Broadband multizone sound rendering by jointly optimizing the sound pressure and particle velocity.

In this paper, a recently proposed approach to multizone sound field synthesis, referred to as joint pressure and velocity matching (JPVM), is investigated analytically using a spherical harmonics representation of the sound field. The approach is motivated by the Kirchhoff-Helmholtz integral equation and aims at controlling the sound field inside the local listening zones by evoking the sound pressure and particle velocity on surrounding contours. Based on the findings of the modal analysis, an improved version of JPVM is proposed, which provides both better performance and lower complexity. In particular, it is shown analytically that the optimization of the tangential component of the particle velocity vector, as is done in the original JPVM approach, is very susceptible to errors and thus not pursued anymore. Furthermore, the analysis provides fundamental insights as to how the spherical harmonics used to describe three-dimensional sound fields translate into two-dimensional basis functions as observed on the contours surrounding the zones. By means of simulations, it is verified that discarding the tangential component of the particle velocity vector ultimately leads to an improved performance. Finally, the impact of sensor noise on the reproduction performance is assessed.

The spatial coherence of noise fields evoked by continuous source distributions.

In this work, analytic expressions for the spatial coherence of noise fields are derived in the modal domain with the aim of providing a sparse representation. For this purpose, the sound field in a region of interest is expressed in terms of a given pressure distribution on a virtual surrounding cylindrical or spherical surface. According to the Huygens-Fresnel principle, the sound pressure on this surface is represented by a continuous distribution of elementary line or point sources, where orthogonal basis functions characterize the spatial properties. To describe spatially windowed pressure distributions with arbitrary angular extensions, orthogonal basis functions of limited angular support are proposed. As special cases, circular and spherical pressure distributions with uncorrelated source modes of equal power are investigated. It is shown that these distributions result, respectively, in cylindrically isotropic and spherically isotropic, i.e., diffuse noise fields. The analytic expressions derived in this work allow for a prediction of the spatial coherence between arbitrary positions within the region of interest, such that no microphones need to be placed at the actual points of interest. Simulation results are presented to validate the derived relations.

Real time heart ischemia detection in the smart home care system.

In this paper, a novel real-time algorithm for detecting ischemia in the ECG signal is proposed. The goal of this research is to meet the requirements of some smart cardiac home care devices, which can automatically diagnose the ECG and detect the heart risks outside the hospital, especially heart ischemia without symptoms in their early stages. The algorithm is developed based on a real time R peak detector, time domain traditional ECG parameters, the advanced morphologic parameters from Karhunen-Loève transform, and the adaptive neurofuzzy logic classification. Besides, in order to improve the reliability of our algorithm, several significant constraints of the ECG signal are considered. As a result, the ischemia episodes can be detected if the ischemic alteration persists longer than one minute in the ECG signal.

[Preoperative ECG in routine preoperative assessment of children]. / Das präoperative EKG als Routineuntersuchung bei Kindern.

OBJECTIVE: The aim of this study is to examine whether a routine preoperative ECG is necessary in children to assess the risks in anaesthesia and surgery. METHODS: We examined the records of 3030 children anaesthetized in our hospital in 1990 and compared records of complications with preoperative ECGs. We also evaluated questionnaires on this subject which we had sent to 51 large pediatric hospitals in Germany in 1991. RESULTS: During 3030 anaesthetic procedures there were 93 complications, 67 of which were not of cardiac origin. Of the 26 cardiac complications only 4 needed therapy (AV-Block 2 degrees, fall in blood pressure). Preoperative ECGs were recorded in 180 cases: 152 were normal, 8 showed harmless deviations from normal and 16 were recorded because of known cardiac defects. None of the 180 children developed complications during anaesthesia. Our questionnaire was returned completed carefully by 36 of the 51 hospitals. In most hospitals a preoperative ECG is only recorded when heart disease is known or suspected. CONCLUSION: Routine preoperative ECGs are unnecessary in children unless there are clinical symptoms of heart diseases or heart disease is suspected.

Reducing pain during propofol injection: the role of the solvent.

