Download Pericardial Pressure during Transverse Acceleration in Dogs without

Pericardial Pressure during Transverse
Acceleration in Dogs without Thoracotomy
By Natalio Banchero, M.D., Wilhelm J. Rutishauser, M.D.,
Anastasios G. Tsakiris, M.D., and Earl H. Wood, M.D., Ph.D.
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ABSTRACT
Intrapericardial pressures were recorded via a saline-filled Teflon catheter
(o. d., 1.3 mm) in 11 anesthetized dogs studied without thoracotomy. Seven
animals were studied before, during, and after 1-min exposures to transverse
accelerations that ranged from 1G (normal gravitational environment) to 7G
when in the supine (+Gj), prone (—Gx), left decubitus (+G V ), and right
decubitus (—Gy) positions. Four additional animals were studied at 1G only,
while in these same body positions. Pressures also were recorded from both
atria, right ventricle, aorta, esophagus, and the potential pleural space. Mean
end-expiratory intrapericardial pressure varied directly with the vertical height
of the recording site in the thorax during all conditions studied, as would be
expected in a hydrostatic system. Transpericardial pressures were not significantly different from zero at all levels of acceleration studied. Transmural
left and right atrial pressures were independent of the height of the recording
site in the thorax and were unchanged during exposures to transverse accelerations that ranged from plus to minus 7GX.
ADDITIONAL KEY WORDS
pulmonary artery to vein shunts
arterial hypoxemia
acceleration
pulmonary mechanics
hemoconcentration
manned space flight
hydrostatic effects of acceleration
• In spite of widespread interest in the influence of the pericardium on cardiac hemodynamics, few measurements of intrapericardial pressure under normal conditions have
been made (1-4). In nearly all studies of pericardial pressure, the sensing tip of the transducer assembly used has been introduced into
the pericardial sac through thoracotomy and
pericardiotomy (1-3). Recently a technique
From the Mayo Clinic and the Mayo Foundation,
Rochester, Minnesota.
This investigation was supported in part by research Grants NsG-327 from the National Aeronautics and Space Administration; AF 33 (567)8899 from the United States Air Force; H-3532 and
FR-00007 from the National Institutes of Health,
U. S. Public Health Service; and CI 10 from the
American Heart Association.
Dr. Banchero and Dr. Tsakiris are Career Investigator Fellows of the American Heart Association. Dr.
Wood is a Career Investigator of the American Heart
Association.
Dr. Rutishauser is a Research Fellow of the Swiss
Academy of Medical Sciences.
Accepted for publication November 9, 1968.
Circulation Rtit.rcb, Vol. XX, J,*M*r, 1967
has been described for measuring intrapericardial pressure in dogs without thoracotomy
(5, 6). This technique was used to study the
intrathoracic pressure relationships that occur
during exposures to transverse acceleration
in different body positions.
Method
Intrapericardial pressures were recorded from
11 mongrel dogs. Anesthesia was effected with
morphine sulfate (3 mg/kg) and sodium pentobarbital (20 mg/kg) and maintained throughout
the experiment by additional doses of pentobarbital administered intravenously when deemed
necessary.
Seven dogs (weight 15.5 to 19.9 kg) were
studied before, during, and after 1-min exposures
to average levels of 2.1, 4.4, and 6.7G forward
( + G J , backward ( - G J , right lateral (+G T )
and left lateral (—GT) acceleration on a centrifuge with a radius of 4.42 m. Four dogs
(weight 13.5 to 15.5 kg) were studied at 1G
(normal gravitational environment) only when in
the supine, prone, left lateral, and right lateral
body positions. Animals were supported in the
four different body positions by plastic half-body
67
66
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casts* described previously (7, 8). Dogs breathed
spontaneously through an endotracheal tube secured by an inflatable cuff.
Pericardial pressures were measured via a no.
4 French, radiopaque, Teflon, bird's-eye opentip catheter introduced percutaneously into the
pericardial space by means of a suprasternal approach developed in this laboratory (6). The
assembly used for the percutaneous introduction
of this pericardial catheter (length, 40 cm; o. d.,
1.3 mm; i. d., 0.7 mm) has been described previously (4, 6). In this study the pericardial
catheter tip was positioned at the ventral aspect
of the heart near the inner surface of the sternum;
however, in 2 animals (dogs 1 and 5) the tip
slipped backward soon after insertion so that pressures were recorded in them from more dorsal
aspects of the pericardial sac.
