[Existential hope: a phenomenological key to understanding depression?] / Existentiële hoop: een fenomenologisch leidmotief in het verstaan van depressie?

BACKGROUND: Researchers that try to identify the relationship between hope and mental health often lack a conceptual understanding of 'hope'. Nonetheless, experiences of despair that are central in depression seem to surpass our everyday understanding of hope and hopelessness. How can this despair be understood and recognized? OBJECTIVE To describe depression through a phenomenological understanding of hope and to explore how this insight relates to our current definition of depression as a mood disorder, as well as to clinical practice.
RESULTS: Existential hope arises spontaneously in our experience of the world and through the relationship with significant others. A significant part of the experience of depression amounts to the loss of existential hope. Depressive despair features a radically shifted experiential structure, which seems to be absent in demoralisation; this advocates the view of depression as a 'disorder of attunement'. A therapeutic relationship can recover the loss by cultivating a new sense of possibilities.
CONCLUSION: The idea of existential hope provides a new conceptual framework to understand the experience of depression as well as the possibility for its recovery.

[Parental alienation and the controversy surrounding psychiatric diagnostics]. / Ouderverstotingssyndroom en de controverse rond psychiatrische diagnostiek.

BACKGROUND: The phenomenon of parental alienation can arise when a child allies with one parent and refuses to have contact with the other parent. The concept has attracted a great deal of attention over the last few years. There has been controversy about whether parental alienation should be recognised as a psychiatric syndrome of the alienated child caught up in a conflict between supporters and opponents.
AIM: To try to determine whether parental alienation belongs to psychiatric diagnostics.
METHOD: We made a careful study of various databases in order to find literature relating to parental alienation.
RESULTS: Parental alienation is situated on the border between psychiatry, sociology and justice. One of the main tasks of psychiatry in this border area is to safeguard the domain of diagnostics.
CONCLUSION: Because so much attention is being given to the question of whether parental alienation syndrome should be recognised as a diagnosis, there is often a tendency to ignore the possible impact of parental alienation and to pay very little attention to ways of coping with the problem.

[Phenomenology and science. On the foundations of psychiatry in Heidegger's Zollikon Seminars]. / Fenomenologie en wetenschap; over de grondslagen van de psychiatrie in Heideggers Zollikoner Seminare.

Psychiatrists today feel they are pulled between two schools of thought: on the one hand there is the theory which is based mainly on neuroscientific research, on the other hand there is the theory which puts more emphasis on the narrative character of psychiatric illness. In this article we will overlook this dichotomy and concentrate on psychiatry as a unitas multiplex, based on the foundations of both schools of thought. Both the scientific method and the phenomenological approach play an essential role in medical practice. Heidegger's thinking in the Zollikon Seminars will serve to develop a methodological consciousness.

[Dissociative phenomena: relationship to present and past stress]. / Dissociatieve verschijnselen: verband met stress uit heden én verleden.

BACKGROUND: Up till now research into dissociation has paid little attention to the relationship between current stress and family variables on the one hand and dissociative phenomena on the other hand. By contrast, however, many studies have investigated the link between traumatic experiences in the past and dissociative phenomena. AIM: To investigate, in a clinical population, whether dissociation is linked to current stress (within and outside the family) and to traumatic experiences in the past. METHOD: Dissociation was predicted on the basis of current stress (within and outside the family) and trauma by means of a multiple regression conducted on a population of patients with an eating disorder. RESULTS: Results indicated a clear link between current stress and dissociation. Patients with particularly high dissociation scores reported significantly more stress both on the measures of current stress and on the list of trauma. CONCLUSION: Dissociation is associated with stressful experiences, but not only with sexual trauma. Dissociation is also linked to stress experienced in current living conditions. Therefore the simple model that links dissociative experiences directly with trauma needs to be revised. This finding demonstrates that more attention should be given to stress factors in the treatment of dissociative phenomena.

Hemodynamic comparison of two different pediatric aortic cannulas.

