Measurement of the separate volume changes of rib cage and abdomen during breathing

16 Pages·2003·3.32 MB·English

Measurement of the separate volume
changes of rib cage and abdomen during breathing
KIM10 KONNO AND JERE MEAD
Department of Physiology, Harvard School of Public Health,
Boston, Massachusetts
KONNO, KIMIO, AND JERE MEAD. Measurement of the separate parts of the body outside the lung which share changes
volume changes of rib cage and abdomen during breathing. J. Appl. in the volume of the lungs. Its surface is coextensive with
Physiol. 22(3) : 407-422. I 967 .-Changes in the antero- that of the torso. Anatomically, this surface has two sub-
posterior diameters of the rib cage and abdomen were re- divisions: the “rib cage” and the “abdomen’‘-the di-
corded on the axes of a direct-writing X-Y recorder both during
viding line between them being the costal margin. D
relaxation against a closed airway at different lung volumes, Viewed in terms of motion of the surface, the chest wall ow
and while, at fixed lung volumes, displacements of volume were appears to have functional separation between the rib nloa
made voluntarily back and forth between the rib cage and d
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relationships for the rib cage and abdomen, and this in turn erable independence of motion. For example, it is easy h
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tween the rib cage and abdomen was demonstrated under iso- moving the other inward. It occurred to us that we could .ph
volume conditions, while a high degree of volume indepen- take advantage both of the apparently unitary behavior ysio
dence between these parts was demonstrated when total volume of the rib cage and abdomen and of the ability to move log
change was unconstrained. During breathing the chest wall one or the other independently, to measure their volume y.o
deviated substantially from its passive configuration. In six rg
subjects the abdomen accounted for about half or more of the changes separately. by/
tidal volume, but much less than half of the vital capacity, in 10
both postures. THEORY .22
0
.3
2
mechanics of breathing; chest-wall mechanics Our method is based on the relationships between .24
linear motion and volume displacement. These are com- 7 o
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mon to all mechanical systems in which volumes are A
p
displaced. We begin by defining some terms. ril 3
C , 2
OMPARED TO PRESENT KNOWLEDGE of pulmonary me- Dejnition of Terms 017
chanics relatively little is known about the mechanics of
the chest wall. The major difficulties have been two: The number of degrees of freedom is defined by the
first, the problem of measuring the volumes displaced by number of independent variables. A single independent
motions of different parts of the chest wall, and second, variable corresponds to a single degree of freedom.
the problem of measuring the pressures applied to and A ‘cpart” is a mechanism which displaces volume as it
by these parts. Recently, Agostoni and Rahn (2) showed moves and for which volume change is the only inde-
that esophageal and gastric pressures could be used to pendent variable with respect to its motion. A part has
estimate the pressure differences across the major struc- I df.
tures of the chest wall-the rib cage, diaphragm, and A CCsy stem” is an arrangement of parts. An open
abdominal wall. As yet, however, there has been no system can exchange volume with its surroundings. A
comparably satisfactory method for estimating the vol- closed system is an arrangement of parts which together
ume displacements of these parts. This paper presents a have a constant volume so that all volume changes take
method for measuring separately the volume changes of place among the parts.
two of them: the rib cage and abdominal wall. Relationshz) between number of parts and number of degrees
The “chest wall,” in respiratory terms, includes all of freedom in open and closed systems. The number of degrees
of freedom in a particular system depends on how its
Received for publication 7 March 1966. parts are arranged an on whether it is closed or open.
407
K. KONNO AND J. MEAD
PART I PART a
3
VOLUME OF
PART I
3
MOTION MOTION
0 2
I
0 I 2 D
o
VOLUME w
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lo
0 a
C d
e
VOLUME OF TOTAL SYSTEM: 5 *UNITS d fro
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FIG. I. A. volume relationships of a system with two parts, I lo
g
MOTION OF 3 and II, operating as a closed system at various total volumes. The y
PART I total volume within the system, shown by the diagonal lines with .org
the negative slope of I, varies from o to 5 arbitrary volume units. b/
y
The volume change of each part also varies from o to 5. B. 1
hypothetical relationships between volume changes of parts I and 0.2
II and some aspect of their motions. The volume change of part I 20
varied from o to 3 and that of part II from o to 2, so that the total .32
potential volume change of the system is 5 units. The motion of .2
4
each part varies from o to 5 arbitrary units of motion. The lines 7 o
are seen to be continuous monotonic increasing functions. These n A
functional relationships are arbitrary. C: relative motion relation- p
MOTION OF ships between parts I and II at different total volumes of the closed ril 3
FART l.i system. , 20
1
7
First concerning the arrangement, parts interconnected A closed system with three parts can have no more
so that their volume changes are equal are said to be than 2 df. Once the volume of one part is determined
arranged in series. All such serial arrangements have a only a single degree of freedom remains. The same
single degree of freedom. reasoning leads to the conclusion that the number of
The number of degrees of freedom of an open system degrees of freedom of a closed system is one less than that
equals the number of serial arrangements it is made up of the same system when open.