Pressures were also recorded in other parts of
the cardiovascular system, the pleural space, and
the esophagus. Two no. 6 French Lehman catheters (80 cm long; o.d., 2.0 mm; i.d., 1.2 mm)
and a no. 5 French Lehman catheter (80 cm long;
o.d., 1.7 mm; i.d., 0.9 mm) were introduced percutaneously via the left jugular vein and positioned
so that their tips were in the main pulmonary
artery, the outflow tract of the right ventricle, and
the right atrium, respectively. A no. 6 French, Teflon, open-tip catheter (80 cm long; o.d., 1.9 mm;
i.d., 1.3 mm) was introduced into the left atrium
from the right external jugular vein by a transseptal technique (9). A no. 5 French, Teflon,
bird's-eye, open-tip catheter (100 cm long; o.d.,
1.7 mm; i.d., 1.0 mm) was advanced to the aortic arch via a 16-gauge needle introduced into
the right femoral artery. A nylon catheter (20
cm long; o.d., 1.2 mm; i.d., 0.7 mm) for the
recording of arterial oxygen saturation and dilution curves was introduced percutaneously into
the left femoral artery.
Four Teflon, bird's-eye, open-tip catheters
(60 cm long; o.d., 1.3 mm; i.d., 0.7 mm) were
introduced percutaneously into the potential
pleural space by means of a technique previously
described from this laboratory (6-8). An esophageal catheter (40 cm long; o.d., 3 mm; i.d., 1.5
mm) was placed in the esophagus at the level of
the heart. All catheters were fluid-filled and connected to Model P23D-Statham strain gauges.
In the group of animals exposed to transverse
acceleration, the oxygen saturation of blood from
femoral and pulmonary arteries was continuously
recorded by cuvette oximeters (10). The results
of measurements of pleural pressure and the oxygen saturation of blood are reported elsewhere (7,
10). Atrial, pulmonary artery, and systemic ar'Fabricated and supplied through the courtesy of
David Clark and Company, Worcester, Mass.
BANCHERO, RUTISHAUSER, TSAKIRIS, WOOD
terial pressures, blood oxygen saturation, die contours of arterial dilution curves, and the calculated
cardiac output were normal in all animals at 1G,
thus excluding the presence of practically significant intracardiac or great vessel shunts or other
gross cardiac abnormalities (11, 12).
Lateral and anteroposterior roentgenograms of
the chest were taken at end-expiration (Fig. 1).
In the animals exposed to acceleration, the roentgenograms were taken at 1G and at 55 sec after
the plateau level of acceleration was reached (7).
DP
^ ^ 1
*- Ao
Mid-Ll/t
-LP^PA]
FIGURE 1
Lateral wentgenogram of 1 animal (dog 6) supported
in a half-body cast in the prone position at 1G,
showing the topographic relation of heart, lungs, and
catheters used for simultaneous recording of intrathoracic pressures in a dog without thoracotomy. The
mid-lung coronal plane, indicated by a horizontal
steel wire, was used as a zero reference level. Saline
menisci in the thistle tubes Mt and M3 are also set at
this level. "PerC indicates the catheter in the pericardial space inserted via a suprasternal approach. In
this instance its tip is located in the most ventral
part of the pericardial sac just dorsal to the sternum.
In addition, pressures were recorded from catheters
whose tips were in the right atrium (RA), right ventricle (RV), pulmonary artery (PA), aorta (Ao), and
esophagus (Eso). The catheter marked PV was inserted into the left atrium by transseptal puncture
(via the right external jugular vein) and in this instance advanced so that its tip was just upstream to
the atrial orifice of a pulmonary vein. DP, LP, RP,
and VP are catheters in the pleural space. Note in
this dog the close proximity of the tips of the pericardial and ventral pleural (VP) catheters.
CirCKUlwn Resurcb, Vol XX, Jsmmtry 1967
67
PERICARDIAL PRESSURES IN DOGS
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The position in the centrifuge cockpit of the supporting half-body cast was adjusted so that the
longitudinal marker (steel wire) of the x-ray
cassette matched the mid-lung coronal and the
mid-lung sagittal planes of the dog, respectively (7). The level of intersection of these planes
with the cephalocaudad position of the tricuspid
valve was used as the zero reference point. In
the 4 animals studied at IG, the mid-thoracic
coronal and the mid-thoracic sagittal planes were
used as zero levels when in the supine and prone
and right and left lateral body positions, respectively.
Tntrapericardial pressures were referred to the
level of the catheter tip on the basis of its position (height from zero reference level) measured
from the biplane roentgenograms (7, 8).
Correction for the influence of acceleration on
the catheter-manometer systems was made by the
"thistle tube" technique described elsewhere (7).
The level of acceleration was calculated from the
rate of rotation of the centrifuge (rpm) measured
by a tachometer, and the angle of tilt of the
centrifuge cockpit was recorded from a potentiometer coupled to the axis of the cockpit. Acceleration was also measured by an accelerometer (Statham Model A3-10-350) (7). Recordings
were made simultaneously on two photokymographic cameras (paper widths, 44.5 and 30.5
cm, and speeds, 5.0 and 25.0 mm/sec, respectively) and in parallel on magnetic tape (13).
