PubMed · 8926467
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T Nakamura. 1996-07-10. [Milk intolerance].. https://pubmed.ncbi.nlm.nih.gov/8926467/
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We consider two and 50 compartment lung models for use with two techniques used to investigate the efficiency of the lungs: the Multiple Breath Nitrogen Washout (MBNW) technique used for investigating the ventilation-volume distribution; and the Multiple Inert Gas Elimination Technique (MIGET) used for investigating the ventilation-perfusion distribution. In each of these techniques pulmonary respiratory gas exchange is described by conservation of mass equations which may be written in identical form, and in each the underlying distributions of ventilation to volume and ventilation to perfusion are assumed to be continuous functions (usually assumed to be a linear sum of log-normal distributions). The mathematical models used to describe the lung have predominantly used a collection of discrete compartments to approximate these continuous distributions. The most commonly used models have used one, two or 50 compartments. In this paper, we begin by showing that in the limit as the width of the peaks of the distribution tend to zero, the continuous distributions may be replaced by a single discrete compartment placed at each peak of the distribution. We investigate the various methods used previously for parameter recovery, and show that one commonly used method for the MBNW is not suitable and suggest a modification to this recovery technique. Using simulated error-free data, we show that both the two compartment model and the 50 compartment model contain information about the ventilation-volume (or ventilation-perfusion) distribution, and investigate the extent to which this information can be used to recover the parameters which define these distributions. We go on to use Monte-Carlo methods to investigate the stability of the recovery process.
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OBJECTIVE: To determine how small differences in the efficacy and cost of two antibiotic regimens to eradicate Helicobacter pylori can affect the overall cost effectiveness of H pylori eradication in duodenal ulcer disease. DESIGN: A decision analysis to examine the cost effectiveness of eight H pylori eradication strategies for duodenal ulcer disease with and without 13C-urea breath testing to confirm eradication. MAIN OUTCOME MEASURES: Cumulative direct treatment costs per 100 patients with duodenal ulcer disease who were positive for H pylori. RESULTS: In model 1 the strategy of omeprazole, clarithromycin, and metronidazole alone was the most cost effective of the four strategies assessed. The addition of the 13C-urea breath test and a second course of omeprazole, clarithromycin, and metronidazole achieved the highest eradication rate (97%) but was the most expensive (62.63 pounds per patient). The cost of each additional effective eradication was 589.00 pounds (incremental cost per case) when compared with the cost of treating once only with omeprazole, clarithromycin, and metronidazole; equivalent to the cost of a patient receiving ranitidine for duodenal ulcer relapse for more than 15 years. Eradication strategies of omeprazole, amoxycillin, and metronidazole were less cost effective than omeprazole, clarithromycin, and metronidazole alone. In model 2 the addition of the 13C-urea breath test after treatment, and maintenance treatment, increased the cost of all the strategies and reduced the cost advantage of omeprazole, clarithromycin, and metronidazole alone. CONCLUSION: Small differences in efficacy can influence the comparative cost effectiveness of strategies for eradicating H pylori. Of the strategies tested the most cost effective (omeprazole, clarithromycin, and metronidazole alone) was neither the least expensive (omeprazole, amoxycillin, and metronidazole alone) nor the most effective (omeprazole, clarithromycin, and metronidazole with further treatment for patients found positive for H pylori on 13C-urea breath testing). Cost effectiveness should be an important part of choosing an eradication strategy for H pylori.