Segmented Flow Research Articles

Comparison of computed tomography angiography versus cardiac catheterization for preoperative evaluation of major aortopulmonary collateral arteries in pulmonary atresia with ventricular septal defect.

Introduction:Pulmonary atresia with the ventricular septal defect is a rare congenital heart defect with high anatomic variability. The most important management question relates to the sources of pulmonary blood flow. The ability to differentiate between ductal dependence and major aortopulmonary collateral arteries is critical to achieving good outcomes and avoiding life-threatening hypoxia in the postneonatal period. Having accurate information about pulmonary arteries, major aortopulmonary collateral arteries, and sources of blood supply to each pulmonary segment is crucial for choosing the optimal surgical strategy. The purpose of this study is to compare computed tomography angiography (CTA) with cardiac catheterization for anatomic delineation of surgically relevant anatomy in pulmonary atresia with ventricular septal defect with major aortopulmonary collateral arteries.Materials and Methods:Retrospective review of all children with pulmonary atresia with ventricular septal defect with major aortopulmonary collateral arteries cared for at a large tertiary children's hospital who underwent cardiac catheterization with angiography and CTA close to each other without interval therapy. All studies were performed between 2007 and 2011.Results:There were 9 patients who met the inclusion criteria. Pulmonary artery anatomy (confluent vs. nonconfluent) was correctly identified in 9 patients by CTA and 8 patients by catheterization. There were no significant differences between CTA and catheterization in the identification of major aortopulmonary collateral arteries (mean = 3.4 collaterals/study via catheterization; mean = 3.1 collaterals/study via CTA; P = 0.67). CTA was superior to catheterization in the delineation of segmental pulmonary blood flow (P = 0.006).Conclusion:CTA and catheterization are equivalent in their ability to delineate pulmonary artery anatomy and major aortopulmonary collateral arteries.

Novel SERS-based process analysis for label-free segmented flow screenings.

In microfluidic segmented flow processes label-free analytical techniques like surface enhanced Raman spectroscopy (SERS) can reveal the chemical composition of the individual droplet contents. The SERS system developed in this work enables a simple connection to micro segmented flow processes through miniaturization. The concept is based on the parallelization of silver/polyacrylamide composite SERS spots on a carrier plate on which the segments are deposited. The transfer of the segments allows an easy connection to existing flow processes and provides optimal conditions for Raman measurements using miniaturized spectrometers. The preparation of the SERS polymer composite was optimized in terms of the silver content in the polymer matrix to obtain a high SERS signal. The performance and long-term stability of the polymer have been successfully demonstrated. The deamination of adenine with sodium nitrite to hypoxanthine was chosen as a case study to demonstrate the capability of the novel SERS-based process analysis. A sequence of approximately one hundred segments in combination with a gradient of the nitrite concentration (0 to 0.4 mol L-1) was generated at two temperatures. The concentration of adenine and hypoxanthine were determined by using a multivariate calibration model, since the Raman spectra of both substances are overlapping. It was shown that the conversion of adenine is increased with higher nitrite concentration and temperature. A conversion of 35% was obtained at 50 °C and a conversion of 60% at 80 °C, respectively.

In situ non-invasive Raman spectroscopic characterisation of succinic acid polymorphism during segmented flow crystallisation

Non-invasive confocal Raman spectroscopy has been integrated into a highly controllable tri-segmented flow crystallisation environment to uncover the crystallisation pathway from nucleation to crystal growth of the polymorphic compound succinic acid.

Droplet-based optofluidic systems for measuring enzyme kinetics.

The study of enzyme kinetics is of high significance in understanding metabolic networks in living cells and using enzymes in industrial applications. To gain insight into the catalytic mechanisms of enzymes, it is necessary to screen an enormous number of reaction conditions, a process that is typically laborious, time-consuming, and costly when using conventional measurement techniques. In recent times, droplet-based microfluidic systems have proved themselves to be of great utility in large-scale biological experimentation, since they consume a minimal sample, operate at high analytical throughput, are characterized by efficient mass and heat transfer, and offer high levels of integration and automation. The primary goal of this review is the introduction of novel microfluidic tools and detection methods for use in high-throughput and sensitive analysis of enzyme kinetics. The first part of this review focuses on introducing basic concepts of enzyme kinetics and describing most common microfluidic approaches, with a particular focus on segmented flow. Herein, the key advantages include accurate control over the flow behavior, efficient mass and heat transfer, multiplexing, and high-level integration with detection modalities. The second part describes the current state-of-the-art platforms for high-throughput and sensitive analysis of enzyme kinetics. In addition to our categorization of recent advances in measuring enzyme kinetics, we have endeavored to critically assess the limitations of each of these detection approaches and propose strategies to improve measurements in droplet-based microfluidics. Graphical abstract.

