title: Tracheostomy Tube Type and Inner Cannula Selection Impact Pressure and Resistance to Air Flow.
abstract: BACKGROUND
  Advancements in tracheostomy tube design now provide clinicians with a range of options to facilitate communication for individuals receiving ventilator assistance through a cuffed tube. Little is known about the impact of these modern design features on resistance to air flow.
  
  
  METHODS
  We undertook a bench model test to measure pressure-flow characteristics and resistance of a range of tubes of similar outer diameter, including those enabling subglottic suction and speech. A constant inspiratory ± expiratory air flow was generated at increasing flows up to 150 L/min through each tube (with or without optional, mandatory, or interchangeable inner cannula). Driving pressures were measured, and resistance was calculated (cm H2O/L/s).
  
  
  RESULTS
  Pressures changed with increasing flow (P < .001) and tube type (P < .001), with differing patterns of pressure change according to the type of tube (P < .001) and direction of air flow. The single-lumen reference tube encountered the lowest inspiratory and expiratory pressures compared with all double-lumen tubes (P < .001); placement of an optional inner cannula increased bidirectional tube resistance by a factor of 3. For a tube with interchangeable inner cannulas, the type of cannula altered pressure and resistance differently (P < .001); the speech cannula in particular amplified pressure-flow changes and increased tube resistance by more than a factor of 4.
  
  
  CONCLUSIONS
  Tracheostomy tube type and inner cannula selection imposed differing pressures and resistance to air flow during inspiration and expiration. These differences may be important when selecting airway equipment or when setting parameters for monitoring, particularly for patients receiving supported ventilation or during the weaning process.
authors: Intensive Care Unit, Royal Adelaide Hospital, Adelaide, South Australia, Australia and the University of Queensland, School of Health and Rehabilitation Sciences, Brisbane, Queensland, Australia. lee.pryor@health.sa.gov.au.
authors: Lee N
authors: LN
authors: Pryor
authors: International Centre for Allied Health Evidence and the Sansom Institute, University of South Australia, Adelaide, South Australia, Australia and the Intensive Care Unit, Flinders Medical Centre, Adelaide, South Australia, Australia.
authors: Claire E
authors: CE
authors: Baldwin
authors: University of Queensland, School of Health and Rehabilitation Sciences, Brisbane, Queensland, Australia and the Centre for Functioning and Health Research, Queensland Health, Brisbane, Queensland, Australia.
authors: Elizabeth C
authors: EC
authors: Ward
authors: Prince Charles Hospital, Metro North Hospital and Health Service, Brisbane, Queensland, Australia and the School of Applied Psychology, Menzies Health Institute Queensland, Griffith University Brisbane, Queensland, Australia.
authors: Petrea L
authors: PL
authors: Cornwell
authors: Intensive Care Unit, Royal Adelaide Hospital, Adelaide, South Australia, Australia and the University of Adelaide, School of Medicine, Adelaide, South Australia, Australia.
authors: Stephanie N
authors: SN
authors: O'Connor
authors: Intensive Care Unit, Royal Adelaide Hospital, Adelaide, South Australia, Australia and the University of Adelaide, School of Medicine, Adelaide, South Australia, Australia.
authors: Marianne J
authors: MJ
authors: Chapman
authors: School of Medicine, Flinders University, Adelaide, South Australia, Australia and the Intensive Care Unit, Flinders Medical Centre, Adelaide, South Australia, Australia.
authors: Andrew D
authors: AD
authors: Bersten
mesh_terms: D000403:Airway Resistance / Q000502:physiology; D000072601:Cannula; D004867:Equipment Design; D007442:Intubation, Intratracheal / Q000295:instrumentation*; D008962:Models, Theoretical; D011312:Pressure; D014139:Tracheostomy / Q000295:instrumentation*; D014939:Work of Breathing / Q000502:physiology
keywords: airway resistance; phonation; speech; tracheostomy; ventilator weaning; work of breathing