Intrapericardial pressures reported in this paper were those obtained during runs in which
the angle of tilt of the cockpit was within 1 degree and the resultant acceleration level within
5% of the values during the respective thistletube run used for zero base-line correction. Within these limits the maximal error at the highest
level of acceleration would be less than 3 cm
H,O. Transient high-pressure flushes were used
to check the validity of recorded pressures (7).
No pressure recording with evidence of damping
was measured. The amount of Ringer's fluid introduced by one flush is about 0.02 ml. Periodical
aspirations of pericardial fluid were attempted,
and volumes from a fraction to several milliliters
of clear or blood-tinged fluid could frequently be
obtained both as soon as the catheter was introduced and at intervals during the procedure. Similar flushes were performed for the intravascular
pressures, and only those tracings without evidence of damping were analyzed. At the end of
the experiment, autopsy was performed on all
dogs to verify the position of the catheter tips
and the absence of air within the thorax. No air
was detected in any of the animals in this study.
The maximal dorsal-ventral and lateral dimensions
of the heart and the lungs of these dogs, measured
from the biplane roentgenograms, have been reported previously along with the changes in their
dimensions and topographic relationships produced by acceleration in the four body positions
studied (7).
Results
PERICARDIAL PRESSURES AT IG
Relationships between mean intrapericardial
pressures and vertical positions of the respective catheter tips in the thorax when in the
supine (+G X ), prone (—G*), left lateral
(+G y ) and right lateral (—Gr) body positions
were similar to those observed in a hydrostatic system, that is, changes in pressure of 1 cm
H^.O/cm of vertical distance (Fig. 2, Table
1). This relationship was also observed in
dog 8 in which pressures were recorded simultaneously from two sites in the pericardial
space near the ventral and dorsal margins of
the heart, respectively. In this animal the stepwise withdrawal of one catheter showed a
linear tntrapericardial pressure gradient
of about 1 cm H 2 0/cm of vertical distance
(Fig. 2). The same relationship was maintained when changes in pericardial pressure
were produced by injection or withdrawal of
different amounts of Ringer's solution into the
pericardial sac while pericardial pressures
TABLE 1
Mean Intrapericardial Pressure Recorded at IG When Dogs Were in Different Body Positions
Body position
Supine ( + 1GX)
Prone ( - 1 C J
Left lateral
decubitus (+1GV)
Right lateral
decubihis ( - l G y )
#
Mean values from 7 dogs ± 1 SD.
CircuUiion Rtsurcb, Vol. XX, ],nu*rj 1967
Verticil distance*
from mid-lunf plane (cm)
Pressure*
(cm HiO)
3.8 ±1.6
—4.1 ± 1.4
-5.9 ± 3.7
0.6 ±2.1
-1.3 ±2.3
-5.3 ±3.1
—0.7 ± 2.8
-3.0 ±2.1
BANCHERO, RUTISHAUSER, TSAKIRIS, WOOD
68
were recorded simultaneously from these two
sites (Fig. 3).
PERICARDIAL PRESSURES DURING
TRANSVERSE ACCELERATION
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Intrapericardial pressures during exposures
to transverse acceleration in the four body
positions were related to the position of the
recording catheter tips (Figs. 4, 5, and 6).
During exposures to backward acceleration (— G x ), when the position of the pericardial catheter tip was uniformly below the
mid-lung coronal plane (Figs. 1 and 4), progressively higher intrapericardial pressures
were recorded with increasing levels of acceleration; and the values attained were as
high as 45 cm HL.O during exposures
to —6.5d. During exposures to forward
(+Gj) acceleration, a variable degree of dor-
sal (backward) displacement of the catheter
tips occurred at the higher levels of acceleration as a consequence of the dorsal displacement of the heart during the exposures (Figs.
4 and 7). The changes in intrapericardial pressures recorded during these exposures were
dependent on the position of the recording
catheter tips. In the 2 dogs in which the catheter tip moved to sites below the mid-lung
coronal plane, positive pericardial pressures
were recorded, while increasingly negative
pressures were recorded in the 5 dogs in
which the catheter tip remained above the
mid-lung level (Fig. 4). Similarly, progressively more positive intrapericardial pressures
were recorded at increasing levels of right
Dog 8
PERICARDIAL
A -
_I
•
A
•
•
8r
Do« /0
•
5
\
BOOY
POSITION
Suplnt
HG,
-IGK
Pront
L. LoiTol+I tIC,
R.Laltnl-I -IG,
Do« /0
•
\
X
e
I_I
o
•
N
\
\
\
•
\
A
i
1
i
1
\
\
i
-/5
-/0
-/5
MEAN END-EXPIRATORY PERICARDIAL
PRESSURE at CATHETER TIP (cm H,O)
FIGURE 2
Relation of mean end-expiratory pericardial pressure to vertical position in the thorax in the 4 dogs studied at
IG only. Pressures recorded in the four body positions are indicated by the symbols. A negative value on each
ordinate indicates that the catheter tip was positioned below the mid-thoracic plane. The dashed lines indicate
a gradient of 1 cm H,O/cm of vertical distance. Note that the gradients for intrapericardial pressure were about
1 cm Hfilcm of vertical distance from the mid-thoracic plane. In dog 8, changes in intrapericardial pressure
were also studied during stepwise withdrawal of a second catheter (II) inserted in the pericardial sac (open
symbols) while the dog was in the supine position.
