Mouth-to-mouth ventilation's role in CPR questioned

September 16, 1997

A blue-ribbon panel of experts assembled by the American Heart Association (AHA) has called into question the role of mouth-to-mouth ventilation as an integral part of cardiopulmonary resuscitation (CPR).

Their analysis, to be published as a "Special Report" in the September 16, 1997 issue of the AHA's journal, Circulation, will also appear in coming issues of Annals of Emergency Medicine, Journal of Respiratory Care, and Resuscitation.

Although they are not yet ready to change the current AHA guidelines for performance of CPR, the Ventilation Working Group's consensus statement suggests that in many cases of adult cardiac arrest, mouth-to-mouth ventilation as a part of CPR rarely helps and may even harm the patient.

The experts believe that mouth-to-mouth ventilation can interfere with the rescuer's efforts to perform chest compressions and cause significant adverse effects. It makes CPR more difficult to teach, learn and perform, and dissuades bystanders from initiating therapy.

More than 350,000 people die from cardiac arrest each year in the United States. Nationally, only a little more than 30 percent receive any form of CPR. In Chicago, that rate falls to 22 percent.

"Early CPR using chest compression clearly saves lives," said Lance Becker, MD, associate professor of medicine at the University of Chicago and chairman of the AHA panel, "but in part because of the complications, complexity and concern associated with mouth-to-mouth ventilation, CPR is not performed for the majority of those who need it."

More research needs to be done, the panel insists, to prepare new guidelines for the year 2000.

Although it has a long history--the first references to mouth-to-mouth resuscitation involve the prophets Elijah and Elisha in the Old Testament--this form of assisted ventilation became part of CPR dogma only in the 1960s, when it replaced manual techniques such as raising and lowering the arms to encourage breathing.

More recently, however, studies have cast doubt on the effectiveness of mouth-to-mouth ventilation in the setting of adult cardiac arrest, where the key determinant of survival is the time from arrest until defibrillation, when the heart is shocked back into a normal rhythm.

Unlike victims of near drowning or choking where mouth-to-mouth ventilation can quickly improve oxygen levels, low blood flow is the primary disorder for those who suffer a cardiac arrest. Without significant blood flow, even with the low level of blood flow produced by chest compressions, forcing air into the lungs will not make much difference.

Besides, when the heart stops, oxygen levels in the blood decline gradually. Many patients continue to gasp for air and chest compressions induce some air exchange. Assisted ventilation appears to become important only after four to 10 minutes of CPR.

"It may be time to reshuffle the cardiac-arrest survival alphabet," suggests Dr. Becker, "from the old ABC (for Airway, Breathing and Circulation) to CAB (Circulation, Airway, Breathing), as they have already done in the Netherlands."

Mouth-to-mouth ventilation has its own costs. Exhaled air contains 17 percent oxygen, less than 21 percent of fresh air, and 4 percent carbon-dioxide, which can inhibit cardiac contraction. Studies have found that from 10 to 35 percent of patients who receive CPR inhale stomach contents, emitted after air is blown into the stomach rather than to the lungs. And time allocated to ventilation, especially if only one rescuer is involved, is subtracted from the efforts to provide chest compressions.

Even for healthcare professionals, with continuous coaching, only 15 percent involved in studies of one-rescuer CPR on a mannequin achieved the recommended rate of 80 compressions per minute when they tried to perform both chest compression and mouth-to-mouth ventilation.

Perhaps most important, mouth-to-mouth ventilation appears to discourage bystanders from providing needed CPR. "When mouth-to-mouth ventilation is combined with chest compression, the CPR technique becomes a complex psychomotor task that can be difficult to learn, teach, remember, and perform," note the authors.

"A simpler technique might lead to more widespread performance," added Dr. Becker, "which would improve survival rates."

Mouth-to-mouth Contact also makes potential rescuers squeamish. Not only lay persons, but many physicians, nurses and even CPR instructors are extremely reluctant to perform mouth-to-mouth ventilation. Although the risks of disease transmission are quite small, and there have been no reports of HIV transmission, there have been isolated reports of infectious agents such as herpes, TB, salmonella and others being exchanged during CPR.

"It can be pretty yucky," admits Dr. Becker. "When people practice CPR on a dummy they imagine Cindy Crawford or Tom Cruise, but the guys who drop in the supermarket tend to resemble Rodney Dangerfield. I think that's yet another reason bystander CPR is already far too rare and is becoming even less common."

Until new guidelines are formulated, Dr. Becker advises those who witness a cardiac arrest: "Just do it. First, call 911. Then, if mouth-to-mouth ventilation bothers you, skip it and concentrate on chest compressions. That is far, far better than doing nothing."

The panel also emphasized that immediate mouth-to-mouth ventilation remains critically important for children and for adults where cardiopulmonary arrest results from airway obstruction, drowning, or respiratory problems.

Other members of the panel were Robert A. Berg, MD; Paul E. Pepe, MD; Ahamed H. Idris, MD; Thomas P. Aufderheide, MD; Thomas A. Barnes, EdD., RRT.; Samuel J. Stratton, MD; and Nisha C. Chandra, MD.

Summary:
An expert panel suggests that in adult cardiac arrest, mouth-to-mouth ventilation as a part of CPR rarely helps and may even harm the patient. It can interfere with chest compressions, cause significant adverse effects, make CPR more difficult to teach, learn and perform, and dissuades bystanders from initiating therapy.