ABSTRACT
INTRODUCTION The term "upper airway resistance syndrome" (UARS) was first coined in 1992 (1) and 1993 (2). Prior to these reports, in the late 1980s, we conducted a series of studies at Stanford University aimed at the pathophysiologic mechanisms of subtle flow limitation associated with snoring during sleep. Using a pneumotachometer and esophageal pressure monitoring it became apparent that there existed a number of individuals with impaired respiration during sleep, who did not fit the typical diag nostic criteria of obstructive sleep apnea (OSA). This is to say that they presented with daytime sleepiness and snoring but without clear polysomnographic diagno stic criteria of apnea, hypopnea or oxygen desaturation. Despite the absence of these diagnostic criteria for OSA they still showed signs of abnormal breathing during sleep when investigated with pneumotachometers and esophageal pressure moni toring instead of oronasal thermistors. This led us to pose the question: "Obstructive sleep apnea or abnormal upper airway resistance during sleep?" (3). In 1991, we published the pathophysiologic phenomena of increased upper airway resistance leading to sleep fragmentation in the absence of apnea, hypopnea, and hypoxemia (4). For further reference into the historic development of UARS please refer to the article by Exar and Collop (5) for a more comprehensive review.
