(Received November 16, 1967; revision accepted for publication January 31, 1968.)
ADDRESS: 1525 West Jackson Street, Muncie, Indiana.
336
LENGTH
AND
CROSS-SECTION
GROWTH
PATTERNS
IN THE
HUMAN
TRACHEA
Ralph 0. Butz, Jr., M.D.
Department of Surgery, Ball Memorial Hospital, Muncie, indiana
ABSTRACT. Twent-four tracheas taken from
au-topsies of children ranging in age from premature
to 14 years and in weight from 13i pounds to 155
pounds, were studied. Details of the growth
pat-tems in length and cross section are discussed.
Length and cross-section area are found to have
different growth curves. “Flattening” of the
tra-chea is also found to be age related. Application of
the data to the selection of proper endotracheal
tubes for anesthesia is made in this study, including special attention to length in the newborn infant.
Pediatrics, 42:336, 1938, ANATOMY, TRACHEA,
AXES-THESIA, RESPIRATION, GROWTH, BRONCHI, .4 IRWAY
LENGTH.
D
ATA On the growth of the trachea andbronchi are not readily available to
the anesthesiologist and bronchoscopist in
spite of the obvious clinical interest.
Cilles-pie has only two references to tracheal
di-mensions: “the first of these is the size of
the trachea, which has been found to
in-crease with age, regardless of other
fac-tors,” and “both the size of the glottis and
length of the trachea vary widely in infants
and children, and no rules can be laid
down in advance.” A general rule for “air-way length” has been given by Schellinger3
on the basis of measurements made on
seven autopsy specimens. The
measure-ments involve the whole airway rather than
the trachea itself. Tracheal length is given
without reference by Benson, et al. for
three age ranges. The figures can be
consid-ered as only the roughest guide. Morris’
Human Anatomy gives the figures of See
for the “diameter of lumen of trachea when
distended to cylindrical form” for four age
ranges.5 As the present material will show,
the shape as well as the circumference is
significant.
The most extensive data on tracheal
mea-surements appears in Handbook of
Respiration.6 These tables give only ages
and not weight or height of the bodies. Nor
are the levels of trachea distinguished or
the method of making the measurements.
The last factor particularly may account for
the significantly lower values obtained in
the present study, which presents details of
the method and body measurements for
each specimen.
MATERIALS AND METHODS
Fresh autopsy specimens of intact
tra-cheobronchial trees were studied. Cleanly
dissected specimens with the attached
lar-ynx were photographed on color slides.
Slides were then made of the specimen with
thin cross sections taken out and laid beside
the trachea at the sectioned levels. Using the
metric rule photographed with the
speci-men, the desired measurements were read
from the projected slides. Figures 1 and 2
show pictures of a typical specimen.
RESU LTS
Table I records the major and minor
di-arneters of each cross section and the length
of the trachea from origin to carina. The
cross-section area at each level was
calcu-lated assuming the shape to be
approxi-mately an ellipse and using the formula:
A = 3ab
where a and b are the minor and major
di-ameters in millimeters and A is the area in
square millimeters. In order to express the
shape as a number, a “roundness” index
(
I)PATY 77.
. .-.L
_________
V
80
F .E60
F-40
2 LU
-I
20
00
...
‘ LENGTH OF TRICHEA
AGE-YEARS 2 34 0 iS
2 3 ib w o so i#{228}o
WEIGHT- POUNDS ARTICLES
w,as devised. This index expresses the area
of the cross section as a fraction of the area
of a circle with the same circumference.
Again, an elliptical shape is assumed and
the circumference of the elipse is
approxi-IThlt(’(l:
.a2 + j)2
C = w
2ab
-The glottis and tracheal origin were
sounded with urethral dilators
(
2 Frgrada-tions
)
in seven of the infant specimens andresults are sllO\Vfl in Table II. In each case
the dilator which fit snugly but was not
tight was recorded. In all cases the glottis
accepted a dilator at least 4 Fr larger than
the tracheal origin. It is further of interest
that the sounded diameter exceeded the
di-aineter measured on the projections by 1.1
to I .9 mm, showing the considerable
plialil-ity remaining even in autopsy specimeiis.
DISCUSSION
Certain qualitative observations are of
interest. Because of the irregular contours
of the larynx and the rather pliable
charac-tT-Fe --r , T , , - g1
p-_..,_...._.
