Chest compression are the core of resuscitation efforts in any patient with confirmed or suspected cardiac arrest. Good CPR should not be thought as heart-only process, but a combination of heart and brain.
Standard cardiopulmonary resuscitation consists of manual chest compressions to maintain blood flow and
positive-pressure breathing to maintain oxygenation until spontaneous
circulation is restored. Chest compressions are interrupted frequently by ventilations
given as rescue breathing during the treatment of out-of-hospital cardiac
arrest. These interruptions reduce blood flow and potentially reduce the
effectiveness of CPR. Observational studies involving humans with
out-of-hospital cardiac arrest of presumed cardiac cause have suggested that
continuous compressions are associated with better survival than interrupted
compressions. Nichol et al. conducted a randomized trial to test whether
continuous chest compressions, as compared with chest compressions
interrupted for ventilation, during CPR performed by emergency medical
service (EMS) providers affected the rate of survival, neurologic function,
or the rate of adverse events.
In the
large randomized trial conducted by Nichol et al. involving adults with
out-of-hospital cardiac arrest, a strategy of continuous manual chest
compressions with positive-pressure ventilation was not associated with a
significantly higher rate of survival to discharge. During the
active-enrollment phase, 1129 of 12,613 patients (9.0%) in the intervention
group (which received continuous chest compression) and 1072 of 11,035 (9.7%)
in the control group (which received interrupted chest compressions) survived
to hospital discharge (difference with adjustment for cluster and sequential
monitoring, −0.7 percentage points; 95% confidence interval [CI], −1.5 to
0.1; P=0.07).
In the
study by Nichol et al., secondary outcomes included neurologic function at
discharge, which was measured with the use of the modified Rankin scale
(scores range from 0, indicating no symptoms, to 6, indicating death, with a
score of ≤3 indicating favorable neurologic function) on the basis of review
of the clinical record, and adverse events. Among patients with available
data on neurologic status, 883 of 12,560 patients (7.0%) in the intervention
group and 844 of 10,995 (7.7%) in the control group survived with a modified
Rankin scale score of 3 or less (difference with adjustment for cluster, −0.6
percentage points; 95% CI, −1.4 to 0.1; P=0.09).
Hospital-free
survival in the Nichol trial was defined as the number of days alive and
permanently out of the hospital during the first 30 days after the cardiac
arrest. Hospital-free survival was significantly shorter in the intervention
group than in the control group (mean difference, −0.2 days; 95% CI, −0.3 to −0.1;
P=0.004).
Previous
observational studies have shown large increases in survival rates among
patients with a shockable rhythm with the implementation of continuous
compressions by EMS providers versus compressions interrupted for
ventilations. Among patients with a noncardiac cause of cardiac arrest who
were treated by laypersons or those with a nonshockable rhythm who were
treated by EMS providers, continuous compressions were not associated with a
significant improvement in outcome. In these previous studies, participating
EMS agencies did not measure CPR process when implementing continuous
compressions, and implementation occurred simultaneously with other changes,
including directions to give intravenous epinephrine early, to use a
nonrebreather mask with passive ventilation, to defer airway insertion, and
to reduce the number of defibrillations given with each rhythm analysis. In
the initial reports of implementation of continuous compressions, most
patients received rescue breathing by means of positive-pressure ventilation
with a bag-valve mask. Other interventions that each patient received were
not reported. It seems plausible that some of the observed improvement in
these previous studies was due to improved CPR process (e.g., compression
rate and depth), concurrent improvements in the system of care, or Hawthorne
effects (changes in behavior resulting from awareness of being observed)
rather than to the implementation of continuous compressions alone.
In Summary...
- Rapid initiation of chest compression increases survival with better neurological outcome.
- Avoiding interruptions during chest compression is key for brain perfusion.
- Defibrillate for shockable rhythms.
- Teaching the general public on how to do high quality chest compressions can make a real difference.
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Thursday, December 3, 2015
Chest Compression During CPR ... Don't Forget The Brain !
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