Lung tissue injury and hemodynamic effects of ventilations synchronized or unsynchronized to continuous chest compressions in a porcine cardiac arrest model

Theresa M Olasveengen; Christiane Skåre; Marianne Skjerven-Martinsen; Per Hoff-Olsen; Jo Kramer-Johansen; Fredrik Hoff Nordum; Morten Eriksen; Per Anderas Norseng; Lars Wik

doi:10.1016/j.resplu.2023.100530

Lung tissue injury and hemodynamic effects of ventilations synchronized or unsynchronized to continuous chest compressions in a porcine cardiac arrest model

Resusc Plus. 2023 Dec 20:17:100530. doi: 10.1016/j.resplu.2023.100530. eCollection 2024 Mar.

Authors

Affiliations

¹ Department of Anesthesia and Intensive Care Medicine, Oslo University Hospital, Norway.
² Institute of Clinical Medicine, University of Oslo, Norway.
³ Division of Forensic Medicine and Drug Abuse, Norwegian Institute of Public Health, Norway.
⁴ Norwegian National Advisory Unit for Prehospital Emergency Care (NAKOS), Division of Prehospital Services, Oslo University Hospital, Norway.
⁵ Department of Research and Development and Norwegian Centre for Prehospital Emergency Care (NAKOS), Oslo University Hospital, Norway.
⁶ Institute for Experimental Medical Research, Oslo University Hospital, Norway.
⁷ Norwegian National Advisory Unit for Prehospital Emergency Care (NAKOS), Oslo University Hospital, Oslo, Norway.

Abstract

Aim: Compare lung injury and hemodynamic effects in synchronized ventilations (between two chest compressions) vs. unsynchronized ventilations during cardiopulmonary resuscitation (CPR) in a porcine model of cardiac arrest.

Methods: Twenty pigs were randomized to either synchronized or unsynchronized group. Ventricular fibrillation was induced electrically and left for 1.5 minutes. Four minutes of basic chest compression:ventilation (30:2) CPR was followed by eight minutes of either synchronized or unsynchronized ventilations (10/min) during continuous compressions before defibrillation was attempted. Aortic, right atrial and intracerebral pressures, carotid and cerebral blood flow and cardiac output were measured. Airway monitoring included capnography and respiratory function monitor. Macro- and microscopic lung injuries were assessed post-mortem.

Results: There were no significant differences between groups in any of the measured hemodynamic variables or inspiration time (0.4 vs. 1.0 s, p = 0.05). The synchronized ventilation group had lower median peak inspiratory airway pressure (57 vs. 94 cm H₂O, p < 0.001), lower minute ventilation (3.7 vs. 9.4 l min^-1, p < 0.001), lower pH (7.31 vs. 7.53, p < 0.001), higher pCO₂ (5.2 vs. 2.5 kPa, p < 0.001) and lower pO₂ (31.6 vs. 54.7 kPa, p < 0.001) compared to the unsynchronized group after 12 minutes of CPR. There was significant lung injury after CPR in both synchronized and unsynchronized groups.

Conclusion: Synchronized and unsynchronized ventilations resulted in similar hemodynamics and lung injury during continuous mechanical compressions of pigs in cardiac arrest. Animals that received unsynchronized ventilations with one second inspiration time at a rate of ten ventilations per minute were hyperventilated and hyperoxygenated.Institutional protocol number: FOTS, id 6948.

Keywords: Cardiac arrest; Cardiopulmonary resuscitation; Experimental study; Resuscitation; Ventilation.