FIG. 1. This is a black and white print of a color
slide made of specimen number 77-66. The slide
s’as projected1 and the incorporated scale was used
to obtain the nicasurements ivliicli are oi
Table I.
OQ
. o’
?r-r- -‘
-
- - ..-- ,;--‘-: - - ---O- IfPtAn1 77.’
FIG. 2. A black and white print of the color slide made of the sectionedl specinlen shown in Figure 1. This slide was used to obtain cross-section
measur(nlcnts.
Fic. 3. This is a plot of the length of trachea in millimeters aS a function of l)O(l\’ weight in pounds. Using a log scale for body weight gives it linear
Child
Trachea
Length (in in) JJ’eight
(iii)
Tracheal Origin
Size (In in)
Area (1,1,112) I Specimen Number 13-66 1-61 11A62 10A(i’2 44-61 39A6i2 139-60 I 1-61 75A65 13A65 4A61 31A63 4A64 17A65 77-66 50A65 19A66 34A63 11A66 199-66 150-65 41A66 1’3-6.5 68-65 height Age (in.) Hours 14.0 Flours 12.4 26da 18.0 2da 18.0 ll2hr 18.4 8da 21.2 9da 121.4 241ir 19.5 Swk 20.5 2mo 21.4 4.51410 22.5 4nio 21.4 4mo 25.4 4nso 125.5 5mo 28.5
I yr 129.0
2vr -Syr 40.6 4yr 36.5 lOyr 54.5 9yr 53.0 1Oyr -lSyr 61.8 I4yr 56.0 I.8 3.1 4.7 5.1 5.6 7.0 7.12 7.4 7.8 8.3 8.4 8.8 14.2 15.2 16.1 125 312 40 50 55 69 91 130 155 1212.0 129.0 312.0 312.0 129.0 34.0 38.0 312.0 37.0 39.0 41.0 37.0 46.0 46.0 45.0 48.0 54.0 58.0 54.0 71.0 66.0 69.0 74.0 76.0 2.0X12.6
12.6X3 .6
3.9X4.l
4.0X4 .0
4.0X4.4
3.9X4 .0
4.1XS.1
3.8X3.9
3.6X4.6
4.5X4.7
4.7X5 .0
4.4X4.4 4.1X4.1 4.4X4.5 4.5X5.9 4.9X4.9 5.8X6.6 6.8X7.0 6.9X6.9 8.12X 10.12 8.4X9.4 6.9X8.0 11.6X11 .8 11.1X112.1 4.08 7.34 12.55
12 .5.5 13.812 12.126 16.41 11.65 13.00 16.60 18.46 15.120 13.120 15.56 120.86 18 .86 30.10 37.4 37.4 65.7 62.0 43.3 107.5 105.4 Mi(l Trachea Size’ .lrea (iii,,:) (,,,,,,2)
1.’3X12.8 12.86 .76
2.lX4i) 6.60 .812
3.1X3.12 i 7.78 : .99
2.9X4.H 1(1.912 .88
12.6X4.0 8.16 .91
2.8X4.0 8.8(1 .94
2.4X5.12 9.81) .812
2.6X4.6 9.4(1 .86
3.6X5.4 15.26 .912
3.7X4.9 14.124 .96
2.9X.5.5 12.53 .812
3.5X4.I 112.10 .97
4.1X3.3 17.08 .97
4.3X5.3 18.58 .97
3.9X6.12 19.0() .88
4.0X6.7 21.4)6 .89
.5.1X6.6 26.46 .97
6.0X9.0 412.5 .912
.5.3X7.9 32.9 .90
8.OXII.2 7(1.4 .95
8.0X12.0 75.4 .912
7.9X8.12 50.1) 1.00
7.SXI1.1 68.6 .912
13.6X14.1 15(1.6 1.00
.97 .95 .99 I .00 .99 1 .00 .98 I.(10
.95 1.00 I .00 1.00 I .00 1 .00 .96 1.00 .99 1.00
1.(10 .98 .99 .99 I .00 I (8) Sounded Diameter Autopxy Number 75A65 Body IVeight (ib) 7.8 13A65 8.3 48A64 14.12 17A65 15.12 50A65 125 19A66 312 34A63 40 Glotti.s Snug Fit (Fr) Tracheal Origin Sung Fit (Fr) 1212 1212 1212 1212 26 126 Diameter H Soniuled Exceeds Projection Diai,ieter by (iii in) I .9 I .4 I .9 I .6 I .1 1.1 1.1 18 18 18 18 is 24 338 TABLE I
TRACHEAL LENGTh AND CROSS-SECTION AREAS IN ChILDREN OF \ARIOIS Ac
ter of the glottis, no method was devised to in all specimens tended to a circular cross
give quantitative comparison with the tra- section. As the mid-trachea is approached,
cheal measurements. As has been noted, the there is an anterior-posterior flattening
larynx seems to consistenfly funnel down to which yields a more elliptical section. From
the opening diameter of the trachea, which the mid-trachea to the carina, the section
TABLE II
I00
80
6O
LU
40
20
CROSS-3 ECT ION
AREA 0F TRACHEA
AT ORiGIN //////
,7/
%do
ISO
0 50
8 ACE-YERS
)50
I
I-(5
2
La
0
IOo
WEtCHT- POUNDS
Fic. 5. Length and cross-section area of the
trachea are plotted on the same graft as a
func-tion of body weight to illustrate the difference in growth functions.
