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Andreas Voss

Publications and source records attributed to Andreas Voss.

At least 55 records · Page 3Linked to original sources
PubMed2004

Detection of the Candida antigen mannan in cerebrospinal fluid specimens from patients suspected of having Candida meningitis.

Cerebrospinal fluid samples from five patients from which Candida cells were cultured were tested for the presence of mannan. Samples from four patients categorized as having proven candidosis reacted positively. Samples from the remaining patient and from patients with other central nervous system infections were negative. Detection of mannan may be valuable in the diagnosis of Candida meningitis.

Aged↗
PubMed2004

Changes of blood pressure and heart rate variability precede a grand mal seizure in a pregnant woman.

In order to evaluate blood pressure and heart rate variability as a potent diagnostic tool for different hypertensive pregnancy disorders we started a clinical trial recording these variables in early pregnancies predisposed for preeclampsia. During routine measurements one of the patients experienced a grand mal epileptic seizure. Since the parameters of both heart rate and blood pressure variability were sequentially altered immediately before the seizure, this case report provides an interesting insight into autonomic cardiovascular control in a developing convulsive fit and the pathophysiological generation of a grand mal seizure in pregnancy.

Adult↗
PubMed2004

Interpreting the parameters of the diffusion model: an empirical validation.

The diffusion model (Ratcliff, 1978) allows for the statistical separation of different components of a speeded binary decision process (decision threshold, bias, information uptake, and motor response). These components are represented by different parameters of the model. Two experiments were conducted to test the interpretational validity of the parameters. Using a color discrimination task, we investigated whether experimental manipulations of specific aspects of the decision process had specific effects on the corresponding parameters in a diffusion model data analysis (see Ratcliff, 2002; Ratcliff & Rouder, 1998; Ratcliff, Thapar, & McKoon, 2001, 2003). In support of the model, we found that (1) decision thresholds were higher when we induced accuracy motivation, (2) drift rates (i.e., information uptake) were lower when stimuli were harder to discriminate, (3) the motor components were increased when a more difficult form of response was required, and (4) the process was biased toward rewarded responses.

Adult↗
PubMed2003

Estimating the valence of single stimuli: a new variant of the Affective Simon Task.

In this article, a modified variant of the Affective Simon Task (AST; De Houwer & Eelen, 1998) is presented as a measure of implicit evaluations of single stimuli. In the AST, the words "good" or "bad" have to be given as responses depending on the color of the stimuli. The AST was combined with an evaluation task to increase the salience of the valence of the presented stimuli. Experiment 1 investigated evaluations of schematic faces showing emotional expressions. In Experiment 2 we measured the valence of artificial stimuli that acquired valence in a game context during the experiment. Both experiments confirm the validity of the modified AST. The results also revealed a dissociation between explicit and implicit evaluations.

Adult↗
PubMed2002

Potential of feature selection methods in heart rate variability analysis for the classification of different cardiovascular diseases.

In this study heart rate variability (HRV) analysis was applied to characterize patients suffering from coronary heart disease (CHD), dilated cardiomyopathy (DCM) and patients who had survived an acute myocardial infarction (MI). On the basis of several HRV parameters, an optimal discrimination between the different kinds of cardiovascular diseases and between the diseases and healthy controls (HC) was derived by feature selection and linear classification. For each task a small favourable subset of a set of 33 potentially interesting HRV measures was selected with the intention of improving the diagnostic value and facilitating the physiological interpretation of HRV analysis. Time- and frequency-domain parameters as well as parameters from non-linear dynamics were included in the analysis. With the expectation that different diseases are characterized by different phenomena, feature selection was applied for each task separately. Using the features optimal for one task to another task can reveal a loss in performance, but it turned out that one specific parameter set (set1: normalized low frequency LF/P and a non-linear variability measure WPSUM13) was applicable for all tasks, where diseased and healthy subjects have to be distinguished, without significant reduction in performance. This set seems to be a general marker for pathologic changes in HRV and might be used for early detection of heart diseases. The classification between different heart diseases requires another parameter set (set2: meanNN and sdaNN, reflecting the steady state behaviour of the heart rate and long and short term SEAR describing the spectral composition). However, the use of set1 for the separation of different kinds of diseases, where set2 is appropriate, led to significant reduction in performance and vice versa. This observation may be important for future developments of HRV measures especially suitable for the assessment of disease severity.

Cardiovascular Diseases↗
PubMed2002

Postextrasystolic regulation patterns of blood pressure and heart rate in patients with idiopathic dilated cardiomyopathy.

