title: Is increased positive end-expiratory pressure the culprit? Autoresuscitation in a 44-year-old man after prolonged cardiopulmonary resuscitation: a case report.
abstract: BACKGROUND
  The phenomenon of autoresuscitation is rare, yet it is known to most emergency physicians. However, the pathophysiology of the delayed return of spontaneous circulation remains enigmatic. Among other causes hyperinflation of the lungs and excessively high positive end-expiratory pressure have been suggested, but reports including cardiopulmonary monitoring during cardiopulmonary resuscitation are scarce to support this hypothesis.
  
  
  METHODS
  We report a case of autoresuscitation in a 44-year-old white man after 80 minutes of advanced cardiac life support accompanied by continuous capnometry and repeated evaluation by ultrasound and echocardiography. After prolonged cardiopulmonary resuscitation, refractory electromechanical dissociation on electrocardiogram and ventricular akinesis were recorded. In addition, a precipitous drop in end-tidal partial pressure of carbon dioxide was noted and cardiopulmonary resuscitation was discontinued. Five minutes after withdrawal of all supportive measures his breathing resumed and a perfusing rhythm ensued.
  
  
  CONCLUSIONS
  Understanding the underlying pathophysiology of autoresuscitation is hampered by a lack of reports including extensive cardiopulmonary monitoring during cardiopulmonary resuscitation in a preclinical setting. In this case, continuous capnometry was combined with repetitive ultrasound evaluation, which ruled out most assumed causes of autoresuscitation. Our observation of a rapid decline in end-tidal partial pressure of carbon dioxide supports the hypothesis of increased intrathoracic pressure. Continuous capnometry can be performed easily during cardiopulmonary resuscitation, also in a preclinical setting. Knowledge of the pathophysiologic mechanisms may lead to facile interventions to be incorporated into cardiopulmonary resuscitation algorithms. A drop in end-tidal partial pressure of carbon dioxide, for example, might prompt disconnection of the ventilation to allow left ventricular filling. Further reports and research on this topic are encouraged.
authors.affiliation: Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany. henning.hagmann@uk-koeln.de.|Department II of Internal Medicine, University Hospital Cologne, Kerpener Str. 62, 50937, Cologne, Germany. henning.hagmann@uk-koeln.de.
authors.forename: Henning
authors.initials: H
authors.lastname: Hagmann
authors.affiliation: Fire Department and Emergency Medical Service Cologne, Cologne, Germany.
authors.forename: Katrin
authors.initials: K
authors.lastname: Oelmann
authors.affiliation: Fire Department and Emergency Medical Service Cologne, Cologne, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Stangl
authors.affiliation: Department III of Internal Medicine, Heart Center of the University of Cologne, Cologne, Germany.
authors.forename: Guido
authors.initials: G
authors.lastname: Michels
mesh_terms: D000328:Adult; D016887:Cardiopulmonary Resuscitation / Q000009:adverse effects* / Q000379:methods; D002320:Cardiovascular Physiological Phenomena; D004562:Electrocardiography; D006323:Heart Arrest / Q000628:therapy*; D006801:Humans; D008297:Male; D008991:Monitoring, Physiologic; D011175:Positive-Pressure Respiration / Q000009:adverse effects* / Q000379:methods; D011379:Prognosis; D013997:Time Factors
keywords: Advanced cardiac life support; Autoresuscitation; Capnometry; Emergency ultrasound; Lazarus phenomenon