Safar Center for Resuscitation Research,
University of Pittsburgh Medical Center,
Pittsburgh, Pa
To the Editor:
The "reappraisal" of the literature on mouth-to-mouth ventilation
during bystander-initiated CPR, by a working group of the Basic Life
Support and Pediatric Life Support subcommittees of the American Heart
Association (AHA),1 is misleading and incomplete.
There is no convincing evidence that the low incidence of initiation of
CPR out of hospital by lay bystanders is the result of fear of becoming
infected by mouth-to-mouth ventilation. Such fear should not be
promoted. If such fear exists, however, it should be mitigated by
explaining that initiating CPR is safe and by carrying a pocket-size
barrier for ventilation of strangers. The errors in this article
concerning behavioral, educational, epidemiological, and logistics
issues will be summarized in a separate letter by Braslow and
Brennan.
Although the article says "... it is not intended to change any
current AHA recommendations," its publication has created confusion
and the erroneous impression for laypersons and the media that in
sudden coma, bystanders will save lives by merely pushing on the
sternum (step C, circulation support). In cardiac arrest,
oxygenated blood must be circulated to restore heartbeat
and to keep the brain viable, requiring "head tilt plus blowing plus
pumping." The article suggests that mouth-to-mouth ventilation can be
omitted in various forms of sudden loss of
consciousness.1 Laypersons cannot differentiate
between various forms of sudden coma and between the absence versus
presence of a weak pulse. Coma always results in upper airway
obstruction if the neck is flexed (references 26 to 31 in the article
by Becker et al),2 3 4 5 6 as experienced by
anesthesiologists every day. There are 20 million general
anesthesias given in the United States each year. The data
in Figure 1 are misleading1 because Gordon's
measurements of 1950 (reference 24 in the article by Becker et al) were
made via tracheal tubes.
The omission of lifesaving step A (upper airway control by backward
tilt of the head; reference 26 in the article by Becker et
al)2 3 4 5 6 and step B (breathing support by
mouth-to-mouth; references 27 and 30 in the article by Becker et al)
will harm not only victims of sudden cardiac death but also those of
trauma (particularly head trauma with impact apnea), intoxication,
asphyxiation (common in children), and other causes of sudden coma with
or without pulselessness. Indeed, step A was not even suggested by the
authors1 during sternal compressions alone; at
least the shoulders should be elevated so the head assumes
spontaneously a backward-tilted position that might support a patent
hypopharyngeal air passage (references 26 to 31 in the article by
Becker et al).3 If there is still a faint pulse,
steps A and B alone can often reverse the dying process. Even in cases
of out-of-hospital sudden ventricular fibrillation,
reoxygenation should precede countershocks, which will
not result in heartbeat after >2 to 3 minutes of untreated
ventricular fibrillation (reference 33 in the article by
Becker et al).
This article's "historical rationale" includes errors and
omissions.1 For comatose humans with pulse and a
natural air passage, the failure of chest-pressure methods to ventilate
was documented in 1957.3 For humans both with or
without pulse, the need to combine steps A, B, and C was documented in
19602 : in 30 anesthetized and curarized
adult patients and in 12 patients with cardiac arrest, ventilation
produced by sternal compressions (step C) alone was measured, with or
without backward tilt of the head, and with or without tracheal tube.
In all 30 supine, horizontal, curarized patients, the unsupported head
assumed a semiflexed position that resulted in zero tidal volumes by
sternal compressions. With backward tilt of the head by elevation of
the shoulders (a measure ignored in the article by Becker et al), tidal
volumes were zero in 16 and only 25 to 200 mL in 14
patients.2 In all 12 patients with cardiac
arrest, in spite of tracheal tube in place, forceful sternal
compressions alone moved essentially no
ventilation.2 The authors listed this article
(reference 31) but might not have studied these, the only data
published thus far on ventilation produced by sternal compressions in
humans,2 because that article predates the
earlier citations in MEDLINE. If chest pressure alone ventilates via an
open airway, it would be with unpredictably inadequate tidal volumes
below resting lung volume, which causes lung collapse, particularly in
terminal patients with congested lungs. Hence, not elastic recoil of
the chest, but positive-pressure inflations are needed to ventilate and
oxygenate.
In discussing ventilation requirements, we agree with the article
by Becker et al that low minute ventilation is sufficient to normalize
arterial PO2 and
PCO2 during the low blood flow
produced by external CPR in patients with sudden cardiac arrest.
