Acoustic signature of the normal swallow: Characterization by age, gender, and bolus volume

Despite growing clinical use, cervical auscultation suffers from a lack of research-based data. One of the strongest criticisms of cervical auscultation is that there has been little research to demonstrate how dysphagic swallowing sounds are different from normal swallowing sounds, In order to answer this question, however, one first needs to document the acoustic characteristics of normal, nondysphagic swallowing sounds, This article provides the first normative database of normal swallowing sounds for the adult population. The current investigation documents the acoustic characteristics of normal swallowing sounds for individuals from 18 to more than 60 years of age over a range of thin liquid volumes. Previous research has shown the normal swallow to be a dynamic event. The normal swallow is sensitive to aging of the oropharyngeal system, and also to the volume of bolus swallowed. The current investigation found that the acoustic signals generated during swallowing were sensitive to an individual's age and to the volume of the bolus swallowed. There were also some gender-specific differences in the acoustic profile of the swallowing sound, It is anticipated that the results will provide a catalyst for further research into cervical auscultation.

How thick is thick? Multicenter study of the rheological and material property characteristics of mealtime fluids and videofluoroscopy fluids

Objective rheological assessment of fluids given to dysphagic patients at mealtime and during videofluoroscopy was carried out using a multicenter format. Thin, quarter-thick, half-thick and full-thick fluids were examined for the degree of correlation between mealtime fluids and their allegedly matched videofluoroscopy counterparts. The study was carried out to determine whether perceived subjective differences between mealtime fluids and videofluoroscopy fluids could be quantified using the rheological parameters of viscosity, density, and yield stress. The results showed poor correlation between mealtime fluids and videofluoroscopy fluids over all parameters. In general, the videofluoroscopy fluids were more viscous, more dense, and showed higher yield stress values than their mealtime counterparts. Given these results, it is reasonable to assume that the fluids used during videofluoroscopy do not provide an accurate indication of swallowing ability at mealtime. Therefore, it is suggested that clinicians use objective methods to theologically match videofluoroscopy fluids to mealtime fluids.

What happens after the swallow? Introducing the glottal release sound

Cervical auscultation presents as a noninvasive screening assessment of swallowing. Until now the focus of acoustic research in swallowing has been the characterization of swallowing sounds,. However, it may be that the technique is also suitable for the detection of respiratory sounds post swallow. A healthy relationship between swallowing and respiration is widely accepted as pivotal to safe swallowing. Previous investigators have shown that the expiratory phase of respiration commonly occurs prior to and after swallowing. That the larynx is valved shut during swallowing is also accepted. Previous research indicates that the larynx releases valved air immediately post swallow in healthy individuals. The current investigation sought to explore acoustic evidence of a release of subglottic air post swallow in nondysphagic individuals using a noninvasive medium. Fifty-nine healthy individuals spanning the ages of 18 to 60+ years swallowed 5 and 10 milliliters (ml) of thin and thick liquid boluses. Objective acoustic analysis was used to verify presence of the sound and to characterize its morphological features. The sound, dubbed the glottal release sound, was found to consistently occur in close proximity following the swallowing sound. The results indicated that the sound has distinct morphological features and that these change depending on the volume and viscosity of the bolus swallowed. Further research will be required to translate this information to a clinical tool.

A demonstration of artificial dissipation effects in some finite volume solution methods for the Navier-Stokes equations

The artificial dissipation effects in some solutions obtained with a Navier-Stokes flow solver are demonstrated. The solvers were used to calculate the flow of an artificially dissipative fluid, which is a fluid having dissipative properties which arise entirely from the solution method itself. This was done by setting the viscosity and heat conduction coefficients in the Navier-Stokes solvers to zero everywhere inside the flow, while at the same time applying the usual no-slip and thermal conducting boundary conditions at solid boundaries. An artificially dissipative flow solution is found where the dissipation depends entirely on the solver itself. If the difference between the solutions obtained with the viscosity and thermal conductivity set to zero and their correct values is small, it is clear that the artificial dissipation is dominating and the solutions are unreliable.