of which operate independently. The number of degrees
of freedom in a closed system is equal to the number of Degrees of Freedom of the Chest Wall
degrees of freedom in the same system when open, less
I. This may be seen from the following: We have assumed that, to a useful approximation, the
A closed system with a single part, or a single arrange- chest wall has two moving parts-the rib cage and abdo-
ment of parts in series, cannot move; accordingly, it has men. During ordinary breathing the system is open and
no independent variable and o df. has 2 df. When one breathes from a spirometer the system
A closed system with two parts can have no more than is closed, but a part, the spirometer, has been added and
I df. Any volume change of one part must be equal and the system again has 2 df. When the tubing leading to
opposite to that of the other. There is, at most, one inde- the spirometer is closed, however, the chest wall becomes
pendent variable and I df. a closed system with two parts, and hence, a single degree
SEPARATE VOLUME CHANGES OF RIB CAGE AND ABDOMEN 409
the second approach in conjunction with ideas developed
in the first part of this section, along the following lines.
Figure IA presents volume relationships of an open
TO SPIROMETER
system with two parts and 2 df. It may be closed at
different total volumes, in which case the system has a
single degree of freedom and the relationships between
PING-PONG BALL the volumes of the parts are single straight lines with
slopes of - I, as shown.
Figure I B presents hypothetical relationships between
the volume of the parts and some aspect of their motions.
TRANSDUCERd-
TO VACUUM PUMP The functional relationships are arbitrary but share these
characteristics : each is a monotonic increasing function,
i.e., volume and motion are represented as increasing
together.
Figure I C describes the relationships between the mo-
tions of the two parts when the system is closed at differ-
ent total volumes. The isovolume lines were constructed
L I by plotting pairs of points from Fig. IB which had vol-
FIG. 2. Method for measuring the anteroposterior motion of the umes summing to the total volume in question. These
anterior wall of the rib cage and abdomen in standing subjects. The
lines are seen to be monotonic decreasing functions.
changes in anteroposterior diameters were transmitted by means of
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threads to the cores (823-3PI, Sanborn) within linear differential Our approach is essentially the inverse of the process o
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transducers (535 DT 1000 Bm, Sanborn). The end of the thread just described. We obtain relationships corresponding to n
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was fixed to the body surface by means of a partially evacuated those in Fig. I C experimentally. From these we construct ad
Ping-Pong ball which had been dented in from opposite sides and the functional relationships between motion and volume ed
wenhdic h of wthaes tshereaaledd wtoa s thec onsnkeinc tedw ith toc laay , weigahst show(cna . iIOn Bg). . TThhee oduitsstiodre- change. We then use these to estimate the separate from
tion of anteroposterior motion due to the soft tissue at the point volume changes of the parts. http
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the right nipple line and midline at the nipple level for the rib correspond to motions of one part with the other part iolo
cage and midway between the same lines at the level of the fixed. This is also graphically equivalent to removing one gy
umbilicus for the abdomen. The pulley and the transducer were part and, hence, to reducing the number of degrees of .org
placed together on a plastic plate. Transducers were linear in freedom to one. The total volume change, as measured by b/
rreessppoonnssee cohvaerr acteari striacns ge ooff th&e5 mcema surfirnogm thsyes temm idpwoseirteio n, adequaaten d thfoer spirometer, corresponds to the volume change of the part y 10.2
our purpose. The signal from the rib cage was displayed on the I’ in question, which, in turn, corresponds to the motion 20
axis and that from the abdomen on the X axis of a direct-writing measured along the coordinate between the two lines. By .3
2
X-Y recorder (Autograph model # 135, Mosley). An aneroid repeating this process at known increments of total vol- .24
manometer was used for monitoring mouth pressure. Changes in 7 o
lung volume were measured with a spirometer (9 liters, Collins). n
A
p
of freedom. In this instance any volume change of the ril 3
rib cage must be equal and opposite to that of the abdo- , 20
1
men. 7
Relationships Between Volume Cflange of Parts
and Other Aspects of Their Motion
Since, as defined, all motions of parts are expressed
with a single independent variable, it follows that all
motions of points within parts must bear fixed relation-
ships to volume change. When such a relationship is
known, volume change can be estimated from measure-
ments of motions of a single point within the part in
question. A recording spirometer is an instance of this:
its recording pen moves in fixed relationship to its change
in volume.