Elevated pressure influences relative distribution of segmental regions of the trabecular meshwork

Elevated intraocular pressure (IOP) is the primary risk factor for glaucoma and is the only treatable feature of the disease. There is a correlation between elevated pressure and homeostatic reductions in the aqueous humor outflow resistance via changes in the extracellular matrix of the trabecular meshwork. It is unclear how these extracellular matrix changes affect segmental patterns of aqueous humor outflow, nor do we understand their causal relationship. The goal of this study was to determine whether there are changes in the segmental outflow regions with perfusion in normal eyes, and whether these regions change during the IOP homeostatic response to elevated pressure. Using human anterior segment perfusion organ culture, we measured the amount of high flow (HF), intermediate flow (MF), and low flow (LF) regions before and after 7 days of perfusion at either physiologic pressure (”1x”) or at elevated pressure (”2x”). We found a small but significant decrease in the amount of HF regions over 7 days perfusion at 1x pressure, and a twofold increase in the amount of MF regions over 7 days perfusion at 2x pressure. Small positional differences, or shifts in the specific location of HF, MF, or LF, occurred on a per eye basis and were not found to be statistically significant across biological replicates. Differences in the amount of segmental flow regions of contralateral eyes flowed at 1x pressure for 7 days were small and not statistically significant. These results demonstrate that perfusion at physiologic pressure had little effect on the distribution and amount of HF, MF and LF regions. However, the overall amount of MF regions is significantly increased in response to perfusion at elevated pressure during IOP homeostatic resistance adjustment. The amount of both HF and LF regions was decreased accordingly suggesting a coordinated response in the TM to elevated pressure.

Accuracy, uncertainty, and adaptability of automatic myocardial ASL segmentation using deep CNN.

To apply deep convolution neural network to the segmentation task in myocardial arterial spin labeled perfusion imaging and to develop methods that measure uncertainty and that adapt the convolution neural network model to a specific false-positive versus false-negative tradeoff. The Monte Carlo dropout U-Net was trained on data from 22 subjects and tested on data from 6 heart transplant recipients. Manual segmentation and regional myocardial blood flow were available for comparison. We consider 2 global uncertainty measures, named "Dice uncertainty" and "Monte Carlo dropout uncertainty," which were calculated with and without the use of manual segmentation, respectively. Tversky loss function with a hyperparameter β was used to adapt the model to a specific false-positive versus false-negative tradeoff. The Monte Carlo dropout U-Net achieved a Dice coefficient of 0.91 ± 0.04 on the test set. Myocardial blood flow measured using automatic segmentations was highly correlated to that measured using the manual segmentation (R2 = 0.96). Dice uncertainty and Monte Carlo dropout uncertainty were in good agreement (R2 = 0.64). As β increased, the false-positive rate systematically decreased and false-negative rate systematically increased. We demonstrate the feasibility of deep convolution neural network for automatic segmentation of myocardial arterial spin labeling, with good accuracy. We also introduce 2 simple methods for assessing model uncertainty. Finally, we demonstrate the ability to adapt the convolution neural network model to a specific false-positive versus false-negative tradeoff. These findings are directly relevant to automatic segmentation in quantitative cardiac MRI and are broadly applicable to automatic segmentation problems in diagnostic imaging.

On-chip integration of normal phase high-performance liquid chromatography and droplet microfluidics introducing ethylene glycol as polar continuous phase for the compartmentalization of n-heptane eluents

We introduce an integrated chip-approach for a postcolumn segmentation of normal phase liquid chromatography. This is achieved by the seamless integration of a chiral NP-chip-HPLC column, a flow-focusing droplet generator, and a segmented flow channel in a single microfluidic glass chip. This allows a continuous segmentation of the eluent into droplets which are picked up and transported via an immiscible continuous phase. The combination of NP-chip-HPLC and droplet microfluidics enables to fractionate and conserve chromatographic runs for further downstream processes at picoliter scale. An essential aspect is the proper choice of the continuous phase concerning polarity, wetting properties and viscosity. For this purpose, ethylene glycol is introduced which facilitates this first combination of normal phase chromatography and droplet microfluidics. By adjusting the flow rates and varying the generator geometry, the size and frequency of the droplets could be precisely controlled.

