Radiolabeling an Electronic Cigarette Aerosol Using Technetium Carbon Ultrafine Particles

Respiratory Tract Deposition of E-Cigarette Particles

Total and regional deposition of inhaled electronic cigarette (E-cig) particles in the respiratory tract (RT) depends on both physical properties of the inhaled particles and biological factors of users, for example, breathing pattern or puff profile, airway anatomy, and regional ventilation. Accurate particle sizing of E-cig aerosols is essential for predicting particle deposition in the RT. Studies using a variety of sizing methods have shown mass median aerodynamic diameters ranging from 0.2 to 1.2 um and secondary count diameters in the ultrafine range (<0.1 μm). Incorporating these particle sizes into a multiple-path particle dosimetry (MPPD) model shows 10% to 45% total lung deposition by mass and 30% to 80% for ultrafine particles depending on the breathing patterns. These predictions are consistent with experimental measures of deposition fraction of submicron and ultrafine particles. While box-mod-type E-cig devices allow for full "direct-lung" inhalations of aerosol, the more recent pod-based, and disposable E-cigs (e.g., JUUL, Puff Bar, Stig) deliver the aerosol as a "mouth-to-lung" puff, or bolus, that is inhaled early in the breath followed to various degrees by further inhalation of ambient air. Measurement of realistic ventilation patterns associated with these various devices may further improve deposition predictions. Finally, while in vivo measures of RT deposition present a challenge, a recent methodology to radiolabel E-cig particles may allow for such measurements by gamma scintigraphy. Supported by NIH/NHLBI R01HL139369. © 2022 American Physiological Society. Compr Physiol 12: 1-10, year.

Measurements of deposited aerosol dose in infants and small children

Pediatric patients are very dependent on inhaled aerosol medications. There are significant differences in how these aerosols deposit in the lungs of children vs. adults that may affect the efficacy of the therapies. Inefficient aerosol delivery to children, caused by factors such as high mouth and throat deposition during oral inhalation, significant losses within adjunct devices such as masks, and high rates of nasal deposition during cannula delivery, can lead to dosing that is difficult to control. Here we discuss the methods, such as deposition scintigraphy, that are used to assess inhaled dose in vivo and review previous studies where these techniques have been applied to measure dosing in children. This includes studies of nebulizers and metered dose inhalers and delivery through adjuncts such as facemasks and nasal cannulas. We discuss the factors that can lead to inefficient inhaled drug delivery and high levels of mouth and throat deposition in children. Finally, we propose areas of innovation to improve inhaled drug delivery to this population. There is a need for child-specific technologies for inhaled drug delivery. This includes the use of smart devices that can guide pediatric breathing patterns and better engage children during treatments, the use of smaller aerosols which are less likely to deposit in the upper airways after inhalation, and the design of better nasal cannula interfaces for aerosol delivery to infants.