Liquid thickness vs. vertical pressure gradient in a model of the pleural space

1987 ◽  
Vol 62 (4) ◽  
pp. 1747-1754 ◽  
Author(s):  
S. J. Lai-Fook ◽  
D. C. Price ◽  
N. C. Staub
Keyword(s):  
Body Position ◽  
Vertical Gradient ◽  
Radioactive Tracer ◽  
Pleural Space ◽  
Pleural Pressure ◽  
Cylindrical Shape ◽  
Liquid Pressure ◽  
Rubber Balloon ◽  
Plastic Cylinder ◽  
Pleural Liquid Pressure

In recent studies using relatively noninvasive techniques, the vertical gradient in pleural liquid pressure was 0.2–0.5 cmH2O/cm ht, depending on body position, and pleural liquid pressure closely approximated lung recoil (J. Appl. Physiol. 59: 597–602, 1985). We built a model to discover why the vertical gradient in pleural pressure is less than hydrostatic (1 cmH2O/cm). A long rubber balloon of cylindrical shape was inflated in a plastic cylinder. The “pleural” space between the balloon and cylinder was filled with blue-dyed water. With the cylinder vertical, we measured pleural pressure by a transducer through side taps at 2-cm intervals up the cylinder. The pressure was measured with different amounts of water in the pleural space. With a clear separation between the balloon and the container, the vertical gradient in pleural liquid pressure was hydrostatic. As water was withdrawn from the pleural space, the balloon approached the wall of the container. Over an 8-cm-long midregion of the model where the balloon diameter matched the cylinder diameter, the vertical gradient was not hydrostatic and was virtually absent. In this region, the pleural liquid pressure was uniform and equal to the recoil of the balloon. In this section we could not see any pleural space. By scintillation imaging using 99mTc-diethylenetriamine pentaacetic acid in the water, we estimated the thickness of this flat “costal” pleural space to be approximately 20 microns. Radioactive tracer injected at the top of the pleural space appeared by 24 h at the bottom, which indicated a slow drainage of liquid by gravity.(ABSTRACT TRUNCATED AT 250 WORDS)

Pleural liquid pressure in dogs measured using a rib capsule

1985 ◽  
Vol 59 (2) ◽  
pp. 597-602 ◽  
Author(s):  
J. P. Wiener-Kronish ◽  
M. A. Gropper ◽  
S. J. Lai-Fook
Keyword(s):  
Pleural Space ◽  
Pleural Pressure ◽  
Parietal Pleura ◽  
Liquid Pressure ◽  
Strain Gauge Transducer ◽  
Invasive Method ◽  
The Mean ◽  
Spontaneously Breathing ◽  
Vertical Gradients ◽  
Pleural Liquid Pressure

We have developed a minimally invasive method for measuring the hydrostatic pressure in the pleural space liquid. A liquid-filled capsule is bonded into a rib and a small hole is cut in the parietal pleura to allow direct communication between the liquid in the capsule and the pleural space. The pressure can be measured continuously by a strain gauge transducer connected to the capsule. The rib capsule does not distort the pleural space or require removal of intercostal muscle. Pneumothoraces are easily detected when they occur inadvertently on puncturing the parietal pleura. We examined the effect of height on pleural pressure in 15 anesthetized spontaneously breathing dogs. The vertical gradients in pleural pressure were 0.53, 0.42, 0.46, and 0.23 cmH2O/cm height for the head-up, head-down, supine, and prone body positions, respectively. These vertical gradients were much less than the hydrostatic value (1 cmH2O/cm), indicating that the pleural liquid is not in hydrostatic equilibrium. In most body positions the magnitudes of pleural liquid pressure interpolated to midchest level were similar to the mean transpulmonary (surface) pressure determined postmortem. This suggests that pleural liquid pressure is closely related to the lung static recoil.

