Assessing nicotine pharmacokinetics of new generation tobacco products and conventional cigarettes: a systematic review and meta-analysis.

INTRODUCTION: New generation tobacco products (NGPs) hold promises as modified-risk alternatives to conventional cigarettes (CCs), given their comparable characteristics. This study investigated the nicotine pharmacokinetics (PK) of NGPs, encompassing closed pod systems, refillable e-cigarettes (ECs), and heated tobacco products (HTPs), in comparison to CCs through systematic review and meta-analysis. METHODS: A comprehensive search was conducted on PubMed, Embase, and Web of Science for articles published between January 2013 and July 2023. Maximum nicotine concentration (Cmax), time to the peak concentration (Tmax), and total nicotine exposure (area under the concentration-time curve, AUC) were extracted to evaluate nicotine delivery PK. Random effects meta-analyses were performed to determine pooled standardized mean differences (SMD), facilitating a comparison of PK profiles between NGPs and CCs. Subgroup analyses exploring flavors and nicotine concentrations across NGPs, and CCs were also conducted. RESULTS: The meta-analysis incorporated 30 articles with 2728 participants. Cmax and AUC were significantly lower for NGPs, while Tmax demonstrated statistical similarity compared to CCs. Among three NGPs, Cmax and AUC were lower for closed pod systems and refillable ECs. In HTPs, Cmax was statistically similar while AUC was lower compared to CCs. Tmax was statistically similar in closed pod systems and HTPs compared to that of CCs. No significant difference was observed in the comparisons of PK between each type of NGPs versus CCs. CONCLUSIONS: NGPs delivered less nicotine than CCs but reached Cmax over a similar timeframe, indicating that NGPs may serve as modified-risk alternatives with lower nicotine delivery to CCs for craving relief and smoking cessation. IMPLICATION: This study suggested that NGPs, such as the closed pod systems, the refillable ECs, and the HTPs, delivered either lower or comparable nicotine levels and achieved peak nicotine concentration at a similar rate as CCs. Our findings carry implications that NGPs can serve as modified-risk nicotine alternative to CCs in helping smokers to manage cravings and potentially quit smoking, thereby highlighting their value in the field of tobacco harm reduction.

Effects of chronic electronic cigarettes exposure in inducing respiratory function decline and pulmonary tissue injury - A direct comparison to combustible cigarettes.

BACKGROUND: Electronic cigarette (e-cig) use is increasing worldwide, especially among young individuals. Spirometry measures airflow obstruction and is the primary tool for diagnosing/monitoring respiratory diseases in clinical settings. This study aims to assess the effects of chronic e-cig exposure on spirometric traits, and directly compare to conventional combustible-cigarette (c-cig). METHODS: We employed an e- and c-cig aerosol generation system that resembled human smoking/vaping scenario. Fifty 6-week old C57BL/6 mice were equally divided into five groups and exposed to clean air (control), e-cig aerosol (low- and high-dose), and c-cig aerosol (low- and high-dose), respectively, for 10 weeks. Afterwards, growth trajectory, spirometry and pulmonary pathology were analyzed. RESULTS: Both e- and c-cig exposure slowed down growth and weight gain. Low dose e-cig exposure (1 h exposure per day) resulted in minimal respiratory function damage. At high dose (2 h exposure per day), e-cig exposure deteriorated 7 spirometry traits but by a smaller magnitude than c-cig exposure. For example, comparing to clean air controls, high dose e- and c-cig exposure increased inspiratory resistance by 24.3% (p = 0.026) and 66.7% (p = 2.6e-5), respectively. Low-dose e-cig exposure increased alveolar macrophage count but did not lead to airway remodeling. In contrast, even low-dose c-cig caused alveoli break down and thickening of the small airway, hallmarks of airway obstructive disease. CONCLUSIONS: We conducted well-controlled animal exposure experiments assessing chronic e-cig exposure's effects on spirometry traits. Further, mechanistic study characterized airway remodeling, alveolar tissue lesion and inflammation induced by e- and c-cig exposure. Our findings provided scientific and public health insights on e-cig's health consequences, especially in adolescent users.

Study on Water Displacing Gas Relative Permeability Curves in Fractured Tight Sandstone Reservoirs Under High Pressure and High Temperature.

Water-gas relative permeability is an important parameter for the rational development of gas fields. Conventional measurement methods are carried out at normal temperature and pressure without considering the actual conditions of high temperature and high pressure. The water displacing gas process in fractured tight sandstone reservoirs, under formation condition (116 MPa and 160 °C), was simulated by the self-manufactured displacing apparatus. The results show that cores under formation condition have the larger residual gas saturation, the smaller two-phase coexisting area, the lower water/gas relative permeability, and the lower displacement efficiency than that under normal conditions. The relative permeability declines slowly and the residual gas saturation is high, making the process of replacing the gas more difficult. The number and the interconnection quality of fractures affect the shape and the position of the displacing curves. It provides a reference for the rational development and further research of fractured tight sandstone reservoir.

The fabrication of carbon nanotubes reinforced copper coating by a kinetic spray process.

In this paper, multiwalled carbon nanotubes (MWCNTs) reinforced copper coating was deposited on copper sheet through kinetic spraying process. Effect of heat treatment on microstructure, conductivity, and hardness of the coating was investigated. The incompact MWCNTs reinforced copper coating exhibits a comparable hardness, but higher electrical resistivity than pure copper coating. After heat treatment at 600 degrees C for 2 h, the hardness of copper coatings significantly decreased due to the substantial grain growth. MWCNTs reinforced copper coating showed stable hardness and electrical conductivity against heat treatment owing to the inhibition of CNTs to grain growth and the intimate contact between CNTs and copper matrix.