Biomedical subjects
Publications and source records attributed to L S Wong.
This case is presented to illustrate the imaging and clinical findings of a condition of interest to orthopaedic surgeons. The initial findings are noted on this page. The clinical and imaging diagnoses are presented on the following pages.
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An IBM PC-based real-time data acquisition, monitoring and analysis system for experimental haemodynamic studies was developed. Comprehensive haemodynamic signals, such as aortic and left ventricular pressures, aortic and coronary blood flows, two segmental lengths, two segmental thicknesses, electrocardiogram and airway pressure, were acquired and monitored to assess cardiac function. The system performs computer-aided analysis and derivations on a number of haemodynamic parameters and cardiac function indices. The system has been tested and validated extensively over a number of series of experimental haemodynamic studies to investigate the effects of anaesthetic agents, cardiovascular drugs, and changes in loading on normal and critically ischaemic myocardium of anaesthetised laboratory subjects. Without this specialised and automated system, the analysis of the data acquired from the haemodynamic studies would be too time-consuming and could not be fully performed.
OBJECTIVE: An IBM PC-based real-time data acquisition, monitoring and analysis system was developed for the assessment of cardio-respiratory function, i.e. airway dead space, alveolar volume and pulmonary blood flow, using oscillating inert inspired gas forcing signals. METHODS: The forcing gas mixture was generated by an in-house sinusoid gas delivery unit. The system interfaced with a mass spectrometer and an airway flow transducer, and performed real-time tracking of the breath-by-breath end-inspired, end-expired and mixed-expired concentrations. It calculated the cardiorespiratory parameters using two, i.e. continuous and tidal, in-house mathematical models of the lungs. The system's performance was evaluated using a mechanical bench lung, laboratory subjects and awake adults breathing spontaneously. Its predictive accuracy was compared with the measured volumes of the bench lung; single breath CO2 test for airway dead space and N2 washout for alveolar volume in laboratory subjects and awake adults; and thermal dilution technique for pulmonary blood flow in laboratory subjects. RESULTS: Close agreements were found between the true and predicted airway dead space, i.e. mean differences of -12.39%, 14.47% and -17.49%, respectively, and that of alveolar volume, i.e. -8.03%, -3.62% and 7.22%, respectively, in the bench lung, laboratory subject and awake adult studies; and that of pulmonary blood flow (-23.81%) in the laboratory subjects using the continuous lung model. Even closer agreements were observed for airway dead space (-5.8%) and alveolar volume (-4.01%) of the bench lung and for pulmonary blood flow (-8.47%) in the laboratory subjects using the tidal lung model. CONCLUSIONS: A system was developed to deliver, monitor and analyse on-line, and in real-time, output data from the sinusoid forcing technique. The technique was administered using the system in various subjects, and produced favourable predictions.
We report a rare case of a non-insulin secreting malignant insulinoma of the pancreas and discuss its medical and surgical management. Surgical excision of malignant insulinoma produces good palliation and can increase survival.
We assessed the Bird T-Bird VS ventilator using a model lung constructed to standard 10651-1 of the International Standards Organization. We used different combinations of lung compliance and airway resistance to simulate normal and diseased adult and paediatric lungs. Different preset tidal volumes at various respiratory rates were delivered to the model lung and compared with the actual measured tidal volumes. The results showed that the delivered tidal volumes were within the manufacturer's specification of +/- 10% of the preset tidal volumes in normal adult and paediatric combinations of lung compliance and airway resistance. The ventilator can be powered by mains electricity supply or battery and requires only optional compressed oxygen. The ventilator is suitable for the provision of advanced ventilatory support during prolonged patient transfer.
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With the increasing use of natural rubber products, latex allergy is becoming a major health concern among patients and healthcare workers. The aim of this study was to determine the availability of a latex allergy protocol and essential latex-free products in theatres. The number of latex allergy complaints among patients and theatre personnel were also studied. Postal questionnaires were sent to theatre managers in 205 hospitals in England, Scotland and Wales, 120 (58.5%) of which were returned. Nearly two-thirds of the theatres did not have a latex allergy protocol. Overall less than one-third of theatres in the UK have latex-free products set aside for use. A total of 505 patients with latex allergy underwent surgery; of these, there were four deaths, 18 major anaphylaxes and 483 minor complaints such as skin rash; 239 theatre personnel reported latex allergic reactions and one had a severe anaphylactic reaction. The number of cases with latex-related complications might be reduced if all hospitals had a latex allergy protocol and a range of essential latex-free products.