Pleural pressure as a function of body position in rabbits

1990 ◽  
Vol 69 (1) ◽  
pp. 336-344 ◽  
Author(s):  
L. E. Olson ◽  
R. L. Wardle
Keyword(s):  
Body Position ◽  
Pleural Space ◽  
Pleural Pressure ◽  
Liquid Pressure ◽  
Left Chest ◽  
Minimal Distortion ◽  
Space Capsule ◽  
The Right ◽  
Spontaneously Breathing ◽  
Nondependent Lung

Pleural pressure was measured at end expiration in spontaneously breathing anesthetized rabbits. A liquid-filled capsule was implanted into a rib to measure pleural liquid pressure with minimal distortion of the pleural space. Capsule position relative to lung height was measured from thoracic radiographs. Measurements were made when the rabbits were in the prone, supine, right lateral, and left lateral positions. Average lung heights in the prone and supine positions were 4.21 +/- 0.58 and 4.42 +/- 0.51 (SD) cm, respectively (n = 7). Pleural pressure was -2.60 +/- 1.87 (SD) cmH2O at 50.2 +/- 7.75% lung height in the prone position and -3.10 +/- 1.22 cmH2O at 51.4 +/- 6.75% lung height in the supine position. There was no difference between the values recorded in the prone and supine positions. Placement of the capsule into the right or left chest had no effect on the magnitude of the pleural pressure recorded in rabbits in right and left lateral recumbency (n = 12). Measurements over the nondependent lung were repeatable when rabbits were turned between the right and left lateral positions. Lung height in laterally recumbent rabbits averaged 4.55 +/- 0.52 (SD) cm.

Pleural liquid pressure measured with rib capsules in anesthetized ponies

1988 ◽  
Vol 64 (1) ◽  
pp. 102-107 ◽  
Author(s):  
L. E. Olson ◽  
S. J. Lai-Fook
Keyword(s):  
Prone Position ◽  
Supine Position ◽  
Body Position ◽  
Transpulmonary Pressure ◽  
Vertical Gradient ◽  
Liquid Pressure ◽  
Minimal Distortion ◽  
Poor Ventilation ◽  
Spontaneously Breathing ◽  
Pleural Liquid Pressure

Pleural liquid pressure was measured at end expiration in 11 spontaneously breathing anesthetized ponies in the prone and supine positions. A liquid-filled capsule was implanted into a rib to measure pleural liquid pressure with minimal distortion of the pleural space (Wiener-Kronish et al., J. Appl. Physiol. 59: 597-602, 1985). Capsule position relative to lung height was measured from thoracic radiographs taken in each position. In each body position, pleural liquid pressure was most negative in the superior lung regions and least negative in the inferior lung regions. In the supine position, the magnitude of the vertical gradient in pleural liquid pressure was 0.67 cmH2O/cm ht and was not significantly different from 1 cmH2O/cm ht. In the inferior lung regions (less than 50% lung ht), pleural liquid pressure averaged -1.3 cmH2O, indicating a low transpulmonary pressure over the region of the chest where most of the lung mass is located. When animals were in the prone position, the magnitude of the vertical gradient in pleural liquid pressure was 0.14 cmH2O/cm ht and was not statistically different from 0 cmH2O/cm ht. In each body position, mean transpulmonary pressure, measured postmortem, was similar to the estimated magnitude of pleural liquid pressure at 50% lung ht. This suggests that pleural liquid pressure is closely related to pleural surface pressure. These results are consistent with the poor ventilation distribution and reduced lung volumes measured in anesthetized horses in the supine position compared with values measured in horses in the prone position.

Pleural liquid pressure

1991 ◽  
Vol 71 (2) ◽  
pp. 393-403 ◽  
Author(s):  
E. Agostoni ◽  
E. D'Angelo
Keyword(s):  
Complete Removal ◽  
Vertical Gradient ◽  
Lymphatic Drainage ◽  
Pleural Space ◽  
Parietal Pleura ◽  
Liquid Pressure ◽  
Mechanical Coupling ◽  
The Third ◽  
New Ideas ◽  
Pleural Liquid Pressure

