Intrathoracic Pressure Regulator During Continuous-Chest-Compression Advanced Cardiac Resuscitation Improves Vital Organ Perfusion Pressures in a Porcine Model of Cardiac Arrest

Abstract

Background-A novel device, the intrathoracic pressure regulator (ITPR), combines an inspiratory impedance threshold device (ITD) with a vacuum source for the generation of controlled Ϫ10 mm Hg vacuum in the trachea during cardiopulmonary resuscitation (CPR) while allowing positive pressure ventilation. Compared with standard (STD) CPR, ITPR-CPR will enhance venous return, systemic arterial pressure, and vital organ perfusion in both porcine models of ventricular fibrillation and hypovolemic cardiac arrest. Methods and Results-In protocol 1, 20 pigs (weight, 30Ϯ0.5 kg) were randomized to STD-CPR or ITPR-CPR. After 8 minutes of untreated ventricular fibrillation, CPR was performed for 6 minutes at 100 compressions per minute and positive pressure ventilation (100% O 2 ) with a compression-to-ventilation ratio of 15:2. In protocol 2, 6 animals were bled 50% of their blood volume. After 4 minutes of untreated ventricular fibrillation, interventions were performed for 2 minutes with STD-CPR and 2 minutes of ITPR-CPR. This sequence was repeated. In protocol 3, 6 animals after 8 minutes of untreated VF were treated with ITPR-CPR for 15 minutes, and arterial and venous blood gases were collected at baseline and minutes 5, 10, and 15 of CPR. A newer, leak-proof ITPR device was used. Aortic, right atrial, endotracheal pressure, intracranial pressure, and end-tidal CO 2 values were measured (mm Hg); common carotid arterial flow also was measured (mL/min). Coronary perfusion pressure (diastolic; aortic minus right atrial pressure) and cerebral perfusion pressure (mean arterial minus mean intracranial pressure) were calculated. Unpaired Student t test and Friedman's repeated-measures ANOVA of ranks were used in protocols 1 and 3. A 2-tailed Wilcoxon signed-rank test was used for analysis in protocol 2. Fischer's exact test was used for survival. Significance was set at PϽ0.05. Vital organ perfusion pressures and end-tidal CO 2 were significantly improved with ITPR-CPR in both protocols. In protocol 1, 1-hour survival was 100% with ITPR-CPR and 10% with STD-CPR (Pϭ0.001). Arterial blood pH was significantly lower and PaCO 2 was significantly higher with ITPR-CPR in protocol 1. Arterial oxygen saturation was 100% throughout the study in both protocols. PaCO 2 and PaO 2 remained stable, but metabolic acidosis progressed, as expected, throughout the 15 minutes of CPR in protocol 3. Conclusions-Compared

Intra–Cardiopulmonary Resuscitation Hypothermia With and Without Volume Loading in an Ischemic Model of Cardiac Arrest

“…This model offers a more realistic simulation of human cardiac arrest resuscitation because most of the events are ischemic. The poor resuscitation rates observed in this experiment with shorter untreated ventricular fibrillation and CPR times than our previous work 23,35,36 can be explained by the severity of the model and the significant postresuscitation instability derived from the ischemic and very arrhythmogenic substrate in this animal model. 37,38 Our study has several limitations.…”

Preterminal Gasping During Hypoxic Cardiac Arrest Increases Cardiac Function in Immature Rats

“…Another mechanism that could be responsible for this increase in CC is a gasping-induced increase in myocardial perfusion. Yannopolus et al (20), using an impedance threshold device designed to increase negative intrathoracic pressure during the relaxation phase of chest compression, showed lower right atrial pressure but better coronary perfusion pressure with use of the device, and a similar mechanism could occur during gasping. Additionally, cerebral perfusion pressure increases during gasping (21).…”

Optimizing the Respiratory Pump: Harnessing Inspiratory Resistance to Treat Systemic Hypotension

“…In animals the CirQlator was of significant benefit in CPR after cardiac arrest, hemorrhagic shock, elevated intracranial pressure from traumatic brain injury, septic shock, and combined hemorrhagic shock and cardiac arrest. 28,29,[43][44][45][46][47][48][49] As with the ResQPOD and ResQGard, we speculate that the CirQlator both "pushes" and "pulls" blood through the capillary bed, thereby providing a novel and important new tool to enhance circulation in poorperfusion states secondary to hypovolemia. The CirQlator has been used clinically in patients with normal pulmonary function and with intraoperative hypotension and found to consistently increase pulse pressure and systemic blood pressure.…”