There are two ways to arrive at the relationship be-
FIG. 3. The isovolume maneuver. At constant lung volume the
tween motion and volume change: theoretically, by
subject shifts as much volume as possible from rib cage to abdomen
analysis of the geometry of the part, and experimentally,
in the picture in the left and from abdomen to rib cage in the right.
by displacing known volumes into the part. We have used In the middle picture the subject is relaxed.
4’0 K. KONNO AND J. MEAD
TABLE I. Physical characteristics, values of vital vising a pneumograph adequately free from artifacts,
capacity, and total lung capacity presumably due to soft tissue distortion, and chose instead
to measure changes in anteroposterior diameters. These
Vital Total Lung
Capacity, Capacitf, have the advantage of being among the most prominent
Subj Age, yr Height, cm Weight, kg liters BTPS liters BTPS
EB - 3’ I65 7= 4.87 5.80 motions of breathing and the further advantage of being
KK 32 I73 56 4.40 5*70 easy to record without distortion.
DL 32 785 73 6.10 7.32 Our method of recording is shown in Fig. 2. The
PM 33 ‘75 82.2 5*23 7.40 output of the transducers ran to the axes of a direct-
JM 42 ‘87 86 6.80 8.97 writing X-Y recorder. We used a spirometer to measure
FS 32 773 59.3 4.90 6.19
volumes and these we expressed as percent of the vital
ume the relationships between the volume change of the capacity (VC). During the isovolume maneuver, which
part and its motion can be derived. The same process is described in the next paragraph, mouth pressure was
can be repeated along the other coordinate to derive a indicated on an aneroid manometer in the view of the
similar relationship for the other part. (It should be noted subject. He was instructed to maintain mouth pressure
that this additional step is redundant. Since the total between rt20 cm Hz0 during the maneuver.
volume change is known, once that of one of the two
Isovolume Maneuver
parts is known as well, the volume change of the other
part may be obtained by subtraction. The second vol- With the tubing to the spirometer closed off, the
ume-motion relationship adds nothing new-it merely subject moved as much volume as possible back and
serves to check the estimate made by subtraction.) forth between the rib cage and abdomen without flexing
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If the rib cage and abdomen behave as parts, the or extending the spine. Figure 3 shows an example of o
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volume of one should not affect the volume-motion rela- this. Lung volume is the same in the three pictures. In nlo
tionship of the other. This can be tested experimentally the middle one the subject is relaxed. On the right, he ad
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along different coordinates of the relative motion dia- possible from his rib cage into his abdomen. This maneu- http
grams). ver was accomplished slowly, taking about 5-10 set to ://ja
The graphs of relative motions of the rib cage and complete one “cycle.” p.p
abdomen at different fixed total volumes will be used for The subject first practiced the maneuver while watch- hy
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three purposes : r) to test our assumption that the chest ing the X-Y recording. All subsequent recordings were iolo
wall has, basically, two moving parts (this will be re- obtained with the recorder out of the subject’s field of gy
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flected in the extent to which volume isopleths are view. During the isovolume maneuver, and during all rg
single-valued) ; 2) to test the independence of the volume- other measurements of chest-wall diameters, the subjects by/
motion relationships, along lines described in the pre- tried to maintain contact at fixed points along the spine 10
.2
ceding paragraph; and 3) to estimate the separate and in this way reduced flexion and extension of the 2
0
volume contributions of the rib cage and abdomen spine. Vital capacities were thereby reduced approxi- .32
during breathing. mately 5 %. Some subjects were able to perform the .24
7
maneuver satisfactorily at their first try. Others could do o
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METHODS so after a little practice. All had been subjects in respira- A
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We intended initially to measure motion in terms of tory experiments many times. Some of their physical ril 3
changes in circumference. We were unsuccessful in de- characteristics are given in Table I. , 20
1
7
STANDING
FIG. 4. Relative anteroposterior mo-
tions within the rib cage in the standing
and supine posture. The small open
circles indicate the end-expiratory level
(FRC) and the continuous lines and the
broken lines indicate the tracings during
isovolume maneuver and vital capacity
maneuver, respectively. The motion of
the reference point (midway between
the right nipple line and midline at the
nipple level) is along the Y axis.
