Reconstruction of the Human Airways - Computational Fluid and Particle Dynamics in the Human Respiratory System - page 67

Table 3.2 Representative data for the first six generations of a symmetrical tracheobronchial airway
tree with lung volume of 4800 cm 3 at about 75 % total lung capacity, based on Weibel (1997)

Generation
number

Total airway
volume per
generation
0 (trachea) 1 1.80 12.00 - 2.54 30.5
1 2 1.22 4.76 4.76 2.33 11.1
2 4 0.83 1.90 6.66 2.13 4.11
3 8 0.56 0.76 7.42 2.00 1.50
4 16 0.45 1.27 8.69 2.48 3.23
5 32 0.35 1.07 9.76 3.11 3.29
6 64 0.28 0.90 10.66 3.96 3.55
∗ the carina is the ridge at the lower end of the trachea that runs between the two primary bronchi,
where the trachea bifurcates

Number
of airways

Airway
diameter
(cm)

Airway
length
(cm)

Distance from
the carina ∗ to
end of airway

Total cross
sectional area
per generation

Table 3.3 Representative data for the first six generations of a symmetrical tracheobronchial airway
tree with lung volume of 3300 cm 3 , based on Horsfield (1994)
Generation
number

Number of
airways

Airway
diameter
(cm)

Airway
length
(cm)

Branching
angle

Inclination angle
(0 ◦ = vertical axis,
90 ◦ horizontal axis)

0 (trachea) 1 1.65 9.10 - 0

1 2 1.20 3.80 36 20

2 4 0.85 1.50 35 31

3 8 0.61 0.83 28 43

4 16 0.44 0.90 35 39

5 32 0.36 0.81 39 39

6 64 0.29 0.66 34 40

It is based on measurements of the major conducting airway branches from a plastic
cast of a pair of human lungs. Horsefield et al. (1971) and Yeh and Schum (1980) also
provide similar data but included some asymmetry into the models. Several models
have been developed by the International Commission on Radiological Protection
(ICRP) with each successive model an improved iteration from the previous model.
Their first model is described in ICRP-2 (ICRP 1960) with a successive model pub-
lished in ICRP-66 (ICRP 1994). The published data for the first six generations of the
tracheobronchial airway from the models of Weibel and ICRP are given in Table 3.1 ,
3.2 and 3.3 . In the reconstruction of tracheobronchial airway tree, it is possible to
sketch the model because of the available data. In this example, the geometry details
of Weibel's model are used in a CAD software to sketch and create a 3D-model and
the final CAD model is shown in Fig. 3.18 .

3.4.5 Pulmonary Acinar Region

The acinus region is the terminating region of the respiratory airway. They are also the
smallest in size which makes the image processing difficult. Until recently all models
studied have been simplified models due to limitations in the spatial resolution of