0
Communications to the Editor |

Definitions in Sleep-Disordered Breathing Definitions in Sleep-Disordered Breathing FREE TO VIEW

Barbara Phillips, MD, MSPH, FCCP
Author and Funding Information

Affiliations: University of Kentucky College of Medicine Lexington, KY,  University of South Alabama College of Medicine Mobile, AL

Correspondence to: Barbara Phillips, MD, MSPH, FCCP, University of Kentucky, Chandler Medical Center, 800 Rose St, MN 614, Lexington, KY 40536-0084



Chest. 2001;119(4):1287-1288. doi:10.1378/chest.119.4.1287
Text Size: A A A
Published online

To the Editor:

In his editorial (September 2000),1 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.2 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.2 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.

Broughton, WA (2000) Nasal dilation, sleep and what is hypopnea?Chest118,571-572. [CrossRef] [PubMed]
 
American Academy of Sleep Medicine Task Force.. Sleep-related breathing disorders in adults: recommendations for syndrome definition and measurement techniques in clinical research.Sleep1999;22,667-689. [PubMed]
 

Definitions in Sleep-Disordered Breathing

To the Editor:

I thank Dr. Phillips for her interest in my editorial (September 2000).1I 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.

As we both have noted, the thermal measurement of nasal/oral airflow is less than reliable. Despite that, it is the most common method of estimating airflow in American sleep centers. Snoring sensors provide less than reliable output as well. If improperly placed, they record nothing. However, in the appropriate position, they allow us to look at the relative amplitude of the audio signal that is generated from snoring. In that circumstance, crescendo snoring and snoring dropout (ie, the reduction in snoring volume) are noninvasive, concrete variables that allow us to look at a perceptible reduction in airflow and help us to determine whether hypopnea may be present. A decrease in arterial oxygen saturation and/or arousal in conjunction with these findings helps to confirm hypopnea. In the pages immediately preceding the very article you reference, an editorial by Littner and Shepard3 provides a commentary similar to mine and wonders why the American Academy of Sleep Medicine Task Force failed to comment about snoring.

If snoring changes associated with minor (25 to 50%) drops in thermal nasal/oral airflow do indicate increasing respiratory effort as compensation for obstruction, then let us call that hypopnea. Creating another term for it (ie, respiratory effort-related arousal) only confuses a simple issue. Clearly, more work needs to be done to confirm that changes in snoring truly confirm hypopnea.

Recommendations exist for defining respiratory changes during sleep. The article you reference is a valuable resource. These guidelines are, however, recommendations. It is my impression, as a reviewer of sleep-related manuscripts, that older definitions of hypopnea are still widely used in sleep research, and I find that unfortunate (thus my commentary). I believe that a noninvasive measure (graphic snoring output) is available to us that can help us identify hypopnea with greater accuracy. I believe also that the more closely research definitions resemble the findings of everyday clinical sleep medicine, the more valuable that research will be to practitioners.

I think the task force recommendations are acceptable but could be improved. I stand by the statement that the definition of hypopnea needs to be reevaluated… still! I concede that we are still awaiting conclusive data about snoring and its relationship to hypopnea, but I believe that the changes in snoring associated with hypopnea are intuitively obvious and very revealing.

As I see it, the purpose of the editorials in this journal is to provide commentary about and beyond the subjects of the articles within. In our journal, editorial comments are meant to stimulate thought and, hopefully, lead to the advancement of science. At least some thought has been generated thus far.

References
Broughton, WA Nasal dilation, sleep and what is hypopnea?Chest2000;118,571-572. [CrossRef] [PubMed]
 
American Academy of Sleep Medicine Task Force.. Sleep-related breathing disorders in adults: recommendations for syndrome definition and measurement techniques in clinical research.Sleep1999;22,667-689. [PubMed]
 
Littner, MR, Shepard, JW Recommendations for research into measurement and classification of sleep-disordered breathing: gazing into the crystal ball.Sleep1999;22,665-666. [PubMed]
 

Figures

Tables

References

Broughton, WA (2000) Nasal dilation, sleep and what is hypopnea?Chest118,571-572. [CrossRef] [PubMed]
 
American Academy of Sleep Medicine Task Force.. Sleep-related breathing disorders in adults: recommendations for syndrome definition and measurement techniques in clinical research.Sleep1999;22,667-689. [PubMed]
 
Broughton, WA Nasal dilation, sleep and what is hypopnea?Chest2000;118,571-572. [CrossRef] [PubMed]
 
American Academy of Sleep Medicine Task Force.. Sleep-related breathing disorders in adults: recommendations for syndrome definition and measurement techniques in clinical research.Sleep1999;22,667-689. [PubMed]
 
Littner, MR, Shepard, JW Recommendations for research into measurement and classification of sleep-disordered breathing: gazing into the crystal ball.Sleep1999;22,665-666. [PubMed]
 
NOTE:
Citing articles are presented as examples only. In non-demo SCM6 implementation, integration with CrossRef’s "Cited By" API will populate this tab (http://www.crossref.org/citedby.html).

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging & repositioning the boxes below.

  • CHEST Journal
    Print ISSN: 0012-3692
    Online ISSN: 1931-3543