I.Ows . * x *
9 ROUNDNESS INDEY
. OPICIN OF TRCHEfr
.8 5:0 ,00 ISO
WEIGHT- POUNDS
Fic. 6. A scattergram illustrating the deviation
from round cross section in the tracheal origin.
ARTICLES
rounds out again l)Ut flares into the right
and left bronchi as the carina is
ap-proached. The right bronchus is
consis-tently larger than the left and comes off the
trachea at a lesser angle. Figures 1 and 2
il-liistrate these relationships.
\Veight of the child was chosen over age
and body length as the index of growth
since this parameter gave the best
correla-tion and the most nearly linear relationship.
Clinical usage also favors weight as a more
accurate and readily available measure.
Specimen number 11-61, which would seem
to show better correlation with age than
weight, was an anencephalic monster and
the only specimen showing a congenital
ab-normality.
Length of trachea from larynx to carina
is plotted in Figure 3 against the logarithm
of the weight, yielding approximately a first
degree relationship:
L = 30 (log w) + 10
where w is weight in pounds; L is length in
millimeters. An age scale is added to Figure
3 to show the approximate relationship with
age. In Figure 4 the cross-sectional area of
the origin of the trachea is plotted against
the weight
(
an approximate age scale isadded for reference). The following first
de-gree equation evolves.
A0.7w+8
where A is cross section area in square
mu-limeters; W is weight in pounds.
That the growth rate for the length of the
trachea outstrips the cross-section growth in
the first year of life is shown in Figure 5.
After the first year the tracheal growth rate
falls below that of the cross section and at
about puberty recovers the newborn ratio
of length to cross section. This increase in
length adds to the resistance to airflow and
causes any tracheal narrowing, as from
mu-cosal edema, to markedly increase the work
of respiration. This anatomic effect reaches
its peak at about age 1 year, paralleling the
age group clinically observed to be most
ef-fected by respiratory infection.
In Figures 6 and 7 the roundness index
for the tracheal origin and the mid-trachea
4
! 3 6 8 AcRE-YEARS
50 O0
WEIGI4T- POUNDS
Fie. 4. A plot of the cross-section area of the tracheal origin as a function of body weight.
I.0
ROUNDNESS INDEX
t’WD- TRACHEA
WEIGHT- POUNDS
Fic. 7. A scattergram illustrating the deviation
from round cross section in the mid-trachea.
are plotted against the child’s weight. The
marked scatter fits no curve but reveals
some interesting conditions. For each
speci-men the tracheal opening was more “round”
than the mid-trachea. Flattening, although
not always great in the newborn, seems to
decrease with age. Flattened cross sections
are much more susceptible to impaired area
from mucosal edema. This anatomic
ar-rangement may contribute to the severe
re-spiratory distress from infection seen only
in some children but which improves as the
child grows.
Endotracheal anesthesia in children has
become more common and has led to
con-siderable clinical experience. Selection of
tube diameter aims at using the largest
di-ameter which fits easily into the trachea.
