Sleep Disordered Breathing Associated with Obesity and Craniofacial Abnormalities

Obesity and craniofacial abnormalities work synergistically to increase the collapsibility of the passive pharyngeal airway in patients with sleep disordered breathing (SDB), according to a study by Japanese investigators published in the second of two January issues of the American Thoracic Society's peer-reviewed journal.

Writing in the American Journal of Respiratory and Critical Care Medicine, Shiroh Isono, M.D., of the Department of Anesthesiology, Chiba University School of Medicine, Chiba, Japan, along with four associates, evaluated 54 patients with SDB and 23 normal subjects to show the effect of certain physical characteristics and craniofacial abnormalities on pharyngeal collapse during sleep.

People with serious sleep disordered breathing stop breathing for at least 10 seconds at a time while they are sleeping. Then they resume breathing. During sleep, relaxation of the muscles at the base of the throat can cause obstruction of the airway, with associated snoring and labored breathing. When complete blockage occurs, breathing stops. Among the previously identified causes are narrow airways, enlarged tonsils and adenoids, and relaxed throat muscles.

The investigators results suggest that obesity and craniofacial abnormalities in SDB patients may synergistically increase tissue pressure surrounding the pharynx (throat), leading to an increase in closing pressure of the passive pharyngeal airway.

The Japanese scientists had studied the closing pressure in the pharynx (throat) at several levels. They found positive closing pressure at two levels was associated with smaller upper and lower jaws (maxilla and mandible). Obesity was associated with positive closing pressure at one of the two levels studied.

The researchers said that SDB patients, as compared with normal subjects, had receding lower jaws (mandibles) and long lower faces with downward mandible development.

We believe the position and size of the maxilla and mandible have physiologic importance in determining the collapsibility of the pharyngeal airway. According to the authors, SDB patients have varying degrees of smaller than average cross-section of the bony enclosures of the lower face at the pharyngeal airway level.

Contact: Shiroh Isono, M.D.
Department of Anesthesiology
Chiba University School of Medicine
E-mail: isonos@ho.chiba-u.ac.jp