One thing you should remember is that at the the first couple of years of engineering degrees tend to be very similar in terms of the content. So it doesn't matter if you are doing civil or areo, they will be similar until closer to the end. This is why you get 'general' engineering degrees...you tend to specialise in year 3 on ward I believe.
I don't quite see the point in super specific engineering degrees for undergraduate students. I think you would be better off sticking to the main branches then specialise at MSc level. So if you wanted to get into medical engineering, probably Electrical/Electronic or mechanical would be you best option. This also opens more doors prospect wise post-degree than a medical engineering degree would.
Also, I assume that you are doing a foundation YEAR not degree (completely different things btw), in which case, there is nothing stopping you from transferring after the FY.