The Science of CPR
Many thanks to Dr. Kudenchuk for sharing
his slides
CPR Prior to Shock
First rhythm VF; n=1117
% Survival
50
p=0.04
40
“CPR first” 1994-96, n=478
30
20
10
“Shock first” 1990-93, n=639
0
1
2
3
4
5 >5
1st Unit Arrival Interval (min)
1990-93 n=22
1994-96 n=14
Cobb LA et al. JAMA 1999;281:1182-1188
91
80
205
164
164
114
86
65
71
41
Compression
• Increased intrathoracic pressure
• Ejects blood from heart and lungs
• “Good” compression increases
forward output and BP
Decompression (recoil)
• Decreased intrathoracic pressure
• Refilling of heart and lungs
• “Good” recoil  vacuum 
refilling  forward output
Hemodynamics of CPR
Compression
(“systole”)
mm Hg
Decompression
(“diastole”)
60
RT ATRIUM
Aorta
Organ perfusion
40
Heart + organ perfusion
0
EXTRATHORAIC VEINS
Criley JM et al. Circulation 1986;74(IV):42-50.
LEFT VENTRICLE
RT ATRIUM
Coronary Perfusion Pressure and ROSC in Human CPR
n=100 patients with
cardiac arrest
100%
80%
57%
50%
55+ (normal)
36%
20-24
15-19
0%
No ROSC
n= 76 CorPP 8.4±10 mm Hg
Coronary perfusion pressure (CorPP)
25-39
Coronary perfusion pressure (CorPP)
40-45
ROSC
n=24 CorPP 25.6±7.7 mm Hg
0-14
*CorPP = Aorta – RA pressure gradient during relaxation (diastolic) phase of precordial compression
Paradis NA., et al. JAMA 1990;263:1106-1113
•n
= 60 consecutive VF resuscitations/shock
63% men, 65 y/o
− Time to 1st shock = 3.7min
−
• Measurements
− Compression depth = mm during 30 sec before 1st shock
• Outcomes
− Successful shock = VF terminated ≥ 5 sec
− ROSC = organized rhythm/pulse/BP ≥ 20 min
Edelson DP et al. Resuscitation 2006;71:137-45
Effect of CC Depth on Shock Success
ORadj*1.99/↑5 mm compression depth (95%CI 1-08-3-66, p=0.028)
*Arrest location, age, sex, time-to-shock
†
†
Edelson DP et al. Resuscitation 2006;71:137-45
AHA recommendations 1.5-2” (4-5 cm)
The Price of CPR Pauses
30 compressions
CPR “systole”
CPR “diastole”
Paused CPR
Aorta
RA
16 secs
3 secs
CPR Performance: Observed vs Perceived
(25th-75th quartiles)
n=30 (19 EMTs, 11 Paramedics)
Manikin study
75%
(70-90)
82%
(75-90)
80%
(75-90)
90%
(88-90)
(50/50)
Correct CPR Performance Parameters
Aufderheide TP et al. Resuscitation 2005;64:353-62
CPR Performance: Observed vs Perceived
n=30 (19 EMTs, 11 Paramedics)
Manikin study
NSD
(25th-75th quartiles)
p=0.002
75%
(70-90)
p=0.01
82%
(75-90)
p=0.02
80%
(75-90)
90%
(88-90)
47%
(42-48)
26%
(24-57)
8%
(7-60)
(50/50)
Correct CPR Performance Parameters
Aufderheide TP et al. Resuscitation 2005;64:353-62
99%
(85-100)
• n=176 adults with out-of-hospital cardiac arrest
• Automated resuscitation monitoring
– Compression rate, depth, “hands off” time
– Ventilation rate
– ECG
– Events
Wik L et al JAMA 2005;293:299-304
Quality of CPR During Out-ofHospital Cardiac Arrest
n=176
Vs AHA Guidelines
chest compression
100 ± 10/min
(75 @ 30:2)
Vs AHA Guidelines
compression depth
38-52 mm (1.5-2”)
60

25
64

23
35

10
34

9
*
*Average # compressions given per minute vs instantaneous rate at which
compressions, when given, were administered (120  20)
Wik L et al JAMA 2005;293:299-304
49%

21
48%

18
~12%
@ 30:2
†
† % time without spontaneous circulation or
chest compressions
• 20 instrumented swine
• 7 minutes of unsupported VF
CPR + AED
“Hands-off” interval prior to each shock
(mimicking analysis and charge interval of AEDs (10-19secs))
3 secs
10 secs
Yu T et al. Circulation 2002;106:368-372
15 secs
20 secs
Effect of Interrupted Precordial Compression
on Resuscitation Outcome
Successfully Resuscitated
100%
p<0.01
p<0.05
80%
p<0.05
40%
0
Seconds of Interrupted CPR
n=5 per group
Yu T et al. Circulation 2002;106:368-372
• n=9 instrumented swine
• 6 minutes untreated VF  standard CPR* x 3 min  CPR with 75%
recoil (residual 1.2 cm sternal compression @ end decompression)
x 1 min  standard CPR* x 1 min  defib x 3  ACLS
*Standard CPR = CC @100/min, 50% duty cycle, 5 cm depth, full (100%) recoil, 15:2 ratio
Yannopoulos D et al. Resuscitation 2005;64:363-72
Effect of Incomplete Chest Decompression
On Coronary and Cerebral Perfusion Pressures
n=9 instrumented swine  std CPR (100% recoil) x 3’  CPR (75% recoil) x 1’
*†
*†p<0.05
% Chest recoil
mm Hg
†
*
*
* p<0.05
Critical pressure for ROSC
*
†
*
*(Ao Diastolic-RAP)
Yannopoulos D et al. Resuscitation 2005;64:363-72; Paradis et al JAMA 1990;263:3257-8
†(MAP – mean ICP pressure)
Importance of High-Performance
Resuscitation
Percent Survival from
Witnessed VF Rhythm
60
New Protocol
percent survival
50
40
30
20
35%
48%
10
0
2000 - 2004
2005 - 2009
Take home points
• Quality of CPR is critical
– Rate
– Depth
– Recoil
• High Density CPR (also ‘high performance CPR’)
– Achieved with a carefully choreographed approach
– Chest compressions must occur 90% of the time
Annual Utstein Survival for
Chelan/Douglas Counties
60%
53.8%
50%
41.7%
40%
30%
30.0%*
20%
10%
0%
2010
*Incomplete data for 2010
2011
2012