Table of Contents:
According to the ERC guidelines of 2005 and 2010, two rescuers basic life
support (BLS) with a compression-ventilation ratio of 30:2 is recommended. It
is suggested to switch chest compressors approximately every 2 minutes to
prevent fatigue leading to decreases in CPR efficacy. Otherwise, interruptions
of chest compressions by switching compressors, delivering ventilations or
diagnostic or therapeutic interventions should be minimized to reduce
coronary and cerebral no-flow time during the resuscitation.
The goal of this study was to determine the optimal time to switch
compressors in various climatical conditions. 41 professional health care
providers trained in CPR performed eight minutes of BLS in a randomized
simulation study using an interactive manikin, ResusciAnne® Simulator
(Laerdal™) in normal, warm and cold climatic conditions. Primary endpoints
were changes in total number of chest compressions, depth of compressions,
hands-off-time, number of correctly applied chest compressions minute-byminute
as well as the compressor’s subjective sensation of fatigue. Using the
Laerdal PC SkillReporting Systems™ the chest compressions applied were
recorded and analysed.
Data were analysed using Bonferroni’s univariate analysis of variance
(ANOVA) or Friedman’s analysis with Dunn’s post test where appropriate.
Statistical significance was defined as a P value less than 0,05.
In addition, test persons answered questions regarding their formal
knowledge of current resuscitation guidelines and their CPR experience.
Before and after the simulation study in the cold condition, blood lactate
testing was performed in 34 test persons. The observed increase in blood
lactate after the simulation in the cold condition is equivalent to average effort
exercise. The declared wishes to switch compressors declined during the
study intervals. In the first setting, normal climatic conditions, there were ten
test persons, in the second setting, warm climatic conditions, five test persons and in the last setting, cold climatic conditions, four test persons who wished
to switch during the study period of eight minutes.
Simulated BLS over eight minutes without switching compressors resulted in
less compressions and increases in hands-off-time after one minute as well
as inadequate depth of chest compressions after two minutes. These effects
were more pronounced in the warm and cold climatic conditions without
reaching statistical significance every minute. There was a noticeable training
effect during the study period: the third BLS simulation in the cold climatic
condition resulted in statistically significant more correctly applied chest
compressions. There was discrepancy in test persons’ self-assessment on
physical capacity and total number of wishes to switch with the quality of
chest compressions recorded. Overall, BLS simulation over eight minutes in
all three climatic conditions was consistent with average ERC 2005
standards. According to the updated ERC guidelines of 2010, depth of
compressions as well as frequency of compressions during simulation were in
the lower minimum range.
The results of the study confirm the ERC recommendations of 2005 and 2010
that lack evidence to switch compressors after two minutes independent of
personal fitness and self-assessment. In extreme climatic conditions,
compressor’s switch may be reasonable even after one minute. During
resuscitation in conditions when switching compressors is challenging, this
switch after two minutes is not mandatory. The results of this study are
consistent with the demand to train professional health care providers in CPR
on a routine basis.