title: Transpulmonary hypothermia: a novel method of rapid brain cooling through augmented heat extraction from the lungs.
abstract: OBJECTIVE
  Delay in instituting neuroprotective measures after cardiac arrest increases death and decreases neuronal recovery. Current hypothermia methods are slow, ineffective, unreliable, or highly invasive. We report the feasibility of rapid hypothermia induction in swine through augmented heat extraction from the lungs.
  
  
  METHODS
  Twenty-four domestic crossbred pigs (weight, 50-55kg) were ventilated with room air. Intraparenchymal brain temperature and core temperatures from pulmonary artery, lower esophagus, bladder, rectum, nasopharynx, and tympanum were recorded. In eight animals, ventilation was switched to cooled helium-oxygen mixture (heliox) and perfluorocarbon (PFC) aerosol and continued for 90min or until target brain temperature of 32°C was reached. Eight animals received body-surface cooling with water-circulating blankets; eight control animals continued to be ventilated with room air.
  
  
  RESULTS
  Brain and core temperatures declined rapidly with cooled heliox-PFC ventilation. The brain reached target temperature within the study period (mean [SD], 66 [7.6]min) in only the transpulmonary cooling group. Cardiopulmonary functions and poststudy histopathological examination of the lungs were normal.
  
  
  CONCLUSIONS
  Transpulmonary cooling is novel, rapid, minimally invasive, and an effective technique to induce therapeutic hypothermia. High thermal conductivity of helium and vaporization of PFC produces rapid cooling of alveolar gases. The thinness and large surface area of alveolar membrane facilitate rapid cooling of the pulmonary circulation. Because of differences in thermogenesis, blood flow, insulation, and exposure to the external environment, the brain cools at a different rate than other organs. Transpulmonary hypothermia was significantly faster than body surface cooling in reaching target brain temperature.
authors.affiliation: Department of Anesthesiology, Mayo Clinic, Rochester, MN, United States. Electronic address: mkumar@mayo.edu.
authors.forename: Matthew M
authors.initials: MM
authors.lastname: Kumar
authors.affiliation: Department of Emergency Medicine, Mayo Clinic, Rochester, MN, United States.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Goldberg
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Mayo Clinic, Rochester, MN, United States.
authors.forename: Markos
authors.initials: M
authors.lastname: Kashiouris
authors.affiliation: Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN, United States.
authors.forename: Lawrence R
authors.initials: LR
authors.lastname: Keenan
authors.affiliation: Department of Neurology, Mayo Clinic, Rochester, MN, United States.
authors.forename: Alejandro A
authors.initials: AA
authors.lastname: Rabinstein
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Mayo Clinic, Rochester, MN, United States.
authors.forename: Bekele
authors.initials: B
authors.lastname: Afessa
authors.affiliation: Department of Anesthesiology, Mayo Clinic, Rochester, MN, United States.
authors.forename: Larry D
authors.initials: LD
authors.lastname: Johnson
authors.affiliation: Department of Neurologic Surgery, Mayo Clinic, Rochester, MN, United States.
authors.forename: John L D
authors.initials: JL
authors.lastname: Atkinson
authors.affiliation: Department of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland, OH, United States.
authors.forename: Vedha
authors.initials: V
authors.lastname: Nayagam
mesh_terms: D000818:Animals; D001921:Brain; D001927:Brain Diseases / Q000517:prevention & control*; D005240:Feasibility Studies; D005466:Fluorocarbons / Q000008:administration & dosage; D006371:Helium / Q000008:administration & dosage; D007036:Hypothermia, Induced / Q000379:methods*; D008168:Lung; D010100:Oxygen / Q000008:administration & dosage; D034421:Sus scrofa; D013552:Swine; D013997:Time Factors
chemical_list: D005466:Fluorocarbons; D006371:Helium; C038949:heliox; D010100:Oxygen
keywords: Cardiopulmonary resuscitation; Heliox ventilation; Induced hypothermia; Neuroprotection; Perfluorocarbon; Transpulmonary hypothermia