The knowledge of pleural liquid pressure (Pliq) is essential for understanding the mechanical coupling between lung and chest wall and the liquid exchanges of the pleural space. In the last decade, research in this field contributed new ideas and stimulating controversies but also caused some confusion. These aspects, along with the older contributions, are considered in this review, which is divided into three sections. The topics of the first section are 1) measurements of Pliq with different techniques in various mammals and various regions of the pleural space, 2) comparison of Pliq with the pressure exerted by the lung recoil (Ppl), and 3) vertical gradient of Pliq and downward flow of pleural liquid. In the second section the mechanisms absorbing liquid from the pleural space are analyzed: 1) Starling forces of the visceral pleura, 2) lymphatic drainage through the stomata of the parietal pleura, and 3) active transport of solutes. The third section deals with 1) measurements of pleural liquid thickness with two approaches in the costal region of various mammals and 2) mechanisms preventing a complete removal of pleural liquid and, thus, ensuring the lubrication.

scholarly journals Pleural Mechanics and Fluid Exchange

2004 ◽  
Vol 84 (2) ◽  
pp. 385-410 ◽  
Author(s):  
STEPHEN J. LAI-FOOK
Keyword(s):  
Chest Wall ◽  
Conceptual Understanding ◽  
Surface Pressure ◽  
Vertical Gradient ◽  
Pleural Space ◽  
Liquid Volume ◽  
Liquid Pressure ◽  
Fluid Exchange ◽  
Pleural Surface ◽  
The One

Lai-Fook, Stephen J. Pleural Mechanics and Fluid Exchange. Physiol Rev 84: 385–410, 2004; 10.1152/physrev.00026.2003.—The pleural space separating the lung and chest wall of mammals contains a small amount of liquid that lubricates the pleural surfaces during breathing. Recent studies have pointed to a conceptual understanding of the pleural space that is different from the one advocated some 30 years ago in this journal (Agostoni E. Physiol Rev 52: 57–128, 1972). The fundamental concept is that pleural surface pressure, the result of the opposing recoils of the lung and chest wall, is the major determinant of the pressure in the pleural liquid. Pleural liquid is not in hydrostatic equilibrium because the vertical gradient in pleural liquid pressure, determined by the vertical gradient in pleural surface pressure, does not equal the hydrostatic gradient. As a result, a viscous flow of pleural liquid occurs in the pleural space. Ventilatory and cardiogenic motions serve to redistribute pleural liquid and minimize contact between the pleural surfaces. Pleural liquid is a microvascular filtrate from parietal pleural capillaries in the chest wall. Homeostasis in pleural liquid volume is achieved by an adjustment of the pleural liquid thickness to the filtration rate that is matched by an outflow via lymphatic stomata.

Size-related differences in parietal extrapleural and pleural liquid pressure distribution

1989 ◽  
Vol 67 (5) ◽  
pp. 1967-1972 ◽  
Author(s):  
D. Negrini ◽  
G. Miserocchi
Keyword(s):  
Body Size ◽  
Pressure Gradient ◽  
Right Atrium ◽  
Pleural Space ◽  
Hydraulic Pressure ◽  
Liquid Pressure ◽  
Dependent Part ◽  
The Right ◽  
Spontaneously Breathing ◽  
Pleural Liquid Pressure

The hydraulic pressure in the extrapleural parietal interstitium (Pepl) and in the pleural space over the costal side (Pliq) was measured in anesthetized spontaneously breathing supine adult mammals of increasing size (rats, dogs, and sheep) using saline-filled catheters and cannulas, respectively. From the Pliq and Pepl vs. lung height regressions it appears that in all species Pliq was significantly more subatmospheric than Pepl simultaneously measured at the same lung height. The vertical pleural liquid pressure gradient increased with size, amounting to -1, -0.69, and -0.44 cmH2O/cm in rats, dogs, and sheep, respectively. The vertical extrapleural liquid pressure gradient also increased with size, being -0.6, -0.52, and -0.33 cmH2O/cm in rats, dogs, and sheep, respectively. With increasing body size, the transpleural hydraulic pressure gradient (Ptp = Pepl - Pliq) at the level of the right atrium increased from 1.45 to 5.6 cmH2O going from rats to sheep. In all species Ptp increased, with lung height being greatest in the less dependent part of the pleural space.

