as far as i know is if you received medical request. it means your application is in the admissibility stage and they want to make sure whether you pose danger to Canada health system, they also require police certificate at this stage to make sure u dont have crimes. in other words. u passed eligibility which is the hardest step. i have seen so many rejections before medical requests. so it is a good sign so do your medicals as soon as possible and update us with your final decision