Aerosol delivery during invasive mechanical ventilation is affected by many factors, including the type of nebulizer used and ventilatory settings. Current intensive care guidance gives limited direction on adjusting ventilation for aerosol administration because the evidence is heterogeneous and often derived from simplified in vitro models. The investigators aimed to evaluate how inspiratory flow and inspiratory-to-expiratory (I:E) ratio modify aerosol transport and respiratory tract deposition when using different aerosol generation technologies in a controlled preclinical model. The stated objective was to determine whether ventilatory parameters differently modulate aerosol fate depending on nebulizer technology, not to demonstrate outright superiority of commercial devices.
The study used a validated ex vivo porcine respiratory model ventilated in volume-controlled mode. Two inspiratory flow rates (35 L/min and 60 L/min) and two I:E ratios (1:2 and 1:3) were compared. Experiments were performed with two nebulizer technologies: a vibrating mesh nebulizer (VMN) and a jet nebulizer (JN). Nebulizers were positioned 15 cm upstream of the Y-piece of the ventilator circuit. Active heated humidification was maintained during experiments to reflect clinical conditions.
Both nebulizers were placed 15 cm upstream of the Y-piece to standardize device location. The ventilatory variables deliberately tested were inspiratory flow (35 vs 60 L/min) and I:E ratio (1:2 vs 1:3). Heated active humidification remained in the circuit during aerosol delivery. The experimental design focused on realistic mechanical ventilation conditions rather than isolated component testing.
Deposition was assessed using radiolabeled aerosol with planar scintigraphy imaging combined with a mass-balance approach. This methodology allowed quantification of distribution across the respiratory tract and identification of losses within the circuit. The study reported deposition values as percentages with standard deviations and provided statistical comparisons between conditions.
Across all tested conditions, the vibrating mesh nebulizer (VMN) demonstrated substantially higher delivery efficiency than the jet nebulizer (JN). The JN produced low output and showed no statistically significant variation in respiratory tract deposition across the ventilatory settings evaluated. In contrast, deposition with VMN was sensitive to both inspiratory flow and I:E ratio.
When using the VMN, a lower inspiratory flow (35 L/min) increased respiratory tract deposition compared with the higher flow (60 L/min). Reported values for VMN were 57% ± 8% deposition at the lower flow versus 45% ± 5% at the higher flow, a difference that reached statistical significance (p = 0.022). The increased deposition at lower flow was associated with reduced losses in the inspiratory limb of the circuit.
Prolonging the expiratory phase (I:E 1:3 versus 1:2) further improved respiratory tract deposition with the VMN. The VMN deposition with the longer expiratory time was reported as 60% ± 9% compared with 45% ± 5% at the shorter expiratory time (p < 0.0001). Again, JN delivery did not show meaningful changes across I:E ratios in this experimental setup.
The findings indicate that ventilatory parameters can significantly influence aerosol deposition for certain nebulizer technologies. In this ex vivo porcine model under volume-controlled ventilation with heated humidification, combining lower inspiratory flow and a longer expiratory phase enhanced aerosol deposition to the respiratory tract when using a VMN. The authors emphasize that the study was preclinical and used an ex vivo model; available evidence from simplified or component-focused models may not fully capture interactions occurring under more realistic ventilatory conditions. The investigators also clarified that the study's purpose was not to endorse specific commercial devices but to examine whether ventilatory settings interact differently with aerosol generation technologies.
Details on experimental constraints, potential variability between ex vivo and in vivo physiology, and any device-specific performance characteristics beyond those reported were not expanded upon in the abstract. The full text would be required for additional methodological nuances and complete limitations.
Within the conditions investigated, ventilatory parameters (inspiratory flow and I:E ratio) significantly affected aerosol deposition with a vibrating mesh nebulizer but not with a jet nebulizer. Specifically, lower inspiratory flow and prolonged expiratory time increased respiratory tract deposition with VMN. These results suggest that adjustment of ventilatory settings could modulate aerosol delivery efficiency when using certain nebulizer technologies during mechanical ventilation.
Clinical translation was not assessed in this preclinical work; the authors call for further studies to determine whether the observed differences produce measurable clinical benefit in patients receiving inhaled therapies during mechanical ventilation.
The authors conclude that additional research is required to establish whether these preclinical observations translate into improved clinical outcomes. Future work should address in vivo validation, diverse ventilatory modes, different device positions and humidification strategies, and clinical endpoints related to drug delivery efficacy and patient outcomes. The abstract does not report such follow-up data, and the reader is referred to the full text for expanded discussion and potential experimental details.
Keywords: Aerosol deposition; Drug delivery; Intensive care; Mechanical ventilation settings; Nebulizers; Respiratory diseases.