title: Lung volume changes during cleaning of closed endotracheal suction catheters: a randomized crossover study using electrical impedance tomography.
abstract: BACKGROUND
  Airway suctioning in mechanically ventilated patients is required to maintain airway patency. Closed suction catheters (CSCs) minimize lung volume loss during suctioning but require cleaning post-suction. Despite their widespread use, there is no published evidence examining lung volumes during CSC cleaning. The study objectives were to quantify lung volume changes during CSC cleaning and to determine whether these changes were preventable using a CSC with a valve in situ between the airway and catheter cleaning chamber.
  
  
  METHODS
  This prospective randomized crossover study was conducted in a metropolitan tertiary ICU. Ten patients mechanically ventilated via volume-controlled synchronized intermittent mandatory ventilation (SIMV-VC) and requiring manual hyperinflation (MHI) were included in this study. CSC cleaning was performed using 2 different brands of CSC (one with a valve [Ballard Trach Care 72, Kimberly-Clark, Roswell, Georgia] and one without [Portex Steri-Cath DL, Smiths Medical, Dublin, Ohio]). The maneuvers were performed during both SIMV-VC and MHI. Lung volume change was measured via impedance change using electrical impedance tomography. A mixed model was used to compare the estimated means.
  
  
  RESULTS
  During cleaning of the valveless CSC, significant decreases in lung impedance occurred during MHI (-2563 impedance units, 95% CI 2213-2913, P < .001), and significant increases in lung impedance occurred during SIMV (762 impedance units, 95% CI 452-1072, P < .001). In contrast, cleaning of the CSC with a valve in situ resulted in non-significant lung volume changes and maintenance of normal ventilation during MHI and SIMV-VC, respectively (188 impedance units, 95% CI -136 to 511, P = .22; and 22 impedance units, 95% CI -342 to 299, P = .89).
  
  
  CONCLUSIONS
  When there is no valve between the airway and suction catheter, cleaning of the CSC results in significant derangements in lung volume. Therefore, the presence of such a valve should be considered essential in preserving lung volumes and uninterrupted ventilation in mechanically ventilated patients.
authors.affiliation: Critical Care Research Group, The Prince Charles Hospital, University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Amanda
authors.initials: A
authors.lastname: Corley
authors.forename: Nicola
authors.initials: N
authors.lastname: Sharpe
authors.forename: Lawrence R
authors.initials: LR
authors.lastname: Caruana
authors.forename: Amy J
authors.initials: AJ
authors.lastname: Spooner
authors.forename: John F
authors.initials: JF
authors.lastname: Fraser
mesh_terms: D057785:Catheters; D018592:Cross-Over Studies; D004203:Disinfection; D017097:Electric Impedance; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D007442:Intubation, Intratracheal / Q000295:instrumentation*; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012121:Respiration, Artificial; D013396:Suction / Q000295:instrumentation; D014054:Tomography
keywords: alveolar de-recruitment; electrical impedance tomography; lung volume; lung volume measurement; mechanical ventilation; suctioning