Screening of functional solvent system for automatic aldehyde and ketone separation in aldol reaction: A combined COSMO-RS and experimental approach

An integrated reaction-separation process based on only solvents is presented, and thus without the need for related technical equipment (reactor-separator). Both product purification and reactant recovery are achieved automatically for an asymmetric aldol reaction employing a biphasic solvent system as compartmentalizing soft matter. Firstly, COSMO-RS based simulation is introduced as a theoretical guidance in the solvent selection for the reactant 3-chlorobenzaldehyde and non-solvent selection for the R-aldol product, (R)-4-(3-chlorophenyl)-4-hydroxybutan-2-one. This encompasses solubility as core critical parameter, as well as chemo-physical properties and environmental profiling. Such criteria-cascaded screening could effectively reduce a 7665 solvents-database into 1 candidate solvent, which is dodecane, before experimental process assessment. Secondly, this screening’s top candidate was validated as the best reaction solvent by first a solubility test and then by a batch reaction, in which a conversion of 69% was achieved. As desired, the mono-phase reaction yielded spontaneously the product layer and the separate dodecane phase as the second layer, which indeed allowed facile separation of the product from the residual reactant. In a third step, a segmented flow process was developed giving a highest product yield of 63% and a total conversion 92% respectively after a 2 h residence time.

Totally asymmetric simple exclusion processes on two intersected lanes

This paper carries out a cluster mean field analysis for spontaneous symmetry breaking in a two-lane totally asymmetric exclusion processes with an intersection. We find that the boundaries of the asymmetric phase are determined by differences of upstream segment densities and downstream segment flow rates of two lanes. The spontaneous symmetry breaking phenomenon exists when the interaction of particles is strong enough. The critical values, beyond which the phenomenon disappears, are identified through simulation and analysis, and they are in excellent agreement. The analytical results of the asymmetric phase boundaries are closer to simulation ones than those of simple mean field analysis. The analytical results of density profiles and the simulation ones are also in excellent agreement.

Gas-Directed Production of Noble Metal-Magnetic Heteronanostructures in Continuous Fashion: Application in Catalysis.

Complex nanomaterials produced by scale-up batch processes lack suitable control of shape, size distribution, chemical composition, and quality, because heat and mass transfer are seriously affected as the reactor volume increases. Here we use a novel continuous synthesis procedure, the active gas-liquid segmented flow, to produce noble metal-magnetic heteronanostructures with enormous interest in the fields of catalysis, biomedicine, environmental sensors, food monitoring, and chemical analysis. The microreactor technology proposed scales down the reaction volume to gain advantage of the large surface area to volume ratio with respect to conventional batch-type reactors, improving heat and mass transport and, consequently, promoting a uniform heating and mixing. The gas phase was introduced in the chemical reactor as gas slugs of nanoliter scale with a dual role: (1) passive mixing and (2) chemical directing agent to tune the crystallization of nanostructures in a continuous fashion. The shape, size, and magnetic properties of the resulting heteronanostructures, as well as the density, size, and composition of noble metal nanoparticles were tuned to show the versatility of the proposed approach in a timeline of 4 min. We demonstrated that the produced nanostructures provide excellent catalytic properties in the catalyzed hydrogenation of nitrophenols to aminophenols. Electron microscopy, UV-vis spectroscopy, and cyclic voltammetry studies showed the remarkable catalytic performance of the produced heteronanostructures.

Convective dispersion of particles in a segmented flow

Experiments show that a suspension confined between two bubbles and flowing in a pipe may become heterogeneous when liquid inertia comes into play. Indeed, inertial migration of the particles along the radial direction modifies the axial flux of particles linked to the Poiseuille flow.

