Definitions in Sleep-Disordered Breathing

Abstract

To the Editor: In his editorial (September 2000),1Broughton WA Nasal dilation, sleep and what is hypopnea?.Chest. 2000; : 571-572Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar William Broughton laments the lack of standardization of definitions used to define hypopnea in research. He says, “It may be time to reevaluate the standard definition of hypopnea,” and “…it may be time to consider rethinking the definition of hypopnea for future research.” I would like to direct Dr. Broughton's attention to an article published a year ago in Sleep.2American Academy of Sleep Medicine Task ForceSleep-related breathing disorders in adults: recommendations for syndrome definition and measurement techniques in clinical research.Sleep. 1999; 22: 667-689Crossref PubMed Scopus (4800) Google Scholar The American Academy of Sleep Medicine formed a report task force in conjunction with the European Respiratory Society, the Australasian Sleep Association, and the American Thoracic Society to address precisely those issues that Dr. Broughton raises. After wide circulation, including presentations at both the American Professional Sleep Societies and at the American Thoracic Society Meetings in 1998, this task force published the results.2American Academy of Sleep Medicine Task ForceSleep-related breathing disorders in adults: recommendations for syndrome definition and measurement techniques in clinical research.Sleep. 1999; 22: 667-689Crossref PubMed Scopus (4800) Google Scholar Among the findings in the report are the following: (1) Thermocouples do not truly measure airflow; respiratory inductive plethysmography and pneumotachography (which currently are rarely used in clinical practice) are more reliable and better validated. Nasal pressure also has been recently validated as a more quantitative measure of airflow than are thermocouples. (2) Hypopnea is defined as a 50% reduction in airflow (measured with a validated technique) or a reduction in airflow associated with a 3% fall in arterial oxygen saturation and/or an arousal. (3) A respiratory effort-related arousal event is defined as“ a sequence of breaths characterized by increasing respiratory effort leading to an arousal from sleep, but which does not meet criteria for an apnea or hypopnea.” Further, the report redefines the syndrome of sleep-disordered breathing. Previous nosology included only apneas in the definition. Thus, insurers typically (and with some justification) did not pay for treatment for sleep-disordered breathing in patients who did not meet the published criteria of ≥≥ 30 apneas in a night of sleep. As defined in the new recommendations, the obstructive sleep apnea-hypopnea syndrome exists when clinical features are present and overnight monitoring demonstrates five or more obstructed breathing events per hour of sleep, including any combination of apneas, hypopneas, or respiratory event-related arousals. Investigators (and reviewers!) in the field of sleep-disordered breathing ought to be aware of this article. Definitions in Sleep-Disordered BreathingCHESTVol. 119Issue 4PreviewI thank Dr. Phillips for her interest in my editorial (September 2000).1 I am certainly aware of the article in Sleep2 to which she refers. Please note that my editorial comments do not imply that the redefining of hypopnea has not been considered previously. My intention was to draw attention to the fact that there are more polysomnographic variables than arterial oxygen saturation and arousal to help confirm the occurrence of hypopnea. Full-Text PDF