Detecting Intrathoracic Airway Closure during Prehospital Cardiopulmonary Resuscitation Using Quasi-Static Pressure–Volume Curves: A Pilot Study

Background: Intrathoracic airway closure frequently occurs during cardiac arrest, possibly impairing ventilation. Previously, capnogram analysis was used to detect this pathophysiological process. In other populations, quasi-static pressure–volume curves obtained during constant low-flow inflations are routinely used to detect intrathoracic airway closure. This study reports the first use of quasi-static pressure–volume curves to detect intrathoracic airway closure during prehospital cardiopulmonary resuscitation. Methods: Connecting a pressure and flow sensor to the endotracheal tube enabled the performance of low-flow inflations during cardiopulmonary resuscitation using a manual resuscitator. Users connected the device following intubation and performed a low-flow inflation during the next rhythm analysis when chest compressions were interrupted. Determining the lower inflection point on the resulting pressure–volume curves allowed for the detection and quantification of intrathoracic airway closure. Results: The research device was used during the prehospital treatment of ten cardiac arrest patients. A lower inflection point indicating intrathoracic airway closure was detected in all patients. During cardiac arrest, the median pressure at which the lower inflection point occurred was 5.56 cmH20 (IQR 4.80, 8.23 cmH20). This value varied considerably between cases and was lower in patients who achieved return of spontaneous circulation. Conclusions: In this pilot study, quasi-static pressure–volume curves were obtained during prehospital cardiopulmonary resuscitation. Intrathoracic airway closure was detected in all patients. Further research is needed to determine whether the use of ventilation strategies to counter intrathoracic airway closure could lead to improved outcomes and if the degree of airway closure could serve as a prognostic factor.