Rapid synthesis of [Au25(Cys)18] nanoclusters via carbon monoxide in microfluidic liquid-liquid segmented flow system and their antimicrobial performance

Atomically precise thiolate-gold nanoclusters with well-defined structures attract attention for use in various applications. However, most of the recently reported synthetic methods rely on prolonged synthesis times (a few hours to days) in order to produce high purity materials with a single cluster size. Such extended synthesis times make these processes ill-suited for adaptation to industrial scale production with continuous flow. In this work, an improved method for the synthesis of thiolated Au25 nanoclusters is presented utilising a microfluidic system and CO-mediated reduction. The optimized system, based on a coiled flow inverter with inner diameter of 1 mm operating at 80 °C and 500 kPa took only 3 min for the synthesis of atomically precise cysteine-capped [Au25(Cys)18] nanoclusters, as characterized by ultraviolet–visible spectroscopy and electrospray ionization mass spectrometry. The productivity of the system was increased by using higher reactant concentrations which led to a throughput of 0.9 gAu per day, without changing the reaction time or affecting the product purity. The Au nanoclusters were used as photobactericidal enhancement materials. In antimicrobial testing against S. aureus, encapsulation of the Au nanoclusters into crystal violet impregnated silicone showed high photobactericidal activity (~1.7 log reduction in viable bacteria) upon 6 h illumination of white light at ~312 lx, while crystal violet did not show significant photobactericidal activity on its own.

The effect of remote ischemic conditioning on blood coagulation function and cerebral blood flow in patients with aneurysmal subarachnoid hemorrhage.

To explore the effect of remote ischemic conditioning (RIC) on blood coagulation function and cerebral blood flow in patients with aneurysmal subarachnoid hemorrhage. According to inclusion and exclusion standards, from October 2017 to June 2018, 30 consecutive patients of aneurysmal subarachnoid hemorrhage admitted to Intensive Care Unit, Department of Neurosurgery at Xuanwu Hospital, were given remote ischemic conditioning 5 times intervention to each patient within 7days, and blood coagulation function testing, including prothrombin activity (PTA), prothrombin time (PT), activated partial prothrombin time (APTT), fibrinogen (Fib), D-dimer, and thromboelastogram (TEG, including R, K, Angle, MA, EPL, LY30, A, CI, G, and A30) were performed for each patient before and after the RIC intervention, as well as venous ultrasound monitoring before and after the RIC intervention for detection of deep vein thrombosis (DVT). Transcranial Doppler evaluation (TCD), including cerebral blood flow of bilateral ACA, MCA, PCA and intracranial segments of VA, as well as BA and the ratios of MCA cerebral blood flow/terminal segment of ipsilateral ICA cerebral blood flow, was performed before and after RIC intervention; and fresh infarction was evaluated by head CT or MRI recheck after RIC intervention. Thirty cases without RIC intervention of matched age, gender, and Hunt Hess grade with aneurysmal subarachnoid hemorrhage were selected to compare coagulation function and cerebral blood flow using TCD with RIC group. (1) Comparing the data before and after the RIC intervention, there was no significant difference for APTT, Fib, and D-dimer (P > 0.05), while PTA decreased and PT increased slightly after intervention as well as INR (P < 0.05) but all still in normal reference values. (2) Comparing the data before and after the RIC intervention, within TEG parameters, only the R value increased with significant difference (P< 0.05) but still in normal reference value, while K, Angle, MA, EPL, LY30, A, CI, G, and A30 had no significant difference (P > 0.05). (3) Comparing the data before and after the RIC intervention, DVT was not detected on the pressurized limbs of patients. (4) Comparing the data before and after the RIC intervention, the cerebral blood flow of bilateral MCA, L-ACA, L-VA, and BA increased (P < 0.05), while the elevation ranges were all in 25%, and the other parameters showed no significant difference. (5) Head CT or MRI showed no fresh cerebral infarction after the RIC intervention. (6) Compared with the group without RIC intervention, the coagulation function and the cerebral blood flow evaluated by TCD of the RIC group showed no statistical difference (P > 0.05) except APTT and D-dimer decreased after RIC but still in normal reference values. RIC showed no obvious effect on blood coagulation function and cerebral blood flow in patients with aneurysmal subarachnoid hemorrhage both after the intervention and compared with the non-intervention group. DVT was not detected on the pressurized limbs of patients and no fresh cerebral infarction was detected. This preliminary study confirmed the safety of RIC on blood coagulation function and cerebral blood flow in patients with aneurysmal subarachnoid hemorrhage, and the application of RIC on patients with aneurysmal subarachnoid hemorrhage needs further study to confirm and validate the safety and effectiveness.

Combining position-based dynamics and gradient vector flow for 4D mitral valve segmentation in TEE sequences.