Direct measurement of interstitial pulmonary pressure in in situ lung with intact pleural space

1990 ◽  
Vol 69 (6) ◽  
pp. 2168-2174 ◽  
Author(s):  
G. Miserocchi ◽  
D. Negrini ◽  
C. Gonano
Keyword(s):  
Lateral Position ◽  
Pleural Space ◽  
Measuring System ◽  
Parietal Pleura ◽  
Interstitial Pressure ◽  
Liquid Pressure ◽  
Space Experiments ◽  
Report Data ◽  
Pleural Liquid Pressure

We developed an experimental approach to measure the pulmonary interstitial pressure with the micropuncture technique in in situ lungs with an intact pleural space. Experiments were done in anesthetized paralyzed rabbits that were oxygenated via an endotracheal tube with 50% humidified oxygen and kept in either the supine or the lateral position. A small area of an intercostal space was cleared of the intercostal muscles down to the endothoracic fascia. Subsequently a "pleural window" was opened by stripping the endothoracic fascia over a 0.2-cm2 surface and leaving the parietal pleura (approximately 10 microns thick). Direct micropuncture through the pleural window was performed with 2- to 3-microns-tip pipettes connected to a servo-null pressure-measuring system. We recorded pleural liquid pressure and, after inserting the pipette tip into the lung, we recorded interstitial pressure from subpleural lung tissue. Depth of recording for interstitial pressure averaged 263 +/- 122 (SD) microns. We report data gathered at 26, 53, and 84% lung height (relative to the most dependent portion of the lung). For the three heights, interstitial pressure was -9.8 +/- 3, -10.1 +/- 1.6, and -12.5 +/- 3.7 cmH2O, respectively, whereas the corresponding pleural liquid pressure was -3.4 +/- 0.5, -4.4 +/- 1, and -5.2 +/- 0.3 cmH2O, respectively.

Estimation of regional pleural surface expansile forces in intact dogs

1983 ◽  
Vol 55 (3) ◽  
pp. 935-948 ◽  
Author(s):  
E. A. Hoffman ◽  
T. Behrenbeck ◽  
P. A. Chevalier ◽  
E. H. Wood
Keyword(s):  
Body Position ◽  
Liquid Pressure ◽  
Mean Values ◽  
X Ray ◽  
Pentobarbital Anesthesia ◽  
Counter Pressure ◽  
Pleural Surface ◽  
Computer Based ◽  
Intermarker Distance ◽  
Pleural Liquid Pressure

Distances between percutaneously inserted apical and basal lung markers determined by biplane X-ray, computer-based videometry (J. Appl. Physiol. 34: 544, 1973) were calibrated against dependent percutaneously recorded pleural liquid pressures (J. Appl. Physiol. 31: 277, 1971) in five 10-12 kg mongrel dogs under morphine-pentobarbital anesthesia studied without thoracotomy. At the same apical pleural-liquid pressure values, the apical intermarker distances were uniformly greater when in the head-up rather than head-down position. This finding suggests that the expansile forces acting on the apical regions of the lung, in the head-up position, are greater (-30 +/- 2 cmH2O) than would be predicted from “pleural liquid” pressures (-15 +/- 1 cmH2O) measured at this nondependent site in the thorax, and much greater than the “pleural surface” pressures measured by the generally accepted balloon and counter-pressure techniques. In contrast, in the head-down body position, expansile forces acting on the nondependent basal regions of the lung estimated by the intermarker distance technique were variable to either side of the pressures measured by open-ended liquid-filled catheters, and thus were not significantly different. Mean values measured by the catheters and predicted by the markers were -14 +/- 1 and -10 +/- 3 cmH2O, respectively.

