A study published Online First and in an upcoming Lancet shows that active compression-decompression cardio-pulmonary resuscitation (CPR) with augmentation of negative intrathoracic pressure should be considered as an alternative to standard CPR to increase long-term survival after cardiac arrest. Using this alternative increases survival rates by 53%, conclude the authors, led by Dr Tom P Aufderheide, Department of Emergency Medicine, Medical College of Wisconsin, Milwaukee, WI, USA.

More than 800 000 Europeans and North Americans have an out-of-hospital cardiac arrest every year, with overall survival averaging 5%. Poor survival rates persist, in part, because manual chest compressions and ventilation, termed standard cardiopulmonary resuscitation (CPR), is inherently inefficient, providing less than 25% of healthy blood flow to the heart and brain.

In this randomised trial of 46 emergency medical service agencies (serving 2•3 million people) in urban, suburban, and rural areas of the USA, the authors assessed the proportions of patients surviving with favourable neurological function using both techniques. Adults (presumed age or age ≥18 years) who had a non-traumatic arrest of presumed cardiac cause and met initial and final selection criteria received one of the two types of CPR and were included in the study.

Standard manual CPR was performed by hand according to the American and European Heart Association Guidelines. The new technique uses two devices simultaneously to transform the chest into an active bellows to increase circulation. One is a hand held device to compress and decompress the chest. After each compression the chest is actively lifted upwards with the help of a small suction cup that adheres to the patient's chest. This technique is called active compression-decompression CPR. A second device, called an impedance threshold device, is attached to the patient's airway using a face mask or breathing tube. When the chest is lifted upwards, the impedance threshold device prevents air from rushing into the lungs, creating a vacuum inside the chest that helps to refill the heart after each compression and to lower pressures in the brain. With each compression-decompression cycle the heart and brain receive nearly three times more blood flow when compared with standard CPR. As with standard CPR, patients receive a breath every 10 compressions. The new CPR devices also provide the rescuers wih feedback related to compression depth and rate and help the rescuers know when to provide a breath. The new technique was easy to teach to rescue personnel.

813 standard CPR patients and 840 intervention patients were analysed. The researchers found that 6% of standard CPR patients survived to hospital discharge with favourable neurological function compared with 9% in the intervention group (Improvement in chances of survival of 53% in the intervention group). The same proportions of patients in each group (6% and 9% respectively) survived to one year, with equivalent cognitive skills, disability ratings, and emotional-psychological statuses in both groups. The overall major adverse event rate did not differ between groups.

The authors conclude: "Compression-decompression CPR with augmentation of negative intrathoracic pressure improves survival to hospital discharge with favourable neurological function compared with standard CPR. For the first time, we have shown that a new method of CPR increases hospital-discharge rates and 1-year survival, which are both associated with good neurological outcomes, by nearly 50%, compared with the current standard of care, closed-chest manual CPR."

In a linked Comment, Dr Peter Nagele, Washington University School of Medicine, St Louis, MO, USA, says that combined with evidence from other studies, "it now seems that the combined use of compression - decompression CPR and an impedance-threshold device can improve long-term survival after out-of-hospital cardiac arrest".

Before switching standard practice to this alternative CPR method, Nagele says that the findings should be independently replicated. He also calls for further studies using both larger cohorts and a method that would test the effect that a dummy impedence-threshold device would have on the results.

Click here to view Article and Comment

Source: The Lancet