Evaluation of the Boussignac Cardiac arrest device (B-card) during cardiopulmonary resuscitation in an animal model

IMPACT OF DIFFERENT VENTILATION STRATEGIES ON GAS EXCHANGES AND CIRCULATION DURING PROLONGED MECHANICAL CARDIO-PULMONARY RESUSCITATION IN A PORCINE MODEL

ABSTRACT

Background: Optimal ventilation during cardio-pulmonary resuscitation (CPR) is still controversial. Ventilation is expected to provide sufficient arterial oxygen content and adequate carbon dioxide removal, while minimizing the risk of circulatory impairment. The objective of the present study was to compare three ventilation strategies in a porcine model during mechanical continuous chest compressions (CCC) according to arterial oxygenation and hemodynamic impact. Method: Ventricular fibrillation was induced and followed by five no-flow minutes and thirty low-flow minutes resuscitation with mechanical-CCC without vasopressive drugs administration. Three groups of eight Landras pig were randomized according to the ventilation strategy: 1. Standard nonsynchronized volume-control mode (SD-group); 2. synchronized bilevel pressure-controlled ventilation (CPV-group); 3. continuous insufflation with Boussignac Cardiac-Arrest Device (BC-group). We assessed 1. arterial blood gases, 2. macro hemodynamics, 3. tissular cerebral macro and micro-circulation and 4. airway pressure, minute ventilation at baseline and every 5 minutes during the protocol. Results: Arterial PaO2 level was higher at each measurement time in SD-group (>200 mm Hg) compare to CPV-group and BC-group ( P < 0.01). In BC-group, arterial PaCO2 level was significantly higher (>90mm Hg) than in SD and CPV groups ( P < 0.01). There was no difference between groups concerning hemodynamic parameters, cerebral perfusion and microcirculation. Conclusion: Ventilation modalities in this porcine model of prolonged CPR influence oxygenation and decarboxylation without impairing circulation and cerebral perfusion. Synchronized bi-level pressure-controlled ventilation' use avoid hyperoxia and was as efficient as asynchronized volume ventilation to maintain alveolar ventilation and systemic perfusion during prolonged CPR.

Continuous flow insufflation of oxygen for cardiac arrest: Systematic review of human and animal model studies

OBJECTIVE

To synthetize the evidence regarding the effect of constant flow insufflation of oxygen (CFIO) on the rate of return of spontaneous circulation (ROSC) and other clinical outcomes during cardiac arrest (CA).

METHODS

A systematic review was performed using four databases (PROSPERO: CRD42020071960). Studies reporting on adult CA patients or on animal models simulating CA and assessing the effect of CFIO on ROSC or other clinical outcomes were considered.

RESULTS

A total of 3540 citations were identified, of which 16 studies were included. Four studies (two randomized controlled trials (RCT), two cohort studies), reported on humans while 12 studies used animal models. No meta-analysis was performed due to clinical heterogeneity. There were no differences in the ROSC (18.9% vs 20.8%, p = 0.99; 27.1% vs 21.3%, p = 0.51) and sustained ROSC rates (16.1% vs 17.3%, p = 0.81; 12.5% vs 14.9%, p = 0.73) with CFIO compared to intermitant positive pressure ventilation (IPPV) in the two human RCTs. Survival to ICU discharge was similar between CFIO (2.3%) and IPPV (2.3%) in the largest RCT (p = 0.96). Human studies were at serious or high risk of bias. In animal models' studies, ROSC rates were presented in seven RCTs. CFIO was superior to IPPV in one trial, but was associated with similar ROSC rates using different ventilation strategies in the remaining six studies.

CONCLUSIONS

No definitive association between CFIO and ROSC, sustained ROSC or survival compared to other ventilation strategies could be demonstrated. Future studies should assess CFIO effect on post-survival neurological functions and patient-important CA outcomes.

The Effect of a Modified Constant Flow Insufflation of Oxygen during Cardiopulmonary Resuscitation in a Rat Model of Respiratory Cardiac Arrest on Arterial Oxygenation, Alveolar Barotrauma, and Brain Tissue Injury

Aim

Intermittent positive pressure ventilation (IPPV) can adversely affect cardiopulmonary resuscitation outcomes by increasing the intrathoracic pressure. Continuous flow insufflation of oxygen (CFIO) has been investigated as a potential alternative, but evidence supporting its superiority over intermittent positive pressure ventilation in cases of cardiac arrest is scant. The aim of the current study was to compare the effects of continuous flow insufflation of oxygen using a one-way valve during cardiopulmonary-resuscitation with intermittent positive pressure ventilation in a rat model of respiratory arrest.

Methods

Male Sprague-Dawley rats weighing 400∼450 g (from minimum to maximum) were randomly assigned to either a sham, IPPV, or CFIO group (n = 10 per group). Respiratory arrest was induced by blocking the endotracheal tube. Arterial blood gas analysis was performed during cardiopulmonary resuscitation to compare the oxygenation levels. Tissues were then harvested to compare the degrees of pulmonary barotrauma and ischemic brain injury.

Results

Return of spontaneous circulation was observed in 6/10 rats in the IPPV group and 5/10 in the CFIO group. During cardiopulmonary resuscitation, the mean PaO₂ was significantly higher in the CFIO group (83.10 mmHg) than in the IPPV group (56.10 mmHg). Lung biopsy revealed more inflammatory cells and marked thickening of the alveolar wall in the IPPV group; the group also exhibited a higher frequency of neuroglial cells and apoptotic bodies of pyramidal cells, resulting from ischemic injury.