Any extracorporeal blood treatment requires an adequate and safe connection to the circulation. For cardiopulmonary bypass procedures, aortic and venous cannulas are utilized. However, the performance of these cannulas is not only dependent on their size (diameter), but also on their complete geometric design. In this paper two aortic cannula designs are evaluated hemodynamically for two different sizes (8, 10 Fr) both with aqueous fluids and with blood. Using the novel concept of equivalent diameter, a new performance parameter, and the theory of dynamic similarity the results obtained with different fluids can be compared. Data points of one cannula can be fitted to a parabolic equation. There is a significant performance difference between the two 8 Fr cannulas. The 10 Fr cannulas differ non-significantly except when water is used. Equivalent diameters obtained with water in the turbulent region are significantly higher than those obtained with fluids that have a higher viscosity (blood and aqueous glycerine mixture). The latter fluids have comparable viscosities and render an equal equivalent diameter. The coefficients of their proper parabolic fit lines can easily be recalculated into each other. This provides a simple method to quickly determine pressure drops in cannulas in the operating room.

Evaluation of different paediatric venous cannulae using gravity drainage and VAVD: an in vitro study.

Six different commercially available paediatric venous cannulae, together with a specially constructed cannula, were tested in vitro for their pressure-flow relationship. With the cannulae placed in an open reservoir, flow increased with larger diameters and higher pressures. At a pressure of 30 cm H2O, flows were 219 +/- 20, 285 +/- 13, 422 +/- 11 and 728 +/- 4 ml/min for the 12, 13.2, 14 and 16 French, respectively. No differences were found between angled and straight cannulae. When the cannulae were tested in a latex model simulating the right atrium and vena cavae, the highest flow obtained by gravity was 164 ml/min using an angled 14-French cannula. When vacuum was applied to augment venous return, a maximum flow of 179 ml/min was measured using an angled 14-French cannula. Collapse can occur when the pressure difference becomes too high in the test system. This is important, since most children are selectively cannulated in both major veins. Monitoring of the intravascular pressure might help to prevent collapse. A larger-diameter venous cannula does not always produce the highest flow when placed in a vein. This is most obvious when augmenting venous return. The design of the cannula tip, in combination with VAVD, can affect the venous return.

In vitro evaluation of the hydraulic permeability of polysulfone dialysers.

An in vitro set-up has been designed to study the hydraulic permeability of hollow fiber dialysers. Forward and reverse dialysate ultrafiltration were determined using both sterile dialysers and samples with a protein layer settled on the membrane (Fresenius F6, F8, F60 and F80). The ultrafiltration coefficient KUF (ml/h.mmHg) was calculated as the ratio of volumetrical flow (QUF) and transmembrane pressure (TMP) measurements. The protein layer on the membrane was induced either by recirculating human plasma through the dialysers (in vitro) or by a standard hemodialysis session (in vivo). KUF is largely independent of TMP up to 600mmHg (low flux) and 60mmHg (high flux) for forward and reverse flow In sterile dialysers, backfiltration yields a significantly different KUF except for the F80. An in vitro induced protein layer on the membrane decreases KUF15-30% (forward) and 4-12% (backward) in low flux and 45-70% (forward) and 65-73% (backward) in high flux dialysers.

Mass transfer characteristics of artificial lungs.

An artificial lung is used during cardiopulmonary bypass to oxygenate blood and control blood temperature. The oxygen transfer rate-flow rate characteristics of three hollow fiber membrane artificial lungs (Sarns Turbo 440, Cobe Optima, Dideco Compactflo) were determined in vitro to characterize design features. Results are presented as a unique dimensionless relationship between Sherwood number, NSh (ratio of convective to diffusive mass transfer), Schmidt number, NSc (ratio of momentum to diffusive transport), and Reynolds number, NRe (ratio of inertial to viscous forces). This relationship is a function of device porosity, epsilon, and characteristic device length, xi, defined as the ratio of the mean blood path and manifold length: Nsh/NSc(1/3) x xi(1/2) = phi x (epsilon(1/m) x NRe)(m) where phi = 0.26 and m = 1.00 for NPe < 3,200 and phi = 0.47 and m = 0.64 for NPe > 3,200 where NPe is the dimensionless Péclet number defined as NRe x NSc. We found good correspondence between the model predictions and in vitro blood oxygen transfer rates. We conclude that this dimensionless approach allows us (1) to compare artificial lungs independently, (2) to relate water tests to blood, and (3) to predict the oxygen transfer rate of a new artificial lung design.

Two-dimensional finite element model for oxygen transfer in cross-flow hollow fiber membrane artificial lungs.