Free volume and water uptake in a copolymer hydrogel series

A copolymer of X-hydroxyethyl methacrylate (HEMA) with 2-ethoxy ethyl methacrylate (EEMA) was synthesized and the molecular mobility, free volume, and density properties examined as a function of composition. These properties were correlated with the equilibrium water uptake in order to determine which of the properties were most influential in causing high water sorption, as these materials are suitable candidates for hydrogel systems. It was found that the polar HEMA repeat unit results in a rigid, glassy sample at room temperature due to the high degree of hydrogen bonding between chains whereas high EEMA content leads to rubbery samples with subambient glass transition temperatures. The free volume properties on the molecular scale measured by positron annihilation Lifetime spectroscopy (PALS) showed that higher HEMA content led to smaller, fewer holes and a lower free volume fraction than EEMA. Therefore the high water uptake of HEEMA-containing copolymers is largely related to the high polarity of the HEMA unit compared to EEMA, despite the low content of free volume into which the water can initially diffuse. Trends in density with copolymer composition, as measured on a macroscopic level, differs to that seen by PALS and indicates that the two techniques are measuring different scales of packing. (C) 1998 John Wiley & Sons, Inc.

A phase-segregated model for plant cell culture: The effect of cell volume fraction

Plant cells are characterized by low water content, so the fraction of cell volume (volume fraction) in a vessel is large compared with other cell systems, even if the cell concentrations are the same. Therefore, concentration of plant cells should preferably be expressed by the liquid volume basis rather than by the total vessel volume basis. In this paper, a new model is proposed to analyze behavior of a plant cell culture by dividing the cell suspension into the biotic- and abiotic-phases, Using this model, we analyzed the cell-growth and the alkaloid production by Catharanthus roseus, Large errors in the simulated results were observed if the phase-segregation was not considered.

Kinetic analysis of vascular marker distribution in perfused rat livers after regeneration following partial hepatectomy

Background/Aims: Liver clearance models are based on information (or assumptions) on solute distribution kinetics within the microvasculatory system, The aim was to study albumin distribution kinetics in regenerated livers and in livers of normal adult rats, Methods: A novel mathematical model was used to evaluate the distribution space and the transit time dispersion of albumin in livers following regeneration after a two-thirds hepatectomy compared to livers of normal adult rats. Outflow curves of albumin measured after bolus injection in single-pass perfused rat livers were analyzed by correcting for the influence of catheters and fitting a long-tailed function to the data. Results: The curves were well described by the proposed model. The distribution volume and the transit time dispersion of albumin observed in the partial hepatectomy group were not significantly different from livers of normal adult rats. Conclusions: These findings suggest that the distribution space and the transit time dispersion of albumin (CV2) is relatively constant irrespective of the presence of rapid and extensive repair. This invariance of CV2 implies, as a first approximation, a similar degree of intrasinusoidal mixing, The finding that a sum of two (instead of one) inverse Gaussian densities is an appropriate empirical function to describe the outflow curve of vascular indicators has consequences for an improved prediction of hepatic solute extraction.

An evaluation of the time dependence of the anisotropy of the water diffusion tensor in acute human ischemia

We have performed MRI examinations to determine the water diffusion tensor in the brain of six patients who were admitted to the hospital within 12 h after the onset of cerebral ischemic symptoms. The examinations have been carried out immediately after admission, and thereafter at varying intervals up to 90 days post admission. Maps of the trace of the diffusion tensor, the fractional anisotropy and the lattice index, as well as maps of cerebral blood perfusion parameters, were generated to quantitatively assess the character of the water diffusion tensor in the infarcted area. In patients with significant perfusion deficits and substantial lesion volume changes, four of six cases, our measurements show a monotonic and significant decrease in the diffusion anisotropy within the ischemic lesion as a function of time. We propose that retrospective analysis of this quantity, in combination with brain tissue segmentation and cerebral perfusion maps, may be used in future studies to assess the severity of the ischemic event. (C) 1999 Elsevier Science Inc.

Bioimpedance: Is it a predictor of true water volume?

