Effects of mass loading on the upper airway.

To learn how increased cervical adipose tissue might affect upper airway function, we studied effects of mass loading on upper airway dimensions, stability, and resistance. Eight rabbits were studied (anesthetized and postmortem) using lard-filled bags to simulate cervical fat accumulation. Additionally, a handheld device was used to apply measured loads at localized sites along the airway. Upper airway resistance and closing pressure (a reflection of airway stability) were determined before and after loading. Endoscopy revealed concentric narrowing of the pharynx during loading in anesthetized and postmortem preparations. Upper airway resistance was increased by mass loads, with larger loads having greater effects. Loading caused decreased airway stability as reflected by closing pressures. The area over the thyrohyoid membrane was more vulnerable to mass loading than adjacent areas. Because mass loading of the upper airway causes changes in its configuration and function similar to those seen in obstructive sleep apnea syndrome (OSA), we speculate that such loading may contribute to the pathogenesis of OSA associated with obesity.