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Article title: COPD Research: NHLBI
A study completed several years ago examined the use of oxygen therapy for people who, because of COPD, cannot get enough oxygen into their blood by breathing air. This study has determined that continuous oxygen therapy is more beneficial in extending life than giving oxygen only for 12 hours at night.
Another clinical study compared inhalation therapy using a machine which administers medication to the lungs by intermittent positive pressure breathing (IPPB) with one that delivers the medicine by relying on the patient's own breathing. Although home use of IPPB machines is widespread, previous studies had not been able to show conclusively whether they were effective. In this study, 985 ambulatory patients with COPD were randomly assigned to a treatment group which received a bronchodilator aerosol solution by IPPB, or to a control group which received the medication via a compressor nebulizer. The only difference between the two groups was the positive pressure applied by the IPPB. There was no statistically significant difference between the two treatment groups in numbers of deaths, frequency and length of hospitalization, change in lung function tests, or in measurements of quality of life. This study suggests that the use of IPPB devices may be unnecessary.
An intervention trial called the Lung Health Study, which began in 1983, has enrolled approximately 6,000 smokers in a study to determine whether an intervention program incorporating smoking cessation and use of inhaled bronchodilators (to keep air passages open) in men and women at high risk of developing COPD can slow the decline in pulmonary function compared to a group receiving usual care. When this study is completed, it should help to determine the extent to which identification and treatment of asymptomatic subjects with early signs of obstructive lung disease would be useful as a preventive health measure. In addition, the study will test some of the current theories about behavior and smoking cessation. Early results indicate that cigarette smoking may be more harmful to women than to men. Furthermore, smoking cessation results in greater weight gain in women than in men, and to avoid weight gain women are less likely to quit smoking and more likely to revert to their smoking habit.
Because familial emphysema results from a deficiency of AAT in affected individuals, efforts to minimize the risk of emphysema have been directed at increasing the circulating AAT levels either by promoting or increasing the production of AAT within the individual, or augmenting it from the outside. One strategy for improving the production of AAT is by pharmacological means (e.g., by administration of drugs such as danazol or estrogen/ progesterone combinations), but this has not been found to be effective. Genetic engineering to correct the defective gene or introduce the functional gene in the deficient individuals is being attempted by several NHLBI-supported investigators. The normal gene for AAT as well as the mutant genes causing AAT deficiency have been characterized and cloned, and animal models carrying the mutant gene have been developed. The resulting animals displayed many of the physical and histologic changes seen in human neonatal AAT deficiency. These studies should provide the groundwork for future development of gene replacement therapy for AAT deficiency.
In the meantime, attention is being focused on AAT augmentation therapy for familial emphysema. Studies have shown that intravenous infusion of AAT fractionated from blood is safe and biochemically effective, that is, the needed blood levels of AAT can be maintained by the continued administration of AAT at appropriate intervals.
Because of the practical and fiscal limitations to mounting a clinical trial for establishing the clinical efficacy of AAT augmentation therapy for emphysema, the NHLBI sponsored a national registry of patients with AAT deficiency to assess the natural history of severe AAT deficiency and to examine whether the disease course is altered by the augmentation therapy. This program is enrolling, at various medical centers both in the U.S. and Europe, at least 1,000 adult patients with AAT deficiency satisfying certain other eligibility criteria. The patients will be followed for 3 to 5 years (chest x rays, lung function, blood and urine analysis, etc.) at one of 37 participating clinical centers. The evaluation of the data and the release of the conclusions are expected by early 1995.
Methods to treat emphysema before it becomes disabling remain an important research objective of programs supported by NHLBI. Since it is believed that either excess protease (elastase), or too little useful antiprotease, can lead to development of the disease, scientists have also been attempting to use other approaches to develop animal models which will mimic the human condition of inherited alpha-l-protease inhibitor deficiency and using such models to test if natural or synthetic antiproteases can be used safely to prevent development of emphysema-like lesions in these animals. If found safe and effective in animals, these agents can be tried in humans.
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