Late-breaking abstract: Immediate effects of water-pipe smoking on respiratory mechanics and FENO among young smokers

Introduction The acute response of respiratory system after water-pipe smoking is an area of special interest. Materials and methods 50 young smokers (average age=23±4, 32 males, mean pack-years=3.6) using cigarettes and occasionally water-pipe voluntarily participated in this study. 25 had mild respiratory symptoms (atopic history, mild cough and exercise induced chest tightness) and mild peripheral airways obstruction (FEF25%-75%=74.15% pred., MRS-subgroup). The other 25 had normal dynamic flows and no respiratory complaints (NRS-subgroup). Multi-frequency respiratory system impedance(Z), resistance(R) and reactance(X) assessed with impulse oscillometry, and fractional exhaled nitric oxide(FENO) were measured before and immediately after 30 minutes of water-pipe smoking, or equal session in the smoking area without smoking (control group). Wilcoxon signed rank and U-Mann-Whitney rank sum tests were performed for the statistical analysis. Results Immediately after 30 minutes of water-pipe smoking Z5Hz, R5Hz, R10Hz, R20Hz and meanR5-R20 significantly increased (+10.1% to +12.61%, p≤0.001) both in the whole population(n=50) and the two subgroups. Among the two subgroups, significant difference at the changes of X20Hz was also identified (-7.57% in MRS and +8.49% in NRS respectively, p=0.007). FENO was significantly reduced in the whole population (n=50, -4.78%, p=0.002) and the MRS-subgroup (-2.39%, p=0.003) but not in the NRS-subgroup. In the control group, no significant changes were detected. Conclusions Water-pipe smoking has immediate effects on respiratory function. Mild respiratory symptoms and peripheral airways obstruction predispose to a higher reduction of X20Hz and FENO.