Intrathoracic Airway Closure Impacts CO2 Signal and Delivered Ventilation during Cardiopulmonary Resuscitation.

RATIONALE: End-tidal CO2 (EtCO2) is used to monitor cardiopulmonary resuscitation (CPR), but it can be affected by intrathoracic airway closure. Chest compressions induce oscillations in expired CO2, and this could reflect variable degrees of airway patency. OBJECTIVES: To understand the impact of airway closure during CPR, and the relationship between the capnogram shape, airway closure, and delivered ventilation. METHODS: This study had three parts: 1) a clinical study analyzing capnograms after intubation in patients with out-of-hospital cardiac arrest receiving continuous chest compressions, 2) a bench model, and 3) experiments with human cadavers. For 2 and 3, a constant CO2 flow was added in the lung to simulate CO2 production. Capnograms similar to clinical recordings were obtained and different ventilator settings tested. EtCO2 was compared with alveolar CO2 (bench). An airway opening index was used to quantify chest compression-induced expired CO2 oscillations in all three clinical and experimental settings. MEASUREMENTS AND MAIN RESULTS: A total of 89 patients were analyzed (mean age, 69 ± 15 yr; 23% female; 12% of hospital admission survival): capnograms exhibited various degrees of oscillations, quantified by the opening index. CO2 value varied considerably across oscillations related to consecutive chest compressions. In bench and cadavers, similar capnograms were reproduced with different degrees of airway closure. Differences in airway patency were associated with huge changes in delivered ventilation. The opening index and delivered ventilation increased with positive end-expiratory pressure, without affecting intrathoracic pressure. Maximal EtCO2 recorded between ventilator breaths reflected alveolar CO2 (bench). CONCLUSIONS: During chest compressions, intrathoracic airway patency greatly affects the delivered ventilation. The expired CO2 signal can reflect CPR effectiveness but is also dependent on airway patency. The maximal EtCO2 recorded between consecutive ventilator breaths best reflects alveolar CO2.

Impact of Specific Emergency Measures on Survival in Out-of-Hospital Traumatic Cardiac Arrest.

INTRODUCTION: The management of out-of-hospital traumatic cardiac arrest (TCA) for professional rescuers entails Advanced Life Support (ALS) with specific actions to treat the potential reversible causes of the arrest: hypovolemia, hypoxemia, tension pneumothorax (TPx), and tamponade. The aim of this study was to assess the impact of specific rescue measures on short-term outcomes in the context of resuscitating patients with a TCA. METHODS: This retrospective study concerns all TCA patients treated in two emergency medical units, which are part of the Northern French Alps Emergency Network (RENAU), from January 2004 through December 2017. Utstein variables and specific rescue measures in TCA were compiled: fluid expansion, pelvic stabilization, tourniquet application, bilateral thoracostomy, and thoracotomy procedures. The primary endpoint was survival rate at Day 30 with good neurological status (Cerebral Performance Category [CPC] score CPC 1 and CPC 2). RESULTS: In total, 287 resuscitation attempts in TCA were included and 279 specific interventions were identified: 262 fluid expansions, 41 pelvic stabilizations, five tourniquets, and 175 bilateral thoracostomies (including 44 with TPx). CONCLUSION: Among the standard resuscitation measures to treat the reversible causes of cardiac arrest, this study found that bilateral thoracostomy and tourniquet application on a limb hemorrhage improve survival in TCA. A larger sample for pelvic stabilization is needed.

Acting on the potentially reversible causes of traumatic cardiac arrest: Possible but not sufficient.

INTRODUCTION: Traumatic cardiac arrest (TCA) guidelines emphasize specific actions that aim to treat the potential reversible causes of the arrest. The aim of this study was to measure the impact of these recommendations on specific rescue measures carried out in the field, and their influence on short-term outcomes in the resuscitation of TCA patients. METHODS: We conducted a retrospective study of all TCA patients treated in two emergency medical units, which are part of the Northern Alps Emergency Network, from January 2004 to December 2017. We categorised cases into three periods: pre-guidelines (from January 2004 to December 2007), during guidelines (from January 2008 to December 2011), and post-guidelines (from January 2012 to December 2017). Local guidelines, a physician education programme, and specific training were set up during the post-guidelines period to increase adherence to recommendations. Utstein variables, and specific rescue measures were collected: advanced airway management, fluid administration, pelvic stabilisation or tourniquet application, bilateral thoracostomy, and thoracotomy procedures. The primary endpoint was survival rate at day 30 with good neurological status (cerebral performance category scores 1 & 2) in each period, considering the pre-guidelines period as the reference. RESULTS: There were 287 resuscitation attempts in the TCA cases included, and 279 specific interventions were identified with a significant increase in the number of fluid expansions (+16%), bilateral thoracostomies (+75%), and pelvic stabilisations (+25%) from the pre- to post-guidelines periods. However, no improvement in survival over time was found. CONCLUSION: Reversible measures were applied but to a varying degree, and may not adequately capture pre-hospital performance on overall TCA survival.

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 (CRSTEC 42 ±â€¯12 vs CRSPAT 37.3 ±â€¯10.9 mL/cmH2O and ResTEC 17.5 ±â€¯7.5 vs ResPAT 20.2 ±â€¯5.3 cmH2O/L/sec), and remained stable over time. During CC, ΔITP varied from 32 ±â€¯12 cmH2O to 69 ±â€¯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.