HYPOTHESIS: Patients with melanoma and histologically negative sentinel lymph nodes identified by lymphatic mapping have a very good prognosis. DESIGN: Cohort study with follow-up information obtained from medical records and telephone interviews. SETTING AND PATIENTS: Of all patients with cutaneous melanoma who underwent intraoperative sentinel lymph node mapping between November 15, 1993, and April 18, 1997, at the Massachusetts General Hospital, Boston, 89 were found to have no evidence of melanoma in their sentinel nodes. Forty-six lesions (51%) were on an extremity and 44 (49%) were of axial location. The median tumor thickness was 1.8 mm (range, 0.36-12.0 mm) and 11 tumors (12%) were ulcerated. INTERVENTIONS: Patients underwent intraoperative sentinel lymph node mapping with lymphazurin and radiolabeled sulfur colloid. Sentinel lymph nodes were analyzed by standard hematoxylin-eosin staining. Only 2 patients received adjuvant therapy following wide excision of the primary lesion. MAIN OUTCOME MEASURES: Site of initial recurrence and time to initial recurrence. RESULTS: The median follow-up for all patients was 23 months (range, 2-54 months). Eleven patients (12%) developed melanoma recurrences, and 78 (88%) patients remain disease free. Regional lymph nodes were the initial site of recurrence in 7 (8%) of 89 patients, and 7 (7%) of 106 mapped basins. Four patients had recurrence without involvement of regional lymph nodes: 2 with distant metastases and 2 with in transit metastases. The median time to recurrence was 12 months (range, 2-35 months). Sentinel lymph nodes were reanalyzed using serial sections and immunoperoxidase stains in 7 patients with recurrence and metastatic melanoma was identified in 3 (43%). CONCLUSIONS: The risk for melanoma recurrence is relatively low in patients with histologically negative sentinel nodes identified by lymphatic mapping. Longer follow-up will improve our understanding of the prognostic value of this procedure.
The aim of this study was to compare the ability of artificial neural networks and the Acute Physiology and Chronic Health Evaluation II score to predict mortality in adult intensive care units. The same physiological variables were used in both predictive models to predict hospital mortality from a data set of 8796 patients collected from 26 adult intensive care units in the United Kingdom and Ireland as part of the Intensive Care Society study. The results from the two models were compared with the actual outcome. The overall prediction accuracy and the overall goodness-of-fit of all the models were assessed. Both predictive models showed similar goodness-of-fit and prediction discrimination. The overall predictive and classification performance of the artificial neural network developed matched and in some aspects was better than that of Acute Physiology and Chronic Health Evaluation II.
The military and some civilian rescue agencies have a requirement for portable ventilators in the anaesthetic, resuscitation and pre-hospital environment. This paper describes two new portable ventilators specifically designed to satisfy the military requirement for lightweight, robust and versatile equipment which can also be used in a contaminated environment.
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We report a case of metastasis from a regressed cutaneous melanoma presenting as an acute abdomen. The patient presented with peritonitis, which at operation was found to be due to intraperitoneal haemorrhage from a bleeding metastatic melanoma lesion in the ileum. Surgical resection was performed and the patient remained well 2 years later.
Metastatic melanoma of the small bowel is a pathological entity that is not frequently reported but may present with features of unexplained anaemia. We report a case of a 51-year-old man with occult intestinal bleeding due to metastatic melanoma of the small bowel. Although the diagnosis was somewhat delayed, the patient was managed successfully by small bowel resection. Careful investigation of melanoma patients with gastrointestinal symptoms is important as surgical intervention often results in improved quality of life and survival.
Intrabiliary rupture of a hydatid liver cyst is infrequently reported, but may present with symptoms of choledocholethiasis or cholangitis. We report a case of hydatid liver disease presenting as recurrent pancreatitis, and discuss its clinical, radiological and surgical treatments. Hydatid liver disease has a diverse clinical spectrum, and a diagnosis of acute pancreatitis should be considered in patients with hydatid liver disease presenting with unexplained abdominal pain.
Several endogenous oscillators determine circadian rhythms. One, light-entrained, is in the suprachiasmatic nuclei (SCN), the others, food-entrained, are in unknown sites. To determine how the hypothalamic ventromedial nuclei (VMN) and feeding affect rhythms, we compared nocturnally active rats fed either ad libitum or for 2 hr/d during light [restricted feeding (RF)] and either with or without colchicine-induced disruption of VMN. We measured rhythms in temperature, locomotor activity, feeding, drinking, corticosterone, and the numbers of cells expressing c-Fos in light/dark in hypothalamic nuclei, the suprachiasmatic nuclei, and two major SCN targets, the subparaventricular zone (sPVNz) and paraventricular thalamus (pvTHAL). c-Fos cells were always light > dark in SCN, whereas the VMN and sPVNz lacked light/dark differences except after RF and RF plus VMN disruption, respectively. Controls fed ad libitum had high-amplitude rhythms and, generally, c-Fos cells dark > light. In RF controls, a c-Fos pattern dark > light occurred in VMN; generally, c-Fos cell numbers increased elsewhere maintaining dark > light. By contrast, levels of corticosterone peaked before food. In rats fed ad libitum, VMN with colchicine markedly reduced rhythm amplitudes, not phase. c-Fos patterns were abolished except in pvTHAL and SCN. In RF, VMN disruption blocked corticosterone and light/dark c-Fos patterns in all nuclei but produced a pattern in the sPVNz like SCN. We conclude that VMN amplify rhythmic output from the SCN, and the RF-induced rhythm in VMN enhances c-Fos activity driven by the SCN. The VMN may contain a food-entrained oscillator, and the sPVNz may integrate output from several oscillators.
When a spa bath was installed in the maternity unit of Osborne Park Hospital, a Quality Assurance survey was undertaken to try to identify any potential problems. At the same time a client satisfaction survey was conducted. The study highlighted many benefits to the client as an alternative method of pain management. At the same time no obvious problems were identified. However, due to lack of control of the many variables, and the absence of statistical analysis, no definite conclusions can be drawn from the study. Positive responses from clients encourage us to continue to offer the spa bath as a method of pain management. This is an area which begs research.