If your mother has numerous medical issues, then it's quite possible that your only option is to have her visit for a short time on a TRV (this will not allow her to live in Canada or move to Canada). Your mother will not be covered by the health care system as a visitor in Canada. So if she comes as a tourist, make sure you take out travel insurance to cover any emergency care and be prepared to pay for everything else out of your own pocket.
If you are asking about bringing your mother to Canada permanently, the process is long and only a limited number of applications are accepted each year. It's also possible your mother may be refused immigration due to her medical conditions. If you want to try to apply to sponsor your mother for permanent residency, you must first meet the low income cut off for the last three years before you apply - in other words, you and/or your spouse must be making enough money from Canadian sources to meet the minimum income required to sponsor your mother. CIC only accepts 5,000 parents sponsorship applications each year. They will start accepting applications again the first business day of January. This year the 5,000 application cap was reached in a day and a half. If you want your mother's application to have any chance of being accepted, it will need to arrive in CIC's offices on the first business day of January next year. If your application is accepted, you should expect processing to take 4+ years. More information here: http://www.cic.gc.ca/english/information/applications/sponsor-parents.asp
Another option would be to bring your mother for a longer visit using a super visa. This is a visitor visa and will not allow you mother to permanently move to Canada. Also, she will have to pass a medical to be approved. Once in Canada, any health care services your mother uses will either have to be covered by the medical insurance you have purchased - or you will have to pay for it yourself.
