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Respiratory Tract Deposition of E‐Cigarette Particles

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Abstract

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.

Figure 1. Figure 1. Effect of humidity and PG/VG content on particle size (MMAD) from a Sigelei 213 W TC/Uwell Crown 2 tank measured by low flow Sierra cascade impaction.
Figure 2. Figure 2. Average puff profiles (flow rate vs. time) for four adult vapers using the JUUL E‐cigarette. (AUC = area under the curve)
Figure 3. Figure 3. Lifeshirt (respiratory inductance plethysmography) profile for a single inhalation from an E‐cig device (VaporShark DNA 250 TC box‐mod/SMOK TFV8 tank; 80 W power setting).
Figure 4. Figure 4. Predicted intrathoracic deposition of 1 μm diameter particles for a 750 mL tidal volume at 15 breaths per minute in Weibel's symmetric morphology scaled to a lung volume of 3375 mL. The respiratory tract regions are designated as bronchi, bronchioles, and parenchyma and refer to generations 1 to 8, 9 to 16, and 17 to 23, respectively. Adapted from Bennett and Brown 2005 4.
Figure 5. Figure 5. Calculated deposition fractions, for different pauses (BHT) and flow rates, using ARA software 1. The MMAD is 0.75 μm for all combinations. Adapted from Sundahl et al. 2017 (37)
Figure 6. Figure 6. Average deposition efficiency of five subjects for mouth‐breathing as function of particle diameter, the bars indicate the variation of individual deposition, broken lines: computed curves. Adapted from Heyder et al. 1975 17.
Figure 7. Figure 7. Posterior gamma camera images from a healthy subject of a Xe133 equilibrium scan (left) and a deposition scan for deep inhalation of 1 μm aerosol (center). Right shows the central/peripheral (C/P) analysis of deposition images. Adapted from Bennett et al. 2002 5.
Figure 8. Figure 8. Mass and radioactivity cascade impactor measurements of the unlabeled and radiolabeled E‐cig grouped into seven particle size bins. Adapted from Holbrook et al. 2019 20.


Figure 1. Effect of humidity and PG/VG content on particle size (MMAD) from a Sigelei 213 W TC/Uwell Crown 2 tank measured by low flow Sierra cascade impaction.


Figure 2. Average puff profiles (flow rate vs. time) for four adult vapers using the JUUL E‐cigarette. (AUC = area under the curve)


Figure 3. Lifeshirt (respiratory inductance plethysmography) profile for a single inhalation from an E‐cig device (VaporShark DNA 250 TC box‐mod/SMOK TFV8 tank; 80 W power setting).


Figure 4. Predicted intrathoracic deposition of 1 μm diameter particles for a 750 mL tidal volume at 15 breaths per minute in Weibel's symmetric morphology scaled to a lung volume of 3375 mL. The respiratory tract regions are designated as bronchi, bronchioles, and parenchyma and refer to generations 1 to 8, 9 to 16, and 17 to 23, respectively. Adapted from Bennett and Brown 2005 4.


Figure 5. Calculated deposition fractions, for different pauses (BHT) and flow rates, using ARA software 1. The MMAD is 0.75 μm for all combinations. Adapted from Sundahl et al. 2017 (37)


Figure 6. Average deposition efficiency of five subjects for mouth‐breathing as function of particle diameter, the bars indicate the variation of individual deposition, broken lines: computed curves. Adapted from Heyder et al. 1975 17.


Figure 7. Posterior gamma camera images from a healthy subject of a Xe133 equilibrium scan (left) and a deposition scan for deep inhalation of 1 μm aerosol (center). Right shows the central/peripheral (C/P) analysis of deposition images. Adapted from Bennett et al. 2002 5.


Figure 8. Mass and radioactivity cascade impactor measurements of the unlabeled and radiolabeled E‐cig grouped into seven particle size bins. Adapted from Holbrook et al. 2019 20.
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How to Cite

William D. Bennett, Phillip W. Clapp, Landon T. Holbrook, Kirby L. Zeman. Respiratory Tract Deposition of E‐Cigarette Particles. Compr Physiol 2022, 12: 1-10. doi: 10.1002/cphy.c210038