Yes, your spouse may be able to make your health care decisions before divorce, absent a health care directive naming someone other than your spouse.
Regardless of your marital status, you can execute an Advanced Medical Directive (Health Care Power of Attorney) at any time to name anyone you desire to act as your health care agent.
Health care professionals are required to follow the terms of your written Health Care Power of Attorney, which provides your personal guidelines and desires for treatment and specific authority for your agent to act.
In the absence of a Health Care Power of Attorney, health care providers will often look to your spouse to make your health care decisions before your divorce.
Therefore, if you are contemplating divorce, you should review and/or establish directives that protect your needs and desires in the event of your disability.