We hypothesized that the concentration of propofol in the aqueous phase may be the most important variable responsible for the pain experienced during injection of the drug. The concentration of propofol in the aqueous phase (18.57 micrograms/mL) can be decreased by increasing the fat content of the solvent. To test this hypothesis, 36 patients were randomly allocated to one of three groups, each receiving a different formulation of propofol. Group A received 20 mL of propofol alone in a commercial preparation (Diprivan(R) with 10 mL of saline); Group B, 20 mL of propofol to which 5 mL of long-chain triglyceride (LCT) fat emulsion and 5 mL of saline and been added; and Group C, 20 mL of propofol and 10 mL of LCT fat emulsion. The propofol emulsion was injected over 30-60 s into a dorsal vein of the hand. Patients reported pain during injection as none, mild, moderate, or severe (almost intolerable). In Group A, 8 of 12 patients reported moderate or severe pain upon injection whereas in Group C only mild pain was reported by 6 of 12 patients. Our results suggest that a smaller concentration of propofol in the aqueous phase of the emulsion reduces pain on injection. With the addition of more lipid (10 mL), a higher percentage of propofol is absorbed by fat particles. If solvents that permit a smaller concentration of the drug in the aqueous phase of oil-in-water emulsions were used for propofol and other drugs that cause pain on injection, pain would be reduced and patient satisfaction may be increased.

A multicenter study of phospholipase A2 in patients in intensive care units.

BACKGROUND: Multiple organ failure (MOF) is becoming the most common cause of death in patients in surgical intensive care units. In this respect, a multicenter study in four different groups of patients in surgical intensive care units was done to evaluate the role of phospholipase A2 (PLA2) in comparison with C-reactive protein (CRP) and polymorphonuclear (PMN) elastase. STUDY DESIGN: A total of 223 patients entered the study: 73 patients with multiple injuries, 46 patients with diffuse peritonitis, 52 patients with sepsis, and 52 patients in a control group who were at a higher risk for postoperative sepsis after defined surgical interventions. The patients underwent a daily monitoring of PLA2, CRP, and PMN elastase for seven days. RESULTS: Phospholipase A2 activity remained within the normal range in patients with multiple injuries and patients in the control group, indicating that this parameter is not influenced by the postaggression metabolism. In contrast, in patients with peritonitis, high PLA2 values were found from the beginning. The efficiency for predicting a lethal MOF was 85 percent for PLA2 (cut-off 80 U/L) in patients if determined at the day of operation. A comparably favorable efficiency (84 percent) was demonstrated for PMN elastase in patients with multiple injuries (cut-off 205 micrograms/L) measured at day one. CONCLUSIONS: These efficiency rates of PLA2 in peritonitis and PMN elastase in multiple injuries were comparable or even better than multifactorial scoring systems used in the study. C-reactive protein did not contribute to an early estimation of the prognosis in all groups analyzed. Therefore, the measurement of PLA2 in patients with diffuse peritonitis and PMN elastase in patients with multiple injuries, as single parameters, is recommended to estimate the individual risk for the occurrence of lethal MOF.

Low-dose hydrocortisone infusion attenuates the systemic inflammatory response syndrome. The Phospholipase A2 Study Group.

There is increasing evidence that the hypercortisolemia in inflammatory diseases suppresses the elaboration of proinflammatory cytokines, thus protecting the host from its own defence reactions. In severe sepsis and septic shock cortisol levels are usually elevated, but some patients may have relative adrenal insufficiency. This may contribute to the overwhelming systemic inflammatory response syndrome. We evaluated the impact of low-dose hydrocortisone infusion (10 mg/h) on the course of the systemic inflammatory response syndrome. This dose corresponds to a maximum secretory rate of cortisol achieved in corticotropin-stimulated healthy humans. In a prospective observational study 57 surgical patients with severe sepsis or septic shock were studied, of which in addition to the conventional treatment 12 patients were infused with low-dose hydrocortisone, and 45 were treated without any corticosteroid. In the longitudinal analysis the systemic inflammatory response--as judged by body temperature, cardiovascular response, and kinetics of inflammatory mediators such as phospholipase A2, C-reactive protein, and neutrophil elastase--started to differ in favor of the hydrocortisone-treated patients after 2 days of treatment (P < 0.05, Mann-Whitney U test). The difference disappeared after withdrawal of exogenous cortisol. Shock reversal was achieved in all patients treated with low-dose hydrocortisone. The data provide evidence that low-dose hydrocortisone infusion attenuates the systemic inflammatory response in human septic shock. From an immunological point of view a relative cortisol deficiency may contribute to the amplified immune response in systemic inflammatory diseases. A randomized clinical trial must clarify the impact of low-dose hydrocortisone infusion on the clinical course and outcome of septic shock patients.

[Diagnosis of phlebothrombosis using color-coded duplex sonography. A prospective comparison with phlebography]. / Diagnostik der Phlebothrombose durch farbkodierte Duplexsonographie. Ein prospektiver Vergleich mit der Phlebographie.

