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

Abstract

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 N2 washout (Verbanck S, Schuermans D, Van Muylem A, Noppen M, Paiva M, and Vincken W, J Appl Physiol 83: 1807–1816, 1997), were also measured. The saline bolus test consisted of inhaling 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 consistent with normal values reported in the literature for 0.5- to 1-μm aerosols. In the smoker group ( n = 12; 28 ± 9 pack years, mean ± SD), significant increases were seen on dispersion and skew of the most peripherally inhaled saline boluses (VLD = 800 ml; P < 0.05) as well as on S acin ( P = 0.007) with respect to never-smokers. Shallow inhaled boluses (VLD = 200 ml) and S cond did not reveal any significant differences between smokers and never-smokers. This study shows the consistent response of two conceptually independent tests, in which both saline aerosol and gas-derived indexes point to a heterogeneous distribution of smoking-induced structural alterations in the lung periphery.

Theoretical diagnosis of emphysema by aerosol bolus inhalation

“…Here, it turned out that bolus dispersion in smokers surpassed that of nonsmokers by a certain degree, whilst spirometric data exhibited only slight discrepancies between the two A B C D test groups. According to further medical studies inhaled aerosol boluses also undergo enhanced dispersion in patients suffering from cystic fibrosis (22), COPD (23)(24)(25), chronic asthma (26), and, important in the context of the present contribution, also emphysema (27)(28)(29). Vast majority of these clinical studies came to the essential conclusion that aerosol bolus dispersion might bear a certain potential with regard to the evaluation of modified convective gas transport in diseased lungs and clinical diagnosis of several pulmonary insufficiencies.…”

“…Although measurement of the FEV 1 /FVC quotient has crystallized out as highly effective method for emphysema screening, it still bears some inaccuracies, which can be largely broached by application of an additional or alternative diagnosis technique. Here, aerosol bolus inhalation comes into play, because this method requires rather low technical expenditure and provides a multitude of measurable statistical parameters for diagnostic purposes (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29).…”

“…As outlined in a few theoretical (15)(16)(17)(18)(19)(20) and experimental investigations (21)(22)(23)(24)(25)(26)(27)(28)(29), aerosol bolus dispersion, being quantifiable by four independent statistical parameters (half-width of the exhaled bolus, standard deviation, skewness, mode-shift), exhibits a certain sensitiveness with regard to significantly enlarged pathological structures of the lung periphery. In addition, some hypothetical examinations (19,20) already indicated the enhanced importance of particle deposition from the aerosol bolus as advanced characteristic for medical diagnosis.…”

“…As a physical consequence of this phenomenon, the exhaled aerosol bolus is spread over a larger air volume than the inhaled bolus. This observation termed aerosol bolus dispersion was assessed as an easily measurable parameter showing a certain sensitiveness to specific diseaseinduced modifications of lung architecture (21)(22)(23)(24)(25)(26)(27)(28)(29).…”

“…Vast majority of these clinical studies came to the essential conclusion that aerosol bolus dispersion might bear a certain potential with regard to the evaluation of modified convective gas transport in diseased lungs and clinical diagnosis of several pulmonary insufficiencies. At the same time, it was restrictively stated that the FEV 1 /FVC quotient disposes of disease-specific sensitiveness largely comparable to that of aerosol bolus inhalation, but causes much lower medical expenses (21)(22)(23)(24)(25)(26)(27)(28)(29).…”