Assessment of fluctuations in heart rate (HR) following a premature ventricular complex (PVC) is valuable for identifying patients at high risk of sudden cardiac death. We hypothesised that postextrasystolic potentiation is the main determinant of the regulation patterns of blood pressure (BP) and HR following a PVC. Twelve patients with idiopathic dilated cardiomyopathy (IDC) and 13 control subjects with single PVCs (comparable coupling intervals) were investigated. Non-invasive finger arterial BP and ECGs were analysed. Regulation patterns following a single PVC were quantified using the indices postextrasystolic amplitude potentiation (PEAP) and maximum turbulence slope of five consecutive mean BP values (MBP-TS), and compared with the HR turbulence parameters turbulence slope (HR-TS) and turbulence onset (HR-TO). PEAP was significantly higher in IDC patients compared to controls (48.7 +/- 32.6 vs. 9.8 +/- 5.4 %, P < 0.01), whereas MBP-TS was lower (0.97 +/- 0.60 vs. 2.07 +/- 1.04 mmHg BBI(-1) (BBI, beat-to-beat interval), P < 0.05), as was HR-TS (8.46 +/- 7.90 vs. 30.73 +/- 22.90 ms BBI(-1), P < 0.01). HR-TO was significantly higher in IDC patients (-0.56 +/- 2.19 vs. -5.52 +/- 4.13 %, P < 0.01). In addition, the regulation patterns of BP and HR following a single PVC differed significantly between IDC patients and controls. Specifically, we observed pronounced PEAPs in IDC patients. The baroreflex response initiated by the low pressure amplitude of the PVC was suppressed in IDC patients due to the augmented potentiation of the first postextrasystolic blood pressure. Furthermore, IDC patients displayed impressive postextrasystolic pulsus alternans phenomena, whereas healthy subjects exhibited a typical baroreflex pattern. The pulsus alternans phenomenon seems to be triggered by a PVC.

Adult↗
PubMed2002

Heart rate variability before the onset of ventricular tachycardia: differences between slow and fast arrhythmias.

BACKGROUND: We tested whether or not heart rate variability (HRV) changes can serve as early signs of ventricular tachycardia (VT) and predict slow and fast VT in patients with an implantable cardioverter defibrillator (ICD). METHODS AND RESULTS: We studied the ICD stored 1000 beat-to-beat intervals before the onset of VT (131 episodes) and during a control time without VT (74 series) in 63 chronic heart failure ICD patients. Standard HRV parameters as well as two nonlinear parameters, namely 'Polvar10' from symbolic dynamics and the finite time growth rates 'Fitgra9' were calculated. Comparing the control and the VT series, no linear HRV parameter showed a significant difference. The nonlinear parameters detected a significant increase in short phases with low variability before the onset of VT (for time series with less than 10% ectopy, P<0.05). Subdividing VT into fast (cycle length 270 ms) events, we found that the onset of slow VT was characterized by a significant increase in heart rate, whereas fast VT was triggered during decreased heart rates, compared to the control series. CONCLUSIONS: Our data may permit the development of automatic ICD algorithms based on nonlinear dynamic HRV parameters to predict VT before it starts. Furthermore, they may facilitate improved prevention strategies.

Adult↗
PubMed2002

Alternans of blood pressure and heart rate in dilated cardiomyopathy.

Impaired myocardial performance is known to be associated with electrical and mechanical beat-to-beat alternans phenomena. The alternans in blood pressure and heart rate and their interdependency in idiopathic dilated cardiomyopathy (IDC) were studied. The arterial blood pressure and the electrocardiograph (ECG) were continuously recorded in 22 patients suffering from IDC (age 49 +/- 13 years, ejection fraction 0.33 +/- 0.13, left ventricular diameter of 67 +/- 8 mm) and in 21 healthy controls (age 52 +/- 15 years). The beat-to-beat variations of the interbeat intervals (IBI) and of the blood pressure amplitudes (AMP) were measured. An alternans beat was defined as a beat preceded and followed by beats that had higher or lower values in the respective modality. The percentages of singular and repetitive alternans patterns, and the interdependency of the alternans patterns in AMP and IBI were assessed. The study found significantly more singular and repetitive alternans patterns in the IDC group compared to the control group both in the analysis of AMP and IBI (singular alternans in IBI: 55 +/- 11 vs 47 +/- 7%, P < 0.01; singular alternans in AMP: 61 +/- 15 vs 45 +/- 6%, P < 0.01; triple alternans in IBI: 29 +/- 18 vs 16 +/- 9%, P < 0.01; triple alternans in AMP: 34 +/- 24 vs 12 +/- 7%, P < 0.01). The amplitudes of the AMP alternans patterns were higher in IDC compared to controls (9 +/- 7 vs 4 +/- 2% of AMP, P = 0.01) whereas they did not differ in IBI. The correlation analysis revealed a significant interdependency of the alternans pattern in IBI and AMP in 18 of 22 IDC patients and in 12 of 21 controls (r = 0.50 +/- 0.21 [IDC]; r = 0.26 +/- 0.05 [controls]). The slope of the linear regression (delta AMP vs delta IBI) was steeper in the IDC group compared to the control group (62 +/- 50 vs 20 +/- 22 mmHg/s, P < 0.01). The percentages of alternans patterns appearing in IBI and AMP were positively correlated to the left ventricular diameter (r = 0.70 in the IBI, and r = 0.30 in the AMP). The blood pressure amplitude and the heart rate did not differ between the two groups. Patients suffering from IDC have a higher prevalence, stability, amplitude, and interdependency of alternans patterns in IBI and AMP compared to the control group. The amount of alternans patterns indicates the stage of disease. The alternans analysis may have impact on the functional assessment of patients suffering from heart failure.

