From Alberta health services in Canada. This is a huge misconception harm reduction advocates have been trying to fight.

“While better than doing nothing, performing only chest compressions on a person experiencing an opiate overdose will simply move blood in the at body that has not been oxygenated, causing the vital organs to continue to be deprived of oxygen. Therefore giving rescue breaths to a person who has overdosed on opioids can help prevent that person from going into cardiac arrest, and has the potential to save their life. When a person who is not in cardiac arrest stops breathing and is unconscious because of an opioid overdose, it is very important to CALL 911 and continue giving rescue breaths until Emergency Medical Services arrive.”

“Cardiopulmonary resuscitation (CPR) usually involves giving breaths and/or chest compressions. Breaths serve to re-oxygenate a person’s blood while chest compressions help circulate blood while the person’s heart is not beating. Opioid overdose is one of a number of special circumstances where it is recommended a different approach than CPR. Opioids bind to receptors in the brain responsible for controlling respiration. After binding to the receptors, they decrease the rate of breathing, which can slow to a point where a person stops breathing altogether. Opioid overdose occurs with higher potency of the opioid, reduced tolerance, co-morbidities (such as chronic lung disease) or when combined with alcohol or other drugs that depress respiration. Without enough oxygen, the heart will stop beating and the individual will die due to lack of oxygen to the vital organs particularly the brain. Although death can occur within minutes of taking an opioid, more often there is a longer period of unresponsiveness lasting up to several hours.”