title: Rapid Induction of Therapeutic Hypothermia Using Transnasal High Flow Dry Air.
abstract: Early induction of therapeutic hypothermia (TH) is recommended in out-of-hospital cardiac arrest (CA); however, currently no reliable methods exist to initiate cooling. We investigated the effect of high flow transnasal dry air on brain and body temperatures in adult porcine animals. Adult porcine animals (n = 23) under general anesthesia were subject to high flow of transnasal dry air. Mouth was kept open to create a unidirectional airflow, in through the nostrils and out through the mouth. Brain, internal jugular, and aortic temperatures were recorded. The effect of varying airflow rate and the air humidity (0% or 100%) on the temperature profiles were recorded. The degree of brain cooling was measured as the differential temperature from baseline. A 10-minute exposure of high flow dry air caused rapid cooling of brain and gradual cooling of the jugular and the aortic temperatures in all animals. The degree of brain cooling was flow dependent and significantly higher at higher airflow rates (0.8°C ± 0.3°C, 1.03°C ± 0.6°C, and 1.3°C ± 0.7°C for 20, 40, and 80 L, respectively, p < 0.05 for all comparisons). Air temperature had minimal effect on the brain cooling over 10 minutes with similar decrease in temperature at 4°C and 30°C. At a constant flow rate (40 LPM) and temperature, the degree of cooling over 10 minutes during dry air exposure was significantly higher compared to humid air (100% saturation) (1.22°C ± 0.35°C vs. 0.21°C ± 0.12°C, p < 0.001). High flow transnasal dry air causes flow dependent cooling of the brain and the core temperatures in intubated porcine animals. The mechanism of cooling appears to be evaporation of nasal mucus as cooling is mitigated by humidifying the air. This mechanism may be exploited to initiate TH in CA.
authors.affiliation: Division of Cardiology, Departments of Neuroanesthesia and Neurosurgery, The Johns Hopkins University School of Medicine , Baltimore, Maryland.
authors.forename: Raghuram
authors.initials: R
authors.lastname: Chava
authors.affiliation: Division of Cardiology, Departments of Neuroanesthesia and Neurosurgery, The Johns Hopkins University School of Medicine , Baltimore, Maryland.
authors.forename: Menekhem
authors.initials: M
authors.lastname: Zviman
authors.affiliation: Division of Cardiology, Departments of Neuroanesthesia and Neurosurgery, The Johns Hopkins University School of Medicine , Baltimore, Maryland.
authors.forename: Madhavan Srinivas
authors.initials: MS
authors.lastname: Raghavan
authors.affiliation: Division of Cardiology, Departments of Neuroanesthesia and Neurosurgery, The Johns Hopkins University School of Medicine , Baltimore, Maryland.
authors.forename: Henry
authors.initials: H
authors.lastname: Halperin
authors.affiliation: Division of Cardiology, Departments of Neuroanesthesia and Neurosurgery, The Johns Hopkins University School of Medicine , Baltimore, Maryland.
authors.forename: Farhan
authors.initials: F
authors.lastname: Maqbool
authors.affiliation: Division of Cardiology, Departments of Neuroanesthesia and Neurosurgery, The Johns Hopkins University School of Medicine , Baltimore, Maryland.
authors.forename: Romergryko
authors.initials: R
authors.lastname: Geocadin
authors.affiliation: Division of Cardiology, Departments of Neuroanesthesia and Neurosurgery, The Johns Hopkins University School of Medicine , Baltimore, Maryland.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Quinones-Hinojosa
authors.affiliation: Division of Cardiology, Departments of Neuroanesthesia and Neurosurgery, The Johns Hopkins University School of Medicine , Baltimore, Maryland.
authors.forename: Aravindan
authors.initials: A
authors.lastname: Kolandaivelu
authors.affiliation: Division of Cardiology, Departments of Neuroanesthesia and Neurosurgery, The Johns Hopkins University School of Medicine , Baltimore, Maryland.
authors.forename: Benjamin A
authors.initials: BA
authors.lastname: Rosen
authors.affiliation: Division of Cardiology, Departments of Neuroanesthesia and Neurosurgery, The Johns Hopkins University School of Medicine , Baltimore, Maryland.
authors.forename: Harikrishna
authors.initials: H
authors.lastname: Tandri
mesh_terms: D000388:Air; D000818:Animals; D001833:Body Temperature Regulation; D001921:Brain / Q000502:physiology*; D005260:Female; D006813:Humidity; D007036:Hypothermia, Induced / Q000379:methods*; D023421:Models, Animal; D009297:Nasal Mucosa / Q000502:physiology*; D012121:Respiration, Artificial / Q000379:methods*; D034421:Sus scrofa; D013997:Time Factors
keywords: cardiac arrest; neuroprotection; out-of-hospital cardiac arrest; survival; therapeutic hypothermia