If you are having trouble taking a breath the fact you aren’t getting as much of a forceful application is a big problem. They should have went with co2 or nitrogen but this would require many more inhalers because they wouldn’t contain as much propellant for a given volume
I think that the advantage of the CFC charged inhalers is that the propellant is liquid under moderate pressure and instantly turns to vapor when you press the nozzle, propelling the medicine well. CO2 and nitrogen both have a very low boiling point, meaning the vessel must be able to withstand very high pressures and would freeze the medicine upon release. Probably not a good thing.
I’m not a chemist or chemical engineer, but this make sense to me.