SEPlWATE VOLUME CHL4NGES OF RIB CAGE AND ABDOMEN
STANDING SUPINE
FIG. 5. Relative anteroposterior mo-
tions within the abdomen in the stand-
ing and supine posture. The reference
point is midway between the same lines
as for the rib cage at the level of the
umbilicus.
RESULTS ward the neck the motions were decreased relative to
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these of the reference point while the opposite was the o
Relative Motions Within Parts w
case near the costal margin, particularly below FRC. nlo
a
According to our assumption that the rib cage and Anteroposterior motions of abdomen. Figure 5 shows a rep- d
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abdomen each have single degrees of freedom, all antero- resentative example of tracings of relative anteroposterior fro
posterior motions within these parts should be single- motions of the abdomen. The scale is identical to that of m
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valued functions of their volumes, and, accordingly, Fig. 4, and again, motion of the reference point is along ttp
should be single-valued functions of each other. We made the Y axis. It is apparent that the abdomen moves less ://ja
simultaneous measurements of anteroposterior motions as a unit than the rib cage. This was strikingly the case p.p
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at different points on the surface of the anterior chest for all the subjects. The only points which move nearly ys
wall during quiet breathing, vital capacity maneuvers as single-valued functions of the reference point are those iolo
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and isovolume maneuvers at resting end-expiratory lung at the same level (b3 and c3). The points nearest the costal y.o
volume, both in the standing and supine postures in all margins moved much less during the isovolume maneu- rg
of our subjects. The distribution of the points of measure- vers than during a vital capacity. These points were very by/
1
ment is shown in Figs. 4 and 5. For all measurements of nearly at the border line between the rib cage and 0
.2
the rib cage the reference point was rnidway between the abdomen. Such points would be expected to stay nearly 20
right nipple line and midline at the nipple level and for fixed during the isovolume maneuver but to move when .32
.2
all measurements of the abdomen the reference was both regions changed volume in the same direction, as 4
7
midway between the same lines as for the rib cage, at the during the vital capacity maneuver. on
A
level of the umbilicus. An upward deflection along the Antero;Dosterior and transverse motions of the rib cage during p
Y axis occurred with anterior movement of the reference relaxation at the extremes of lung volumes. A single degree of ril 3
point; deflection to the right along the .X axis occurred freedom dictates a fixed shape at a particular volume. , 20
1
with anterior movement at the test site. We anticipated that changes in the mechanical properties 7
Anteroposterior motions of the rib cage. Figure 4 shows a of the walls of the rib cage and abdomen attending
representative example of tracings of relative anteropos- changes in the degree of muscular contraction, and
terior motions at different points on the anterior wall of changes in the pressure differences across their walls,
the rib cage in the standing and supine posture. The would produce changes in the shape of these structures
tracings are centered at the point sampled. The motion and, hence, introduce additional degrees of freedom.
