Ultrasonic Nebulization and Colistin: Heat Degradation Concerns
The concern about ultrasonic nebulizers heating and degrading colistin is not supported by the evidence—both ultrasonic and jet nebulizers preserve colistin's antimicrobial activity, and current guidelines actually recommend ultrasonic or vibrating plate nebulizers over standard jet nebulizers for optimal drug delivery. 1, 2
Evidence Against Heat Degradation
A direct bench study comparing jet (Pari LL) and ultrasonic (DP100) nebulizers found that neither jet nebulization nor ultrasonic nebulization altered the antibiotic properties of colistin, with post-nebulization minimum inhibitory concentrations (MICs) remaining within acceptable ranges (1.9 μg/mL for ultrasonic vs 0.5 μg/mL for jet, compared to 1 μg/mL for non-nebulized colistin—all within two dilutions of each other) 3
The study specifically tested anti-Pseudomonas aeruginosa activity after nebulization and concluded that both systems can be used to nebulize colistin without compromising drug efficacy 3
Current Guideline Recommendations
The Intensive Care Medicine task force explicitly recommends that nebulized antibiotics should be delivered using ultrasonic or vibrating plate nebulizers (AII level evidence), not standard jet nebulizers 1, 2
The American College of Chest Physicians supports this recommendation, noting that ultrasonic or vibrating plate nebulizers provide superior drug delivery compared to conventional jet nebulizers 2
The European Respiratory Journal consensus acknowledges that nebulization times may be much shorter using ultrasonic devices than using jet nebulizers, which is actually an advantage for patient compliance 1
Why the Misconception Exists
While it's true that ultrasonic nebulizers can generate heat through the vibration mechanism, and that ultrasonic and jet nebulizers may damage protein and other complex agents through heat or shear stress 4, this concern has been specifically tested for colistin and found to be clinically insignificant 3
The theoretical concern about heat degradation does not translate into actual loss of antimicrobial activity for colistin, as demonstrated by direct microbiological testing 3
Practical Implications
Standard jet nebulizers are actually inadequate for proper drug delivery according to the Society of Critical Care Medicine, making ultrasonic or vibrating plate devices the preferred choice 2
Using standard jet nebulizers instead of ultrasonic or vibrating plate nebulizers can lead to inadequate drug delivery, which is a common pitfall warned against by the American College of Chest Physicians 2
The particle size (2-5 μm range) and drug output are more important considerations than the theoretical heat generation, and modern ultrasonic/vibrating plate devices optimize these parameters 1, 2