Sputum cell counts in COPD patients who use electronic cigarettes.

Introduction:
This text is a letter to the editor of a respiratory journal discussing the impact of electronic cigarette (e-cigarette) use on airway inflammation in ex-cigarette smoking patients with Chronic Obstructive Pulmonary Disease (COPD). The authors present an analysis comparing sputum cell counts in COPD current smokers, COPD ex-cigarette smokers, and COPD ex-smokers who use e-cigarettes. The study highlights the potential implications of e-cigarette use on airway inflammation in this patient population.

Key Points:

* The study used a retrospective design with sputum cell count data collected from subjects participating in research at their center between 2014 and 2020.
* The study compared airway inflammatory cell counts in three groups: COPD current smokers (COPDS), COPD ex-cigarette smokers (COPDE), and COPD ex-smokers who use e-cigarettes (COPDE+e-cig).
* The study found that the percentage of sputum neutrophils was significantly higher in COPDE and COPDE+e-cig compared to COPDS (medians 83% and 91%, respectively, vs. median 72%).
* The use of e-cigarettes in COPD ex-smokers appeared to further increase neutrophil percentage counts, almost reaching significance compared to COPDE (p=0.058).
* The authors propose that acute cigarette smoke exposure may induce neutrophil cell death and increase efferocytosis, while e-cigarette use may enhance neutrophil-mediated inflammation due to continued exposure to harmful chemicals in e-cigarette vapour extract.
* The study has limitations, including its cross-sectional design and the relatively small number of participants in the COPDE+e-cig group.

Main Message:
The study suggests that e-cigarette use in COPD ex-smokers may cause increased sputum neutrophil percentages, raising concerns over the long-term impact of e-cigarette use on airway inflammation in this patient population. Further research is needed to confirm these findings and better understand the potential implications for COPD management. healthcare providers should be aware of this potential risk when advising patients on smoking cessation options.

higham a, Beech a, Jackson N, Lea S, Singh D. Sputum cell counts in COPD patients who use electronic cigarettes. The European respiratory journal. 2022;59(5). doi:10.1183/13993003.03016-2021