My Ohio Living Will states that if I am in a Terminal Condition and unable to make my own health care decisions, or in a Permanently Unconscious State, I direct that my physician shall:
1. Administer no life-sustaining treatment, including CPR and artificially or technologically supplied nutrition or hydration; and
2. Withdraw such treatment, including CPR, if such treatment has started; and
3. Issue a DNR Order; and
4. Permit me to die naturally and take no action to postpone my death, providing me with only that care necessary to make me comfortable and to relieve my pain.
I have sent copies of this document to my parents, my sister, my physician, my hospital, and filed it with the County Recorder. It does no good if they do not know your wishes.
You would also need to fill out a Health Care Power of Attorney in order to address the issues that you bring up. I am not a lawyer, but unless you and the person designated as your health care agent both have specific religious objections, such as refusing blood transfusions, it seems to me unlikely that your agent would actually refuse ICU care, a ventilator, an NG tube, and a colostomy for you if you are not terminal or permanently unconscious. The pressure upon the agent to consent to these treatments would be enormous, especially if the ventilator and colostomy are expected to be temporary.
I ended up in the ICU for 2.5 days last May, and had an NG tube for several hours (but no ventilator or colostomy). Not only did I make a full recovery, I actually thought the ICU was fairly peaceful, but then that's me.