title: Mechanical influences on fluid leakage past the tracheal tube cuff in a benchtop model.
abstract: OBJECTIVE
  High-volume low-pressure (HVLP) cuffs on endotracheal tubes do not fully protect the lower airway from leakage of potentially contaminated secretions down the longitudinal folds within the cuff. Here, our purpose was to evaluate potential effects of positive end-expiratory pressure (PEEP), inspiratory effort intensity, and tube characteristics on fluid leakage past the cuff.
  
  
  METHODS
  This benchtop study at a research laboratory used a tracheal tube inserted into an artificial Plexiglas trachea connected to a ventilator and lung model. Methylene blue was deposited above the tube cuff to simulate subglottic secretions. Five PEEP levels (0, 5, 10, 15, and 20 cmH₂O) were tested with volume-controlled ventilation and three simulated inspiratory effort levels with pressure-support ventilation. Several cuff materials and tube sizes were tested.
  
  
  RESULTS
  The leakage occurrence rate ranged from 91% with zero PEEP to 8% with 15 and 20 cmH₂O PEEP and was indirectly proportional to the PEEP level with significant correlation (R² = 0.39, p < 0.001), an effect not explained by higher peak inspiratory pressure. Low, moderate, and high inspiratory effort intensities were associated with 38%, 46%, and 75% leakage rates, respectively (p = 0.024). Leakage flow was considerably less with polyurethane than with polyvinylchloride tubes (mean 0.5 versus 31.8 ml/h). Leakage increased with larger tube diameters.
  
  
  CONCLUSIONS
  This benchtop study shows that PEEP and a polyurethane cuff prevent leakage past the endotracheal tube cuff, whereas greater inspiratory effort and larger tube diameters for given tracheal size induce or worsen leakage.
authors.affiliation: Intensive Care Unit, Fattouma Bourguiba University Hospital, Monastir, Tunisia.
authors.forename: Islem
authors.initials: I
authors.lastname: Ouanes
authors.forename: Aissam
authors.initials: A
authors.lastname: Lyazidi
authors.forename: Pierre Eric
authors.initials: PE
authors.lastname: Danin
authors.forename: Nerlep
authors.initials: N
authors.lastname: Rana
authors.forename: Annalisa
authors.initials: A
authors.lastname: Di Bari
authors.forename: Fekri
authors.initials: F
authors.lastname: Abroug
authors.forename: Bruno
authors.initials: B
authors.lastname: Louis
authors.forename: Laurent
authors.initials: L
authors.lastname: Brochard
mesh_terms: D004868:Equipment Failure; D007442:Intubation, Intratracheal / Q000295:instrumentation* / Q000592:standards; D008953:Models, Anatomic; D011015:Pneumonia, Aspiration / Q000209:etiology*; D053717:Pneumonia, Ventilator-Associated / Q000209:etiology; D011175:Positive-Pressure Respiration