Assessment of regional deposition of inhaled particles in human lungs by serial bolus delivery method

Abstract

Assessment of regional deposition of inhaled particles in human lungs by serial bolus delivery method. J. Appl. Physiol. 81(5): 2203-2213, 1996.-Detailed regional deposition of inhaled particles was investigated in young adults (n 5 11) by use of a serial bolus aerosol delivery technique. A small bolus (45 ml half-width) of monodisperse aerosols [1-, 3-, and 5-µm particle diameter (D p )] was delivered sequentially to a specific volumetric depth of the lung (100-500 ml in 50-ml increments), while the subject inhaled clean air via a laser aerosol photometer (25-ml dead volume) with a constant flow rate (Q 5 150, 250, and 500 ml /s) and exhaled with the same Q without a pause to the residual volume. Deposition efficiency (LDE) and deposition fraction in 10 local volumetric regions and total deposition fraction of the lung were obtained. LDE increased monotonically with increasing lung depth for all three D p . LDE was greater with smaller Q values in all lung regions. Deposition was distributed fairly evenly throughout the lung regions with a tendency for an enhancement in the distal lung regions for D p 5 1 µm. Deposition distribution was highly uneven for D p 5 3 and 5 µm, and the region of the peak deposition shifted toward the proximal regions with increasing D p . Surface dose was 1-5 times greater in the small airway regions and 2-17 times greater in the large airway regions than in the alveolar regions. The results suggest that local or regional enhancement of deposition occurs in healthy subjects and that the local enhancement can be an important factor in health risk assessment of inhaled particles.

A Sampling Train for Rapid Measurement of Regional Lung Deposition

“…These data were repeated more than five times. The local deposition efficiency was calculated for each 50 cm 3 volumetric region to compare with the data reported by Kim et al (1996). Our data agreed well with Kim's data (solid line), except in the deep lung (400-500 mL), i.e., alveolar region.…”

“…Aerosol particles within each volume element of the respiratory tract system are assumed to deposit with an efficiency of x i as they are inhaled and exhaled again with the same deposition efficiency penetrating through the same volume element (i) (Kim et al, 1996;Brand et al, 1999). Aerosol recovery from the i th volume element, RCi, can be obtained by…”

“…The serial bolus delivery technique, developed about three decades ago, is a non-invasive physiological lung test, involving injection of small volumes of monodisperse aerosols (the bolus) into predetermined volumetric in vivo lung regions of humans during inhalation of clean, aerosolfree air (Kim et al, 1996;rand et al, 1997;Heyder et al, 1988;Grgic et al, 2006). The difference in the spread of the bolus between inspiration and expiration is evaluated via plots of aerosol concentration versus respired volume and is thought to be closely related to the conditions of the convective flow in the lungs.…”

“…Another disadvantage is a high concentration of challenge aerosols is needed to ensure the accuracy and precision of the measurement. For the bolus method, the normal aerosol concentrations range from 2 × 10 3 to 4 × 10 4 particles/cm 3 , depending on the size of the challenge aerosols (Kim et al, 1996).…”

Importance of Physical and Physiological Parameters in Simulated Particle Transport in the Alveolar Zone of the Human Lung

“…In this regard Kim et al [26] indicate the increase of deposition efficiency by decreasing the volumetric flow rate (slower breathing) for particles 1 < d p < 5 µm in the distal lunges. In addition, Darquenne et al [24] illustrate the increasing of deposition efficiency with decreasing volumetric flow rate for a whole-lung model by utilizing 0.87-µm particles.…”