Bioelectrical impedance analysis (BIA) has been reported to be insensitive to changes in water volumes in individual subjects, This study was designed to investigate the effect on the intra- and extracellular resistances (Ri and Re) of the segments of subjects for whom body water was changed without significant change to the total amount of electrolyte in the respective fluids, Twelve healthy adult subjects were recruited. Ri and Re of the leg, trunk, and arm of the subjects were determined from BIA measures prior to commencement of two separate studies that involved intervention, resulting in a loss/gain of body water effected either bt a sauna followed by water intake (study 1) or by ingestion (study 2). Ri and Re of the segments were also determined at a number of times following these interventions, The mean change in body water, expressed as a percentage of body weight, was 0.9% in study 1 and 1.25% in study 2. For each study, the results for each subject were normalized for each limb to the initial (prestudy) value and then the normalized results for each segment were pooled for all subjects, ANOVA of these pooled results failed to demonstrate any significant differences between the normalized mean values of Ri or Re of the segments measured through the course of each study, The failure to detect a change in Ri or Re is explained in terms of the basic theory of BIA.

Modeling of hepatic elimination and organ distribution kinetics with the extended convection-dispersion model

The conventional convection-dispersion (also called axial dispersion) model is widely used to interrelate hepatic availability (F) and clearance (Cl) with the morphology and physiology of the liver and to predict effects such as changes in liver blood flow on F and Cl. An extended form of the convection-dispersion model has been developed to adequately describe the outflow concentration-time profiles for vascular markers at both short and long times after bolus injections into perfused livers. The model, based on flux concentration and a convolution of catheters and large vessels, assumes that solute elimination in hepatocytes follows either fast distribution into or radial diffusion in hepatocytes. The model includes a secondary vascular compartment, postulated to be interconnecting sinusoids. Analysis of the mean hepatic transit time (MTT) and normalized variance (CV2) of solutes with extraction showed that the discrepancy between the predictions of MTT and CV2 for the extended and conventional models are essentially identical irrespective of the magnitude of rate constants representing permeability, volume, and clearance parameters, providing that there is significant hepatic extraction. In conclusion, the application of a newly developed extended convection-dispersion model has shown that the unweighted conventional convection-dispersion model can be used to describe the disposition of extracted solutes and, in particular, to estimate hepatic availability and clearance in booth experimental and clinical situations.

Regarding "Edema and leg volume: Methods of assessment" (Letters to the Editor)

I noted with interest the article by Drs Perrin and Guex, entitled &dquo;Edema and leg volume: Methods of assessment,&dquo; published in Angiology 51:9-12, 2000. This was a timely and comprehensive review of the various methods in clinical use for the assessment of peripheral edema, notably in the leg. I would like to take this opportunity to alert readers to a further technique useful for this purpose, namely, bioelectrical impedance analysis. An early reportl described its use for the measurement of edema in the leg, but other than its successful use for the assessment of edema in the arm following masteCtoMy,2,1 the potential of the method remains to be fully realized. This is unfortunate since the method directly and quantifiably measures edema.

Tubular system volume changes in twitch fibres from toad and rat skeletal muscle assessed by confocal microscopy

The volume of the extracellular compartment (tubular system) within intact muscle fibres from cane toad and rat was measured under various conditions using confocal microscopy. Under physiological conditions at rest, the fractional volume of the tubular system (t-sys(Vol)) was 1.38 +/- 0.09% (n = 17),1.41 +/- 0.09% (n = 12) and 0.83 +/- 0.07% (n = 12) of the total fibre volume in the twitch fibres from toad iliofibularis muscle, rat extensor digitorum longus muscle and rat soleus muscle, respectively. In toad muscle fibres, the t-sys(Vol) decreased by 30% when the tubular system was fully depolarized and decreased by 15% when membrane cholesterol was depleted from the tubular system with methyl-beta-cyclodextrin but did not change as the sarcomere length was changed from 1.93 to 3.30 mum. There was also an increase by 30% and a decrease by 25% in t-sys(Vol) when toad fibres were equilibrated in solutions that were 2.5-fold hypertonic and 50% hypotonic, respectively. When the changes in total fibre volume were taken into consideration, the t-sys(Vol) expressed as a percentage of the isotonic fibre volume did actually decrease as tonicity increased, revealing that the tubular system in intact fibres cannot be compressed below 0.9% of the isotonic fibre volume. The results can be explained in terms of forces acting at the level of the tubular wall. These observations have important physiological implications showing that the tubular system is a dynamic membrane structure capable of changing its volume in response to the membrane potential, cholesterol depletion and osmotic stress but not when the sarcomere length is changed in resting muscle.