title: Endotracheal suctioning: from principles to practice.
abstract: OBJECTIVE
  This paper aims to highlight the physical principles of pressure and flow dynamics underlying endotracheal suctioning, to demonstrate these on a simple illustrative model and to discuss the clinical implications of these principles for paediatric practice.
  
  
  METHODS
  Prospective in vitro study.
  
  
  METHODS
  Paediatric intensive care unit of a tertiary, academic hospital.
  
  
  RESULTS
  The peak pressure change (DeltaP) obtained in a "bag-in-box" model was recorded during suctioning, using different combinations of endotracheal tube (ETT) and catheter sizes, different suction pressures and techniques. Suction was also performed on three different consistencies of gelatine, using a range of suction catheter sizes and vacuum pressures. The mass of gelatine suctioned per second was calculated. A large DeltaP was measured when using neonatal-sized ETTs. There was a linear relationship (r=0,8, p<0.05) between DeltaP and the ratio of external catheter area to area difference (internal ETT area-external catheter area). Significantly greater DeltaP was measured when using a short versus long suction catheter ( p<0.001) and when applying suction for longer duration ( p<0,001) and with higher vacuum pressures ( p<0.05). The amount of mucus suctioned in a given time was related to catheter size, suction pressure and mucus density.
  
  
  CONCLUSIONS
  Applied clinically, these results indicate that intrapulmonary pressure changes generated by the endotracheal suctioning of intubated neonates are likely to be considerable, possibly translating into loss of lung volume.
authors.affiliation: Physiotherapy Department, Red Cross War Memorial Children's Hospital, School of Health and Rehabilitation Sciences, University of Cape Town, Klipfontein Road, 7700 Rondebosch, Cape Town, South Africa. bmorrow@ich.uct.ac.za
authors.forename: Brenda M
authors.initials: BM
authors.lastname: Morrow
authors.forename: Merle J
authors.initials: MJ
authors.lastname: Futter
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Argent
mesh_terms: D002404:Catheterization / Q000295:instrumentation; D006801:Humans; D066298:In Vitro Techniques; D007231:Infant, Newborn; D007363:Intensive Care Units, Neonatal; D007442:Intubation, Intratracheal / Q000009:adverse effects; D016014:Linear Models; D008168:Lung / Q000502:physiology*; D008962:Models, Theoretical; D009093:Mucus / Q000502:physiology; D011312:Pressure; D011446:Prospective Studies; D001261:Pulmonary Atelectasis / Q000209:etiology / Q000517:prevention & control; D013396:Suction / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods; D014783:Viscosity