In “Deposition in the human oral cavity of inhaled electronic cigarette aerosol,” the team noted that models developed for combustible tobacco smoke didn’t adequately extend to cover the action of ecig aerosol due to vape’s higher volatility and hygroscopicity. The group state that these features effect how vape moves in the mouth and how it deposits itself on the parts of the oral cavity.
They believe that modelling the process and movement of vape is important for future researchers, so they can factor in these aspects to their studies.
The model they devised included several steps: from representing puff withdrawal into the oral cavity, mouth hold, dilution in the mouth through inhaling additional air, inhalation of the puff into the lower respiratory tract, lung-hold, and exhalation.
They write: “The model accounted for thermodynamic interactions between the droplet and vapour phases of each constituent in the aerosol mixture. Deposition from droplets and uptake of vapour constituents were calculated. The deposited mass fraction for each vapour constituent and droplets were also calculated based on the total mass of the inhaled constituents.”
The assumptions they made were: “Rapid Brownian (thermal) coagulation of droplets occurs immediately after the formation of aerosol, but decreases with decreasing of its number concentration. Kinematic coagulation is insignificant due to small (sub-micrometer) size of droplets and thus may be omitted. Wall losses do not impact coagulation.”
They noted that vapour temperature rapidly dropped from around 87 °C to body temperature shortly after entering the mouth, but this was also dependent on ambient air temperature.
They also discovered that the diameter of the average droplet grows by approximately 50% at the end of mouth hold, before a secondary inhalation of air. They add: “the model provides input parameters to predict the fate of the aerosol in the upper respiratory tract, under a variety of aerosol composition and inhalation conditions.”
While this may not be the most exciting investigation for vapers, the payoff may be better-informed studies in future as they factor in this mathematical model.