In a prospective study the reliability of colour-coded duplex-sonography (CCDS) and phlebography in the diagnosis of deep leg and pelvic vein thrombosis was compared. In 82 consecutive in- or out-patients (42 men, 40 women; mean age 53 [19-86] years) with clinically suspected leg or pelvic vein thrombosis the results of 275 phlebographies (reference method) and 275 CCDS were compared on admission and during follow-up. The two methods were performed less than 6 hours apart. In the diagnosis of thrombosis the sensitivity of CCDS was 99%, specificity 80%. In 88% of all tests, the different thrombosis levels, as diagnosed by phlebography, were also demonstrated by CCDS. These data indicate that, if the clinical picture of suspected deep leg or pelvic vein thrombosis is unclear, CCDS should be done first. Phlebography should be performed only if the results of the former are inconclusive.

Heparin reversal by protamine in humans--complement, prostaglandins, blood cells, and hemodynamics.

Fourteen noncardiac surgical patients received heparin (10,000 IU), which was neutralized by 100 mg protamine injected within 2 min during steady-state anesthesia. After protamine application, plasma complement C3a, thromboxane B2 (TxB2), prostaglandin F2 alpha (PGF2 alpha) and KH2PGF2 alpha increased significantly, whereas prostacyclin (6-keto-PGF2 alpha) levels did not change. This mediator response was associated with transient leukopenia and thrombocytopenia. Arterial pressure, pulmonary arterial pressure, and transpulmonary pressure gradient increased significantly. Heart rate, cardiac output, pulmonary capillary wedge pressure, and arterial PO2 remained constant. Positive correlations of plasma C3a were observed with pulmonary leukosequestration and plasma TxB2. Inverse correlations of C3a were noted with the counts of leukocytes and of platelets. A positive correlation was found between TxB2 and pulmonary arterial pressure. Our results indicate that marked activation of the complement system and the cyclooxygenase pathway is common after heparin reversal by protamine in anesthetized patients. This is in contrast to previous human studies performed after cardiopulmonary bypass but agrees well with results obtained in animal experiments. The mediator response in our patients, however, was not accompanied by hemodynamic instability, suggesting appropriate compensatory mechanisms.

Relationship between angiotensinogen, alpha 1-protease inhibitor elastase complex, antithrombin III and C-reactive protein in septic ARDS.

The time-course of plasma angiotensinogen (Ao), elastase-alpha 1-protease inhibitor complex (EL alpha 1PI), antithrombin III (AT III) and C-reactive protein (CRP) have been investigated of six patients suffering from adult respiratory distress syndrome (ARDS). The total plasma Ao level (active and inactive Ao) varied in individuals but was increased up to five-fold. An increasing amount of inactive Ao is found. From the beginning of their stay in the intensive care unit up to five days half of the patients displayed a positive correlation between the plasma CRP and Ao level. The CRP and Ao values were either not or were negatively correlated with the AT III values. In contrast plasma Ao and AT III levels in all patients were positively correlated during a particular period in the subsequent phase of the disease, where there was no or a negative correlation with CRP. The two acute phase reactants CRP and EL alpha 1PI were only correlated in two patients at the beginning of the disease. The markedly increased plasma level at the beginning of the inflammatory disease indicates that Ao is an acute phase reactant, and this is supported by the parallel changes in plasma CRP and Ao levels during the early days of ARDS. The relationship between the plasma levels of Ao and AT III for more than fourteen days suggests similar regulation of these members of the serpin family after termination of the acute-phase.

Flow cytometric parameters of neutrophil function as early indicators of sepsis- or trauma-related pulmonary or cardiovascular organ failure.

Flow cytometric parameters of neutrophil function, such as phagocytosis and degradation of Escherichia coli, intracellular pH value, esterase activity, and cell volume, were evaluated as risk indicators for sepsis- and trauma-related pulmonary and cardiovascular organ failure in intensive care patients. Serial blood samples (n = 201) were obtained from 47 prospectively identified patients. Each patient's condition was classified daily within four categories: post-traumatic (n = 22) or septic (n = 28) organ failure, transition state (n = 119), and stable organ function after recovery (n = 27). Thirty-two parameters of neutrophil function were automatically calculated for each blood sample from several flow cytometric list mode measurements of cell samples vitally stained with acridine orange for intact and denatured DNA or with 1,4-diacetoxy-2,3-dicyanobenzene for intracellular pH and esterase activity. The DNA of dead cells was simultaneously counterstained with propidium iodide. The cell biochemical parameter pattern was significantly different among samples of patients from the four clinical categories (p less than 0.05). Hyperergic phagocytosis was observed after trauma, in contrast to hypoergic phagocytosis, increased neutrophil cell volume, and elevated intracellular pH during sepsis. The clinical categories were correctly identified in 82% of the samples by automated classification with the DIAGNOS1/SPSS program system from the flow cytometrically determined cell functions. The course of the disease was correctly predicted 3 days in advance to the clinical manifestation of pulmonary or cardiovascular organ failure in 92% of the samples. The multifunctional analysis of neutrophils by flow cytometry seems of interest for early medical intervention in preseptic and preshock patients.

