When a person lies down, a small amount of fluid displaced from the legs to the base of the neck can narrow soft tissue around the throat and increase airflow resistance in the pharynx by more than 100 percent, predisposing the person to obstructive sleep apnea.
The results appear in the second issue for December 2006 of the American Journal of Respiratory and Critical Care Medicine, published by the American Thoracic Society.
T. Douglas Bradley, M.D., of the Toronto General Hospital, and eight associates measured leg fluid volume, neck circumference and airflow resistance in the throats (pharynx) of 11 healthy, non-obese subjects while they lay on their backs. Next, the researchers applied a lower body positive pressure device (anti-shock trousers) for five minutes to displace fluid from the legs to the neck area.
In obstructive sleep apnea, a blockage in the throat or upper airway causes victims to repeatedly stop breathing long enough to decrease the amount of oxygen in the blood and increase the carbon dioxide. The National Heart, Lung, and Blood Institute estimates that 18 million Americans suffer from sleep apnea.
"Obesity and neck circumference are important risk factors in obstructive sleep apnea, but together only account for approximately one-third of the variability in the apnea-hyponea index," said Dr. Bradley. "A factor not ordinarily considered is fluid accumulation at the nape of the neck and around pharyngeal soft tissue. Obstructive sleep apnea is very common in fluid-retaining states such as heart failure, renal failure and peripheral edema of unknown cause."
"Our data show that displacement of a small amount of fluid such as 340 ml, about 12 ounces, from the legs is sufficient to cause a 102 percent increase in airflow resistance of the pharynx in healthy, non-obese subjects," continued Dr. Bradley
According to the authors, when the pharynx narrows in obstructive sleep apnea and in hea
'"/>
Contact: Suzy Martin
smartin@thoracic.org
212-315-8631
American Thoracic Society
15-Dec-2006