A dose-response curve for the negative bias pressure of an intrathoracic pressure regulator during CPR

An intrathoracic pressure regulator (ITPR) is a device that can be added to the external end of a tracheal tube to create controlled negative airway pressure between positive pressure ventilations. The resulting downward bias of the airway pressure baseline promotes increased venous return and enhanced circulation during CPR and also during hypovolemic shock. In the present study, we exercised a mathematical model of the human cardiopulmonary system, including airways, lungs, a four chambered heart, great vessels, peripheral vascular beds, and the biomechanics of chest compression and recoil, to determine the relationship between systemic perfusion pressure during CPR and the value of baseline negative airway pressure in an ITPR. Perfusion pressure increases approximately 50% as baseline airway pressure falls from zero to -10 cm H2O. Thereafter perfusion pressure plateaus. Negative bias pressures exceeding -10 cm H2O are not needed in ITPR-CPR.     

CPR中基础生命支持(BLS)的新进展

简要介绍了心肺复苏中基础生命支持的基本步骤和操作,并概述了基础生命支持的新观念,新方法.     

CPR中基础生命支持(BLS)的新进展

简要介绍了心肺复苏中基础生命支持的基本步骤和操作,并概述了基础生命支持的新观念,新方法.     

Optimal Strategy for Cardiopulmonary Resuscitation with Continuous Chest Compression

Objectives: To apply the mathematical techniques of optimal control theory (OCT) to a validated model of the human circulation during cardiopulmonary resuscitation (CPR), so as to discover improved waveforms for chest compression and decompression that maximize the coronary perfusion pressure (CPP).
Methods: The human circulatory system is represented by seven difference equations that describe the pressure changes in systemic vascular compartments that are caused by chest compression. The forcing term is the intrathoracic pressure that is generated by the external chest compression, which is taken as the control variable for the system. The optimum waveform of this forcing pressure as a function of time, determined from OCT, is that which maximizes the calculated CPP between the thoracic aorta and the superior vena cava over a period of 13.3 seconds of continuous chest compression.
Results: The optimal waveform included both compression and decompression of the chest to the maximum allowable extent. Compression–decompression waveforms were rectangular in shape. The frequency of optimal compression–decompression that was found by OCT was 90 per minute. The optimal duty cycle (compression duration per cycle time) was 40%. The CPP for the optimum control waveform was 36 mm Hg vs. 25 mm Hg for standard CPR.
Conclusions: Optimal control theory suggests that both compression and decompression of the chest are needed for best hemodynamics during CPR.     

Optimal control applied to a thoraco-abdominal CPR model

Suzanne Lenhart Department of Mathematics, University of Tennessee, Knoxville, TN 37996-1300, USA Vladimir Protopopescu Computational Sciences and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA Charles Babbs Basic Medical Sciences, Purdue University, West Lafayette, IN 47907-1246, USA Email: lenhart{at}math.utk.edu Received on June 1, 2007. Revised on March 22, 2008. Accepted on March 25, 2008. The techniques of optimal control are applied to a validatedblood circulation model of cardiopulmonary resuscitation (CPR),consisting of a system of seven difference equations. In thissystem, the non-homogeneous forcing terms are chest and abdominalpressures acting as the ‘controls’. We seek to maximizethe blood flow, as measured by the pressure difference betweenthe thoracic aorta and the right atrium. By applying optimalcontrol methods, we characterize the optimal waveforms for externalchest and abdominal compression during cardiac arrest and CPRin terms of the solutions of the circulation model and of thecorresponding adjoint system. Numerical results are given forvarious scenarios. The optimal waveforms confirm the previouslydiscovered positive effects of active decompression and interposedabdominal compression. These waveforms can be implemented withmanual (Lifestick-like) and mechanical (vest-like) devices toachieve levels of blood flow substantially higher than thoseprovided by standard CPR, a technique which, despite its longhistory, is far from optimal.