CircmUticm Rtsturcb, Vol. XX, JMUMOTJ 1967
PERICARDIAL PRESSURES IN DOGS
69
Pericardial I
Ptrlcordlal II
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/O
-5
Supint Front
+ IG, -/G x
A
•
A
O
0
END-EXPIRATORY
AT CATHETER
PERICARDIAL
TIP (cm HgO)
5
PRESSURE
FIGURE 3
Relation of mean end-expiratory intrapericardial pressure to vertical position in the thorax with changes in the
volume of pericardial fluid in 1 animal (dog 8). Pericardial I (closed symbols) was located at the ventral aspect
of the heart, and pericardial II (open symbols) was at the dorsal asiiect of the heart. The solid lines connect
pressure values recorded simultaneously from the two pericardial catheters. The dashed line indicates a gradient
of 1 cm HgO/cm of vertical distance. Lines 1 and 4 indicate the control values of intrapericardial pressure
gradients when in the supine (circles) and prone (triangles) body positions, respectively. When the dog was
in the supine position, the infusion of 10 ml of Ringer's solution produced similar increases in pericardial pressures recorded at the two sites (line 2). After withdrawal of 10 ml, pericardial pressures returned to levels
similar to those measured at the control state (line 3). In the prone body position, withdrawal of 4 ml produced
a decrease in intrapericardial pressures (line 5). The infusion of 10 ml produced an increase in pressures (line 6).
After withdrawal of 11 ml (line 7), values close to those observed during the previous set of observations laheUed 5 were recorded. Note that in all instances the differences in pressures recorded simultaneously from the
ventral and dorsal sites in the pericardial sac amounted to an average gradient of about 1 cm H.JD/cm of
vertical distance separating the respective catheter tips.
lateral (+GV) and left lateral (-G y ) acceleration when the catheters were below the midlung sagittal plane, and less positive pressures were recorded when the tip was above
this level (Fig. 5).
The interpolated values for intrapericardial
pressure at zero G (that is, the intercepts of
the dashed lines with the zero G axis) of
about —3 cm H2O were similar when dogs
were in the supine and prone positions and
when in the left lateral and right lateral positions (Figs. 4 and 5). This is presumably the
value that would be obtained for pericardial
OrcuUiton Rtsetrcb, Vol. XX, Jmmrj 1967
pressure at zero G, that is, in a weightless environment.
The relationship of mean end-expiratory
intrapericardial pressure to the hydrostatic
distance from mid-lung level, that is, the G
level times the vertical distance in centimeters
from mid-lung level in the four directions of
acceleration is shown in Figure 6. The fact
that individual values of intrapericardial pressure fall along the dashed line indicates that
changes in pressure of about 1 cm H2O/cm of
vertical distance occurred, as would be expected to occur in a hydrostatic system. At the
higher levels of backward (—Gx) acceleration,
70
BANCHERO, RUTISHAUSER, TSAKIRIS, WOOD
RELATIONSHIP BETWEEN INTRAPERICARDIAL
PRESSURE AND INTRAPLEURAL PRESSURE
intrapericardial pressures were higher than
those expected in a hydrostatic system, possibly because the specific gravity of the heart
and its contained blood is greater than one.
Values for intrapericardial pressures at 1G
obtained after exposures to different levels
of acceleration in the four body positions
were not systematically different from the
values obtained before the exposures.
Pressure
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'-60
MEAN
at
-30
Changes in pressure recorded simultaneously on the pericardial and pleural sides of the
pericardium have been studied by comparison
of the pressure values obtained when the tips
of the pericardial and pleural catheters were
located within 1 cm of each other as measured by biplane roentgenograms. This was
Values
0
30
Height
60
END-EXPIRATORY
PRESSURE
CATHETER
TIP
(cm H20)
'8
of
Recording
4
0 - 4
DISTANCE
above
MID-LUNG
(cm)
Site
-8
FIGURE 4
Variations of pericardial pressure with the level of acceleration and the vertical height of the recording site in
the thorax of 7 dogs without thoracotomy studied while in the supine (+GJ and prone (-GJ positions. Acceleration values on the ordinate are plotted as positive values, that is, above the zero C line for fonoard
(+GJ exposures, and as negative values, that is, below the zero G line for backward (-GJ exposures. A
negative sign on the abscissa of the left panel indicates the catheter tip was below the mid4ung plane. Note
that when the dog was supine (+GX acceleration) the pericardial catheter tip was always above mid-lung level
at 1G (right upper panel,) and the pericardial pressure at this site was uniformly negative (average —6 cm H,O).
