title: Use of Normothermic Default Humidifier Settings Causes Excessive Humidification of Respiratory Gases During Therapeutic Hypothermia.
abstract: Adult patients frequently suffer from serious respiratory complications during therapeutic hypothermia. During therapeutic hypothermia, respiratory gases are humidified close to saturated vapor at 37°C (44 mg/L) despite that saturated vapor reduces considerably depending on temperature reduction. Condensation may cause serious adverse events, such as bronchial edema, mucosal dysfunction, and ventilator-associated pneumonia during cooling. To determine clinical variables associated with inadequate humidification of respiratory gases during cooling, humidity of inspiratory gases was measured in 42 cumulative newborn infants who underwent therapeutic hypothermia. Three humidifier settings of 37-default (chamber outlet, 37°C; distal circuit, 40°C), 33.5-theoretical (chamber outlet, 33.5°C; distal circuit, 36.5°C), and 33.5-adjusted (optimized setting to achieve 36.6 mg/L using feedback from a hygrometer) were tested to identify independent variables of excessively high humidity >40.7 mg/L and low humidity <32.9 mg/L. The mean (SD) humidity at the Y-piece was 39.2 (5.2), 33.3 (4.1), and 36.7 (1.2) mg/L for 37-default, 33.5-theoretical, and 33.5-adjusted, respectively. The incidence of excessive high humidity was 10.3% (37-default, 31.0%; 33.5-theoretical, 0.0%; 33.5-adjusted, 0.0%), which was positively associated with the use of a counter-flow humidifier (p < 0.001), 37-default (compared with 33.5-theoretical and 33.5-adjusted, both p < 0.001) and higher fraction of inspired oxygen (p = 0.003). The incidence of excessively low humidity was 17.5% (37-default, 7.1%; 33.5-theoretical, 45.2%; 33.5-adjusted, 0.0%), which was positively associated with the use of a pass-over humidifier and 33.5-theoretical (both p < 0.001). All patients who used a counter-flow humidifier achieved the target gas humidity at the Y-piece (36.6 ± 0.5 mg/L) required for 33.5-adjusted with 33.5-theoretical. During cooling, 37-default is associated with excessively high humidity, whereas 33.5-theoretical leads to excessively low humidity. Future studies are needed to assess whether a new regimen with optimized Y-piece temperature and humidity control reduces serious respiratory adverse events during cooling.
authors.affiliation: 1 Department of Pediatrics and Child Health, Centre for Developmental and Cognitive Neuroscience, Kurume University School of Medicine , Fukuoka, Japan .
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Tanaka
authors.affiliation: 1 Department of Pediatrics and Child Health, Centre for Developmental and Cognitive Neuroscience, Kurume University School of Medicine , Fukuoka, Japan .
authors.forename: Sachiko
authors.initials: S
authors.lastname: Iwata
authors.affiliation: 1 Department of Pediatrics and Child Health, Centre for Developmental and Cognitive Neuroscience, Kurume University School of Medicine , Fukuoka, Japan .
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kinoshita
authors.affiliation: 1 Department of Pediatrics and Child Health, Centre for Developmental and Cognitive Neuroscience, Kurume University School of Medicine , Fukuoka, Japan .
authors.forename: Kennosuke
authors.initials: K
authors.lastname: Tsuda
authors.affiliation: 1 Department of Pediatrics and Child Health, Centre for Developmental and Cognitive Neuroscience, Kurume University School of Medicine , Fukuoka, Japan .
authors.forename: Sayaka
authors.initials: S
authors.lastname: Sakai
authors.affiliation: 1 Department of Pediatrics and Child Health, Centre for Developmental and Cognitive Neuroscience, Kurume University School of Medicine , Fukuoka, Japan .
authors.forename: Mamoru
authors.initials: M
authors.lastname: Saikusa
authors.affiliation: 1 Department of Pediatrics and Child Health, Centre for Developmental and Cognitive Neuroscience, Kurume University School of Medicine , Fukuoka, Japan .
authors.forename: Ryota
authors.initials: R
authors.lastname: Shindo
authors.affiliation: 1 Department of Pediatrics and Child Health, Centre for Developmental and Cognitive Neuroscience, Kurume University School of Medicine , Fukuoka, Japan .
authors.forename: Eimei
authors.initials: E
authors.lastname: Harada
authors.affiliation: 2 Division of Neonatology, St. Mary's Hospital , Fukuoka, Japan .
authors.forename: Junichiro
authors.initials: J
authors.lastname: Okada
authors.affiliation: 2 Division of Neonatology, St. Mary's Hospital , Fukuoka, Japan .
authors.forename: Tadashi
authors.initials: T
authors.lastname: Hisano
authors.affiliation: 1 Department of Pediatrics and Child Health, Centre for Developmental and Cognitive Neuroscience, Kurume University School of Medicine , Fukuoka, Japan .
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kanda
authors.affiliation: 1 Department of Pediatrics and Child Health, Centre for Developmental and Cognitive Neuroscience, Kurume University School of Medicine , Fukuoka, Japan .
authors.forename: Yasuki
authors.initials: Y
authors.lastname: Maeno
authors.affiliation: 3 Department of Informatics, Graduate School of Integrated Science and Technology, Shizuoka University , Shizuoka, Japan .
authors.forename: Yuko
authors.initials: Y
authors.lastname: Araki
authors.affiliation: 4 Department of Anaesthesiology, Kurume University School of Medicine , Fukuoka, Japan .
authors.forename: Kazuo
authors.initials: K
authors.lastname: Ushijima
authors.affiliation: 5 Advanced Emergency Medical Service Centre, Kurume University Hospital , Fukuoka, Japan .
authors.forename: Teruo
authors.initials: T
authors.lastname: Sakamoto
authors.affiliation: 1 Department of Pediatrics and Child Health, Centre for Developmental and Cognitive Neuroscience, Kurume University School of Medicine , Fukuoka, Japan .
authors.forename: Yushiro
authors.initials: Y
authors.lastname: Yamashita
authors.affiliation: 1 Department of Pediatrics and Child Health, Centre for Developmental and Cognitive Neuroscience, Kurume University School of Medicine , Fukuoka, Japan .
authors.forename: Osuke
authors.initials: O
authors.lastname: Iwata
mesh_terms: D001833:Body Temperature Regulation; D004867:Equipment Design; D005260:Female; D005740:Gases; D006801:Humans; D000068998:Humidifiers; D006813:Humidity; D007036:Hypothermia, Induced / Q000009:adverse effects / Q000379:methods*; D007231:Infant, Newborn; D007363:Intensive Care Units, Neonatal; D015931:Intensive Care, Neonatal / Q000379:methods*; D008297:Male; D012119:Respiration; D012121:Respiration, Artificial / Q000009:adverse effects / Q000295:instrumentation*; D012140:Respiratory Tract Diseases / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control; D012307:Risk Factors; D013696:Temperature; D016896:Treatment Outcome; D012122:Ventilators, Mechanical
chemical_list: D005740:Gases
keywords: humidity; respiratory gases; saturated vapor; therapeutic hypothermia