Comparison of capsular and intra-alveolar fluid pressures in the lung

1982 ◽  
Vol 52 (6) ◽  
pp. 1444-1452 ◽  
Author(s):  
J. C. Parker ◽  
A. E. Taylor
Keyword(s):  
Vertical Gradient ◽  
Colloid Osmotic Pressure ◽  
Considerable Variability ◽  
Tissue Pressure ◽  
Capillary Filtration ◽  
Filtration Pressure ◽  
Extravascular Fluid ◽  
Pulmonary Capillary ◽  
Negative Pressures ◽  
Spontaneously Breathing

The fluid pressures measured in chronically implanted capsules were compared with fluid absorptive pressures in small degassed lung segments. Capsules were implanted, and bronchiolar catheters were placed at different vertical heights in the lungs of spontaneously breathing dogs. Increases in pulmonary capillary filtration pressure were produced by volume infusions of Tyrode's solution and increased left atrial pressure. A vertical gradient in fluid pressures was consistently observed with more negative pressures near the top of the lungs. Capsular fluid pressures averaged -7.82 cmH2O with a gradient of -0.60 cmH2O/cm distance up the lung. The intra-alveolar absorptive pressures averaged -14.4 cmH2O with a gradient of -0.78 cmH2O/cm distance up the lung. The fluid pressures in both the capsules and alveolar segments responded to changes in capillary filtration pressure (capillary hydrostatic pressure minus plasma colloid osmotic pressure). The overall change in these extravascular fluid pressures amounted to approximately 25% of the change in filtration pressure, although considerable variability in individual measurements was obtained. Because they respond to imbalances in Starling capillary forces, both the capsular and intra-alveolar fluid pressures may be considered a function of perimicrovascular tissue pressure in the lung.

Effect of endotoxin on lung fluid balance in unanesthetized sheep

1984 ◽  
Vol 56 (2) ◽  
pp. 489-494 ◽  
Author(s):  
J. C. Gabel ◽  
T. N. Hansen ◽  
R. E. Drake
Keyword(s):  
Left Atrial ◽  
Capillary Permeability ◽  
Dry Weight ◽  
Base Line ◽  
Lung Fluid ◽  
Modified Method ◽  
Lung Fluid Balance ◽  
Extravascular Fluid ◽  
Pulmonary Capillary ◽  
Four Levels

We used a gravimetric technique to test for increased pulmonary capillary permeability after Escherichia coli endotoxin infusion in unanesthetized sheep. The sheep were chronically prepared with cannulas placed into the left atrium and pulmonary artery 1–2 wk before the experiments. We estimated pulmonary capillary pressure (Pc) as the average of pulmonary arterial and left atrial pressures, and used the modified method of Pierce to estimate the ratio of extravascular fluid weight (EVF) to blood-free dry weight. In 15 sheep we inflated a left atrial balloon to raise Pc to -10.7, 5, 10, or 15 mmHg above plasma oncotic pressure (IIc) for 3 h, then measured EVF. EVF averaged 4.0 +/- 0.2 (base line), 4.3 +/- 0.1, 4.5 +/- 0.1, and 5.1 +/- 0.5 (SD), respectively, for the four levels of Pc - IIc. We gave seven additional sheep 1 microgram/kg of E. coli endotoxin (0127:B8) and measured EVF after 3 h of stable Pc. Endotoxin increased Pc in each sheep. EVF was higher than control for the endotoxin sheep with Pc - IIc greater than -1. This finding is consistent with an increase in pulmonary capillary permeability caused by endotoxin. However, EVF was not elevated in the endotoxin sheep with Pc - IIc less than 1 mmHg. This shows that the increased permeability was insufficient to cause edema unless Pc was elevated. Thus endotoxin may cause edema by two mechanisms, 1) an increase in capillary permeability, and 2) an increase in Pc.

Effects of posture on regional pulmonary blood flow in rats as measured by PET

2010 ◽  
Vol 108 (2) ◽  
pp. 422-429 ◽  
Author(s):  
Torsten Richter ◽  
Ralf Bergmann ◽  
Jens Pietzsch ◽  
Inge Közle ◽  
Frank Hofheinz ◽  
...  
Keyword(s):  
Blood Flow ◽  
Pulmonary Blood Flow ◽  
Small Animal ◽  
Vertical Gradient ◽  
Human Albumin ◽  
Small Animal Pet ◽  
Longitudinal Measurements ◽  
Spatial Differences ◽  
Spontaneously Breathing