Wlien the dogs were rotated to the prone position (-GJ, the catheter tip was always below mid-lung (right
lower panel) and pericardial pressures at 1G were uniformly less negative (average 0 cm HtO) than the values
obtained at these same anatomic sites at 1G when the dogs were in the supine position. During increased levels
of +GX acceleration, the catheter tip was displaced progressively lower in the thorax with the downward movement of the heart at higher levels of +GX. In the 2 animals in which the pericardial catheter moved to sites
actually below the mid-lung plane during exposures of + 7GT, the pericardial pressure was increased concomitantly to positive values. In contrast, in the animals in which the pericardial datheter tip remained above the
mid-lung plane, the pericardial pressures recorded at +7CX were more negative than the values obtained at
+ 1GW (left upper panel). When the dogs were prone (—Gx acceleration), the heart was resting on the sternum
and ventral rib cage at 1G and there was practically no additional downward (ventral) displacement of the
dependent catheter tip during increased levels of —Gw. In this situation a progressive increase in pericardial
pressure uniformly occurred to attain values as high as 45 cm H,O at —6.5Gm (left lower panelj. The average
level of pericardial pressure interpolated to zero G (intersection of dashed lines with the zero G line) was
about —3 cm Hfi in this presumed weightless condition.
Symbols identify values from same dogs as in Figures 4, 5, and 8. Simultaneous pleural pressure and blood
oxygen saturation values reported elsewhere (7, 8) are identified by same symbols.
CircnUiion Rtsrtrcb, Vol. XX, Jcnturj 1967
PERICARDIAL PRESSURES IN DOGS
71
the case in 3 animals (dogs 4, 6, and 7) (Fig.
1). No systematic differences were observed
in the pressures recorded at these respective
pleural and pericardial sites, the pericardial
pressure being slightly higher in 12 of 21
measurements performed at various levels of
acceleration in all four body positions (Fig.
7). An estimation of the transpericardial pressure was possible by correction of the pleural
pressure to the level of the pericardial catheter tip. The average transpericardial pressure
of 0.8 cm H2O estimated in this manner was
not significantly different from zero.
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RELATIONSHIP BETWEEN INTRAPERICARDIAL PRESSURE
AND ATRIAL PRESSURES
This relationship was studied in the 7 dogs
exposed to acceleration (Fig. 8). Mean left
atrial pressures, referred to mid-lung coronal
plane, were 3.3 and 1.3 cm HoO when dogs
were in the supine (+1GJ and prone (— l G ^
body positions, respectively. The mean right
atrial pressures of 0.7 and 0.4 cm H2O, re-
spectively, were slightly less than the simultaneous left atrial pressures (Fig. 8).
During exposures to different levels of forward (+GX) and backward (— Gx) acceleration, slight increases in atrial pressures were
observed at the higher levels of plus and
minus Gx acceleration. It should be remembered, however, that, due to the sevenfold
increase in the effective weight of the blood
at 7G and the dorsal-ventral dimension of the
lungs of these dogs of about 12 cm, the pulmonary venous pressure at the most dependent (dorsal) regions of the lungs averaged
about 50 cm H2O during exposures to +7G I;
whereas the pulmonary venous pressure at
the most dependent (ventral) regions of the
lungs averaged about 70 cm H2O during exposures to —7GX. Concomitantly in superior
regions of the lungs, if collapse of pulmonary
veins does not occur, highly negative pulmonary venous pressures are present at these
same levels of acceleration.
Pressure -Values
Height
of
Recording
Site
8r
flr
-4 -
-60
-30
0
30
6O
MEAN END - EXPIRATORY PRESSURE
at CATHETER TIP (cm HZO)
-8
4
0
DISTANCE
MID-LUNG
above
(cm)
FIGURE 5
Variations of pericardial pressure with the level of acceleration and the vertical height of the recording site
in the thorax while in the left (+Ct) and right (—CJ decubtius positions. Note that, as was the case for the
Gx acceleration, progressively more positive pericardial pressures were recorded with increasing acceleration
when the catheter tip was below the mid-lung sagittal level and less positive pressures were recorded when
the tip was above this level. The average of the interpolated value for pericardial pressure at zero C when the
dogs were rotated from the left to the right decubitus position of about —3 cm H2O was not significantly
different from the value obtained at zero C for the supine and prone positions.
CircmUlion Rtiurcb,
Vol. XX, ]tntun 1967
72
BANCHERO, RUTISHAUSER, TSAKIRIS, WOOD
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The average of the interpolated values for
left atrial pressure at zero G (intersection of
dashed line with zero G axis) of about 2 cm
H2O was slightly greater than the interpolated value of 0.5 cm H«O obtained for right
atrial pressure in this presumed weightless
condition.
