title: Heated breathing tubes affect humidity output of circle absorber systems.
abstract: OBJECTIVE
  To verify whether the airway climate in circle systems can be improved with heated breathing tubes.
  
  
  METHODS
  Randomized, controlled, prospective clinical study.
  
  
  METHODS
  Operating theater of the Department of Maxillofacial Surgery.
  
  
  METHODS
  26 adult patients undergoing prolonged anesthesia.
  
  
  METHODS
  A total of 26 prolonged anesthetics were conducted in adult patients using a minimal fresh gas flow rate (0.6 L/min) and silicon breathing tubes (16 mm internal diameter) containing a heated coil. Group 1 (n = 10 patients) was the control group; breathing tubes were unheated. In Group 2 (n = 10 patients), breathing tubes were heated to 30 degrees C. In Group 3 (n = 6 patients), breathing tubes were heated to 36 degrees C.
  
  
  RESULTS
  Humidity and temperature were measured at the Y-piece. Inspiratory temperature on Group 2 was significantly higher than in Group 1. In Group 3, both inspiratory temperature and absolute humidity were significantly higher than in Group 1. After 5 minutes of ventilation, water content and temperature of inspiratory gases were significantly higher in Group 3 than in Group 1.
  
  
  CONCLUSIONS
  Low-flow systems need at least 120 minutes to achieve a satisfactory airway climate. Heated breathing tubes effectively reduce this delay.
authors.affiliation: Department of Anaesthesiology, Johannes Gutenberg-University Medical School, Mainz, Germany.
authors.forename: P P
authors.initials: PP
authors.lastname: Kleemann
authors.forename: B K
authors.initials: BK
authors.lastname: Schickel
authors.forename: J P
authors.initials: JP
authors.lastname: Jantzen
mesh_terms: D000042:Absorption; D000328:Adult; D000764:Anesthesia, Closed-Circuit / Q000295:instrumentation*; D000777:Anesthetics / Q000008:administration & dosage; D017097:Electric Impedance; D011211:Electric Power Supplies; D004867:Equipment Design; D004869:Equipment Safety; D006358:Hot Temperature; D006801:Humans; D006813:Humidity; D007442:Intubation, Intratracheal / Q000295:instrumentation*; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000295:instrumentation; D012825:Silicon; D013696:Temperature
chemical_list: D000777:Anesthetics; D012825:Silicon