Q:

Are professional-to-professional questions within the site scope? 

Rationales behind the order of applying the torso straps of a Kendrick Extrication Device
This question refers to the above question on the main site.  The main contention seems to be that it has low applicability to the health and well being of the general public.  This is because it is referring to a device that is used specifically by EMS and similar entities for rescue extractions and immobilization. 
However, it does have merit as a question between specific professionals, i.e. EMS practitioners of various areas and abilities since the application of the straps in different orders could have health implications we don't know about. 
Is the question too narrow and focused, or will we define health to include specific subsets such as EMS to EMS or Doctor to Docter, etc? 

A:

That's awesome: Professionals asking professionals about the questions they have in this field. 
Yes, on topic! 
It would be a bit backward-thinking to exclude the questions that professionals would actually have for a site like this… because they're not "general" enough? 
Think about that. 
You would be excluding the interests of the the very people who will (hopefully) drive the best content of this site.  You would be excluding the people who will make this site "work". 
Embrace these specialized, long-tailed questions
Many sites have the problem that they strive to become soooo generic and applicable to all, that they settle into a Wikipedia-like scope where only uninspired questions that anyone could ask are allowed.  And they’ve all been asked 100 times before on every other site on that subject.  No thank you. 

low applicability to … the general public

To throw in a bit of historical context, this sounds an awful lot like folks looking for things that are too localized. " Too localized" once describe questions involving "…very tiny geographic regions or vanishingly small periods of time", and it's an out-modded artifact we got rid of a long time ago, good riddance.  Too localized is no longer a valid reason to flag or close a post. 
We should not close questions because "it is too narrow and focused." 
If the professionals want to use this site for their specialized interests in this field, you've gotta love it.  Failing to embrace these questions with both arms would be a big mistake. 

"To attract experts, you need a site where people are asking very interesting and challenging questions, not the basic questions found on every other Q&A site. 
Remember, the pro sites WILL attract the enthusiasts, but not the other way around!" 
— Blog Post, Your New Site: Asking the First Questions

A:

Such questions should be on-topic in my opinion.  The same issue exists on other SE sites, Stack Overflow or Server Fault being excellent examples.  On these two: 

some of the questions can be understood and answered by a non-professional-but-interested public, 
some can only be understood but not answered by such a public
and finally, some are tricky questions for professional geeks. 

This sounds natural to me.  On top of that, accepting professional-to-professional questions would be an excellent way to attract professionals on this site: on top of answering questions - so giving time to others -, they would also be in a position to ask their own questions and to have them answered - so finding their own interest.