Referring the mean atrial pressure and mean
end-expiratory intrapericardial pressure to the
same vertical height made an estimation of
transmural atrial pressures possible. The differences between mean atrial pressures referred to the level of the pericardial catheter
tip and the intrapericardial pressures are
shown in the right panels of Figure 8. Transmural left atrial and right atrial pressures of
about 4 and 2 cm H2O, respectively, were observed at 1G in these two body positions. No
significant systematic changes in transmural
atrial pressures occurred during exposures to
increased levels of acceleration of up to plus
and minus 7Gx. Similarly, the values inter-
polated to zero G were also 4 and 2 cm H^O
for left and right atrial transmural pressures,
respectively, in this presumed weightless condition.
Discussion
Investigations of the effects of the pericardium and pericardial pressures on cardiac
hemodynamics have been directed mainly to
abnormal conditions (1-4, 14-22). Data available on normal intrapericardial pressure are
meager (1-4). Because nearly all studies have
been carried out after thoracotomy and pericardiotomy, the relationship of the pressures
recorded to those present in the intact animal
is open to question.
The pericardial sac has been reported to
contain from 0.3 to 1 ml of a clear liquid
called "liquor pericardii" or pericardial fluid,
which makes the pericardial space a real
space, at least in certain parts (23). Aspiration was carried out immediately after
ACCELERATION
• Forward (*GM)
A Backward (-G,)
• Right Lattrol (+Gy)
» tll
Lattral
(-Gr)
c
I
13
h-
o
S
E
-10
-
O •
— ID
la
o
-a
a
-30
-20
MEAN
END-EXPIRATORY PERICARDIAL PRESSURE
at CATHETER TIP (cm HZO)
FIGURE 6
Relation of mean end-expiratory intrapericardial pressure to the hydrostatic distance of the recording site above
mid-lung (that is, G times centimeters from mid-lung), during transverse acceleration of 1 to 7G in the four
body positions. The diagonal dashed line indicates a gradient of 1 cm H,O/G X cm. Note that the values are
scattered along this line; this indicates that changes in pressure within the pericardial sac behave like a hydrostatic system, this effect being independent of the body position.
Circuluion Ruttrcb, Vol. XX, Jtmmsn 1967
73
PERICARDIAL PRESSURES IN DOGS
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each insertion of the pericardial catheter as a
means of verifying a successful pericardial
puncture. One to five milliliters of fluid could
be obtained in each instance when the puncture was successful. If the catheter was inadvertently introduced into the pleural space,
fluid could not be aspirated after the attempted mediastinal pericardial puncture.
Aspiration was attempted at intervals throughout the experiment to verify that the small
volume of fluid normally present within the
pericardial sac was maintained as normal as
possible. Ringer's fluid (5 to 10 ml) introduced
into the pericardial space via the recording
catheter could be completely recovered by
subsequent aspiration.
Values reported herein are mean end-expiratory intrapericardial pressures referred to
the catheter tip. The changes in pericardial
pressure associated with the cardiac and respiratory cycles have not been analyzed in
detail.
In the normal gravitational environment
(1G) as well as under the influence of transverse acceleration in four body positions, mean
end-expiratory intrapericardial pressure was
related to the height of the recording site.
Changes in intrapericardial pressure with vertical distance in the thorax are similar to those
that would be expected in a hydrostatic system, that is, changes in pressure of 1 cm
H20/cm of vertical distance. This type of
relationship has been observed in all conditions studied.
When dogs are exposed to forward (+G*)
acceleration (supine position), the heart is
«
A
•
C
O
6
D
O
Forward i*Gt)
Socl-or, (-G,)
Rlfkt
Llltrel
l*Gr)
LtU Lattrat l-Gy)
21
oa
o
-Q
O
-20
-10
MEAN
at
0
10
20
30
40
END- EXPIRATORY PRESSURE
CATHETER TIP (cm H20)
FIGURE 7
Comparison of simultaneous values of mean end-expiratory pericardial and pleural pressures recorded at contiguous sites in the thorax at different hydrostatic distances from mid-lung during transverse accelerations of 1
to 7C in four body positions. Only values obtained when the tips of the pericardial and pleural catheters were
located within 1 cm of each other are shown. The solid lines connect simultaneously recorded pleural and
pericardial pressure values. Numerals indicate individual dogs. The dashed line indicates a 1 to 1 gradient, as
would be obtained in a hydrostatic system. Note that no systematic difference was observed between these
pleural and pericardial pressures, thus indicating that transpericardial pressure was not systematically different
from zero and therefore that the pericardial membrane was not restricting cardiac dilatation under these circumstances.
Circulation Rtiurcb, Vol. XX, ]inmry
1967
74
BANCHERO, RUTISHAUSER, TSAKIRIS, WOOD
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suspended in the thorax by a band of elastic
fascicles, the stemopericardiac ligament (23).