Using small animal PET with 68Ga-radiolabeled human albumin microspheres (Ga-68-microspheres), we investigated the effect of posture on regional pulmonary blood flow (PBF) in normal rats. This in vivo method is noninvasive and quantitative, and it allows for repeated longitudinal measurements. The purpose of the experiment was to quantify spatial differences in PBF in small animals in different postures. Two studies were performed in anesthetized, spontaneously breathing Wistar rats. Study 1 was designed to determine PBF in the prone and supine positions. Ga-68-microspheres were given to five prone and eight supine animals. We found that PBF increased in dorsal regions of supine animals (0.75) more than in prone animals (0.70; P = 0.037), according to a steeper vertical gradient of flow in supine than in prone animals. No differences in spatial heterogeneity were detected. Study 2 was designed to determine the effects of tissue distribution on PBF measurements. Because microspheres remained fixed in the lung, PET was performed on animals in the position in which they received Ga-68-microsphere injections and thereafter in the opposite posture. The distribution of PBF showed a preference for dorsal regions in both positions, but the distribution was dependent on the position during administration of the microspheres. We conclude that PET using Ga-68-microspheres can detect and quantify regional PBF in animals as small as the rat. PBF distributions differed between the prone and supine postures and were influenced by the distribution of lung tissue within the thorax.

Increase in pulmonary capillary permeability in dogs exposed to 100% O2

1988 ◽  
Vol 65 (3) ◽  
pp. 1140-1146 ◽  
Author(s):  
F. Royer ◽  
D. J. Martin ◽  
G. Benchetrit ◽  
F. A. Grimbert
Keyword(s):  
Protein Concentration ◽  
Reference Data ◽  
Capillary Permeability ◽  
Lymph Flow ◽  
Plasma Protein Concentration ◽  
Capillary Filtration ◽  
Pulmonary Capillary ◽  
Hyperoxic Exposure ◽  
Two Stages ◽  
Minimal Estimate

Changes in pulmonary capillary filtration induced by hyperoxia were investigated in 15 dogs. After 12 h of normobaric hyperoxic exposure, animals were anesthetized and artificially ventilated with 100% O2. A pulmonary lymphatic vessel was cannulated, and lymph flow and protein content were measured together with pulmonary and systemic hemodynamics. An increase in pulmonary capillary filtration was found when compared with reference data (normoxic dogs in similar conditions) gathered from available literature: lymph flow increased from 21.8 +/- 13.4 to 125.2 +/- 131.6 microliter/min, and the lymph-to-plasma protein concentration ratio increased from 0.67 +/- 0.08 to 0.78 +/- 0.08. To characterize the mechanisms involved, left atrial pressure was increased in two stages (approximately 10 and approximately 25 mmHg). The results clearly indicated an increase in pulmonary capillary permeability as evidenced by a decrease of the minimal estimate of the protein reflection coefficient from 0.62 +/- 0.05 to 0.42 +/- 0.05.

Peripharyngeal tissue deformation and stress distributions in response to caudal tracheal displacement: pivotal influence of the hyoid bone?

2014 ◽  
Vol 116 (7) ◽  
pp. 746-756 ◽  
Author(s):  
Jason Amatoury ◽  
Kristina Kairaitis ◽  
John R. Wheatley ◽  
Lynne E. Bilston ◽  
Terence C. Amis
Keyword(s):  
Hyoid Bone ◽  
Upper Airway ◽  
Cross Sectional Area ◽  
Tissue Deformation ◽  
Stress Distributions ◽  
Sectional Area ◽  
Tissue Pressure ◽  
Cross Sectional ◽  
Spontaneously Breathing ◽  
Model Slope

Caudal tracheal displacement (TD) leads to improvements in upper airway (UA) function and decreased collapsibility. To better understand the mechanisms underlying these changes, we examined effects of TD on peripharyngeal tissue stress distributions [i.e., extraluminal tissue pressure (ETP)], deformation of its topographical surface (UA lumen geometry), and hyoid bone position. We studied 13 supine, anesthetized, tracheostomized, spontaneously breathing, adult male New Zealand white rabbits. Graded TD was applied to the cranial tracheal segment from 0 to ∼10 mm. ETP was measured at six locations distributed around/along the length of the UA, covering three regions: tongue, hyoid, and epiglottis. Axial images of the UA (nasal choanae to glottis) were acquired with computed tomography and used to measure lumen geometry (UA length; regional cross-sectional area) and hyoid bone displacement. TD resulted in nonuniform decreases in ETP (generally greatest at tongue region), ranging from −0.07 (−0.11 to −0.03) [linear mixed-effects model slope (95% confidence interval)] to −0.27 (−0.31 to −0.23) cmH2O/mm TD, across all sites. UA length increased by 1.6 (1.5–1.8)%/mm, accompanied by nonuniform increases in cross-sectional area (greatest at hyoid region) ranging from 2.8 (1.7–3.9) to 4.9 (3.8–6.0)%/mm. The hyoid bone was displaced caudally by 0.22 (0.18–0.25) mm/mm TD. In summary, TD imposes a load on the UA that results in heterogeneous changes in peripharyngeal tissue stress distributions and resultant lumen geometry. The hyoid bone may play a pivotal role in redistributing applied caudal tracheal loads, thus modifying tissue deformation distributions and determining resultant UA geometry outcomes.

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.

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