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 CO 2 excretion  Increase PvCO buffering acid causes a ↓HCO ↑tissue partial pressure of CO 2  Reduce CaCO 2 and PaCO 2  Low end-tidal CO 2 （ ET- CO 2 correlate well with cardiac output during CPR ）

ET-CO 2 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-CO 2 to ＞ 40 mmHg  Higher ET-CO 2 associated with an increase in resuscitation

Blood movement during closed chest compression  Cardiac compression pump theory  Intrathoracic 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 ﹪ 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 ： ml/min/loog  Aortic diastolic pressure ＞ 40 mmHg  Coronary perfusion pressure ＞ 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 ） CPR  Invasive CPR

IAC-CPR ：  Abdominal compression during the relaxation phase of chest compression  “Priming of the intrathoracic pump” before systole  “Abdominal pump” mechanism, as IABP  Abdominal compression point & force  Class II b

IAC-CPR  50 ﹪ increase in MAP & 37 ﹪ increase in 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-sternum  A rate of /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 ventilation  Class 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 ﹪）＜ Survival ＞ 24hr13 （ 45 ﹪） 3（9﹪）3（9﹪）＜ Hospital discharge 2（7﹪）2（7﹪） 0NS From ： Cohen T J.N Engl J Med 1993 ； 329 ：

Outcome according to the resuscitation procedure ROSCHospitalDischarge 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 ：

Factors with improvement in ACD-CPR  Rigorous and repetitive training  Concurrent 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 deformation  Greater transmission of vest pressure to intrathoracic space  Class II b  Used 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 /min to optimize CBF  Improve C.O. & aortic diastolic pressure  Class ： indeterminate

Mechanical （ Piston ） CPR  Optimize effective ext. chest compression and reduce rescuer fatigue  Should be limited to adult  Delivery 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  Expense  Size, weight  Restriction on mobility  Dislocation 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 compression  Emergency cardiopulmonary bypass

Direct cardiac compression  Provide near-normal perfusion  Used early （＜ 25min ）, compression rate of 60-80/min  Associated with some morbidity  Should not be used as a last-ditch effort  Class 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 thoracotomy  For specific, potentially reversible causes ---drug overdoses ---hypothermic arrest  Class ： Indeterminate

Summary of CPR adjuncts  Specific clinical setting  Additional personnel, training, equipment  Increase forward flow ： ﹪  Produce little benefit when started late or late last-ditch measure

Assessment of CPR  Assess hemodynamics  Assess respiratory gases  Assess chest compression

Assessment of Hemodynamics  Pefusion pressure  Pulse

Assessment of Resp. gases  ABG  Oximetry ： limitated factors  Capnometry ---as an early indicator of ROSC ---Class II b

Assessment of chest compression  Quality of chest compression  Resuscitative 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