A predictive, two-dimensional model with good absolute accuracy for flow and mass transfer in cross-flow hollow fiber membrane artificial lungs is developed. The proposed model is able to predict the gas transfer to water flowing outside and perpendicular to hollow fibers in the artificial lung. The model uses a finite element technique to solve the Navier-Stokes equations and the convection-diffusion equation on the computational domain of a unit fiber cell. Subsequent stream-wise and cross-wise unit fiber cells are then coupled/assembled to the relationship between the oxygen transfer rate and flow rate of a cross-flow hollow fiber membrane artificial lung. The model is compared to experimental water data obtained by perfusing three commercial artificial lungs with water.

Blood flow around hollow fibers.

In an artificial lung, blood is oxygenated and flows around a bundle of hollow fibers while gas flows inside the fiber. The objective of this study is to understand the hydrodynamics of three different fiber banks (inline square IS, staggered square SS and equilateral triangle ET) and to investigate the influence of both a Newtonian and non-Newtonian Casson viscosity model on the flow field. A two-dimensional finite element model for permanent, isothermal, laminar blood flow perpendicular to hollow fibers is used. All fibers are assumed identical, straight and parallel. Porosity ranges from 0.4 to 0.6 and Reynolds number varies from 1 to 60. For a given Re, ET generates less resistance than SS, the latter being comparable with IS. A lower porosity increases resistance. Non-Newtonian viscosity affects velocity patterns only at low Re (<0.5) and higher porosity (>0.5). Resistance at low Re is significantly elevated in the fiber banks due to an overall increase in viscosity. This model makes it possible to study the influence of geometry and viscosity on hydrodynamics in fiber banks and may aid in the optimization of hollow fiber artificial lung design.

Hydrodynamic characteristics of artificial lungs.

An artificial lung is used during cardiopulmonary bypass to oxygenate blood and to control blood temperature. The pressure drop-flow rate characteristics of the membrane compartment in three hollow fiber membrane oxygenators were determined in vitro to characterize design features. Results are presented in a unique dimensionless relationship between Euler number, N(Eu) (ratio of pressure drop to kinetic energy), and Reynolds number, N(Re) (ratio of inertial to viscous forces), and are a function of the device porosity, epsilon, and a characteristic device length, xi, defined as the ratio of the mean blood path and manifold length: [equation in text]. This dimensionless approach allows us (1) to compare oxygenators independently, and (2) to relate water tests to blood.

Predialysis urea concentration is sufficient to characterize hemodialysis adequacy.

Mathematical description of urea kinetics for a week showed that, under steady state conditions (i.e., total removal equals total synthesis), any predialysis urea concentration is expressed as a linear function of specific urea generation (G/V) and of dialysis schedule timing and sessional Kt/V (product of clearance, K, and session time, t, divided by the urea distribution volume, V). It also predicts that TACurea is proportional to the predialysis concentrations. The ratio between the two depends linearly on delivered weekly dialysis dose ([wDD] = T(G/V)/TACurea, with T the number of hours in 1 week). These hypotheses have been tested by retrospectively analyzing urea kinetc modelling data that include all predialysis and post dialysis concentrations of 163 patient-weeks. All patients were anuric, and dialysis frequency was thrice weekly. Accuracy is assessed with regression analysis between database numbers and computed values. The theoretical ratio between midweek concentration and TACurea (1.43) is close to the computed ratio (1.46, r2 = 0.909). TACurea (slope = 1.002, r2 = 0.997), specific generation rate G/V as a precursor to PCRn (slope = 1.007, r2 = 0.985), and wDD (slope = 1.002, r2 = 0.909) are all accurately computed from predialysis concentrations. To aid in the determination of the ratio for the different predialysis, concentrations using wDD a nomogram is included.

Hydrodynamical comparison of aortic arch cannulae.