Unnecessarily small tubes increase dead
space and resistance. Carzon, et al.
esti-mate that an adult airway must have at
least a 10 mm tube to avoid increasing
resis-tance over mouth breathing. The Cole tube,
which is an oversize tube which funnels
down to a short segment of endotracheal
TABLE III
CLINICAL GUIDES FOR TUBE SIZE
Body Weight
(ib)
Tube Size (Fr)
5-7 14-18
50 124-126
tube of specified size, has been devised to
ensure proper positioning of the tube,
pre-vent excessive movement during anesthesia,
and create a snug fit in the glottis. The
en-dotracheal portion of the Cole tubes varies
in length from 28 mm to 35 mm in the
col-lection on hand in our hospital. Reference to
Table I shows that the tubes with shorter
endotracheal segments should be used for
children under S lb and that 28 mm tubes
would be safest for children of this size.
Rapid growth in length during the first
years makes length a less critical
consider-ation after age 1 year.
Tube size by clinical experience has been
found to be better estimated by weight
than age. The clinical guides used at our
in-stitution are shown in Table III. Reference
to Table
II shows that the sounded sizes ofthe specimens in this study confirm these
estimates.
Instrument catalogs0 list 3.0 mm
broncho-scopes as adequate for the premature
new-born and 3.5 mm scopes as suitable for
larger newborns. Again, this clinical
obser-vation is readily confirmed by reference to
Table I, which shows that these sizes would
be loose in all but the 3 lb premature infant,
and that only the 1.8 lb premature infant
would not accept the smaller bronchoscope
at all.
Any attempt to apply the absolute
mea-surements on autopsy material to living
children is subject to caution. It is
well-known that the carina lies a full interspace
lower in the chest in the live child than it
does in autopsy specimens. However, the
growth relationships should not be altered
by autopsy measurements, nor should
clini-cal use of the measurements given be
pre-cluded if proper allowance is made for
pos-sible necropsy changes.
REFERENCES
1. Gillespie, N. A.: Endotracheal Anesthesia.
Mad-ison, Wisconsin: University of Wisconsin
Press, p. 81, 1941.
0 For example, Pilling Armamentanium of
Endo-scopic Instruments, p. 29, 1962. George Pilling and
BIRTH WEIGHT OF NEWBORN INFANTS ACCORDING TO DR. JAMES KENNEDY IN 1825 2. Cillespie, N. A. : Endotracheal Anesthesia.
Mad-iSOI1, \\iscOnsin : University of Wisconsin
Press, p. 150, 1941.
3. Schellinger. R. IL : The length of the airway to the bifurcation of the trachea. Anesthesiology, 25:169, 1964.
4. Benson, C. D., Mustard, \V. T., Ravitch, M. M.,
Snyder, \V. H., and Welch, K. J.: Pediatric
SLlrger\’. Chicago: Year Book Medical Publishers, Inc., p. 208, 1962.
5. Schaeffer, J. P., ed. : Morris’ Human Anatomy.
New York: The Blakiston Co., p. 1401, 1951.
6. Altman, P. L., Gibson, J. F., Jr., and Wang,
C. C., compilers: Handbook of Respiration.
Philadelphia: W. B. Saunders Co., pp. 18-19, 1958.
7. Garzon, A., Seltzer, B., Lichtenstein, S., and
Karlson, K. : Influence of tracheostomy can-nula size on work of breathing. Ann. Surg.,
162:315, 1965.
Erroneously high values for the birth weight
of newborn infants were given by many eminent
physicians as late as the middle of the last cen-tury.’
Writing in 1825, Dr. James Kennedy of
Glas-gow states:
Some new-born children have been known to be
sixteell :-almost all the individuals of two large
families were more than fifteen;-my own
expeni-ence has furnished me with examples of two infants
who were nineteen, one who was twenty, and
an-other who had two teeth and was twenty-two
poUfl(15, at the time of their passing from the foetal
state-Such facts are curious : -they may after-wards come to be useful illustrations of the natural
history’ of man.
NOTED BY T.E.C., Jii., M.D.
REFERENCES
1. Cone, T. E., Jr. : De pondere infantum recens
natorum : The history of weighing the
new-born infant. PEDIATRICS, 28:490, 1961. 2. Kennedy, J.: Instructions to Mothers and Nurses
on the Management of Children in Health and
Disease. Glasgow: Richard Griffin and Co.,
