What Is Hypopnea, Anyway?

doi:10.1378/chest.105.2.426

Chest

Volume 105, Issue 2, February 1994, Pages 426-428

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Quantitation of apneas and hypopneas is routinely included in studies of epidemiology, diagnosis, and treatment of sleep-disordered breathing (SDB). The definition of apnea appears clear-cut in the sleep literature. 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 techniques used to identify hypopnea in clinical sleep laboratories. One hundred surveys were mailed to 100 accredited sleep laboratories. Each laboratory was asked to provide its criteria and equipment used to define hypopnea. Forty-five surveys (45 percent) were returned. No two laboratories used the same definition and measures of hypopnea. We conclude that there is no consensus about either recording techniques or definitions of hypopnea. Thus, epidemiologic studies and reports of interventions on SDB that do not include precise definitions of hypopnea must be interpreted with caution.

Section snippets

Methods

We constructed a six-page survey, which we informally piloted with the aid of five sleep research colleagues across the country. After revision, the survey was mailed to each of the 100 sleep laboratories accredited by the American Sleep Disorders Association (ASDA). Each institution was characterized according to accreditation, the number of studies performed each month, parameters measured, and criteria used to define both apnea and hypopnea. Of the 100 surveys mailed, 40 surveys were

Results

Forty-four of the 45 responding sleep laboratories were accredited by the ASDA. Thirty-nine of the respondents were full Sleep Centers (which evaluate the full gamut of sleep disorders) and five were accredited as Cardiopulmonary Laboratories (which evaluate primarily disorders of breathing during sleep). The number of sleep evaluations performed was distributed evenly, and ranged from 10 to 50 per month.

To define hypopnea, 44 laboratories used some method to detect airflow. However, the amount

Conclusions

It appears that there is no precise definition of hypopnea in use in sleep laboratories in the United States. Furthermore, we have shown that the measuring techniques employed to gather the data have not been standardized. This lack of precision leads to great difficulty in comparing data from individual research laboratories. We suggest that any report of hypopneas must include specific description of both the criteria used to define hypopnea and the equipment used to assess each of these

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Supported in part by a Preventive Pulmonary Academic Award from the National Heart, Lung, and Blood Institute, National Institutes of Health.

revision accepted May 28.

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Chest

Clinical InvestigationsSleep, Breathing and Nasal VentilationWhat Is Hypopnea, Anyway?

Section snippets

Methods

Results

Conclusions

Clin Psych Rev

Indications and standards for cardiopulmonary sleep studies

Am Rev Respir Dis

The sleep hypopnea syndrome

Am Rev Respir Dis

Handbook of sleep disorders

Peripheral edema in the sleep apnea/hypopnea syndrome

Sleep

When is an apnea not an apnea?

Am Rev Respir Dis

Clinical Investigations
Sleep, Breathing and Nasal Ventilation
What Is Hypopnea, Anyway?