In reference to Air Splints.
You can still buy them and there are people still using them however they considered antiquated and most EMS agencies have removed them from their equipment or they have been proscribed in protocols.

There are a few reasons that Air Splint have go by the wayside:

• They are limited in their utility compared to other options like SAM Splints or Vacum Splints.
• They have contraindications that other types of splints don't have due to the splints fully encapsulating the extremities. Compartment syndrome is a real concern with long times to definitive care.
• While you can visualize the extremity better with an air splint, other reassessments can be more difficult than with other properly applied splints.
• MOST providers do not properly reassess the pressure of the splint but simply assess for distal pulses. Venous flow is restricted before arterial flow is; compartment syndrome can be developing with a distal pulse present. This issue is compounded in air medical evacuations.

People do still use them, but there are a lot of treatments that are still being performed that aren't considered best practices.

Personally, I have never been a fan of air splints. They are easy to apply and that's it. They were an ok option for a long time, but newer technologies have improved the options.

If room and weight aren't an issue, vacuum splints are significantly better; they aren't affected by temperature or elevation and most can be manipulated to fit the patient's needs.

If room and weight is an issue, I am going with SAM splints. While more difficult to apply than a vacuum splint, they can be manipulated to fit the patient's need and are lighter and more compact.

If you search the internet you can find some cool pictures of a hydration bladder being used as an improvised splint... in wilderness and survival medicine. Improvised splinting is the standard I don't carry too much in the way of splinting supplies when I am in the backcountry in a non-professional role like backpacking.