However, reoxygenation in asphyxiation (reference 29 of
the article by Becker et al) and ventilation after restoration of
spontaneous circulation, both with high blood flow, require
hyperventilation, which is possible even with exhaled air (references
27, 29, and 30 of the article by Becker et al). Also, the authors'
concern about gastric insufflation by mouth-to-mouth
ventilation1 is exaggerated.
Regurgitation can also occur with sternal compressions
alone, and gastric insufflation during mouth-to-mouth ventilation is
self-limiting (reference 29 of the article by Becker et al).
Furthermore, the presently recommended ventilation:compression
ratios of 2:15 or 1:5, which is a compromise, were based on a study in
dogs,7 which was not quoted.
Animal data of ventilation by chest compressions alone, the main
argument presented for the "reappraisal," have no clinical
relevance. Rats, pigs, and dogs have straight airways that do not
obstruct, even in the absence of a tracheal tube. Humans have kinked
airways that always obstruct in the absence of backward tilt of the
head in coma (references 26 to 31 in the article by Becker et
al).2 3 4 5 6 Also, the thoraces of animals are more
compliant and have greater elastic recoil. Furthermore, the authors'
admission that after 6 minutes, ventilation is
needed1 is a concern, because response times for
paramedics are usually longer than that.
In sudden ventricular fibrillation cardiac arrest with
healthy lungs, arterial oxygen levels indeed remain near
normal during a long period of no blood flow without
CPR.8 This occurrence does not obviate the need
for mouth-to-mouth ventilation, because sternal compressions alone in
the presence of complete airway obstruction recirculate venous blood
and cause arterial deoxygenation within
<60 seconds.8
Clinical studies by the excellent CPCR registry of Belgium (references
38 and 39 in the article by Becker et al) have been overinterpreted.
The fact that 10% of prehospital cardiac arrest patients survived
among those who were found on arrival of the ambulance with bystanders
doing only chest compressions does not prove that mouth-to-mouth
ventilation is not needed; it may have been used earlier or was not
necessary because of short arrest times with continued breathing
(gasping). Moreover, the efficacy of individual resuscitation measures
must be determined by physiological measurements in
humans, rather than clinical, epidemiological, statistically
significant outcome correlations, which do not prove cause-effect
relationships on mechanisms.
What and how to teach the public must be extremely simple, with only 1
sequence of steps, ie, A-B-C. We agree with the authors' first
recommendation1 that CPR guidelines should not be
changed at this time. Their second recommendation, to restudy details
of mouth-to-mouth ventilation, is laudable but has low priority. Higher
priority should be given to promoting the motivation and skill
acquisition of the public with use of media and self-training systems;
to early automatic external defibrillation by first responders; and to
clinical documentation of cerebral resuscitation with mild hypothermia
and blood pressure support. We strongly disagree with their third
recommendation1 that "clinical trials of chest
compressions without mouth-to-mouth ventilation are ethical," for the
obvious reason that randomly withholding ventilation and thereby
condoning the moving of deoxygenated blood would be
irresponsible.
References
Ventilation Working Group of the Basic Life Support and
Pediatric Life Support Subcommittees,
American Heart Association
We appreciate the thoughtful comments from Dr Safar and
his colleagues regarding the role of mouth-to-mouth ventilation in
adult CPR. The world will remain forever in the debt of James Elam, MD,
who rediscovered the value of mouth-to-mouth ventilation in the 1950s,
and Dr Safar, who meticulously documented the superiority of expired
air ventilation to maintain blood oxygen levels. The combination of the
Safar-Elam techniques with the chest compression rediscovered by
Kouwenhoven, Jude, and Knickerbocker ushered in the modern era of CPR
in the 1960s and has saved literally thousands of lives.
By the 1990s, however, a number of questions had arisen about CPR: Why
is CPR so difficult for laypeople to learn and remember? Why is CPR
started on such a small percentage of witnessed cardiac arrests? Is
poorly performed CPR perhaps capable of doing harm? Are there different
causes of cardiac arrest that merit modifications of the traditional
"pump and blow" of basic CPR?
Our Ventilation Working Group started its work with open minds. For
this report, we decided to address the particular CPR feature of
mouth-to-mouth ventilation. This focus was because of
indirect evidence suggesting that the disagreeable features of
mouth-to-mouth ventilation, combined with a growing fear of disease
transmission, were making people reluctant to start CPR. Adding
mouth-to-mouth ventilation to the task of chest compression may create
a complex psychomotor skill that is simply too difficult for lay
rescuers to remember at the time of an event as dramatic as sudden
cardiac arrest.
