By inhaling a saltwater aerosol solution almost twice as salty as the Atlantic Ocean for between 10 and 15 minutes at least twice a day, young patients should be able to avoid a significant part of the damage the disease causes to their lungs, the researchers said. That's because the aerosolized saltwater restores the thin lubricant layer of water that normally coats airway surfaces. This water layer promotes the clearance of the naturally occurring mucus the body uses to trap harmful bacteria, viruses and other foreign particles.
One scientific team consists of faculty members at the University of North Carolina at Chapel Hill School of Medicine and UNC Hospitals. The other, also supported in part by the U.S. and Australian CF foundations, includes faculty and staff at the Royal Prince Alfred Hospital, the University of Sydney and the Woolcock Institute of Medical Research, all in Sydney.
Reports on both studies, which were collaborative and complementary, appear in the Jan. 19 issue of the New England Journal of Medicine.
Authors of the first report, all at UNC, are Drs. Scott H. Donaldson, assistant professor of medicine; William D. Bennett, research associate professor of medicine; Kirby L. Zeman, research associate at the Center for Environmental Medicine, Asthma and Lung Biology; Michael R. Knowles, professor of medicine; Robert Tarran, assistant professor of medicine; and Richard C. Boucher, professor and director of the Cystic Fibrosis Research and Treatment Center.
"We are very excited that this simple and inexpensive therapy turned out to be so effective and well-tolerated in patients with CF," said Donaldson, who, along with Bennett, was the paper's first author. "It is especially gratifying to see patients in our own clinical practice embrace and benefit from it.
"These results could change how physicians elsewhere care for patients with CF," he said. "As we look at the combined results of our study and those of our Australian colleagues, it gives us great hope that use of this therapy will reduce how often patients feel ill, will slow the decline of lung function over time and will help these people live longer."
Dr. James Kiley, director of the National Heart, Lung and Blood Institute's Division of Lung Diseases, said the treatment "sets the stage for the development of additional therapies in CF patients."
Cystic fibrosis appears on average in one of four children of parents who both carry a defective copy of a gene known as CFTR, Donaldson said. Children born with the disease soon develop chronic lung damage, since their lungs cannot clear excessively sticky mucus by sweeping it to the mouth, where it is swallowed and eliminated. Respiratory failure is the leading cause of death in CF patients.
This research is important both for its immediate application and because it provides the roadmap for development of future effective therapies for CF, Boucher said. This study appears to establish the concept that the surfaces of the lungs of CF patients are dehydrated, and restoring hydration with hypertonic saline treats the basic cause of this disease.
In healthy people, a thin film of water only five-to-10 microns thick coats and lubricates the open areas of the lungs, Boucher said. "Our studies demonstrate that CF lungs are missing this watery layer, and, hence, to treat the disease effectively, you have to re-hydrate CF airway surfaces. This can be done with inhaled water solutions that are seven or eight times more salty than blood or about three-quarters as salty as the Dead Sea.
"Salt essentially sucks water from the lung tissues out onto the airways. The irony is that the therapy works better in CF subjects than non-CF subjects," Boucher added.
The UNC study involved 24 CF patients who each inhaled the salt solution with or without pretreatment with a compound known as amiloride over two-week periods. Analysis of mucus clearance and lung function showed that the high-salt aerosol alone worked best, which somewhat surprised the medical scientists. Laboratory studies established that the failure of amiloride to promote the effect of hypertonic saline reflected a novel action of the drug - i.e., to block water transport. This novel observation in part established hydration of airway surfaces as the mechanism of action for hypertonic saline.
Following communication with the UNC group, the Australian researchers used a comparable protocol to study another 164 patients for a longer period, almost a year. During the longer span, the Sydney researchers also found fewer lung problems with the concentrated saline than with normal saline, less need for antibiotics to treat lung infections over time, and improved attendance by patients at school, work and other activities during the 48 weeks.
Because salt solutions are so cheap to make, another attractive aspect of this new therapy is that its clinical benefits will come at a minimal treatment expense, in contrast to many other available therapies, Donaldson said.