Lungs mucociliary transport

Several groups investigated the use of liposomes for the intra-pulmonary delivery. Farr et al. (1985) showed that the deposition of aerosolized liposomes in the human lung depends on the aerosol particle size. Short-term retention profiles for MLVs and SUVs deposited in the lung were indicative of clearance via the mucociliary transport mechanism. 

While the lung is the major organ exposed to airborne dusts, such agents may also be swallowed following mucociliary transport and removal from the lung. Contaminating particles contained in food and drink also gain direct access into the gut. 

If inhalant is a solid mucociliary transport from lungs to GI tract may clear it out. 

If a solid, mucociliary transport may serve to clear from lungs to GI tract. 

The bronchodilation produced by the methylxanthines is the major therapeutic action in asthma. Tolerance does not develop, but adverse effects, especially in the central nervous system, may limit the dose (see below). In addition to their effect on airway smooth muscle, these agents—in sufficient concentration—inhibit antigen-induced release of histamine from lung tissue their effect on mucociliary transport is unknown. 

Mucociliary clearance reduces the retention time of drags within the lungs. Efficient drag delivery of slowly absorbed drags must overcome the ability of the lung to remove drag particles by mucociliary transport. 

As discussed in Section 3.4.4 inhaled asbestos fibers that are deposited in the lung are principally removed by mucociliary transport into the alimentary canal and eventually are excreted in the feces. Chrysotile fibers appear to be cleared more readily than amphibole fibers, and long fibers are cleared more slowly than short fibers (Coin et al. 1992 Morgan 1991). 

How long does the drug remain in the lung (dissolution rate, mucociliary transport rate, rates of cellular entrapment) ... 

Figure 9 Effect of pulmonary dissolution rate on pulmonary selectivity. The dose of 300 p,g was allowed to dissolve immediately (A), with a half-life of 3 hr (B), or with a half-life of 24 hr (C). Pulmonary selectivity [area between pulmonary (upper line) and systemic (lower line) receptor occupancies] observed in A-C are summarized in D. The dose was given once a day at steady state. A slower release/dissolution of the drug in the lung does significantly increase pulmonary selectivity however, very slow dissolution rates further decrease pulmonary selectivity as the undissolved drug particles are removed from the lung by the mucociliary transport system.

Three of the cell types in the epithelium have secretory functions. These cells are the mucous (goblet) cells, serous cells, and Clara cells. These cells contribute to the secretion of airway mucus, a complex mixture of water, glycoproteins, immunoglobulins, lipids, and salts. The secretion of mucus is a defense function that contributes to the removal of foreign objects from lung airways via the mucociliary transport process, as described in later sections of this chapter. Excess mucus secretion can be detrimental, however, since it can obstruct the movement of air through the airways and is a component of certain pulmonary diseases such as asthma, emphysema, chronic bronchitis, and cystic fibrosis. A hypertrophy of secretory cells in the epithelial layer of the airways is often characteristic of these diseases. 

Another manual chest physical therapy technique is vibration. Vibration is a sustained cocontraction of the upper extremities of a caregiver to produce a vibratory force that is transmitted to the thorax over an involved lung segment. Vibration is applied throughout exhalation concurrently with mild compression of the patient s chest wall. Vibration is proposed to enhance mucociliary transport from the peripheral of the lung fields to the larger airways. Since vibration is used in conjunction with PD (Fig. 5) and percussion, many studies do not isolate the effects of vibration from the other components. 

---