We decided to review the entire body of research regarding chest
compression and ventilation in CPR. We noted a scarcity of human
research on this topic and think there are areas that merit further
investigation. The purpose of the article was to stimulate interest and
promote CPR research. We reached the following conclusions:
1. Two-person CPR with chest compression and mouth-to-mouth
ventilation, performed by experienced professionals, is indisputably
the most effective method to maintain brain and heart viability and to
prolong ventricular fibrillation during cardiac arrest.
2. Single-person CPR with chest compression and mouth-to-mouth
ventilation, performed by inexperienced laypeople, is probably less
effective but should be taught without reservation in all AHA CPR
courses.
3. We completely reject the hypothesis that mouth-to-mouth ventilation
should be eliminated from CPR training. This conclusion is a distortion
of our work and is without valid scientific support.
4. Single-person CPR with chest compression but without mouth-to-mouth
ventilation is suboptimal and is not recommended by the AHA. However,
the optimal single rescuer technique for lay rescuers is not known
because it must both "optimize" the physiology of promoting
oxygenated blood flow as well as promote maximal
community-wide implementation (which may be affected by ease of
training, skill retention, willingness to act, and ability). Animal
studies suggest that mouth-to-mouth plus chest compression improves
oxygen saturation. But as the single rescuer switches from compression
to ventilation, fewer compressions are performed, which may adversely
impact circulation of blood and myocardial perfusion. The obtainment of
additional knowledge on these competing processes seems important, and
these processes have not yet been well studied.
5. Human data on lay single-rescuer CPR without mouth-to-mouth
ventilation are scant. The data from the Belgian CPR registry and
reports from the Netherlands fail to find any disadvantage for patients
who received compression but not mouth-to-mouth ventilation. Moreover,
our BLS instructors need practical guidance when confronted with a CPR
learner they are certain will not perform mouth-to-mouth ventilation in
an emergency. In such situations, the CPR learner must be encouraged to
"at least do something." There is good evidence that chest
compression alone is far better than no rescue attempts at all.
6. We found a theme in the research regarding adults who collapse
with sudden fibrillation and well-oxygenated blood. These
individuals compose a significant proportion of adult out-of-hospital
arrests and may maintain acceptable blood oxygen levels for a few
minutes after collapse with chest compression alone. We could
hypothesize that mouth-to-mouth ventilation could be delayed for these
patients for a few minutes. This window of time, however, is limited,
and ventilation will eventually be required. These data suggest an
avenue for future research. We encourage creative research on this
hypothesis; it is ethical if properly designed.
7. Further research is needed to improve community CPR rates. We
cannot expect lay rescuers to make judgments about the cause of
collapse nor to switch from 1 rescue sequence to another based on the
passage of time. For successful community CPR, the techniques must be
easy to learn, remember, and perform during a crisis. We have called
for more research because we agree that our current data do not provide
complete answers to some important questions. We believe that the
public is best served by conducting research to answer unresolved
issues.
8. Finally, readers should not mistake "confusion" with
legitimate controversy. That letters with divergent viewpoints are
printed reflects the fact that scientific controversy still exists. In
our deliberations, we adhere to the principles of evidence-based
decision making. CPR has been advocated for nearly 40 years, yet most
victims of cardiac arrest never receive CPR efforts, and survival rates
are poor. These controversies have existed for too long without
resolution. Let us resolve to perform the research to turn scientific
controversy into consensus among scientists. This duty falls to all of
us as guardians of public health and safety.
The Safar Resuscitation Research Center has been a beacon of
quality research on the topic of CPR. We appreciate their comments and
their interest in this topic. We are sure they join with us in
encouraging more research evaluation in this rich and dynamic area of
resuscitation.
© 1998 American Heart Association, Inc.
Correspondence
Reappraisal of Mouth-to-Mouth Ventilation During Bystander-Initiated CPR
Response
This article has been cited by other articles:
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  E. Oschatz, P. Wunderbaldinger, F. Sterz, M. Holzer, J. Kofler, H. Slatin, K. Janata, P. Eisenburger, A. A. Bankier, and A. N. Laggner Cardiopulmonary Resuscitation Performed by Bystanders Does Not Increase Adverse Effects as Assessed by Chest Radiography Anesth. Analg., July 1, 2001; 93(1): 128 - 133. [Abstract] [Full Text] [PDF]
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