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R J Roselli

Publications and source records attributed to R J Roselli.

49 records · Page 3Linked to original sources
PubMed1981

A theoretical model of protein, fluid, and small molecule transport in the lung.

The purposes of this research were to derive a mathematical model of blood-intestinal transport for the lung and to study the ability of this model to describe the results of previous lymph-collection and multiple-indicator experiments on the lungs of unanesthetized sheep. We used a three-pore model of the microvascular barrier to describe lymph flow, lymph-to-plasma ratios (L/P) of eight endogenous proteins, and the microvascular permeability-surface area (PST) of the lungs to [14C]urea in sheep experiments under base-line conditions and after acute elevation of the left atrial pressure. The results indicate that endothelial pathways consisting of a small pore (28 A), intermediate pore (180 A), and a large pore (1,000 A) can describe experimental L/P values and PST. The description of lymph flow required either than interstitial fluid pressure increase with left atrial pressure or that postcapillary venous resistance decrease relative to precapillary values. We concluded that multiple-pore theory is a useful approach to the description of lung blood-interstitial transport.

Animals↗
PubMed1981

Effects of graded increases in pulmonary vascular pressures on lung fluid balance in unanesthetized sheep.

Fourteen experiments were conducted on 12 chronically instrumented unanesthetized sheep in which we monitored pulmonary arterial, left atrial, and aortic pressures, lung lymph flow, and lymph-to-plasma ratios (L/P) of total proteins and four endogenous protein fractions during baseline and progressive elevations of left atrial pressure. We found that L/P for total proteins decreased as lung lymph flow increased until lymph flow exceeded four to five times baseline and thereafter remained nearly constant (filtration independent) at 0.26. The four protein fractions exhibited a filtration independent L/P that was related to the effective molecular radius of the protein fraction. The minimal L/P were 0.36, 0.28, 0.18, and 0.09 for the protein fractions that had effective molecular radii of 36, 38.5, 59, and 101 A, respectively. In addition, we found no evidence supporting a stretched pore phenomenon over the pressure range utilized in this investigation.

Anesthesia↗
PubMed1981

Comparison of the effects of saline and homologous plasma infusion on lung fluid balance during endotoxemia in the unanesthetized sheep.

The effects of saline infusion (20 ml/kg/30 minutes) and homologous plasma infusion (20 ml/kg/30 minutes) on the lung fluid balance during increased pulmonary capillary permeability secondary to Escherichia coli endotoxin infusion (1 microgram/kg/15 minutes) were studied in unanesthetized sheep. Saline and homologous plasma infusion increased lung lymph flow by 10.6% and 10.8%, respectively. The bloodless wet-to-dry ratio was 5.1 +/- 0.2 in the saline group and 5.2 +/- 0.2 in the homologous plasma group. The saline infusion decreased the plasma oncotic pressure while the plasma infusion increased plasma oncotic pressure. However, the increase in plasma oncotic pressure was negated by concomitant changes in the lymph oncotic pressure and greater increases in pulmonary microvascular pressure during the plasma infusion. Changes in pulmonary microvascular pressure predominated over changes in the oncotic pressure gradient. Both saline and homologous plasma infusion increase fluid filtration into the interstitial space by the same magnitude. Therefore neither has a clear advantage in the treatment of pulmonary edema during increased permeability.

Animals↗
PubMed1979

Lung vascular permeability: inferences from measurements of plasma to lung lymph protein transport.

In chronically instrumented unanesthetized sheep, we measured steady-state hemodynamic and lung lymph responses to mechanically increased pressure and to intravenous infusions of histamine, Pseudomonas bacteria and E. coli endotoxin. Histamine, Pseudomonas bacteria and E. coli endotoxin caused exchanging vessel permeability to increase, as evidenced by high flows of protein rich lung lymph. This contrasts to the effects of increased pressure where lymph protein concentration falls as lymph flow increases. Microvascular sieving of proteins less than 100 Angstrom radius persisted in all increased permeability states, but with endotoxin, lymph clearance of larger proteins increased much more than with histamine or Pseudomonas. We compared several approaches to quantitative interpretations of lymph data and found that direct methods for calculating permeability-surface area products and reflection coefficients for proteins produced values which were difficult to interpret, probably because fundamental assumptions of the methods were violated in our experiments. A mathematical model based on multiple pore theory produced more plausible coefficients.

Animals↗
PubMedDate not supplied

Optical measurements of lung microvascular filtration coefficient using polysulfone fibers.