of the reference point is along the Y axis. The tracings Under the conditions of our experiments these changes
are representative in the following respects: Over the would be greatest at the extremes of lung volume as
mid rib cage points moved relative to the reference point subjects passed from the active state-airways open-to
along nearly single lines for both vital capacity and relaxation against a closed glottis. At both IOO 70 of
isovolume maneuvers. These lines very nearly superim- vital capacity and at residual volume (RV), in the active
posed and had slopes of approximately + I. We conclude state, muscular contraction is nearly maximal. At IOO 70
that a substantial part of the anterior rib cage not only of VC pleural pressure is about -30 cm Hz0 and at
operated with a single degree of freedom, but moved RV, approximately atmospheric. With relaxation against
equally, in the manner of a piston. Near the upper and a closed airway, pleural pressure rises some 40 cm Hz0
lower margins the tracings tended to be more looped and at IOO 7c VC and falls by almost the same amount at
the two maneuvers were less nearly superimposed. To- RV. Thus at high lung volume as the subject relaxes
K. KONNO AND J. MEAD
Subj A-P(a), cm Trans (a), cm A-P(r), cm Trans (r), cm AA-P, cm ATrans, cm A (a), cm2 A (r), cm2 AA, cm2
Nipple Level
TLC EB 25.6 33.6 25.2 34-o - 037 +.32 675 669 +6
KK lg.6 28.5 19.0 28.8 - .56 +*30 439 430 +9
DL 24.0 32.6 23.0 33.1 -1 .o +.50 615 596 +19
PM 25.3 33.6 24-7 34.1 - .60 +.52 667 660 +7
JM 28.7 37-o 28.0 37.2 - .63 +.25 835 816 +19
FS 23.2 31.5 22.0 32.2 -1 .I2 +*77 572 556 +16
Mean 24.40 32.80 23 -65 33.23 - .71 +a44 633 -8 621.2 +12.6
RV EB 24-4 33-o 23.9 33.3 - -47 +*37 632 621 +I1
KK 17.4 27.8 17.0 28.0 - -37 +.22 380 374 +6
DL 20.6 32. I I9*3 32.6 -I .31 +.52 520 49’ +29
PM 23.0 33-o 22. I 33.2 - -94 +.21 596 575 +21
JM 25.1 34.5 24.7 34-7 - -37 +.21 677 673 +4
FS 20.5 30.7 lg.8 31.3 - .65 +.65 492 486 +6
Mean 21.83 31.85 21.13 32.21 - .685 + -363 549.5 536.4 +12.g
Xiphoid Level Do
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TLC EKBK 2‘95..91 3291.0-4 2148..67 330’ .09 7 -- -. 4138 ++.*130 641566 641425 ++4I1 nload
DL 24.0 32.7 23.5 33.4 - .50 +a75 616 615 +I ed
PM 26.0 31.6 25.4 32.2 - .62 +*57 645 634 +I1 fro
JM 29.0 35.2 28.6 33.3 - -37 +.12 804 790 +14 m
FS 23.0 31 .o 22.6 31.2 - -37 +.21 560 554 +6 http
Mean 24.50 31.81 23.90 31.96 - .411 + -341 616. I 608.3 -f-7.8 ://jap
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RV ER 23.4 30.5 22.9 31.1 - -45 +.60 560 556 +4 ys
KK 17.8 27.1 ‘7.3 27-4 - 05 +.25 383 369 +I4 iolo
DL 20.7 31.5 19.9 32.5 - I .81 +1 .o 513 506 +7 gy
JPMM 2243..08 3239.*67 2242..35 3330..82 +-I -.2255 ++.*250o 654563 654343 ++22 0 b.org/
FS lg.8 30.0 ‘9.9 29.7 + .I2 -.25 466 462 +4 y 1
0
.2
Mean 21.58 30.40 21.13 30.78 - .6go -t-.38 520. I 511.6 He5 20
.3
A-P indicates anteroposterior diamerer. 1 I rans lnalcates transverse diameter. A .m a 1. icare.s cross-sectional area and was calcu- 2.2
4
ltaivteedly . asAs uminindgic ates the driifbfe recnacgee asb eatwn eeen llipse.a ctive(a ) aanndd r(er)l axeidn dicates tate. active state (airway open) and relaxed state (airway closed), respec- 7 on
A
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the rib cage is subjected to an increase in transmural ner shown in Fig. 2. For transverse motions we used ril 3
pressure while at low volumes it is subjected to a de- two such devices- one at each side-and added their , 20
1
crease in transmural pressure. To the extent that the outputs with a mixing circuit. 7
cross section of the rib cage is elliptical, and to the Table 2 presents individual values and Fig. 6 averages
extent that the influence of changing muscle forces can for anteroposterior and transverse diameters of the rib
be neglected, one would expect relaxation at high cage at the extremes of the vital capacity, both as main-
lung volumes to be associated with an increase in the tained with airways open and after relaxation against a
ratio of the minor to the major diameter, i.e., an in- closed airway. The pattern was similar, with minor
crease in the anteroposterior diameter relative to the exceptions, in all individuals. Over the vital capacity
transverse diameter. Relaxation at RV should produce range both diameters increased as lung volume increased
the opposite change. -the anteroposterior diameters approximately 3 cm and
To examine these possibilities we measured transverse the transverse diameters about one-third that amount.
