Tracheobronchial tree

The estimated number of tubes in each airway generation depends on the bifurcation model used in describing the tracheobronchial tree. Though bronchial bifurcations are asymmetric, symmetric models, exemplified by Weibel, or asymmetric models, such as one suggested by Horsfield, can... 

Finer particles ( < 3 pm), termed respirable particles, pass beyond the ex-trathoracic airways and enter the tracheobronchial tree. Impaction plays a significant role near the tracheal jet, but sedimentation predominates as the effects of rapid conduit expansion dampen in the distal trachea and beyond. Sedimentation occurs when gravitational forces exerted on a particle equal drag forces, i.e., when particle velocity falls to u . As mean inspiratory air-stream velocity gradually declines along the tracheobronchial tree, particle momentum diminishes and 0.5-3 pm MMAD particles settle out of the airflow and onto mucosal surfaces. 

Tracheobronchial tree Series of bifurcating tubes originating at the trachea... 

The particle size is the most important factor that contributes to the clearance of particles. For particles deposited in the anterior parts of the nose, wiping and blowing are important mechanisms whereas particles on the other areas of the nose are removed with mucus. The cilia move the mucus toward the glottis where the mucus and the particles are swallowed. In the tracheobronchial area, the mucus covering the tracheobronchial tree is moved upward by the cilia beating under the mucus. This mucociliary escalator transports deposited particles and particle-filled macrophages to the pharynx, where they are also swallowed. Mucociliary clearance is rapid in healthy adults and is complete within one to two days for particles in the lower airways. Infection and inflammation due to irritation or allergic reaction can markedly impair this form of clearance. 

Bronchoscopy An examination used for inspection of the interior of the tracheobronchial tree. 

Obliterative bronchiolitis Inflammation of the bronchioles (the small elements of the tracheobronchial tree) characterized by obliteration and/or permanent narrowing of the airways. 

Cohen, B.S., Deposition of Ultrafine Particles in the Human Tracheobronchial Tree A Determinant of the Dose from Radon Daughters, this volume (1987). 

The deposition of ultrafine particles has been measured in replicate hollow casts of the human tracheobronchial tree. The deposition pattern and efficiency are critical determinants of the radiation dose from the short lived decay products of Rn-222. The experimental deposition efficiency for the six airway generations just beyond the trachea was about twice the value calculated if uniform deposition from laminar flow is assumed. The measured deposition was greater at bifurcations than along the airway lengths for 0.2 and 0.15 ym diameter particles ... 

Deposition experiments were carried out in replicate hollow casts of the upper airways or a human tracheobronchial tree using 0.2, 0.15 and 0.04 ym diameter particles and cyclic inspiratory flow rates of approximately 1 8 and 34 liters per minute (L/min) (see Table I). The replicates were produced from a single solid master airway cast prepared from the lungs of 34 year old male. The airway dimensions of the cast corresponded closely with the population mean of eight adult males as reported by Nikiforov and Schlesinger (1985). The airway diameters are somewhat larger and... 

Cohen, B. S., R. G. Sussman and M. Lippmann, Deposition of Ultrafine Particles in Hollow Airway Casts of the Human Tracheobronchial Tree. In Preparation. 

Gurman, J. L., M. Lippmann and R. B. Schlesinger, Particle Deposition in Replicate Casts of the Human Upper Tracheobronchial Tree Under Constant and Cyclic Inspiratory Flow. I. Experimental, Aerosol Science and Technology 3 245-252 (1984). 

Therapy is aimed at minimizing the quantity of antigenic material released in the tracheobronchial tree. 

Bronchitis refers to an inflammatory condition of the large elements of the tracheobronchial tree that is usually associated with a generalized respiratory infection. The inflammatory process does not extend to include the alveoli. The disease entity is frequently classified as either acute or chronic. Acute bronchitis occurs in all ages, whereas chronic bronchitis primarily affects adults. 

The dynamic properties of the mucus fluid, serous fluid, and epithelial layers of the respiratory tract are important for the transport, absorption, and desorption of reactive gases. The cilia beat at a fairly constant frequency within the stationary serous layer and cause the outer mucus layer to move up the respiratory tract. Clearance of deposited particles and absorbed gases in the ciliated tracheobronchial tree depends partly on the movement of this mucus layer. 

There are no published models that adequately describe ozone uptake in the tracheobronchial tree. To present the methodology, a few published and unpublished models of the uptake of various gases are reviewed. 

---