Lung fluid balance, which is governed by the product of net transvascular pressure difference and lung filtration coefficient, can be altered in pulmonary diseases. A simple measurement of the lung filtration coefficient (Kfc) would be clinically useful and has been examined by several researchers. Current methods of determining Kfc include gravimetric measurement in isolated lungs and lymph node cannulation, neither of which can be extended to human use. Optical measurements of protein concentration changes in venous blood can be combined with pressure measurements to calculate Kfc. Blood, though, contains red corpuscles, which tend to absorb and scatter light, obscuring these optical measurements. In this study, an optical system was developed in which a polysulfone filter cartridge was used to remove red blood cells before the filtrate was passed through a spectrophotometer. Absorbance changes caused by changes in concentration of albumin labeled with Evans Blue were monitored at 620 nm after venous pressure was elevated by about 13 cm H2O. Optical measurements of Kfc averaged 0.401 +/- 0.074 (ml/min cm H2O 100 g DLW) for an isolated canine lung. Optical measurements of Kfc (0.363 +/- 0.120 ml/min cm H2O 100 g DLW) were made for the first time in an intact, closed chest sheep in which pulmonary pressure was altered by inflating a Foley balloon in the left atrium. We conclude that absorbance and scattering artifacts introduced by red blood cells can be eliminated by first filtering the blood through polysulfone fibers. Kfc measurements using the optical method are similar to values obtained by others using gravimetric methods. Finally, we have demonstrated that the technique can be used to estimate Kfc in an intact animal.

Animals↗
PubMedDate not supplied

A model of fluid, erythrocyte, and solute transport in the lung.

A mathematical model of fluid, solute, and red cell transport in the lung has been developed that includes the effects of simultaneous changes in lung vascular and interstitial volumes. The model provides separate arterial, microvascular, and venous pulmonary regions and a systemic vascular region in addition to a pulmonary interstitial compartment. Pressure, volume, hematocrit, flow, and concentration of up to 12 solutes and tracers can be computed in each compartment. Computer code is written in the C programming language, with Microsoft Excel serving as a user interface. Implementation is currently on PC-486 microcomputer systems, but the core program can easily be moved to other computer systems. The user can select different models for the blood-interstitial barrier (e.g., multiple pore, nonlinear Patlak equation), osmotic pressure-concentration relationships (e.g., Nitta, Navar-Navar), solute reflection coefficients interstitial macromolecule exclusion, or lymph barrier characteristics. Each model parameter or a combination of parameters can be altered with time in a predetermined fashion. The model is particularly useful in interpreting lung experimental data where simultaneous changes occur in vascular and extravascular compartments. Several applications are presented and discussed, including interpretation of optical filtration experiments, venous occlusion experiments, external detection of macromolecular exchange, and blood-lymph studies that use exogenous tracers. A number of limitations of the model are identified and improvements are proposed. A major strength of the model is that it is specifically designed to incorporate newly discovered relationships as the field of lung physiology expands.

Animals↗
PubMedDate not supplied

Normal three-dimensional pulmonary artery flow determined by phase contrast magnetic resonance imaging.

In this study, an application was developed to measure three-dimensional blood flow in the main, right, and left pulmonary arteries of seven healthy volunteers using phase contrast magnetic resonance imaging (MRI). Presently, no other noninvasive technique is capable of providing this information. Flow, mean velocity, kinetic energy, and cross-sectional area were measured at multiple phases of the cardiac cycle and were consistent with previously reported values measured with one-dimensional velocity encoded MRI and Doppler echocardiography. Additionally, axial, circumferential, and radial shear stresses near the wall of the vessel at multiple phases of the cardiac cycle were estimated using the in-plane velocities. All three shear stresses were relatively constant along the vessel wall and throughout the cardiac cycle (approximately 7 dyn/cm2). This three-dimensional characterization of normal pulmonary blood flow provides a base line to which effects of altered pulmonary artery flow patterns in disease can be compared. [Morgan, V. L., T. P. Graham, Jr., and C. H. Lorenz. Circulation Suppl. 94:I-417 (abstract), 1996].

Adolescent↗
PubMedDate not supplied

Laser system for measuring small changes in plasma tracer concentrations.

The authors developed a laser-diode system that can be used for on-line optical concentration measurements in physiologic systems. Previous optical systems applied to whole blood have been hampered by artifacts introduced by red blood cells (RBCs). The system introduced here uses a commercially available filter cartridge to separate RBCs from plasma before plasma concentration measurements are made at a single wavelength. The filtering characteristics of the Cellco filter cartridge (#4007-10, German-town, MD) were adequate for use in the on-line measurement system. The response time of the filter cartridge was less than 40 seconds, and the sieving characteristics of the filter for macromolecules were excellent, with filtrate-to-plasma albumin ratios of 0.98 +/- 0.11 for studies in sheep and 0.94 +/- 0.15 for studies in dogs. The 635-nm laser diode system developed was shown to be more sensitive than the spectrophotometer used in previous studies (Klaesner et al., Annals of Biomedical Engineering, 1994; 22, 660-73). The new system was used to measure the product of filtration coefficient (Kfc) and reflection coefficient for albumin (delta f) in an isolated canine lung preparation. The delta fKfc values [mL/(cmH2O.min.100 g dry lung weight)] measured with the laser diode system (0.33 +/- 0.22) compared favorably with the delta fKfc obtained using a spectrophotometer (0.27 +/- 0.20) and with the Kfc obtained using the blood-corrected gravimetric method (0.32 +/- 0.23). Thus, this new optical system was shown to accurately measure plasma concentration changes in whole blood for physiologic levels of Kfc. The same system can be used with different optical tracers and different source wavelengths to make optical plasma concentration measurements for other physiologic applications.

Analysis of Variance↗