A variable degree of dorsal (backward) displacement always occurred at high levels of
forward acceleration (7). The pericardial
catheter tip was displaced downward along
with the heart, and changes in intrapericardial pressure were related to these displacements (Fig. 4). Smaller displacements of the
heart and catheter tip were observed during
exposures to right lateral (+G y ) acceleration
(dogs in left decubitus position) and to the left
lateral (—GT) acceleration (dogs in right decubitus position). However, displacements of the
heart and pericardial catheter tip, when dogs
were exposed to backward (— Gx) acceleration (dogs prone), were negligible (7). In
this body position, the heart rests on and is
Atrial
LEFT
supported by the inner surface of the sternum
and ventral rib cage. Therefore, the distance
from the pericardial catheter tip to the midlung reference plane was practically unchanged in the range of acceleration from
- l t o ^ G , (Fig. 4).
Since atrial pressures were only slightly
changed during exposures to forward and
backward acceleration, the hydrostatic indifference point of atrial pressures in dogs is
about mid-lung level (24, 25). The fact that
transpericardial pressure was not significantly
different from zero and unchanged at different levels of transverse acceleration, irrespective of body positions, indicates that
this membrane plays only a passive role under these circumstances and is not subjected
to the pressure imbalances that occur in the
Pressures
8r
Transmural Pressures
(Atrial - Pericardial)
LEFT
RIGHT
RIGHT
/
Uj
-4 -
-20
O
20
-8
-20
PRESSURE REFERRED Io
(cm H20)
IF
0
20
M-ID- LUNG
-20
0
20
-20
0
20
PRESSURE at PERICARDIAL
CATHETER TIP (cm H20)
FIGURE 8
Relation of atrial pressures to the level of transverse acceleration when in the supine (-\-GJ and the prone
(-GJ body positions. Note (left panels) that at mid-lung level there was only a slight increase in atrial presures over the range from + 7GX to —7GX acceleration. The average of the interpolated values for zero G
(intersections of dashed lines with zero G line) of 2 cm H,O for left atrial pressure was slightly greater than
the interpolated average value of 1 cm HtO obtained for right atrial pressure in this presumed weightless
condition. Note fright panels) transmural atrial pressures (that is, the difference between mean atrial and mean
pericardial pressures corrected to the same vertical height in the thorax) were not systematically affected by
the level of acceleration in the range from + 7GX to —7Gr. The average interpolated values for transmural left
atrial pressure at zero C of about 5 cm HtO were slightly in excess of the analogous value for right atrial pressure of about 3 cm HtO.
OrcnUliom Rtstmrcb, Vol. XX, Jtmutry 1967
PERICARDIAL PRESSURES IN DOGS
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lungs. However, because the average values
of pulmonary venous pressure in dependent
regions of the lungs of about 50 and 70 cm
HL.O at levels of +7G r and —7GX, respectively, were considerably in excess of the colloido-osmotic pressure of plasma, rapid formation of pulmonary edema in these regions of
the lungs would be expected to occur at these
levels of acceleration (26). In these same animals a progressive decrease in transmission
of the infrared light of arterial blood, indicating hemoconcentration, was observed during exposures to acceleration of 4G or above
in all body positions (10); this suggests that
excessive loss of fluid from the bloodstream
was occurring presumably via dependent capillary beds in the pulmonary and the systemic
circulation over which effective counter pressures were not being applied.
The gradient in pressure with vertical position observed within the pericardial sac probably is due to the weight of the heart and
other thoracic contents. The slightly higher
pericardial pressures obtained at the higher
levels of backward acceleration (Fig. 6) may
be related to the fact that the specific gravity
of the heart and its contained blood, which
overlay the catheter tip in the prone body
position, is slightly greater than one. The fact
that pericardial pressures were equal and independent of body positions in the interpolated zero G condition confirms the hypothesis
that the differences in pericardial pressures
at different sites in the thorax obtained at 1G
and during exposures to acceleration are
caused by the weight of the thoracic contents, since, if this were the case, these differences would be expected to disappear under
conditions of weightlessness, as our results
suggest.
In the case of the potential pleural space,
a distinction has been made between "fluid"
and "surface" pleural pressures, the fluid pressure being more negative than the surface
pressure (27). Under the conditions of our
experiments (dogs in the horizontal position,
pleural and pericardial catheters of 1.3 mm,
o. d.), no evidence was elicited that the fluid
pressures at the lung or heart surfaces were
CircuUlioa Risurcb, Vot
XX, Jtnuary 1967
75
different from the surface pressures at the
same surfaces. End-expiratory pressures recorded at the catheter tip were stable over
long periods, indicating that, if fluid were being absorbed from the tip of the catheter, it
was being continually replaced from the normally present pools of pleural and pericardial fluids via the aqueous film separating the
pleural or periepicardial surfaces. When small
amounts of fluid were introduced via the
catheter tips by transient high pressure
flushes, the pressures immediately returned
to the preflush values. If a localized, more
negative fluid pressure was being recorded
by these fluid-filled catheter systems, it would
be expected that introduction of fluid via the
catheter tip would cause the recorded pressures to become more positive and approach
the surface pressures until the injected fluid
was absorbed and the more negative fluid
pressure was again recorded. No evidence of
this phenomenon was obtained in these experiments.
