Do the decisions of my medical proxy over-ride my husband's decisions?

Yes the proxy's decision would be followed over your husband's objections, if you have executed a valid advance health care directive -- which might be in the form of a Power of Attorney for Health Care, a Living Will, or a document with some other name under your state's laws -- that names a specific person other than your husband to make health care decisions for you if you aren't able to do so yourself. The person named in that document becomes your "proxy," just as you describe it, which means that this person stands in for you. If there were a medical decision to be made about you and you were capable of making the decision yourself, your decision would be honored even if your husband objected. The same would be true for the person named in the document as your proxy.

There are good reasons for this. Many people are legally married but are separated or otherwise not on very good terms. Or, a married person may simply better trust the judgment of someone other than a spouse. Also, spouses may have different views on the question of life-prolonging medical interventions. Or, someone may believe that his or her spouse would be too easily swayed by the opinions of others and prefer that decision-making be given to someone who can better stand up to pressures in following the patient's wishes.

If you have named someone other than your husband as your health care proxy and you are concerned that there might be a conflict with your husband if the proxy needs to make a decision, it would be good to make sure that the health care directive or similar document be distributed to all the trusted people who might be present and involved in the decision, including your primary care physician, any other physician who regularly treats you, a family lawyer if you have one, and any adult children or siblings you have.