Devices to Assist Circulation

Alternative CPR techniques

Assessment of CPR

Physiology of Ventilation during CPR

Gas distribution will be determined by the relative impedance to flow

Lower esophageal opening pressure and reduced lung-thorax compliance

insp. pressure must be kept low to avoid gastric insufflation

If airway remains patent, chest compression cause substantial air exchange.

Physiology of gas transport during CPR

Decrease CO2 excretion Increase PvCO2

--- buffering acid causes a ↓HCO3-

---↑tissue partial pressure of CO2

Reduce CaCO2 and PaCO2 Low end-tidal CO2 （ ET- CO2 correlate

well with cardiac output during CPR ）

ET-CO2 monitoring

High correlation with C.O. ,CPP, initial resuscitation and survival during CPR

Usually to ＞ 20 mmHg during successful CPR

When ROSC , the earliest sign is a sudden increase in ET-CO2 to ＞ 40 mmHg

Higher ET-CO2 associated with an increase in resuscitation

Blood movement during closed chest compression

Cardiac compression pump theoryIntrathoracic pressure pump theory

Blood movement during CPR

Fluctuations in intrathoracic pressure play a significant role in blood flow during CPR

The amount of chest compression is a critical determination of flow , and the quality of chest compression will likely be a major factor in the effectiveness of CPR

Physiology of circulation during standard manual CPR

C.O. severly depressed to 10-30 of ﹪prearrest

Brain blood flow ： 20﹪Coronary blood flow ： 5-15﹪Lower extremity & abd. visceral flow

＜ 5 of C.O.﹪

Successful resuscitation

Myocardial blood flow ： 15-30 ml/min/loog

Aortic diastolic pressure ＞ 40 mmHgCoronary perfusion pressure

＞ 20-25 mmHg

CPP higher than 15 mmHg to achieve ROSC

Alternative CPR techniques

Interposed abdominal compression （ IAC ） CPR Active compresion-decompression （ ACD ） CPR Phased thoracic-abd. compression-decompression

（ PTACD ） CPR High frequency CPR Vest CPR Simultaneous ventilation-compression （ SVC ） C

PR Invasive CPR

IAC-CPR：Abdominal compression during the rel

axation phase of chest compression“Priming of the intrathoracic pump” be

fore systole“Abdominal pump” mechanism , as IA

BPAbdominal compression point & forceClass II b

IAC-CPR

50 increase in MAP & 37 increase i﹪ ﹪n CPP campared with standard CPR

Survival studies with IAC-CPR haven’t produced consistent results.

ACD-CPR

A suction-cup device to pull up the chest during chest relaxation

“Prime the thoracic pump”Place over mid-sternumA rate of 80-100/min with compression

depth of 1.5~2.0 inches

ACD-CPR

Greater chest expansion

more negative intrathoracic pressure

1. augment venous return

2. increase minute ventilationClass II b

Outcomes of p’t assigned to ACD or standard CPR

ACD

（ N=29 ）Standard

（ N=33）

P-value

Resuscitator 18 （ 62﹪）

10 （ 30﹪）

＜ 0.003

Survival ＞ 24hr 13 （ 45﹪）

3 （ 9﹪）

＜ 0.004

Hospital discharge 2 （ 7﹪） 0 NS

From ： Cohen T J.N Engl J Med 1993 ； 329 ： 1918-21

Outcome according to the resuscitation procedure

ROSC Hospital Discharge

1993 Total 22/56 （ 39.3﹪）

7/56 （ 12.5﹪）

1993 ACD-CPR 10/26 （ 38.5﹪）

3/26 （ 11.5﹪）

1992 STD-CPR 13/43 （ 30.2﹪）

3/43 （ 7.0﹪）

1993 STD-CPR 12/30 （ 40.0﹪）

4/30 （ 13.3﹪）

From ： J Cardiothorac Vasc Anesth 1996 ； 10 ： 178-186

Factors with improvement in ACD-CPR

Rigorous and repetitive trainingConcurrent use of low-rather than high-dose

Epi.Use of the force gauge Peformance of CPR for a duration sufficient

to prime the pump

PTACD-CPR

Hand-held device that alternates chest compression and abd. decompression with chest decom & abd. compression

Combines the concepts of IAC-CPR & ACD-CPR

Combined 4-phase approach Class ： Indeterminate

Vest-CPR“Thoracic pump mechanism” of blood flow Increased inthrathoracic pressure fluctuations ---increased chest compression force ---increased airway collapse during compression Reduced amount of chest deformationGreater transmission of vest pressure to intrathoracic s

paceClass II bUsed in-hospital or during ambulance

High-Frequency CPR（ Rapid Compression Rate）

High velocity , moderate force , and brief duration to optimize cardiac stroke volume

A rate of 100-120/min to optimize CBFImprove C.O. & aortic diastolic pressure Class ： indeterminate

Mechanical （ Piston） CPR

Optimize effective ext. chest compression and reduce rescuer fatigue

Should be limited to adultDelivery of a consistent rate & depth of

compression Compression-ventilation ratio of 5 ： 1

compression duration is 50 of the cycle﹪Class II b

Mechanical （ Piston） CPR

Sternal fracture ExpenseSize , weightRestriction on mobilityDislocation of the plunger

SVC-CPR

Improved peak compression （ systolic ） pressure

Thoracic pump mechanism Pressure gradient between intra & extra-

thoracic vascular beds.Is not currently available for clinical use

Invasive CPR：

Direct cardiac compressionEmergency cardiopulmonary bypass

Direct cardiac compression

Provide near-normal perfusionUsed early （＜ 25min ） , compression

rate of 60-80/minAssociated with some morbidityShould not be used as a last-ditch effortClass II b

Indication for “open chest” CPR

Penetrating chest trauma with developing cardiac arrest

Cardiac arrest caused by hypothermia , pul. embolism or pericardial tamponade

Chest deformity where closed-chest CPR is ineffective

Penetrating abd. trauma with deterioration & cardiac arrest

Emergency C-P-B

Femoral artery & vein with thoracotomyFor specific , potentially reversible causes

---drug overdoses

---hypothermic arrestClass ： Indeterminate

Summary of CPR adjuncts

Specific clinical settingAdditional personnel , training ,

equipmentIncrease forward flow ： 20-100﹪Produce little benefit when started late

or late last-ditch measure

Assessment of CPR

Assess hemodynamicsAssess respiratory gasesAssess chest compression

Assessment of Hemodynamics

Pefusion pressurePulse

Assessment of Resp. gases

ABGOximetry ： limitated factorsCapnometry

---as an early indicator of ROSC

---Class II b

Assessment of chest compression

Quality of chest compressionResuscitative effort“CPR-plus” during CPR

Class Indeterminate

No good prognostic criteria to assess the efficacy of CPR

Clinical outcome is often the only way to judge CPR efforts

Faster definitive therapy improves surrival better than any variations in CPR technique

Conclusion