageal high pressure zone (HPZ) was examined in 15 Helicobacter Pylori negative healthy volunteers. Strong negative correlations were seen between SCJ position relative to the proximal HPZ and increasing age, body mass index (BMI) and waist circumference (WC) respectively. These correlations were stronger in the male sub-group. • In 25 healthy volunteers, parietal cell density was measured from endoscopic biopsies taken from the macroscopic SCJ, 1cm distal to the SCJ, the gastric body and the gastric antrum. Again, a strong negative correlation was seen between increasing age and parietal cell density at the SCJ. This effect was localised to the SCJ and not seen at the other biopsy sites. • Our findings suggest that salivary nitrite does not alter gastro-oesophageal function, the integrity of the gastro-oesophageal barrier or gastro-oesophageal reflux in healthy volunteers. They confirm distal opening of the LOS after meals. The strong negative correlations between age and both SCJ position relative to the proximal HPZ and parietal cell density support the hypothesis of an ‘acquired’ cardia. The development of cardia mucosa may also be linked to obesity, visceral obesity and male sex. • Future work could examine the carcinogenic effect of salivary nitrite and its luminal chemistry but this would require large scale epidemiological research. Further, larger clinical studies are needed to investigate the role of distal opening of the LOS after meals and to improve our understanding of the gastric cardia. Such studies should focus on the role of obesity and posture

A study of incidence of early complications in thyroid surgery

In the Present study 156 patients were observed, 138 were females and 18 were males. Females were more commonly affected by thyroid diseases. Male and Female ratio was 1:8. 60% of thyroid disease occurred during the age between 20-40 years. • The incidence of early postoperative complications were the following: The incidence of haemorrhage with respiratory obstruction was 1.28%. The incidence of neural complications, recurrent laryngeal nerve and superior laryngeal nerve palsy were 3.21% and 0.64% respectively. Incidence of hypocalcemia was 5.13%, wound infections was1.92%, thyroid storm was 0.64% and incidence of seroma was 2.56%. • The incidence of complications in various thyroid disorders were the following: 35% of complications were observed in Toxic goiter followed by 21.87% in Multinodular goiter, 20% in colloid goiter and 16.66% in carcinoma thyroid. There was no reported complication in solitary nodular goiter. The incidence of complications in various thyroidectomy procedures were following: • Haemorrhage with airway obstruction was documented only in 4.44 % of cases following total thyroidectomy. • Postoperative hypocalcemia was documented in 11.11% of cases following total thyroidectomy and in 8.33% of cases following near total thyroidectomy. • Recurrent laryngeal nerve palsy was documented in 6.66% of cases following total thyroidectomy and in 5.55% of cases following near total thyroidectomy. • The superior laryngeal nerve palsy was documented only in 2.22% of cases following total thyroidectomy. • Thyroid crisis was documented only in 2.22% of cases following total thyroidectomy. • Seroma was documented in 8.33% of cases following near-total thyroidectomy and in 5.26% of cases following subtotal thyroidectomy. • The wound infection was documented in 5.55% of cases following near total thyroidectomy and in 5.26% of cases following subtotalthyroidectomy. CONCLUSION: The following conclusions are drawn from this study: 1. Incidence of hypocalcemia is a relatively common complication than recurrent laryngeal nerve injury after thyroidectomy. 2. Relatively more complications occur after Total Thyroidectomy than neartotal, subtotal thyroidectomy. No complications occurred after hemithyroidectomy. 3. Multi nodular goiter, Toxic multi nodular goiter, Carcinoma thyroid are risk factors for post operative complication. 4. Post operative complications can be reduced by a careful clinical evaluation, a thorough knowledge of the surgical anatomy, a systematic dissection of parathyroid gland and recurrent laryngeal nerve during the surgery

An investigation of a novel, non-invasive technique for the assessment of oxidative stress in aerobic and isometric exercise

