Over 750,000 citizens of
the US and Europe suffers sudden cardiac arrest each year, and
survival remains dismal: over 75% of victims do not leave the
hospital alive. Cardiac arrest requires treatment within minutes to
attain survival. Cardiopulmonary resuscitation (CPR) and electrical
defibrillation remain the two crucial interventions that can be
life-saving during cardiac arrest. Through CPR training offered by
the American Heart Association (AHA) and other organizations,
laypersons can provide treatment to cardiac arrest victims before
the arrival of emergency medical personnel. This review will
summarize current knowledge about the importance of CPR in the
treatment of cardiac arrest, and will describe several exciting new
technologies that will make CPR more effective in coming years.
The Clinical Importance of CPR
:
A
number of studies have confirmed that CPR can be life-saving when
provided either by laypersons or medical professionals. In several
large investigations, the prompt delivery of CPR served as an
important predictor of survival—bystander CPR may almost double the
chance of survival. Other work has shown that the probability of
survival from cardiac arrest falls by 10–15% per minute without
treatment, and well-performed CPR likely shifts this curve towards
higher probability of survival. Furthermore, recent investigations
have suggested that CPR maintains the heart in a state favorable for
defibrillation. That is, fatal cardiac arrhythmias common in cardiac
arrest have a greater chance of being successfully terminated by
electrical shock if CPR is performed first. Recent work has also
shown that during actual human CPR, shallow chest compressions have
an adverse impact on outcomes. Therefore, it is crucial that CPR be
performed in accordance with published guidelines, which are
formulated based on the best available data and updated every five
years. Given the importance of CPR quality, it is perhaps surprising
that the performance of CPR has only recently been assessed during
actual cases of cardiac arrest. In a number of investigations over
the past few years, CPR quality was found to be lacking during both
in-hospital and out-of-hospital cardiac arrest, both in Europe and
the US. In other words, poor CPR quality is endemic. In general,
chest compressions are delivered too slowly and in too shallow a
fashion, and ventilations are given too rapidly. There are several
reasons why this might be the case despite the best intentions of
providers. First,CPR is deceptively simple to describe and
remarkably difficult to perform, as humans generally do not have a
good internal sense of timing to recognize 100 compressions or 8–12
ventilations per minute, and fatigue often prevents adequate depth
efforts. Second, CPR is taught in the sterile conditions of a
classroom, but performed in the volatile environment of a
dramatically ill person surrounded by anxious onlookers—training can
be easily forgotten in the panic of the moment, especially if that
training has not taken place recently. Third, CPR courses until
recently did not adequately emphasize the importance of CPR quality
as a determinant of survival. Improving CPR and Cardiac Arrest Care
What, then, can be done to improve the care of cardiac arrest
patients? It is clear from a variety of data that the majority of
cardiac arrest patients do not receive CPR at all until the arrival
of medical personnel precious minutes after the onset of arrest. CPR
training must be simplified and widely disseminated. Why, for
example, can we not require CPR competence as a prerequisite for a
driver’s license, or provide CPR training to every parent during the
hospital stay before the birth of their child or before they leave
the hospital with their newborn? CPR quality must also be improved.
A variety of new technologies have been developed over the past
decade to assist in this goal. First, devices have been developed
that detect CPR parameters during actual resuscitation, and these
devices can trigger alarms or audio messages when incorrect CPR is
detected, for example if the chest compression rate is too slow.
Such devices assist the provider during human CPR by acting as
real-time ‘CPR coaches’, and are currently being marketed by a
number of biomedical companies. Second, devices are currently in use
that delivers CPR mechanically, via either a motorized compression
band wrapped around the chest or a compressed-air driven piston
pump. These tools provide uniform chest compression rate and depth
by removing the human performance element. Clinical studies are
currently under way with both audio- feedback and mechanical
compression devices to assess whether they improve patient
outcomes.