Devices that produce aerosol particles of < 2 µm in mass median aerodynamic diameter are more efficient during me-chanical ventilation than are those that produce larger particles. Other factors influencing aerosol drug delivery to me-chanically ventilated patients include the aerosol-generating device, the condition of the ventilator circuit, the artificial airway, and the ventilator settings. Next-generation nebulizers known as vibrating membrane nebulizers or vibrating mesh nebulizers have recently been developed, their aerosol delivery efficiency having been estimated to be twice to three times as high as that of jet nebulizers.

Ari et al.(1) conducted an experimental study comparing jet nebulizers and vibrating membrane nebulizers in terms of their efficacy in simulated pediatric and adult lung models during mechanical ventilation. The authors found that drug (albuterol sulfate) delivery was 2- to 4-fold greater with a vibrating mesh nebulizer than with a jet nebulizer (p = 0.001). It is of note that active humidification was used in that study.

Given the wide range of variables that can influence inhaled drug delivery to patients on mechanical ventilation, we read with great interest the review article by Maccari et al.(2) However, we found it surprising that the authors did not include vibrating membrane nebulizers among the nebulizers for use in mechanically ventilated patients. In addition, Figure 1 in the aforementioned study(2) shows a heat and moisture exchanger. The authors reported that the use of humid-ifying devices reduces aerosol deposition and the number of deposited particles by as much as 40%. An update of the American Association for Respiratory Care guidelines recommends that filtered heat and moisture exchangers be re-moved during nebulization. (3) This can be confusing and misleading to the reader.

REFERENCES

1. Ari A, Atalay OT, Harwood R, Sheard MM, Aljamhan EA, Fink JB. Influence of nebulizer type, position, and bias flow on aerosol drug delivery in simulated pediatric and adult lung models during mechanical ventilation. Respir Care. 2010;55(7):845-51.
2. Maccari JG, Teixeira C, Gazzana MB, Savi A, Dexheimer-Neto FL, Knorst MM. Inhalation therapy in mechanical ventilation. J Bras Pneumol. 2015;41(5):467-72. http://dx.doi.org/10.1590/S1806-37132015000000035
3. American Association for Respiratory Care, Restrepo RD, Walsh BK. Humidification during invasive and noninvasive mechanical ventilation: 2012. Respir Care. 2012;57(5):782-8. http://dx.doi.org/10.4187/respcare.01766