SEATTLE--The combination of chest compression and mouth-to-mouth ventilation during dispatcher-instructed cardiopulmonary resuscitation (CPR) does not appear to offer any benefits over chest compression alone. In fact, chest compression alone improved survival to hospital discharge in a recent study of bystander-initiated CPR.[1]

"Providing instructions in chest compressions will probably be more effective than attempts to convey the conventional CPR paradigm," suggested Alfred P. Hallstrom, PhD, director of the department of biostatistics at the University of Washington in Seattle. Dr. Hallstrom and colleagues sought to determine whether dispatcher-instructed bystander CPR by chest compression alone would result in improved rates of survival to hospital discharge when compared with standard instructions for chest compression plus mouth-to-mouth ventilation.

The trial was conducted at a fire-department-based emergency medical care system. Telephone dispatchers gave bystanders--who had no CPR training--at the scene of apparent cardiac arrest instructions in either chest compression alone or chest compression plus mouth-to-mouth ventilation. A total of 520 patients with cardiac arrest received either chest compression and mouth-to-mouth ventilation or chest compression alone. Dispatchers were able to give complete instructions in 81% of episodes for the group receiving chest compression alone, compared with only 62% of episodes for the group receiving both chest compression and mouth-to-mouth ventilation.

The proportion of patients who survived to hospital discharge was significantly higher in the group receiving chest compression only (14.6%) than in the group receiving chest compression plus ventilation (10.4%). When the two groups were compared, the unadjusted odds ratio (OR) for survival to hospital discharge was 0.68 in the chest compression plus ventilation group; the adjusted odds ratio was 0.75. However, none of these differences reached statistical significance. Three variables were found to be significant predictors of survival: location (OR, 0.59), whether the arrest was witnessed (OR, 2.32), and age of the victim (OR, 1.02).

The instructions for performing ventilation are time-consuming and difficult to carry out, whereas the chest compression instructions are relatively straightforward and easier to perform, the authors pointed out. They also noted that cardiac arrest due to primary ventilatory failure is much less common than arrest due to cardiac causes, except in children and adult patients with drug overdose, alcohol intoxication, or carbon monoxide poisoning. Therefore, with the exception of the latter conditions, it may be more useful to provide instructions for chest compression in the general setting of bystander-initiated CPR, the authors suggested.

"At the time of primary cardiac arrest, the blood is fully oxygenated. Initiating chest compression to increase blood circulation will provide protection and may result in less damage to vital organs," said Dr. Hallstrom.

--Deborah L. O' Connor

Reference
1. Hallstrom A, Cobb L, Johnson E, Copass M. Cardiopulmonary resuscitation by chest compression alone or with mouth-to-mouth ventilation. N Engl J Med. 2000;342:1546-1553.

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