title: Reduced airway resistance and work of breathing during mechanical ventilation with an ultra-thin, two-stage polyurethane endotracheal tube (the Kolobow tube).
abstract: OBJECTIVE
  To compare dynamic pulmonary function studies using the ultrathin walled Kolobow endotracheal tube, with conventional endotracheal tubes of similar external diameter on rabbits during mechanical ventilation. To test the hypothesis that the increased internal diameter of the Kolobow tube will result in decreased airway resistance and work of breathing.
  
  
  METHODS
  Controlled animal study.
  
  
  METHODS
  Institutional animal research facility.
  
  
  METHODS
  Adult female Dutch Belted rabbits (n = 6), weighing 1.4 to 1.6 kg.
  
  
  METHODS
  The animals were initially intubated with a conventional endotracheal tube (2.5-mm internal diameter; 3.6-mm outer diameter); they were paralyzed and placed on a mechanical ventilator. Ventilatory settings were adjusted to obtain standard arterial blood gases: pH of 7.35 to 7.45; PaCO2 of 35 to 40 torr (4.7 to 5.3 kPa), and PaO2 of 90 to 100 torr (12.0 to 13.3 kPa). After the stabilization period, pulmonary function tests (PFTs) were measured (period 1), the conventional endotracheal tube was replaced with a Kolobow tube, and PFTs were measured again and recorded (period 2). While continuously monitoring tidal volume, the peak inspiratory pressure was decreased to match the tidal volume measured during ventilation with the conventional endotracheal tube. Once the desired tidal volume was reached, PFTs were recorded (period 3). Flows were unchanged during the experiment and the length of the endotracheal tubes was the same for both the conventional and the Kolobow tube.
  
  
  RESULTS
  Mean values of the airway resistance and work of breathing from periods 1 and 3 were compared using the Student's t-test. There was a 59% decrease in total airway resistance (p = .001) and 45% decrease in the work of breathing (p = .0006).
  
  
  CONCLUSIONS
  The use of the ultrathin walled Kolobow endotracheal tube resulted in significant decreases in airway resistance and work of breathing, which has the potential for improving the ventilatory mechanics in very small premature newborns.
authors.affiliation: Department of Pediatrics, George Washington University School of Medicine and Health Sciences, Children's National Medical Center, Washington, DC 20010-2970, USA.
authors.forename: C A
authors.initials: CA
authors.lastname: Velarde
authors.forename: B L
authors.initials: BL
authors.lastname: Short
authors.forename: O
authors.initials: O
authors.lastname: Rivera
authors.forename: W
authors.initials: W
authors.lastname: Seale
authors.forename: R
authors.initials: R
authors.lastname: Howard
authors.forename: T
authors.initials: T
authors.lastname: Kolobow
mesh_terms: D000403:Airway Resistance; D000818:Animals; D004867:Equipment Design; D005260:Female; D007442:Intubation, Intratracheal / Q000295:instrumentation*; D011817:Rabbits; D012121:Respiration, Artificial / Q000379:methods*; D012129:Respiratory Function Tests; D014939:Work of Breathing