FIG. 33:  TE-CSA is a relatively new description of a condition that has only recently been systemically described, and much remains unknown about the risk factors, clinical associations, treatment response, and outcomes.  While it is recognized that these events may produce clinical symptoms such as sleepiness or insomnia, the problem is how to define or characterize TE-CSA. 

In this Figure I am proposing four different phenotypes: 

• CSA may not be present during the diagnostic portion of the sleep study but emerge during initial titration; this is the emergent type. CSAs that are not present during the initial titration but occur during titrations after some time on CPAP therapy are delayed emergent type. 
• CSA on the initial titration study that does not resolve over time is the persistent phenotype.
• CSA that is substantial during the diagnostic portion of the study and does not improve during PAP titration is referred to as resistant.
• CSA that is present to some degree during the diagnostic portion but is significantly exacerbated during the titration study is referred to as aggravated.

The premise is that the primary sleep disorder, OSA, is generally, although not always improved on CPAP therapy, despite any of these changes in the CSA.  So the question is, do these different states represent different pathologic syndromes or phenotypes? Do they respond to therapy differently, should we expect them to, and do they have similar clinical outcomes?

The answers to these questions are unclear at present, so for the time being we will combine these states is into one definition, TE-CSA.