Blood Pressure↗
PubMed2002

Prevention of postsurgical infections: some like it hot.

PURPOSE OF THE REVIEW: The present review covers the literature on prevention of surgical site infections published during 2001. Only papers that offer new insights or question current recommendations are included. RECENT FINDINGS: The most interesting advances have been made in the preoperative preparation of the patient. In particular, the effects of preoperative warming of the patient, either generally or locally at the incision site, on the rate of surgical site infections are impressive and warrant further investigation. Also, the effects of strict control of perioperative blood glucose levels and of preoperative eradication of nasal carriage of Staphylococcus aureus should be studied in greater detail. SUMMARY: The protective effect of local and systemic warming before surgical procedures has been described in two well designed studies. Although a final judgement regarding effectiveness can only be made after more extensive investigations have been conducted, there appear to be few arguments against application of this cheap and safe measure. Thus, implementation of preoperative warming can be justified in settings associated with high rates of surgical site infections.

Humans↗
PubMed2002

Advanced analysis of spontaneous baroreflex sensitivity, blood pressure and heart rate variability in patients with dilated cardiomyopathy.

Baroreflex sensitivity (BRS) is an important parameter in the classification of patients with reduced left ventricular function. This study aimed at investigating BRS in patients with dilated cardiomyopathy (DCM) and in healthy subjects (controls), as well as comparing the values of BRS parameters with parameters of heart rate variability (HRV) and blood pressure variability (BPV). ECG, continuous blood pressure and respiration curves were recorded for 30 min in 27 DCM patients and 27 control subjects. The Dual Sequence Method (DSM) includes the analysis of spontaneous fluctuations in systolic blood pressure and the corresponding beat-to-beat intervals of heart rate to estimate bradycardic, opposite tachycardic and delayed baroreflex fluctuations. The number of systolic blood pressure/beat-to-beat interval fluctuations in DCM patients was reduced in comparison with controls (DCM patients: male, 154.4+/-93.9 ms/mmHg; female, 93.7+/-40.5 ms/mmHg; controls: male, 245.5+/-112.9 ms/mmHg; female, 150.6+/-55.8 ms/mmHg, P<0.05). The average slope in DCM patients was lower than in controls (DCM, 5.3+/-1.9 ms/mmHg; controls, 8.0+/-5.4 ms/mmHg; P<0.05). Discriminant function analysis showed that, in the synchronous range of the standard sequence method, the DCM and control groups could be discriminated to only 76% accuracy, whereas the DSM gave an improved accuracy of 84%. The combination of six parameters of HRV, BPV and DSM gives an accuracy of classification of 96%, whereas six parameters of HRV and BPV could separate the two groups to only 88% accuracy. Thus the DSM leads to an improved characterization of autonomous regulation in order to differentiate between DCM patients and healthy subjects. BRS in DCM patients is significantly reduced and apparently less effective.

Adult↗
PubMed1998

Evaluation of the discriminatory power of pulsed-field gel electrophoresis and PCR fingerprinting for epidemiologic typing of Candida species.

OBJECTIVE: To evaluate the discriminatory power of genotyping methods (PCR fingerprinting and pulsed-field gel electrophoresis) validated for Candida albicans in other Candida species. METHODS: Molecular typing methods are increasingly being applied for studies where the interpretation of data essentially relies on the typing results rather than epidemiologic data. In this situation, the discriminatory power (ability to identify differences among epidemiologically unrelated strains) of the typing method is important in allowing one to draw valid conclusions. By applying PCR fingerprinting, electrophoretic karyotyping, and restriction fragment endonuclease analysis using standard restriction enzymes and primers proven to be useful in previous studies, we evaluated whether the use of multiple genotyping methods is sufficient to delineate known unrelated strains among seven Candida species. RESULTS: All three methods identified individual genotypes for each of the seven Candida species studied. However, optimal strain delineation required the combined use of all three typing methods and was observed only within the small number of C. albicans and C. tropicalis isolates tested in this study. CONCLUSION: Typing assays that are able to delineate a certain Candida species may not be used blindly for other species of that genus. Regarding the limited number of strains tested, further validation of the discriminative power of genotyping methods (including in C. tropicalis) should be done.

Journal Article↗