Saline aerosol bolus dispersion. I. The effect of acinar airway alteration

We explored the possibility of using a saline aerosol for bolus dispersion measurements to detect peripheral airway alterations in smokers. Indexes of ventilation inhomogeneity in conductive (S-cond) and acinar (S-acin) lung zones, as derived from the multiple-breath N-2 washout (Verbanck S, Schuerm ans D, Van Muylem A, Noppen M, Paiva M, and Vincken W, J Appl Physiol 83: 1 807-1816, 1997), were also measured. The saline bolus test consisted of inh aling 60-ml saline aerosol boluses to different volumetric lung depths (VLD ) in the 1.1 liter volume above functional residual capacity. In the never- smoker group (n = 12), saline boluses showed bolus dispersion values consis tent with normal values reported in the literature for 0.5- to 1-mum aeroso ls. In the smoker group (n = 12; 28 +/- 9 pack years, mean +/- SD), signifi cant increases were seen on dispersion and skew of the most peripherally in haled saline boluses (VLD = 800 ml; P < 0.05) as well as on S-acin (P = 0.0 07) with respect to never-smokers. Shallow inhaled boluses (VLD = 200 ml) a nd S-cond did not reveal any significant differences between smokers and ne ver-smokers. This study shows the consistent response of two conceptually i ndependent tests, in which both saline aerosol and gas-derived indexes poin t to a heterogeneous distribution of smoking-induced structural alterations in the lung periphery.