Conclusion

In a rat model of respiratory arrest, CFIO using a one-way valve resulted in a greater level of oxygenation and less lung and brain injuries than with IPPV.

New physiological insights in ventilation during cardiopulmonary resuscitation

PURPOSE OF REVIEW

In the setting of cardiopulmonary resuscitation (CPR), classical physiological concept about ventilation become challenging. Ventilation may exert detrimental hemodynamic effects that must be balanced with its expected benefits. The risks of hyperventilation have been thoroughly addressed, even questioning the need for ventilation, emphasizing the need to prioritize chest compression quality. However, ventilation is mandatory for adequate gas exchange as soon as CPR is prolonged. Factors affecting the capability of chest compressions to produce alveolar ventilation are poorly understood. In this review, we discuss the conventional interpretation of interactions between ventilation and circulation, from the perspective of novel physiological observations.

RECENT FINDINGS

Many patients with cardiac arrest exhibit 'intrathoracic airway closure.' This phenomenon is associated with lung volume reduction, impedes chest compressions to generate ventilation and overall limits the delivered ventilation. This phenomenon can be reversed by the application of small levels of positive end-expiratory pressure. Also, a novel interpretation of the capnogram can rate the magnitude of this phenomenon, contributing to clarify the physiological meaning of exhaled CO2 and may help assess the real amount of delivered ventilation.

SUMMARY

Recent advances in the understanding of ventilatory physiology during CPR shows that capnogram analysis not only provides information on the quality of resuscitation but also on the amount of ventilation produced by chest compressions and on the total amount of ventilation.

Combination of cardiac and thoracic pump theories in rodent cardiopulmonary resuscitation: a new method of three-side chest compression

BACKGROUND

High-quality cardiopulmonary resuscitation (HQ-CPR) is of paramount importance to improve neurological outcomes of cardiac arrest (CA). The purpose of this study was to evaluate chest compression methods by combining two theories: cardiac and thoracic pumps.

METHODS

Male Sprague-Dawley rats were used. Three types of chest compression methods were studied. The 1-side method was performed vertically with 2 fingers over the sternum. The 2-side method was performed horizontally with 2 fingers, bilaterally squeezing the chest wall. The 3-side method combined the 1-side and the 2-side methods. Rats underwent 10 min of asphyxial CA. We examined ROSC rates, the left ventricular functions, several arterial pressures, intrathoracic pressure, and brain tissue oxygen.

RESULTS

The 3-side group achieved 100% return of spontaneous circulation (ROSC) from asphyxial CA, while the 1-side group and 2-side group achieved 80% and 60% ROSC, respectively. Three-side chest compression significantly shortened the time for ROSC among the groups (1-side, 105 ± 36.0; 2-side, 141 ± 21.7; 3-side, 57.8 ± 12.3 s, respectively, P < 0.05). Three-side significantly increased the intrathoracic pressure (esophagus, 7.6 ± 1.9, 7.3 ± 2.8, vs. 12.7 ± 2.2; mmHg, P < 0.01), the cardiac stroke volume (the ratio of the baseline 1.2 ± 0.6, 1.3 ± 0.1, vs. 2.1 ± 0.6, P < 0.05), and the common carotid arterial pressure (subtracted by femoral arterial pressure 4.0 ± 2.5, 0.3 ± 1.6, vs. 8.4 ± 2.6; mmHg, P < 0.01). Three-side significantly increased the brain tissue oxygen (the ratio of baseline 1.4±0.1, 1.3±0.2, vs. 1.6 ± 0.04, P < 0.05).

CONCLUSIONS

These results suggest that increased intrathoracic pressure by 3-side CPR improves the cardiac output, which may in turn help brain oxygenation during CPR.

A new physiological model for studying the effect of chest compression and ventilation during cardiopulmonary resuscitation: The Thiel cadaver

BACKGROUND

Studying ventilation and intrathoracic pressure (ITP) induced by chest compressions (CC) during Cardio Pulmonary Resuscitation is challenging and important aspects such as airway closure have been mostly ignored. We hypothesized that Thiel Embalmed Cadavers could constitute an appropriate model.

METHODS

We assessed respiratory mechanics and ITP during CC in 11 cadavers, and we compared it to measurements obtained in 9 out-of-hospital cardiac arrest patients and to predicted values from a bench model. An oesophageal catheter was inserted to assess chest wall compliance, and ITP variation (ΔITP). Airway pressure variation (ΔPaw) at airway opening and ΔITP generated by CC were measured at decremental positive end expiratory pressure (PEEP) to test its impact on flow and ΔPaw. The patient's data were derived from flow and airway pressure captured via the ventilator during resuscitation.

RESULTS

Resistance and Compliance of the respiratory system were comparable to those of the out-of-hospital cardiac arrest patients (C_RS^TEC 42 ± 12 vs C_RS^PAT 37.3 ± 10.9 mL/cmH₂O and Res^TEC 17.5 ± 7.5 vs Res^PAT 20.2 ± 5.3 cmH₂O/L/sec), and remained stable over time. During CC, ΔITP varied from 32 ± 12 cmH₂O to 69 ± 14 cmH₂O with manual and automatic CC respectively. Transmission of ΔITP at the airway opening was significantly affected by PEEP, suggesting dynamic small airway closure at low lung volumes. This phenomenon was similarly observed in patients.

CONCLUSION

Respiratory mechanics and dynamic pressures during CC of cadavers behave as predicted by a theoretical model and similarly to patients. The Thiel model is a suitable to assess ITP variations induced by ventilation during CC.