Effects of Nebulizer Mode and Position in a Mechanical Ventilator Circuit on Dose Efficiency

With an in-vitro model, we evaluated the effect of nebulizer mode and position on the amount of medication available to the mechanically ventilated patient. Method: Our test circuit included two bacteria filters to capture aerosol that was routed either to the patient or to the Y-piece into the exhalation tubing. Technetium Tc-99m was nebulized while the ventilator cycled, then individual scintillation counts of the two filters were performed. Five trials in each of four test groups were conducted to study the combinations of the two variables, nebulizer mode and position. Results: Scans of Group 1 (continuous nebulization at the circuit's manifold) indicated that 61.0 ± 1.5% of the total aerosol collected in both filters was routed to the patient. Scans of Group 2 (intermittent nebulization at the manifold) yielded 68.3 ± 1.2%, of Group 3 (continuous nebulization at the Y-piece) 30.0 ± 2.0%, and of Group 4 (intermittent nebulization at the Y-piece) 57.1±2.2% Conclusion: Intermittent nebulization at the manifold offers the patient significantly more (P < 0.001) medication than does either continuous or intermittent nebulization at the Y-piece.