The influence of solvent in e-cigarettes on ciliary beat frequency of nasal epithelial cells. An in vitro study.

Introduction Vaporizing is promoted as less harmful than cigarette smoking. Vaporizing involves inhaling a liquid mixture of nicotine, optionally with flavors and solvents such as glycerol or propylene glycol. To date, only one study postulates cytotoxic damage to cilia from these solvents.

Method To investigate ciliary beat frequency (CBF) under the influence of the solvents, nasal epithelial cells were collected by brush cytology from 32 healthy volunteers. Glycerol, proylgen glycol, and sodium chloride solution (control) were added at varying concentrations generated during steaming. CBF was evaluated every 2 minutes for a total of 20 minutes by inverted high-frequency phase-contrast microscopy, and Sissons-Ammons video analysis was used for evaluation. Statistics were calculated using multivariance analyses and testing of between-subject factors.

Results The control group showed an averaged CBF over the whole time of 6.9 Hz (± 1.7) at 8% NaCl solution. Addition of glycerol resulted in an averaged CBF of 4.3 Hz (± 1.4) at 1%, 4.9 Hz (± 1.7) at 5%, and 3.5 (±1.4) Hz at 8%. After addition of propylene glycol, an averaged CBF of 4.3 Hz (± 1.5) at 1%, 3.8 Hz (± 1.3) at 5%, and 3.1 Hz (±1.1) at 8% was shown. In each case, this results in a concentration- and time-dependent significant reduction (p<0.01) in CBF.

Conclusion The solvents glycerol and propylgenglycol statistically significantly reduce CBF at concentrations generated during vaporization. It can be assumed that the self-cleaning function of the upper respiratory tract is also reduced in vivo during vaporization. Long-term in vivo studies of the effects are desirable.

Conflict of Interest

The authors declare that they have no conflict of interest.

Publication History

Article published online:
12 May 2023