It appears that a thin film of pericardial
fluid is present in all portions of the periepicardial space because small (I to 5 ml)
volumes of pericardial fluid could always be
withdrawn immediately after puncture of the
pericardium in these dogs, and volumes of
Ringer's fluid injected via the pericardial catheter could be almost completely recovered by
application of negative pressure to the extrathoracic end of the catheter. These findings
indicate that pericardial fluid is transmitted
relatively freely throughout the periepicardial
space and, hence, it would be anticipated
that hydrostatic pressures would likewise be
transmitted throughout this space. The finding
of a pressure gradient of 1 cm of water/cm
of vertical distance in this space supports this
concept.
During life on earth, blood in the cardiac
chambers is continually subjected to gravitational hydrostatic forces as well as to inertia! hydrostatic forces whenever the motion
(velocity) of the body is changed in magnitude or direction. Since the heart is relatively
flaccid and fluid filled, the maintenance of
proper function of this pump would be much
76
BANCHERO, RUTISHAUSER, TSAKIRIS, WOOD
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more certain if it were suspended in a hydrostatic system which automatically applied perfectly compensated hydrostatic pressures to
all of its external surfaces whenever the gravitational or inertial forces acting on this organ
were altered. The pericardial pressure values
obtained in this study in different body positions and at levels of acceleration varying
from the normal (1G) gravitational attraction of the earth up to an inertial force of 7G
suggest that, within this range of environmental force, this is the case.
The finding that pleural and pericardia]
pressures recorded at contiguous sites in the
thorax were not significantly different (Fig. 6)
indicates that in these regions the pericardium is not subjected to transverse tensions
and suggests that the pleural pressure in regions juxtaposed to the heart must also have
a gradient of approximately 1 cm of water/cm of vertical distance in the thorax. Recent studies in this laboratory of both pleura]
and esophageal pressures in dogs and esophageal pressures in man in the erect position
support this interpretation (28, 29).
cardial, esophageal, and atrial pressures in
dogs without thoracotomy. Physiologist 5:
1.35, 1962.
6.
Technics for measuremerf of intrapleural and
pericardial pressures in dogs studied without
thoracotomy and methods for their application
to study of intrathoracic pressure relationships
during exposure to forward acceleration
(+Gx). Tech. Doc. Rep. AMRL-TDR-63-107.
U. S. Air Force 6570 Aerospace Med. Res.
Lab. 1-24, December, 1963.
7.
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NEWCOMBE, C. P., SINCLAIR, J. D., DONALD,
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1196, 1961.
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BANCHERO, N., CRONIN, L., RUTISHAUSER, W. J.,
TSAKIRIS, A. C., AND WOOD, E. H.: Effects
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saturation. J. Appl. Physiol. (In press.)
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catheterization. In Cardiology: An Encyclopedia of the Cardiovascular System, vol. 2,
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A. G., EDMUNDOWICZ, A. C, AND WOOD,
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Acknowledgments
These studies were made possible by the assistance
of many of our colleagues, among whom the help of
Ralph Sturm, Robert Hansen, Patrick Caskey, Don
Hegland, Julius Zarins, Ray Swanson, Volney Streifert,
Miss Lucille Cronin, and Mrs. Jean Frank was of
particular importance.
WOOD, E. H., NOLAN, A. C, DONALD, D. E.,
EDMUNDOWICZ, A. C, AND MARSHALL, H. W.:
16.
BERGLUND,
E.,
SARNOFF,
S.
J.,
AND
ISAACS,
J. P.: Ventricular function: Role of the pericardium in regulation of cardiovascular hemodynamics. Circulation Res. 3: 133, 1955.
EDMUNDOWICZ, A. C, DONALD, D. E., AND
WOOD, E. H.: Relationship of intrapleural
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pressures at multiple thoracic sites to peri-
tional anatomy of cardiac pumping. In HandCircmUtion Rutsrcb, Vol XX, Jtniuirj 1967
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book of Physiology, Sec. 2, vol. 2, Circulation.
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E. H.: Regional differences in pleural and
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Pericardial Pressure during Transverse Acceleration in Dogs without Thoracotomy
NATALIO BANCHERO, WILHELM J. RUTISHAUSER, ANASTASIOS G. TSAKIRIS and
EARL H. WOOD
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Circ Res. 1967;20:65-77
doi: 10.1161/01.RES.20.1.65
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