Phospholipase A in acute lung injury after trauma and sepsis: its relation to the inflammatory mediators PMN-elastase, C3a, and neopterin.

Inflammatory mediators involved in the pathogenesis of the adult respiratory distress syndrome (ARDS) are products of the humeral cascade systems like the complement cascade and substances released from neutrophil granulocytes and macrophages like proteases, O2-radicals and arachidonate products. Phospholipase A2 (PLA) was shown by Vadas et al. to be correlated with circulatory shock in the sepsis syndrome, the probably most important underlying disease of ARDS. In a clinical study in 48 patients at risk for ARDS after trauma and sepsis we found plasma PLA elevated (52 +/- 5 U/l) in sepsis, with a positive correlation to the complement split product C3a (r = 0.42, p less than 0.01) and neopterin (r = 0.49, p less than 0.05), which serves as a marker of macrophage stimulation. Elastase-alpha 1PI and C3a showed higher plasma levels in patients with ARDS compared with non-ARDS patients, whereas the neopterin and PLA concentrations were not different with regard to ARDS. The relation between PLA and neopterin shown in the study is consistent with the possibility of macrophages being a source of the plasma PLA, as reported in experimental studies.

[The equilibrium of nitrogen, potassium and phosphate and renal excretion of creatinine and creatinine over the course of 3 weeks following severe trauma]. / Die Bilanzierung von Stickstoff, Kalium und Phosphat und die renale Ausscheidung von Kreatinin und Kreatin über drei Wochen nach schwerem Trauma.

In 19 patients after accidental trauma and with intact renal function during an observation time of 21 days we found a cumulated negative balance of nitrogen (N), phosphate (P) and potassium (K) amounting to a mean of 214g, 357 and 447 mmol, respectively. Median daily potassium balance was positive on day 2 to 5 and this was interpreted as an increased extrarenal potassium deposition due to increased levels of circulating catecholamines. Median renal creatinine excretion was about 120% of predicted normal till day 10 and continuously decreased thereafter to values lower than predicted normal. Three patients did not show creatinuria (greater than 200 mg/day) during the whole observation time. In 15 patients after a "free interval" with a mean duration of 7 days creatinuria frequently developed rather quickly and maximal excretion of creatine was as high as 4 g/day. In 7 patients creatinuria persisted to the end of the 21 days observation time. During the phase of creatinuria the median cumulated excretion of creatine amounted to 14.4 g. The "free interval" of creatinuria after severe trauma is remarkable. Most of the N, K and P, which is lost from the body during this time obviously stems from tissues other than sceletal muscle. During the phase of creatinuria, however, the negative balance of N, K and P seems to be mainly due to muscle wasting. Hypophosphatemia was prominent during the first 5 days after trauma and obviously was caused by a decrease in renal phosphate threshold (TmPO4/GFR). The underlying mechanism of this primary change in renal function after severe trauma could not yet be identified.

[Water-electrolyte balance and kidney function for 3 weeks following severe trauma]. / Beobachtungen zum Wasser-Elektrolythaushalt und zur Nierenfunktion über drei Wochen nach schwerem Trauma.

A study on water-electrolyte metabolism and renal function was performed in 32 patients (mainly young to middle-aged males) over three weeks after severe accidental trauma (mainly brain trauma), who did not suffer from acute renal failure. With a mean water input of 4 l/day the difference of water input and urine volume was positive over the whole observation time. Patients had a mean osmolar excretion of 1800 mosm/day which was twice normal and was mainly caused by a high urea excretion. They were almost invariably in the state of antidiuresis and achieved unusually high values for negative free-water clearance around 2 ml/min. This, however, was adequate in terms of normotonicity of body water. Cumulated sodium balance over 21 days was negative and, on the average, amounted to minus 440 mmol. The median value for creatinine clearance was in the range of predicted normal (156 ml/min.) between day 5 and 10 and a little less before and thereafter. We frequently observed an elevation of creatinine clearance to 120-150% of normal. Renal clearance of urea was around 100 ml/min. during the phase of maximal protein catabolism. Therefore the reasonable increases in urea production up to a mean of 60 g/day resulted only in moderately elevated levels of plasma urea (40-50 mg/100 ml). In 14 patients we performed a total of 83 measurements of plasma volume (Evans-Blue). In patients with intact renal function mean plasma volume amounted to 110% normal. This, in combination with a reduced red all volume on the average, resulted in mild hypovolaemia (blood volume about 90% of predicted normal).(ABSTRACT TRUNCATED AT 250 WORDS)