A comparison of the effectiveness of open and closed endotracheal suction

Objective: To compare the effectiveness of open and closed endotracheal suction in recovering thin and thick secretions in normal and injured lungs during conventional and high frequency ventilation. Design and setting: Randomised study in a paediatric intensive care model in the animal research laboratory of a tertiary paediatric hospital. Subjects: 16 New Zealand White rabbits. Interventions: Anaesthetised animals were intubated with a 3.5- mm endotracheal tube. Simulated thin and thick secretions ( iopamidol 2 ml, a watery radioopaque fluid, and fluorescent mucin 1 ml) were instilled in turn 1 cm below the tube tip through a catheter placed via a tracheostomy. Open or closed suction, randomly assigned, was applied for 6 s at - 140 mmHg using a 6- F gauge catheter. Following lung injury with repeated saline lavage the procedure was repeated on conventional and high frequency ventilation. Measurements and results: Iopamidol recovery was determined by digitally subtracting the post- contrast and post- suction radiographic images. Mucin recovery was determined by fluorescence assay of the aspirate. In the normal lung similar amounts were recovered by both suction methods. In the lavaged lung closed suction recovered less iopamidol during conventional ( 22 +/- 7.5%) and high frequency ventilation ( 11 +/- 2.4%) than open suction ( 36 +/- 12% and 22 +/- 8.1%, respectively). Mucin recovery was less with closed suction during conventional ( 32 +/- 28 mu l) and high frequency ventilation ( 30 +/- 31 mu l) than with open suction ( 382 +/- 235 mu l and 241 +/- 153 mu l). Conclusions: In the injured lung closed suction was less effective than open suction at recovering thin and thick simulated secretions, irrespective of ventilation mode.