Position of different nebulizer types for aerosol delivery in an adult model of mechanical ventilation

BACKGROUND: The optimal positions of different types of nebulizer for aerosol delivery remain unclear. METHODS: Three ICU ventilators employing three types of nebulizer were separately connected to a simulated lung to simulate nebulization during invasive ventilation. Assist/control-pressure control (A/C-PC) mode was utilized, with inspiratory pressure (Pi) set to 12 cmH(2)O and positive end expiratory pressure (PEEP) set to 5 cmH(2)O, and with a target Vt of 500 ml. The bias flow of all the ventilators was set to 2 L/min. The three nebulizers were the continuous jet nebulizer (c-JN), the inspiratory synchronized jet nebulizer (i-JN), and the vibrating mesh nebulizer (VMN). The five nebulizer positions were as follows: at the Y-piece (position 1) and 15 cm from the Y-piece (position 2) between the endotracheal tube and the Y-piece, at the Y-piece (position 3) and 15 cm from the Y-piece (position 4) in the inspiratory limb; and at the humidifier inlet (position 5). Aerosols were collected with a disposable filter placed at the simulated lung outlet (n = 3) and were measured by UV spectrophotometry (276 nm). The measurements were compared under different experimental conditions. RESULTS: The aerosol delivery of c-JN, i-JN, and VMN was 5.33 ± 0.49~11.12 ± 0.36%, 7.73 ± 0.76~13.75 ± 0.46% and 11.13 ± 56–30.2 ± 1.63%, respectively. The higher aerosol delivery: for c-JN~Positions 2 (10.95 ± 0.15%), fori-JN~Positions 1 or 2 (12.91 ± 0.88% or 13.45 ± 0.42%), for VMN~Positions 4(29.03 ± 1.08%); the lower aerosol delivery: for c-JN~Positions 1, 3 or 5, fori-JN~Positions 4 or 5, for VMN~Positions 5. The highest aerosol delivery:For c-JN at Position 2 (10.95 ± .15%), for i-JN at Position 1 or 2 (12.91 ± .88% or 13.45 ± .42%), for VMN at Positions 4 (29. 03 ± 1.08%); the lower aerosol delivery: for c-JN at Positions 1, 3 or 5, for i-JN at Positions 4 or 5, for VMN at Positions 5. The highest aerosol deliveryof c-JN was lower than that of i-JN while the VMN was the highest (all P < .05). However, no differences were observed between the highest aerosol delivery with c-JN and the lowest aerosol delivery with i-JN. Similar results were found between the lowest aerosol delivery with VMN and the highest aerosol delivery with c-JN /i-JN in the Avea ventilator. There were no differences in the highest aerosol delivery of each nebulizer among the different ventilators (all p > 0.05). CONCLUSION: During adult mechanical ventilation, the type and position of nebulizer influences aerosol delivery efficiency, with no differences between ventilators.