Impact of chicago draft criteria on assessment of respiratory disturbance index and severity grading

Michael Hibbert*, David Joffe, Craig Phillips, Norbert Berend

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


Introduction: Since the initial description of the different types of sleep disordered breathing, sleep laboratory technology has changed and original definitions have been modified to incorporate methods of uncertain clinical validity. It has therefore been difficult to compare results from different centres due to a lack of standard definitions. The Chicago draft criteria for measurements, definitions and severity ratings were put forward to address these problems. We aimed to examine the impact of these new criteria on the scoring of abnormal events in sleep and on the assessment of overall severity. Methods: We selected thirty 16 channel polysomnograms employing respiratory inductance plethysmography bands, with the RDI scored as apnoea or hypopnoea accompanied by a 4% or greater fall in oxygen saturation. 10 studies were classified as severe (RDI>30), 10 as moderate (RDI 15-30) and 10 as mild (RDI 5-15). We then rescored these according to the Chicago draft criteria and compared results within the three groups. Results: Severity Grade MeanTotal RDI (standard) Mean Total RDI (Chicago) P Value Mild 9.8 (+/- 0.9) 29.2 (+/- 3.0) < 0.0001 Moderate 19.5 (+/-1.0) 36.9 (+/-1.6) < 0.0001 Severe 56.7 (+/-5.8) 67.5 (+/-5.1) <0.01 Total 28.7 (+/- 4.2) 44.5 (+/- 3.7) < 0 0001 Conclusion: The Chicago draft criteria have a significant impact on assessment of RDI in all grades of severity of sleep related breathing disorder. This impact is most marked in milder disease and has the effect of grouping previously defined mild and moderate disease together. The clinical relevance of these changes needs to be addressed in the future.

Original languageEnglish
Pages (from-to)A13
Number of pages1
Issue numberSupplement 1
Publication statusPublished - 1999
Externally publishedYes


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