WHAT IS HYPOPNEA, ANYWAY

Quantitation of apneas and hypopneas is routinely included in studies of epidemiology, diagnosis, and treatment of sleep-disordered breathin g (SDB). The definition of apnea appears clear-cut in the sleep litera ture. In contrast, the literature contains remarkable variety in both recording techniques and definitions of hypopnea. The purpose of this study was to characterize the variety in the definitions and technique s used to identify hypopnea in clinical sleep laboratories. One hundre d surveys were mailed to 100 accredited sleep laboratories. Each labor atory was asked to provide its criteria and equipment used to define h ypopnea. Forty-five surveys (45 percent) were returned. No two laborat ories used the same definition and measures of hypopnea. We conclude t hat there is no consensus about either recording techniques or definit ions of hypopnea. Thus, epidemiologic studies and reports of intervent ions on SDB that do not include precise definitions of hypopnea must b e interpreted with caution.