and anteroposterior diameters at two levels of the rib During relaxation at both maximum and minimum
cage at the extremes of lung volume in the standing volumes the diameters changed in the opposite sense;
posture. We measured absolute diameters in the active the anteroposterior diameter decreased while the trans-
state with anthropometrist’s calipers (means of three verse diameter increased.
determinations were used) and changes in diameters The changes at RV were in the direction to be ex-
electrically with linear transducers. For anteroposterior petted on the basis of the fall in pleural pressure ac-
motions the contralateral poi nt w ‘as fixed an d only the companying relaxation : a decrease in transmural
motion of th e anterior surface was measured in the man- pressure would be expected to reduce the anteroposterior
SEPARATE VOLUME CHANGES OF RIB CAGE AND ABDOMEN
413
NIPPLE LEVEL XIWOID LEVEL
25
FIG. 6. Anteroposterior and transverse diameters
of the rib cage during relaxation at the extremes of
lung volume in the standing posture. Closed and open
circles indicate the active state (airway open) and the
RV relaxed state (airway closed), respectively.
20
TRANSVERSE DIAMETER 1 cm
1 191 , , 1
34
30 31 32 33 30 31 32 33
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DL A-P MOTION I NSP,O F ABDOMEN FS DL A-P MOTIONI NSP OF ABDOM0E N FS 0 .physiolo
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FIG. 7. Individual relative motion isovolume diagrams for six relaxed configuration of the chest wall in terms of its anteroposterior 7
subjects in the standing and supine postures. The anteroposterior diameters and the continuous lines indicate isovolume lines at
motion of the rib cage was measured from the reference point different fixed lung volumes. The light dotted outermost envelope
shown in Fig. 4 and was displayed on the Y axis. Abdominal in one subject (JM) shows the maximum range of deviation from
motion was measured from the reference point shown in Fig. 5 the relaxed configuration in terms of anteroposterior diameter.
and was displayed on the X axis. Open circles indicate the active The heavy dotted lines indicate the tracings during quiet breathing
state with airway open at the extremes of the lung volume and including the end-expiratory level (FRC).
closed circles indicate the relaxed state. The dashed lines show the
diameter relative to the transverse diameter. At TLC the chest wall does have more than a single degree of
pleural pressure rises during relaxation and the rib cage freedom in particular circumstances. We think that we
is subjected to relative expansion. We reasoned that this have probably examined the furthest departures from a
would tend to make the rib cage more circular in cross single degree of freedom on the part of the rib cage that
section. We observed the opposite, which suggests that existed under the conditions of our experiments: namely,
changes in muscle forces operating within the wall of the the condition in which maximum change in the activity
rib cage or directly on the wall through tissue attach- of the respiratory muscles and the maximum change in
ments override the influence of transmural pressures. transmural pressures occurred. Changes in shape of the
The results given up to this point demonstrate that rib cage as great or greater than these must take place
414 K. KONNO AND J. MEAD
STANDING
FIG. 8. ,4verage relative motion isovolume
diagrams for six subjects; anteroposterior mo-
tions of the rib cage and abdomen are dis-
played on the Y and X axis, respectively. All
motions are expressed as a percent of the total
excursions observed during a vital capacity
maneuver. The solid lines indicate the iso-
pleths at 8oy0, 607& 4oy0, and 2oyo of VC,
based on averages of three points each:
the two extremes of the isopleth and the
relaxation point. Open circles indicate the
relaxed state at the different fixedlung volumes.
