Devices to Assist Circulation

1. Devices to Assist Circulation • Alternative CPR techniques • Assessment of CPR

2. 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.

3. 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）

4. 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

5. Blood movement during closed chest compression • Cardiac compression pump theory • Intrathoracic pressure pump theory

6. 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

7. 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.

8. Successful resuscitation • Myocardial blood flow：15-30 ml/min/loog • Aortic diastolic pressure＞40 mmHg • Coronary perfusion pressure ＞20-25 mmHg CPP higher than 15 mmHg to achieve ROSC

9. 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

10. 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

13. IAC-CPR • 50﹪increase in MAP & 37﹪increase in CPP campared with standard CPR • Survival studies with IAC-CPR haven’t produced consistent results.

14. 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 80-100/min with compression depth of 1.5~2.0 inches

15. ACD-CPR • Greater chest expansion more negative intrathoracic pressure 1. augment venous return 2. increase minute ventilation • Class II b

17. Outcomes of p’t assigned to ACD or standard CPR

18. Outcome according to the resuscitation procedure

19. 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

20. 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

25. 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

28. 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 CBF • Improve C.O. & aortic diastolic pressure • Class：indeterminate

31. 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

32. Mechanical （Piston）CPR • Sternal fracture • Expense • Size , weight • Restriction on mobility • Dislocation of the plunger

33. 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

35. Invasive CPR： • Direct cardiac compression • Emergency cardiopulmonary bypass

36. 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

37. 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

38. Emergency C-P-B • Femoral artery & vein with thoracotomy • For specific , potentially reversible causes ---drug overdoses ---hypothermic arrest • Class：Indeterminate

39. Summary of CPR adjuncts • Specific clinical setting • Additional personnel , training , equipment • Increase forward flow ： 20-100﹪ • Produce little benefit when started late or late last-ditch measure

40. Assessment of CPR • Assess hemodynamics • Assess respiratory gases • Assess chest compression

41. Assessment of Hemodynamics • Pefusion pressure • Pulse

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

43. Assessment of chest compression • Quality of chest compression • Resuscitative effort • “CPR-plus” during CPR Class Indeterminate

44. Conclusion • 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