The oxidative stress response to exercise is a well-established phenomenon; however, the time course of this response has not been well characterised. There is little information in the literature regarding the oxidative stress response during exercise; most authors have measured oxidative stress solely during the recovery period from exercise. There are several different invasive methods available for assessment of oxidative stress, although there is no “gold standard” technique. A novel non-invasive technique utilising laser spectroscopy to quantify expired ethane concentration has become available, but has not yet been tested in relation to exercise. The first study described here aimed to use the laser spectroscopy technique for the first time to assess exercise-induced oxidative stress in three species: humans, horses and dogs; and to determine the utility of carbon monoxide monitoring as a means of assessment of oxidative stress. A further objective was to better characterise the oxidative stress response by the collection of data at frequent intervals during exercise and during recovery. Eight endurance-trained males performed incremental treadmill exercise to volitional exhaustion. Twelve racehorses and twelve racing greyhounds performed maximal exercise on a race track. Expired ethane concentration was measured throughout exercise in humans, and pre- and post-exercise in horses and dogs. Carbon monoxide concentration was assessed pre- and post-exercise in all species. Results indicated that the technique of laser spectroscopy was viable for use in relation to exercise in all three species. Oxidative stress was shown to increase significantly following exercise in all three species, thus supporting previous literature, and extending this finding to a trained human population for the first time. The pattern of response during incremental treadmill exercise was characterised for the first time and indicated a non-significant increase in oxidative stress in humans within 2 minutes of the onset of exercise, with the response progressively increasing alongside increases in work rate until exercise was terminated at exhaustion. The response returned close to the resting value by 20 minutes into the recovery period. Low subject number may have contributed to the lack of significant findings during exercise. Carbon monoxide was not a useful indicator of oxidative stress in any species. Increased functionality of the laser spectroscopy technique was investigated by pilot work in which real-time monitoring of expired ethane was attempted for the first time in relation to exercise. This allowed the observation of the oxidative stress response on a breath by breath basis. Initial tests, in which two healthy males performed incremental cycle ergometer exercise to exhaustion whilst breathing through a valve connected directly to the spectrometer, indicated that a useful output could be recorded during a prolonged period of exercise. However, the measurement of ambient ethane concentration, essential for accuracy, was not undertaken in the initial tests. Thus, further pilot work was successfully carried out in three healthy males to replicate the initial tests with concurrent ambient ethane monitoring. This pilot testing allowed development of data editing techniques. The oxidative stress response profile for incremental exercise in real-time was similar to that reported in the previous chapter. Additional tests were undertaken which illustrated that the rise in ethane output observed during incremental exercise was not simply a manifestation of the ventilatory response to exercise, rather than an indication of exercise-induced oxidative stress. This was accomplished by forcing an increase in ventilation, by imposition of an additional dead space volume during normal breathing in two individuals. This technique shows promise for more detailed characterisation of the time course of the oxidative stress response in future exercise studies via the capability for extremely high density data collection. The main aims of the second study were to investigate the oxidative stress response throughout the entire work rate range from rest to volitional exhaustion, rather than just the higher end of the work rate range as observed in study one; and to examine the magnitude and time course of the oxidative stress response to constant load exercise performed below and above the lactate threshold. Six healthy males performed incremental cycle ergometer exercise to exhaustion during which blood samples were collected regularly for later analysis for the presence of F2-isoprostanes. Results of the analysis were disappointing, with a high proportion of samples displaying a concentration outwith the range of the assay. However, preliminary malondialdehyde analysis suggested that the oxidative stress response may increase progressively alongside work rate throughout the entire work rate range. However, this observation is far from conclusive as it is based on data from a single subject only. The final study was intended to investigate the effect of contraction intensity on the oxidative stress response to isometric handgrip exercise sustained to exhaustion, and to clarify the time course of the oxidative stress response during the recovery period. Due to logistical limitations, it was possible to study one contraction intensity only. Initially, pilot work was undertaken to determine the suitability of the novel non-invasive technique for ethane assessment in relation to isometric exercise, since this assessment method had not been used previously with this exercise mode. Then, six healthy males performed sustained isometric exercise at 60 % of maximal voluntary contraction until fatigue. Oxidative stress was assessed during a 30 minute recovery period via expired ethane and also via F2-isoprostanes concentration in blood collected from both the exercised arm and the non-exercised arm. This was intended to allow comparison of blood sampling site, and of the systemic oxidative stress response measured both invasively and non-invasively; however this was not possible due to poor assay results. The previous finding of a peak oxidative stress response following isometric exercise within the first 5 minutes of the recovery period was supported. Oxidative stress was assessed by ethane output for the first time in relation to isometric exercise and was found to be a viable technique; however, its use remains to be validated against more traditional plasma markers. The potential value of non-invasive assessment was underlined by F2-isoprostanes analysis issues. In conclusion, the use of laser spectroscopy, including the use of real-time monitoring, appears to be a viable technique for the non-invasive assessment of exercise-induced oxidative stress, and may enhance our ability to characterise this response in future studies