Next time you have to do CPR on some adult who suddenly collapses, you may keep doing chest compression, but don't bother to do the mouth-to-mouth ventilation.   A new Japanese study published on March 17, 2007 in The Lancet revealed that the so-called rescue breathing may do more harm than good, potentially increasing the risk of brain damage in the survivors.

CPR, short for cardiopulmonary resuscitation, is used on people who experience cardiac arrest or whose heart suddenly stops beating.   This is an emergency measure used to keep the patient alive while waiting for medical processionals to arrive.

"CPR consists of chest compressions and rescue breaths (i.e. artificial blood circulation and lung ventilation) as a circle and is intended to maintain a flow of oxygenated blood to the brain and the heart, thereby extending the brief window of opportunity for a successful resuscitation without permanent brain damage," according to wikipedia.

The standard or recommended CPR includes 30 chest compressions and two mouth-to- mouth breaths.   Chest compression requires pressing the patient's chest down at least one and a half inches within less than one second before releasing.

Often times, bystanders would not want to do CPR on strangers because they are reluctant to do rescue breaths.    Even if they do, they may skip rescue resuscitation because of fears that they could get a contagious disease from the victim.  

But the new study indicates that people don't have to feel guilty if they do not provide mouth-to-mouth resuscitation because if they do, they might even hurt the patient.

In the study, Ken Nagao MD of Surugadai Nihon University Hospital in Tokyo, Japan and colleagues went through data from 4,068 adults who had an out-of-hospital cardiac arrest.

In more than 70 percent of cases, patients were not helped by bystanders when they suddenly collapsed. 18 percent of these patients received from bystanders traditional or standard CPR including both chest compression and rescue breathing.

The researchers found that those who did not receive any CPR from bystanders were less likely to survive. Even if they did, they were more likely to suffer brain damage compared to those who received the traditional CPR.

In contrast, 11 percent of victims received CPR with chest compression, but no mouth-to-mouth resuscitation.   These people were 2.2 times less likely to suffer brain damage compared to those who got the guideline CPR consisting of 30 chest compressions and two rescue breaths.

Studies show that the chance of survival is greatest in stricken patients whose heart is in a condition that allows paramedics to shock it back into a normal rhythm with a defibrillator.

Among these patients, the researchers found the percentage surviving with a favorable neurological outcome to be 19.4 percent if bystanders administered chest compressions without mouth-to-mouth ventilations. In contrast, the favorable neurological survival rate in those who received traditional or recommended CPR was only 11.2 percent.

Experts explain that time is critical when it comes to the rescuing of a patient who suffers cardiac arrest.   Mouth-to-mouth ventilation is not only unnecessary in those who suffer cardiac arrest, but also wastes time and disrupts chest compression, which should be continuous to increase the odds of survival.

Rescue breathing is added to CPR in some cases in which people collapse not because of cardiac arrest, but because of something else that causes a situation in which there is no oxygen in the blood.   Breathing can introduce oxygen into the patient, which along with chest compression may keep the patient alive without much brain damage which would otherwise result from lack of oxygen in the blood.

In most cases, people suddenly collapse because of cardiac arrest.    These patients have enough oxygen in the blood.   So the mouth-to-mouth is not necessary.   Chest compression can force the blood to circulate and prevent brain damage.

"The report confirms that what we have learned in animal experiments applies to humans as well," says Gordon A. Ewy, MD, director of the Sarver Heart Center at The University of Arizona in Tucson where chest-compression-only resuscitation was developed.

"Bystander-initiated continuous chest compressions without mouth-to-mouth breathing are the preferable approach for witnessed unexpected collapse, which is usually due to cardiac arrest."

In an editorial titled "Cardiac Arrest – Guideline Changes Urgently Needed," published in the same issue of the journal, Ewy notes that eliminating the need for mouth-to-mouth ventilation not only is more effective, but also should dramatically increase the odds of bystander-initiated resuscitation efforts, which would increase the survival rate of cardiac arrest.

Ewy explained that chest compression is critical.   "We have found that the survival rate is higher even when the blood has less oxygen content, but is moved through the body by continuous chest compressions, than when the blood contains a lot of oxygen but is not circulated well because chest compressions are interrupted for mouth-to-mouth ventilations."

However, Ewy pointed out that the guideline CPR consisting of 2 breaths after every 30 chest compressions is still appropriate for respiratory arrest including near-drowning, drug overdose or chocking.

The take home message is that doing whatever type of CPR is better than doing nothing and simple chest compressions without rescue breathing can increase the odds of survival and reduce the risk of brain damage in a patient who suffers a cardiac arrest.

The following is the instruction about how to do the chest compression only CPR prepared by the University of Arizona Sarver Heart Center.

Be a Lifesaver with Continuous Chest Compression CPR

It's safe. It's easy. It's legal.

It requires no mouth-to-mouth contact.

If you witness a sudden unexpected collapse in an adult, follow these simple steps:

1. Direct someone to call 911 or make the call yourself.

2. Position the patient on the floor.   Place the heel of one hand on the Center of the chest with the other hand on top of the first. Lock your elbows and perform fast, forceful chest compressions. Lift your hands slightly after each push to allow the chest to recoil.   Take turns with a bystander until paramedics arrive.

3. If an automated external defibrillator (AED) is available, attach it to the patient and follow the machine's voice instructions. Otherwise, keep pumping.

Remember: If you just call 911 and do not perform chest compressions, the patients most likely WILL NOT SURVIVE!

Note: Gasping is not an indication of normal breathing or recovery.   Initiate and continue compressions even if patient gasps.

For cases of suspected drowning, drug overdose or collapse in children, follow standard CPR (2 mouth-to-breaths for every 30 chest compressions).

For more information about CPR, read cardiopulmonary resuscitation .

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Acknowledgement:  Some content in the article is adapted from a new release by the University of Arizona.