Endoscopic laser treatment. III. Development and testing of a gas-jet-assisted argon laser waveguide in control of bleeding experimental ulcers.
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Biomedical subjects
J Piercey
Publications and source records attributed to J Piercey.
Endoscopic laser treatment. II. Comparison of the efficacy of high and low power photocoagulation in control of severely bleeding experimental ulcers in dogs.
The coagulative efficacy of a "high power" argon laser which delivers 6.5 +/- 1.0 w was compared to that of a "low power" argon laser which delivers 1.0 +/- 0.1 w. The wave-guide angle of divergence was 8 degrees. For the high power laser, the distance between the wave-guide tip and the mucosa varied from 1.0 to 1.5 cm with a delivered power density range of 160 to 487 w per cm2. For the low power laser, the distance between the tip and mucosa varied from 0.7 to 1.3 cm with a power density of 35 to 146 w per cm2. Group A consisted of acute experiments in 6 heparinized dogs in which 51 standard-sized acute gastric ulcers extending into the submucosa were made at laparotomy via a large gastrotomy. Ulcer bleeding rates were quantified into three categories of severity. Within each category, ulcers were randomized to high power, low power, or untreated control. All 19 low power-treated ulcers and 16 untreated controls continued bleeding; 13 of 16 high power-treated ulcers stopped bleeding completely. Representative ulcers were examined histologically. Group B consisted of chronic experiments on 31 ulcers in 7 unheparinized dogs. These ulcers were either treated with high power or left as untreated controls. Dogs were killed and the ulcers were examined histologically at 7, 14, and 28 days. Only rarely did the laser injury penetrate into the muscularis externa. There were no perforations. By 14 days, all lesions were covered with normal surface epithelium. These data encourage further development of congruent to 7.0 w argon laser photocoagulation for eventual clinical use in man.
Animals↗
A reproducible animal model of acute bleeding ulcer-the "ulcer maker".
An instrument has been developed which creates an experimental model of an acute bleeding gastric ulcer. The diameter and depth of these gastric ulcers are reproducible. The instrument can be used endoscopically or at laparotomy. Using this ulcer model nonsurgical modalities for the treatment of upper gastrointestinal bleeding can be compared in a controlled manner. This standard experimental model may also facilitate comparison of results among different research groups.
Animals↗
Valve data collection: problems and pitfalls.
Since 1981, the Department of Medical Physics and Clinical Engineering at the University of Sheffield has been responsible for the organization, management and data collection associated with the largest multicentre heart valve implant patient follow-up study in the Western world. At the present time, the database comprises information on over 16,000 valve implants, which have been provided by 57 surgeons working at 22 centres in the UK. All this data is available for in-depth statistical analysis. Over 30 individual valve models presently are included in the Study and these can be categorized into five main types: ball, disc, porcine, pericardial and homograft. Analysis includes descriptive statistics as well as valuable information on the various performances of the different valves. Survival and event-free survival graphs are obtained by actuarial methods and individual valve types can be studied in depth in terms of freedom from thromboembolic complications and valve dysfunction. Whilst this approach provides interesting and valuable survival data, it does not take account of the wide variation in prognostic factors which occur within large groups of patients. This latter problem can be addressed by the use of proportional hazards analysis and this paper provides details of this approach and typical results obtained from the use of this method. These include the comparative performances of the major types of valves currently in use in terms of the event-free survival of the patients.
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