The dashed lines indicate the theoretical iso-
pleths at IOO% and RV. The intercepts
(closed triangles) of the dashed line on the
horizontal line indicate theoretical points A - P MOTION OF ABDOMEN
corresponding to 100% VC and RV at the
active state with the airway open. Notice that SUPINE
the deviations of the closed triangles from the
closed circles corresponding to the observed
point at 100% VC and RV are marked in the
supine posture as compared to those in the Do
standing posture. The dotted lines indicate the wn
theoretical isopleths which correspond to loa
volumes obtaining during relaxation at 100% de
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Open squares indicates theoretical points h
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when pleural pressure is changed beyond the limits of against an obstructed airway. Each run was repeated y 1
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ordinary breathing, as during muscular efforts produced more than three times on a given occasion, and the .2
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against a closed airway or during forced breathing. measurements were repeated on a separate occasion with 0.3
an interval of several months. All data presented here 2.2
4
Relative Motions of Rib Cage and Abdomen were based on the latest run. 7 o
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was midway between the right nipple line and the mid- 7
with the over-all areas contained by the extremes of all
line at the nipple level. For the abdomen the point was
isopleths (indicated by the dotted line in one of the
midway between the right nipple line and the midline at
examples) gives an idea of the validity of our assumption
the level of the umbilicus. Rib cage motion was dis-
that the chest wall has basically two moving parts. When
played on the Y axis (diameter increasing in the upward
lung volume is fixed, the relative motions of the rib cage
direction) and abdominal motion on the X axis (diameter
and abdomen are greatly confined and could be reason-
increasing to the right) of the X-Y recorder.
ably well approximated with single lines.
Procedure for obtaining isopleths at diferent fixed lung vol-
The dashed line is drawn through points of relaxation.
umes.* relative motion isovolume diagram. After several quiet Departures from this line indicate the extent to which
breaths the subject inspired room air slowly and maxi-
voluntary action distorts the chest wall from the relaxed
mally and relaxed against an obstructed airway. After a
configuration. (The potential for this distortion is only
few seconds he was allowed to breathe out into the spi-
partially exhibited inasmuch as the subjects were con-
rometer until he reached a volume which corresponded to
strained to the extent of maintaining mouth pressure
80 % VC, where he again relaxed against the closed
airway, and following a pause of a few seconds performed within rt20 cm HzO-except during relaxation at the
the isovolume maneuver. The same sequence was re- volume extremes.)
peated at 60 %, 40 %, and 20 ci: of VC. The subject then In general th e isopleths have similar slopes. In all
expired maximally to residual volume and relaxed cases motion of the abdomen is greater than that of the
SEPARATE VOLUME CHANGES OF RIB CAGE AND ABDOMEN 415
A
0
STANDING
FIG. g. Corrected average relative motion
isovolunle diagrams (for basis of “correction,”
see text). Open circles indicate the relaxed
A- P 14OTION OF ABDOMEN states at the different fixed lung volumes.
SUPINE D
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A- P MOTION OF ABDOMEN 0.2
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rib cage as volume is shifted between them. The total the rib cage as volume is shifted from the rib cage to .3
2
range of anteroposterior motion of the abdomen is some- abdomen and for the isopleths to be curved in the sense .24
7
what greater than that of the rib cage, and is considerably observed. o
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greater than the excursion occurring between the ex- When one adds to these considerations the influence A
p
tremes of lung volume. This is in contrast to the rib cage of gravity, an explanation for the greater degree of curva- ril 3
where the excursion during the vital capacity is very ture of the isopleths in the supine posture may be given. , 2
0
nearly equal to its maximal range of motion. In the standing posture pressures within the abdomen at 17
The isopleths are somewhat curved and, in several the reference level will, in general, be greater than at-
instances, distinctly so in the supine posture. The rela- mospheric and will tend to push the wall outward and
tionship between motion of a surface and the volume increase its convexity. In the supine the pressure within
displaced by it as it moves is constant only if the surface the wall at the reference point will be closer to atmos-
moves like a piston, i.e., without change in shape. Al- pheric and the abdominal wall will tend to become more
though this may be approximately true for the rib cage nearly flat. One would expect on these grounds that the
it is clearly not the case for the abdominal wall. The ratio of anteroposterior motion to volume change would
abdominal wall may be more appropriately likened to a be greater in standing than in supine subjects. If one
loosely stretched elastic membrane. At low lung volumes assumes that the rib cage is less influenced by posture, an
it is nearly flat or even slightly concave, while as it is increased ratio of motion to volume changes for the
displaced outward it becomes increasingly convex. In abdomen would result in an increased ratio of abdominal
such a membrane the ratio of linear motion of points at to rib cage motion as volumes are shifted between them.
the surface to the volumes displaced by the surface tends The decreased slopes of the isopleths in standing as
to be smallest when the surface is most nearly flat and compared to supine subjects is then to be expected.
