title: Dynamic computed tomography: a novel technique to study lung aeration and atelectasis formation during experimental CPR.
abstract: OBJECTIVE
  To develop an image based technique to study the effect of different ventilatory strategies on lung ventilation and alveolar recruitment during cardiopulmonary resuscitation (CPR).
  
  
  METHODS
  (1) Technical development of the following components: (a) construction of an external chest compression device, which does not interfere with CT imaging, and (b) development of a software tool to detect lung parenchyma automatically and to calculate radiological density parameters. (2) Feasibility studies: three strategies of CPR ventilation were performed and imaged in one animal each (pigs, 25 kg): volume-constant ventilation (VCV), no ventilation, or continuous airway pressure (CPAP). One minute after induction of circulatory arrest inside the CT scanner, external chest compressions started at a rate of 100 cpm, and one of the ventilation modes was initiated. After 1 min, intravenous epinephrine was added as a bolus (40 microg/kg), followed by a continuous infusion (13 microg/kg per min). Six minutes later, dynamic CT acquisitions (temporal resolution: 100 ms) commenced. Simultaneously, arterial blood gases, acid base status and haemodynamics were sampled.
  
  
  RESULTS
  Using a modified chest compression device, dynamic CT acquisitions are feasible during closed-chest CPR. In three pilot experiments with different ventilation strategies, the dedicated software tool allowed to quantify ventilated, atelectatic and over-distended fractions of total lung area. VCV showed a large amount of atelectasis, which was recruited during every respiratory cycle. No ventilation led to atelectasis to govern over 50% of the total lung area. CPAP caused less atelectasis as VCV, and no cyclic recruitment and de-recruitment phenomena were observed.
  
  
  CONCLUSIONS
  We demonstrate a novel experimental set up, which allows quantification of different lung compartments during ongoing CPR and may become useful in comparing the direct pulmonary effects of different ventilatory strategies in the settings of Basic and Advanced Cardiac Life Support.
authors.affiliation: Department of Anesthesiology, Johannes Gutenberg-University, Medical School, Langenbeckstr. 1, D-55131 Mainz, Germany. klm@mail.uni-mainz.de
authors.forename: Klaus
authors.initials: K
authors.lastname: Markstaller
authors.forename: Jens
authors.initials: J
authors.lastname: Karmrodt
authors.forename: Marcus
authors.initials: M
authors.lastname: Doebrich
authors.forename: Benno
authors.initials: B
authors.lastname: Wolcke
authors.forename: Hendrik
authors.initials: H
authors.lastname: Gervais
authors.forename: Norbert
authors.initials: N
authors.lastname: Weiler
authors.forename: Manfred
authors.initials: M
authors.lastname: Thelen
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Dick
authors.forename: Hans-Ulrich
authors.initials: HU
authors.lastname: Kauczor
authors.forename: Balthasar
authors.initials: B
authors.lastname: Eberle
mesh_terms: D000818:Animals; D016887:Cardiopulmonary Resuscitation / Q000295:instrumentation* / Q000379:methods; D005240:Feasibility Studies; D006323:Heart Arrest / Q000503:physiopathology; D006439:Hemodynamics; D001261:Pulmonary Atelectasis / Q000000981:diagnostic imaging* / Q000503:physiopathology; D012123:Pulmonary Ventilation / Q000502:physiology*; D013552:Swine; D014057:Tomography, X-Ray Computed / Q000379:methods*