For planning and guidance of minimally invasive mitral valve repair procedures, 3D+t transesophageal echocardiography (TEE) sequences are acquired before and after the intervention. The valve is then visually and quantitatively assessed in selected phases. To enable a quantitative assessment of valve geometry and pathological properties in all heart phases, as well as the changes achieved through surgery, we aim to provide a new 4D segmentation method. We propose a tracking-based approach combining gradient vector flow (GVF) and position-based dynamics (PBD). An open-state surface model of the valve is propagated through time to the closed state, attracted by the GVF field of the leaflet area. The PBD method ensures topological consistency during deformation. For evaluation, one expert in cardiac surgery annotated the closed-state leaflets in 10 TEE sequences of patients with normal and abnormal mitral valves, and defined the corresponding open-state models. The average point-to-surface distance between the manual annotations and the final tracked model was [Formula: see text]. Qualitatively, four cases were satisfactory, five passable and one unsatisfactory. Each sequence could be segmented in 2-6min. Our approach enables to segment the mitral valve in 4D TEE image data with normal and pathological valve closing behavior. With this method, in addition to the quantification of the remaining orifice area, shape and dimensions of the coaptation zone can be analyzed and considered for planning and surgical result assessment.

Sodium cholate as efficient green reducing agent for graphene oxide via flow reaction for flexible supercapacitor electrodes

In this work, sodium cholate (NaC) was used as novel green reducing agent for graphene oxide (GO) reduction at 90 °C and short synthesis time using a continuous segmented flow reaction system. As a comparison, we had used the common reducing agent which is glucose to study its chemical and electrochemical properties. The morphologies of GO and reduced-graphene oxide (rGO) were characterized with X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FESEM), Fourier transformed infrared (FTIR), Raman and Ultraviolet–Visible (UV–Vis) spectroscopy analysis demonstrated that reduction of GO occurred. For electrochemical measurements, the rGO was cast on carbon cloth to investigate the electrochemical performance with cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) measurements. NaC assisted rGO (rGO–NaC) was able to achieve a specific capacitance up to 94 F g−1 at 0.1 A g−1 and remarkable capacitance retention of 103% after 10,000 cycles. A flexible test shows that rGO–NaC bendable at 0°–60°. These results demonstrate that rGO–NaC is promising as flexible supercapacitors electrodes.

Multistep Solvent-Free 3 m2 Footprint Pilot Miniplant for the Synthesis of Annual Half-Ton Rufinamide Precursor.

The development of a pilot-scale synthesis of the rufinamide precursor in flow chemistry is reported. Complex steps such as Taylor-flow, segmented flow, and high-temperature processing at high pressure (high-p,T) are successfully combined, overcoming the mixing and heat transfer issues of the scale-up. The cascaded multistep process operates essentially solvent-free in just 3 m2 giving a productivity of 47 g/h (>400 kg/year), which increases by a factor of 7 the lab-scale productivity previously reported as a scale-up proof-of-concept. This publication also includes an economic study of the feasible implementation of this technology for a possible manufacturer, as well as an outline on business development strategies of how to implement such a disruptive technology.

Digital Rock Approach to Model the Permeability in an Artificially Heated and Fractured Granodiorite from the Liquiñe Geothermal System (39°S)

The Southern Volcanic Zone of the Andes has a high potential in terms of geothermal resources and is an exceptional and poorly explored natural laboratory to study the interplay between tectonic stresses, thermal damage, low-permeable crystalline rocks, and fluid flow. Permeability is mostly related to the damage zones associated with the faults controlling regional tectonics, namely, the Liquine–Ofqui Fault System and Andean Transverse Faults. This research presents a laboratory approach comprising a characterization of the analogue host rock from a shallow, low-to-medium temperature geothermal system surrounding the Liquine area in Southern Chile (39°S) to better constrain intrinsic and extrinsic factors which allow permeable pathways to exist. We analyse the effect of thermal stress at 25, 150, and 210 °C in a granodiorite, measuring some petrophysical properties before and after applying thermal damage, and then loaded the samples until failure. We also compared petrophysical properties with the fracture network characterization using X-ray microcomputed tomography imaging, segmentation, and fluid flow computational simulations. The results show that thermal stress produces intercrystalline microcracks, which result in: (1) an increase in capillary absorption; (2) a decrease in ultrasonic wave velocities; (3) a decrease in compressive strength; (4) a decrease in fracture aperture, and (5) fluid flow simulations indicate that permeability is similar at different temperatures. We conclude that for the granodiorite host rock of the Liquine geothermal system, the combined effect of thermal stress, even at low temperature, may constitute an effective mechanism for sustaining permeability at shallowest depths.

