Biomedical Engineering Reference
In-Depth Information
Ta b l e 2 . 1
The tube
parameters for the sub-glottal
airways depths, whereas
depth 1 denotes the trachea
and depth 24 the alveoli, as
used in
[
59
,
66
,
85
,
97
,
100
,
164
]
Depth
m
Length
(cm)
Radius
R
(cm)
Wall thickness
h
(cm)
Cartilage
fraction
κ
1
10
.
0
0.80
0.3724
0.67
2
5
.
0
0.6
0.1735
0.5000
3
2
.
2
0.55
0.1348
0.5000
4
1
.
1
0.40
0.0528
0.3300
5
1
.
05
0.365
0.0409
0.2500
6
1
.
13
0.295
0.0182
0.2000
7
1
.
13
0.295
0.0182
0.0922
8
0
.
97
0.270
0.0168
0.0848
9
1
.
08
0.215
0.0137
0.0669
10
0
.
950
0.175
0.0114
0.0525
11
0
.
860
0.175
0.0114
0.0525
12
0
.
990
0.155
0.0103
0.0449
13
0
.
800
0.145
0.0097
0.0409
14
0
.
920
0.140
0.0094
0.0389
15
0
.
820
0.135
0.0091
0.0369
16
0
.
810
0.125
0.0086
0.0329
17
0
.
770
0.120
0.0083
0.0308
18
0
.
640
0.109
0.0077
0.0262
19
0
.
630
0.100
0.0072
0.0224
20
0
.
517
0.090
0.0066
0.0000
21
0
.
480
0.080
0.0060
0.0000
22
0
.
420
0.070
0.0055
0.0000
23
0
.
360
0.055
0.0047
0.0000
24
0
.
310
0.048
0.0043
0.0000
Asthma
is characterized by spastic contraction of the bronchioles, which causes
extremely difficult breathing [
17
,
53
]. The usual cause is bronchial hyperresponsive-
ness towards a variety of specific and a-specific stimuli. In fact, in younger patients,
under the age of 30, the asthma is in about 70 % of the cases caused by allergic
hypersensitivity (i.e. plant pollen, dust mite, cats, dogs). In elder persons, the hyper-
sensitivity is to non-allergic types of irritants in air, such as smog.
As a result of the irritants, the allergic person has a tendency to produce a high
amount of antibodies, which attach to specific cells in the bronchioles and small
bronchi. As a result of the antibodies reaction with the irritant, some substances are
released (e.g. histamine). The combined effect of all these factors will produce:
•
localized edema in the walls of the small bronchioles as well as secretion of thick
mucus into bronchiolar airways, and
•
spasm of the bronchiolar smooth muscle.
