Daily E‐cigarette Vapor Exposure Does Not Modify Response to 10% Normobaric Hypoxia in Long‐Evans Rats

Abstract

E‐cigarettes or electronic nicotine delivery systems are devices used to deliver aerosolized liquids often containing nicotine and other chemicals. The short and long term effects of e‐cigarette vapor exposure are still under active investigation with many studies focusing on changes in cardiovascular function, lung tissue morphology, and inflammatory markers. This pilot study aimed to investigate the effects of seven days of e‐cigarette vapor exposure in adult rats on lung function and the physiological response to acute hypoxia. Since the chemicals found in e‐cigarette solutions have been shown to alter properties of the lung tissue, we predicted that response to acute hypoxia may be altered with vape exposure. Using random assignment, ten adult male Long‐Evans rats were assigned to vape (experimental) or air (control) groups. The animals were exposed to either air (n=4) or JUUL 5% nicotine vapor (n=6) using a whole‐body exposure chamber, twice a day for ten minutes for seven consecutive days. Ventilation was recorded on day 0 (baseline, pre‐exposure) and day 8 (post‐exposure) using unrestrained whole‐body plethysmography. Minute ventilation, tidal volume, and breathing frequency were assessed in normoxia and normobaric hypoxia (10% oxygen). Blood was collected on day 8 for cotinine (a nicotine metabolite) detection in serum. Cotinine was found to be present in the serum samples of the vape groups (86.6 ng/ml ± 1.0 ng/mL) but not the air groups (0.0 ng/mL) confirming e‐cigarette vapor exposure in the experimental group only. Baseline ventilation data collected on day 0 and post‐exposure ventilation data collected on day 8 were compared between air and vape groups across three different parameters: minute ventilation, frequency, and tidal volume. These parameters were first compared in normoxic conditions resulting in three distinct two‐way ANOVAs comparing the variables time and treatment. These parameters were also compared in hypoxic conditions resulting in an additional three distinct two‐way ANOVAs comparing the variables time and treatment. No significant difference was found among any of the comparisons (p > 0.05 for all). In this pilot study, a seven day vape exposure in adult rats did not affect the response to acute hypoxia. We plan to repeat this study with modifications to the vape protocol and exposure duration.