Vasospasm and delayed cerebral ischemia after uneventful clipping of an unruptured intracranial aneurysm \u2013 a case report

BackgroundDue to improvements in both the quality and availability of intracranial imaging as well as the evolution of surgical and endovascular techniques during the last decade, the number of treatments of unruptured intracranial aneurysms (UIA) has increased steadily. However, it is not generally known that vasospasm can arise after an uneventful clipping.Case presentationWe present a case of a 69-year-old woman who suffered from vasospasm and delayed cerebral ischemia that occurred after an uneventful clipping of a UIA.The aneurysm of the right middle cerebral artery was found incidentally via magnetic resonance imaging ordered after the patient complained of a short period of slight gait disturbances. To avoid a subarachnoid hemorrhage and consecutive complications like vasospasms, the patient elected microsurgical treatment. Clipping was managed by keyhole approach. Temporal clipping of the M1 was not necessary. After clip placement, appropriate flow in all distal segments was confirmed by indocyanine green video-angiography and micro-Doppler. The patient was discharged seven days after surgery without neurological deficits.After 12 days, the patient developed at home a sudden drooping on the left side of the face. Upon admission to the emergency room, the patient was alert but slightly confused. Neurological examination revealed a left-sided hemiparesis and motor speech disorder. In contrast to the preoperative transfemoral catheter angiography, the subsequent right internal carotid angiogram showed clear signs of vasospasm along the M1 and M2 segments of the right middle cerebral artery.Antithrombotic treatment with acetylsalicylic acid was begun. In accordance with guidelines for the treatment of subarachnoid hemorrhage and vasospasm, nimodipine was added. After 11 days the patient was discharged with no symptoms.ConclusionCerebral vasospasm as a cause of ischemic stroke after uneventful surgery for a UIA seems to be a rare but possibly underestimated etiology that demands particular attention with respect to providing appropriate treatment. In future, it may be prudent to perform follow-up transcranial ultrasonography testing after the clipping of a UIA, especially considering the availability of potentially neuroprotective medications like nimodipine.

"On-the-Fly" Fabrication of Highly-Ordered Interconnected Cylindrical and Spherical Porous Microparticles via Dual Polymerization Zone Microfluidics.

A microfluidic platform with dual photopolymerization zones has been developed for production of novel uniform interconnected porous particles with shapes imposed either by the geometry of the external capillary or by the thermodynamic minimization of interfacial area. Double w/o/w (water/oil/water) drops with well-defined internal droplet size and number were produced and then exposed to online photopolymerization to create the porous particles. Cylindrical interconnected porous particles were produced in a segmented flow where the drops took the shape of the capillary. The microfluidic setup included an extension capillary where the drops relaxed and conformed to their thermodynamically favored morphology. Window opening of the particles occurred "on-the-fly" during UV polymerization without using any offline auxiliary methods. A distinction was made between critically and highly packed arrangements in double drops. The window opening occurred consistently for highly packed spherical drops, but only for critically packed drops containing more than six internal cores at internal phase ratios as low as 0.35. The size and number of cores and shape and structure of double drops could be precisely tuned by the flow rate and by packing structure of the inner droplets.

Segmental Intracellular, Interstitial, and Intravascular Volume Changes during Simulated Hemorrhage and Resuscitation: A Case Study.

This paper describes a new combined impedance plethysmographic (IPG) and electrical bioimpedance spectroscopic (BIS) instrument and software that will allow noninvasive real-time measurement of segmental blood flow, intracellular, interstitial, and intravascular volume changes during various fluid management procedures. The impedance device can be operated either as a fixed frequency IPG for the quantification of segmental blood flow and hemodynamics or as a multi-frequency BIS for the recording of intracellular and extracellular resistances at 40 discrete input frequencies. The extracellular volume is then deconvoluted to obtain its intravascular and interstitial component volumes as functions of elapsed time. The purpose of this paper is to describe this instrumentation and to demonstrate the information that can be obtained by using it to monitor segmental compartment volume responses of a pig model during simulated hemorrhage and resuscitation. Such information may prove valuable in the diagnosis and management of rapid changes in the body fluid balance and various clinical treatments.