Shallow bolus

Measurements of whole-lung clearance in healthy subjects using inhaled radiolabeled test aerosols show a rapid clearance phase, which is completed within 24 hr (44,45,52). The rapidly cleared fraction has generally been equated with tracheobronchial deposition, and the retained fraction with alveolar deposition. Recently, results from studies using a shallow bolus technique indicate that particles... 

The aerosol bolus inhalation technique provides a tool to deposit particles preferentially in the airways. A small volume of aerosol is inserted into a breath of elean air at a preselected volume of inhalation. Hence, the aerosol is a label of a Iraction of the inhaled air volume. Inhaling a small aerosol bolus (20-50 mL) of particles at the end of a breath (a shallow bolus), the particles penetrate only into the lumen of the proximal airways and eventually deposit there. Partiele deposition can be enhanced by a postinhalation breath-hold. 

With 3-pm particles in shallow bolus experiments, only about 50% were cleared rapidly (40-42 Fig, 1). The particles remaining in the lungs after 24 hr were cleared with half-times between 5 and 30 days (38,41) and in most investiga-... 

Whipple, Chen, and Wang S showed that the distribution of an inhaled aerosol bolus depends on the orientation of the successive airway bifurcations and the volume of the bolus. On the basis of skewed velocity profiles, they made theoretical calculations of the distribution of aerosol boli in branching airways that were in fair agreement with the experimental data. Their results suggested that slow and shallow breaths should show greater differences in dispersion of irritant gases in the airways. 

C Heyder, J. Stahlhofen, W. Regional deposition and retention of particles in the shallow, inhaled boluses effect of lung volume. J. Appl. Physiol. 1999, 86 (1), 168-179. 

FIGURE 1.1 The three most commonly used pharmacokinetic models in explaining the pharmacokinetic behavior of drugs. The symbols C, P, S, and D represent central, peripheral, shallow, and deep compartments, whereas the first-order rate constants, symbolized by k j, represent drug transport from compartment i to compartment j. ka, and kd represent a bolus rV dose, the absorption rate constant, and constant rate infusion, respectively. 

Kreyling WG, Blanchard JD, Godleski JJ, Hausermann S, Heyder J, Schulz H, Sweeney TD, Takenaka S. Shallow aerosol bolus inhalation in beagle dogs sites of retention and clearance. J Aerosol Med 1995 8 82. 

Shallow aerosol bolus studies were also performed on dogs ventilated with a servoventilator using red and green fluoreseent and " Te-labeled 2-pm-poly-styrene particles (45,46). Also, in these dogs, a fraetion A was slowly eleared ... 

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