Domenico L Grieco1,2,3, Laurent J Brochard1,2, Adrien Drouet4, Irene Telias1,2, Stéphane Delisle5, Gilles Bronchti6, Cecile Ricard4, Marceau Rigollot7, Bilal Badat7, Paul Ouellet8, Emmanuel Charbonney5,6, Jordi Mancebo9, Alain Mercat10, Dominique Savary4, Jean-Christophe M Richard4,11. 1. 1 Keenan Centre for Biomedical Research, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Canada. 2. 2 Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Canada. 3. 3 Department of Anesthesiology and Intensive Care Medicine, Catholic University of The Sacred Heart, Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy. 4. 4 SAMU74, Emergency Department, General Hospital of Annecy, Annecy, France. 5. 5 Université de Montréal, Montreal, Canada. 6. 6 Laboratoire d'anatomie, Université du Québec à Trois-Rivières et CIUSSS MCQ, Trois-Rivières, Canada. 7. 7 Air Liquide Medical Systems, Antony, France. 8. 8 Vitalité Health Network, North West Zone, Edmundston, Canada. 9. 9 Department of Intensive Care, Sant Pau University Hospital, Barcelona, Spain. 10. 10 Critical Care Department, Angers University Hospital, Angers, France; and. 11. 11 INSERM UMR 1066, Créteil, France.
Abstract
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.
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.
Authors: Jasmeet Soar; Bernd W Böttiger; Pierre Carli; Keith Couper; Charles D Deakin; Therese Djärv; Carsten Lott; Theresa Olasveengen; Peter Paal; Tommaso Pellis; Gavin D Perkins; Claudio Sandroni; Jerry P Nolan Journal: Notf Rett Med Date: 2021-06-08 Impact factor: 0.826