Dimensions Of The Trachea And Bronchi

Sources: A Manual Of Peroral Endoscopy And Laryngeal Surgery

It will be noted that the

bronchi divide monopodially, not dichotomously. While the lumina of

the individual bronchi diminish as the bronchi divide, the sum of the

areas shows a progressive increase in total tubular area of

cross-section. Thus, the sum of the areas of cross-section of the two

main bronchi, right and left, is greater than the area of cross

section of the trachea. This follows the well known dynamic law. The

relative increase in surface as the tubes branch and diminish in size

increases the friction of the passing air, so that an actual increase

in area of cross section is necessary, to avoid increasing resistance

to the passage of air.

The cadaveric dimensions of the tracheobronchial tree may be

epitomized approximately as follows:


Male Female Child Infant

Diameter trachea, 14 X 20 12 X 16 8 X 10 6 X 7

Length trachea, cm. 12.0 10.0 6.0 4.0

Length right bronchus 2.5 2.5 2.0 1.5

Length left bronchus 5.0 5.0 3.0 2.5

Length upper teeth to trachea 15.0 23.0 10.0 9.0

Length total to secondary bronchus 32.0 28.0 19.0 15.0

In considering the foregoing table it is to be remembered that in life

muscle tonus varies the lumen and on the whole renders it smaller. In

the selection of tubes it must be remembered that the full diameter of

the trachea is not available on account of the glottic aperture which

in the adult is a triangle measuring approximately 12 X 22 X 22 mm.

and permitting the passage of a tube not over 10 mm. in diameter

without risk of injury. Furthermore a tube which filled the trachea

would be too large to enter either main bronchus.

The normal movements of the trachea and bronchi are respiratory,

pulsatory, bechic, and deglutitory. The two former are rhythmic while

the two latter are intermittently noted during bronchoscopy. It is

readily observed that the bronchi elongate and expand during

inspiration while during expiration they shorten and contract. The

bronchoscopist must learn to work in spite of the fact that the

bronchi dilate, contract, elongate, shorten, kink, and are dinged and

pushed this way and that. It is this resiliency and movability that

make bronchoscopy possible. The inspiratory enlargement of lumen opens

up the forceps spaces, and the facile bronchoscopist avails himself of

the opportunity to seize the foreign body.