Carrying fixed blades in EMS? In my experience....yes...it's safe, and yes it's practical.
the up points are that it's a much sturdier more foolproof blade that's easier to manipulate and clean gunk offa. (not necessarily from decontamination activities, but more like cutting food and such) On top of that, as long as a glass breakers not being used on it, there's also zero chance of a knife folding on your precious fingers.
As far as disadvantages, there's only a couple that come to mind.
first is comfort...fixed blades are just not nearly as comfortable as a folding knife under most circumstances. when I spent most of my days walking it was hard to find one that would ride okay with the suspender pack or O2 kit on my shoulder. If I was sitting most of the day, they wanted to find places to dig into then also. add the problem that it's often a REALLY good idea to conceal a fixed blade when you carry one on duty and the problem becomes more difficult. I know there's alot of really greath sheath makers, and knife designers out there, but as a rule...they're less comfortable.
Secondly is PERCEPTION PERCEPTION PERCEPTION. Believe it or not, EMT's are very much in the CARE and COMFORT business. and the fact is most of your patients aren't going to be knife people, or even if they are they are used to seeing knives, they may not be used to fixed blades on duty belts, it has a tendency to make them less comfortable. Also among your peers, alot of them will tend to not be knife knuts, and therefore will quickly brand you as a jackass "Rescue Ricky" type. the ER Department and Hospital Securiy wouldn't be a big fan of it either for the most part. I know these issues are silly, insipid, and basically kinda chickensh!t, but...they do exist. Best way around both of these issues is to conceal a fixed blade really, really well if that's what yer gonna carry.
Third issue is basically...the realities of the job. If it falls or gets knocked out of the sheath, that's an automatically sharp edge falling down, possibly towards a patient. Granted once again, a proper sheath helps eliminate these things, but sometimes things just snag... coats, straps, doorways, gurneys, etc. If you snag a knife handle on something wrong, it's just plain gonna come out, no matter how good the sheath is made.
It would be a VERY rare set of circumstances for me to choose a fixed blade personally, but...to each thier own. People in more specialized or unique areasa such as a Military Medic, SWAT Medic, Dive Rescue, etc. may very well have different needs, perceptions, and circumstances than those that I'm familliar with. Hell, I used to know a guy with Dive Rescue that kept a Beretta 92 with three extra mags in his dive bag. What for? I'll never know....