title: Suction catheter size: an assessment and comparison of 3 different calculation methods.
abstract: BACKGROUND
  Current American Association for Respiratory Care (AARC) clinical practice guidelines recommend a suction catheter to endotracheal tube ratio (SC/ETT) based on the external diameter of the SC and the internal diameter of the ETT. An SC/ETT ratio of < 50% is consistent with the current recommendation. We theorized that a more satisfactory assessment of SC/ETT ratio could be accomplished using volume or area formulas and expansion of diameter recommendations. Some respiratory care texts recommend an SC/ETT ratio that exceeds the clinical practice guideline standard.
  
  
  METHODS
  We calculated the internal volume and cross-sectional area of various ETT sizes, the external volume and cross-sectional area of various SC sizes, and the SC/ETT ratios. We also measured negative pressures created by suction in a lung model, during multiple suction maneuvers.
  
  
  RESULTS
  Volume and area calculations provide an alternative method for determining the SC/ETT ratio. A volume or area ratio of 50% corresponds to a diameter ratio of 70%. Negative pressures during suctioning remain low at the new ratios, so a larger SC than current clinical practice guidelines still allows adequate air passage between the SC and ETT.
  
  
  CONCLUSIONS
  Our results support an alternative SC/ETT ratio when pairing SCs and ETTs.
authors.affiliation: Department of Respiratory Care, Texas State University, San Marcos, Texas.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Russian
authors.forename: Joshua F
authors.initials: JF
authors.lastname: Gonzales
authors.forename: Nicholas R
authors.initials: NR
authors.lastname: Henry
mesh_terms: D057785:Catheters; D006801:Humans; D007442:Intubation, Intratracheal / Q000295:instrumentation*; D055641:Mathematical Concepts; D017410:Practice Guidelines as Topic; D011312:Pressure; D012121:Respiration, Artificial / Q000295:instrumentation*; D013396:Suction / Q000295:instrumentation
keywords: airway clearance; endotracheal suctioning; endotracheal tube; suction catheter