Background. Diaphragmatic sleep disordered breathing (dSDB) has been recently identified as sleep dysfunction secondary to the diaphragmatic weakness in Duchenne Muscular Dystrophy (DMD). However, scoring criteria for dSDB are missing.

Aims. To define and validate dSDB scoring criteria in DMD and to evaluate whether dSDB severity correlates with disease respiratory progression.

Methods. Scoring criteria for diaphragmatic apnoea (dA) and hypopnoeas (dH) have been defined by the authors considering the events? cardiorespiratory polygraphy (CR) pattern and the existing literature.

Ten sleep professionals (physiologists, consultants) blinded to each other were involved in a three-round Delphi survey to rate each item of dSDB criteria (Likert scale 1-5) and to recognise dSDB amongst 18 SDB snapshots. Scorers? accuracy was tested against the authors (M.D, F.T. F.A) panel.

CR previously conducted in DMD and diagnosed with SDB (i.e.apnoea-hypopnoea index,AHI?1) were re-scored and a dAHI was derived. Age and pulmonary function (FVC% pred.) were correlated with dAHI.

Results. After two Delphi rounds, the criteria were finalised. At third round scorers deemed each item of dA and dH criteria as relevant as 4 or 5 out of 5.

The agreement with the panel in recognising dSDB was 81%, kappa agreement 0.71, sensitivity 77%, specificity 85%.

Thirty-two DMD CR were reviewed. dSDB were previously scored as obstructive events. dSDB correlated positively with age (p<0.05) and negatively with FVC%pred z-score (p<0.05).

Conclusions. dSDB is a newly defined sleep entity that correlates with DMD progression. A broader, prospective study to evaluate dSDB as a novel respiratory measure for DMD in clinical and research settings is planned.