The high velocity of blood flow exiting aortic arch cannulae may erode atherosclerotic material from the aortic intima causing non-cardiac complications such as stroke, multiple organ failure and death. Five 24 Fr cannulae from the Sarns product line (straight open tip, angled open tip with and without round side holes, straight and angled closed tip with four rectangular, lateral side holes), and a flexible cannula used at the University Hospital of Gent (straight open tip) are compared in an in vitro steady flow setup, to study the spatial velocity distribution inside the jet. The setup consists of an ultrasound Doppler velocimeter, mounted opposite to the cannula tip in an outflow reservoir. An elevated supply tank supplies steady flow of 1.3 L/min of water. Exit forces at various distances from the tip are calculated by integrating the assessed velocity profiles. The pressure drop across the cannula tip is measured using fluid filled pressure transducers. The four sidehole design provides the lowest exit velocity (0.85 versus 1.08 m/s) and force per jet (0.03 vs 0.15-0.20 N). The round sideholes are useless as less than 1% of the flow is directed through them. Furthermore, the use of angled tip cannulae is suggested because the force exerted on the aortic wall decreases the more the angle of incidence of the jet deviates from 90 degrees. Pressure drop is the lowest for the 4 side hole design and highest for the open tip and increases when an angled tip is used.

Blood trauma in plastic haemodialysis cannulae.

To investigate the haemolysis in haemodialysis cannulae, an in-vitro set up is built, using a unipuncture dialysis system. This system is connected to a bag with fresh calf's blood, by the cannula under test, mounted in a large bloodline (5 mm diameter). The blood characteristics are kept constant by means of a bicarbonate dialysate in the dialyser. During a 6 h period, haematological parameters are regularly samples. Flow through the cannulae is recorded, which is about 500 mL/min. Four different cannulae are tested and compared to the results obtained without any cannula in the circuit. In all cases a linear increase in plasma free haemoglobin levels is found after 6 h. The cannulae can be ranked from 8F catheter over 13G, 14G to 16G cannula, the latter producing the highest degree of haemolysis. When using plastic cannulae at high blood flows, their haemolytic effect may not be neglected.

Distribution of Marcaine in an in vitro model of the subarachnoid space conforming to actual spinal column geometries.

To study factors influencing the distribution of local anaesthetics in the subarachnoid space, an in vitro model is constructed which takes into account the natural curvature of the spinal column and the volume occupation of spinal cord and nerve fibres to resemble the in vivo situation. Three Marcaine solutions of different baricity (1003, 1008, 1030 kg/m3) are injected with a 22 G, a 27 G Quincke point needle and a 18 G multiport catheter into three models of non-pathological spinal columns with injection flow speeds of 0.6, 0.2 or 0.1 ml/s. Methylene blue is added for visual and qualitative assessment of drug distribution. Baricity is the main actor in the spreading of the drug solution. For all other variables, no significant difference is found after ten minutes, though the initial distribution may differ according to the geometry used. A hypobaric solution yields a remarked difference between fast and slower injections. The position of the catheter should be controlled.

Red cell injury assessed in a numeric model of a peripheral dialysis needle.

The highest shear stresses in a dialysis system are expected to be found in the needle, where the largest velocity-diameter ratio appears. Shear is a known source of hemolysis and related patients' discomfort. To assess the magnitude of blood cell injury and the location of its sources, a finite element model is used to calculate three-dimensional velocities and shear stresses in peripheral dialysis needles, concentrically placed in a rigid wall fistula. The boundary conditions consist of time dependent in vivo measured pressures. Cell damage is computed for different cell tracks into the needle by means of Wurzinger's empirical formula, which expresses the hemoglobin (Hb) release as a function of shear stress and shearing time. Near the needle wall, velocities are low and shear stresses high, resulting in a significantly higher level of cell damage: 0.1% vs 0.001% in bulk flow for a mean flow of 91 ml/min into a 14G needle with a peak velocity of 220 cm/sec. The deviation from the classic Poiseuille velocity profile is shown. Less than 5% of the flow passes through this high damage path. A vortex at the inner side of the needle has a cumulative damage of 0.007% per 0.23 sec trip around the vortex.

Comparison of a new and a standard single-needle dialysis system using a mathematical model.

Two single-needle dialysis systems are compared for their hydrodynamic and kinetic behavior, the classic double-headed pump system and a newer bidirectional blood pump. First, discharges and pressures are calculated in a time-space grid to learn about the flow characteristics of the single-needle systems. These parameters are important for they control ultrafiltration and clearance rates in the artificial kidney. Also, the influence of different artificial kidneys and expansion chambers on the flow parameters is studied. Second, starting from these results, the removal of urea and creatinine is simulated using a double-pool model for both a normal dialysis session and an ultrashort daily autodialysis. As a result, the use of a single marker molecule to study or characterize solute removal is questioned. The new blood pump is able to perform dialysis filtering equivalently to the classic system but has its own specific advantages.