to increase as the surface becomes more highly curved. Furthermore, to the extent that the degree of curvature
On this basis one would expect the anteroposterior mo- of the abdominal wall changes more with volume change
tion of the abdominal wall to increase relative to that of in the supine posture, which is reasonable, one would
416 K. KONNO AND J. MEAD
STANDING : RI6 - CAGE SUPINE: ABDOMEN
I
0A
80
60
40
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1 L
60 80 100
A - P MOTION OF RIB - CAGE A- P MOTION OF ABDOMEN
FIG. IO. A; volume-motion relationship of the rib cage in the dotted line indicates a linear approximation of the relationship. B.
standing posture. Volume is expressed as percent of VC and motion volume-motion relationship of the abdomen in the standing
D
as percent of total excursion observed during a VC. Closed circles posture. Closed circles correspond to “fixation” of the rib cage at o
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indicate the volume-motion relationship with abdominal motion 40~3 of its total excursion during a VC and open circles to fixation n
“fixed” at 0% of its total motion, i.e., at RV, and open circles at 60% of its total motion. The dotted line indicates a linear loa
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that with abdominal motion fixed at 807~ of its total motion. The approximation of the relationship. e
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expect greater curvilinearity of isopleths, with a tendency ception of RV in the supine posture. We feel that the hm
for the slopes to approach those seen in the standing discrepancy at RV in the supine posture is due mainly ttp
posture as abdominal volume increases. Again, Fig. 7, A to contraction of the rectus abdominus, although we have ://ja
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and B, appear to be consistent with this prediction. nothing more substantial than direct observation of the .p
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The isopleths at different lung volumes are nearly contour of the abdomen on which to base this. ys
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parallel and the spacing of the isopleths is quite uniform. To include the extremes of lung volume in our analysis lo
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This is strikingly the case for diagrams based on averages of relative volume changes we h ave assumed that the y.o
for the six subjects. These are shown in Fig. 8, A and B. theoretical isopleths obtained by extrapolation are cor- brg/
The solid lines are based on averages of three points rect and that deviations from these isopleths reflect ab- y 1
each: the two extremes of the isopleths and the point dur- dominal rather than rib cage distortion. This iS 0.2
2
ing voluntary relaxation. All points are expressed as reasonable on the grounds of the relative rigidity of the 0
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percent of the total excursions observed during a vital rib cage. It should be borne in mind that all estimates 2.2
capacity mane1 Aver. The isopleths are very nearly equidis- of relative volumes of the rib cage and abdomen beyond 47
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tant. This will be more clearly seen when the volume- the range of the directly measured isopleths represent n
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dashed lines are theoretical isopleths which would obtain B, presents the isopleths replotted on the basis of the 0
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at RV and IOO % VC if the spacing of the isopleths were “corrected” abdominal excursion between the volume 7
maintained at these levels, or, in other words, if the extremes.
volume-motion relationships were the same at these vol- Volume-motion relationsi@ of rib cage and abdomen. The
umes as at intermediate ones. The dotted lines are theo- relative motion isovol ume diagram .s were used to con-
retical isopleths corresponding to volumes that would be struct volume-motion rela tionships in the man ner de-
obtained during relaxation at IOO % VC and at RV. scribed in connection with Fig. I. Figure IO, A and B,
(During relaxation against a closed airway at TLC, shows volume-motion relationships of the rib cage and
volume decreases due to gas compression, while during abdomen in the standing posture, derived from the cor-
relaxation against a closed airway at RV, volume in- rected relative motion isovolume diagram (Fig. gA).
creases due to gas expansion.) We have assumed that Volume-motion relationships were obtained at two dif-
deviations of the observed points from the theoretical ferent fixed positions of the other part. Volumes are
isopleths (i.e., of the solid circles from the dashed isopleth expressed as percent of VC and motion as percent of the
and of the open circles from the dotted isopleth) reflect total excursion between the maximal inspiratory and
changes in shape of the rib cage and abdomen associated expiratory levels. Figure IO A shows volume-motion
with maximal muscular contraction in the active state relationships of the rib cage with abdominal motion at
and the substantial transmural pressures in the relaxed o % and 80 70 of its total excursion. The volume-motion
state. In general, the distortions are small with the ex- relationships are closely similar and nearly linear. The