Regional variations in lung expansion in rabbits: prone vs. supine positions

1989 ◽  
Vol 67 (4) ◽  
pp. 1371-1376 ◽  
Author(s):  
Q. H. Yang ◽  
M. R. Kaplowitz ◽  
S. J. Lai-Fook
Keyword(s):  
Prone Position ◽  
Surface Pressure ◽  
Supine Position ◽  
Transpulmonary Pressure ◽  
Vertical Gradient ◽  
Liquid Pressure ◽  
Pleural Surface ◽  
Lung Expansion ◽  
Pleural Liquid Pressure

We studied the vertical gradient in lung expansion in rabbits in the prone and supine body positions. Postmortem, we used videomicroscopy to measure the size of surface alveoli through transparent parietal pleural windows at dependent and nondependent sites separated in height by 2–3 cm at functional residual capacity (FRC). We compared the alveolar size measured in situ with that measured in the isolated lungs at different deflationary transpulmonary pressures to obtain transpulmonary pressure (pleural surface pressure) in situ. The vertical gradient in transpulmonary pressure averaged 0.48 +/- 0.16 (SD) cmH2O/cm height (n = 10) in the supine position and 0.022 +/- 0.014 (SD) cmH2O/cm (n = 5) in the prone position. In mechanically ventilated rabbits, we used the rib capsule technique to measure pleural liquid pressure at different heights of the chest in prone and supine positions. At FRC, the vertical gradient in pleural liquid pressure averaged 0.63 cmH2O/cm in the supine position and 0.091 cmH2O/cm in the prone position. The vertical gradients in pleural liquid pressure were all less than the hydrostatic value (1 cmH2O/cm), which indicates that pleural liquid is not generally in hydrostatic equilibrium. Both pleural surface pressure and pleural liquid pressure measurements show a greater vertical gradient in the supine than in the prone position. This suggests a close relationship between pleural surface pressure and pleural liquid pressure. Previous results in the dog and pony showed relatively high vertical gradients in the supine position and relatively small gradients in the prone position. This behavior is similar to the present results in rabbits. Thus the vertical gradient is independent of animal size and might be related to chest shape and weight of heart and abdominal contents.

Pleural liquid pressure measured by micropipettes in rabbits

1984 ◽  
Vol 56 (6) ◽  
pp. 1633-1639 ◽  
Author(s):  
S. J. Lai-Fook ◽  
K. C. Beck ◽  
P. A. Southorn
Keyword(s):  
Dorsal Surface ◽  
Absolute Magnitude ◽  
Vertical Gradient ◽  
Repeated Measurements ◽  
Parietal Pleura ◽  
Liquid Pressure ◽  
Lung Lobe ◽  
Residual Capacity ◽  
Lung Base ◽  
Pleural Liquid Pressure

Pleural liquid pressure (Ppl) was measured by the micropipette servo-nulling method. In anesthetized, paralyzed, and mechanically ventilated rabbits, windows were made by dissecting away the intercostal muscle layers, exposing the parietal pleura over the right caudal lung lobe. Repeated measurements of Ppl were made at the windows by puncturing the parietal pleura with micropipettes during apnea at functional residual capacity. In five supine rabbits, Ppl relative to atmospheric pressure averaged -3.32 +/- 1.22 (SD) cmH2O at a distance of 5.64 +/- 0.34 (SD) cm above the lung base and -1.64 +/- 0.79 cmH2O at a distance of 2.35 +/- 0.64 cm above the lung base; the vertical Ppl gradient was 0.51 cmH2O/cm height. Ppl interpolated to midlung height was equal in absolute magnitude to mean lung static recoil (Pst) of 2.00 cmH2O. In prone rabbits, Ppl measured near the dorsal surface, 3.9 cm above the lung base, averaged -1.32 +/- 0.46 cmH2O on the costal surface, not statistically different in magnitude from mean Pst of 1.59 +/- 0.09. In contrast, Ppl measured at the same vertical height off the edge of the caudal lung in the costo-diaphragmatic recess was -4.64 +/- 0.65 cmH2O. We concluded from these data that Ppl was equal to pleural surface pressure over the costal surface and that the vertical gradient in Ppl was not hydrostatic, except in large fluid spaces off the sharp edges of the lung.

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