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A Vonk Noordegraaf

Publications and source records attributed to A Vonk Noordegraaf.

At least 19 recordsLinked to original sources
PubMed2007

Diagnosis and management of pulmonary hypertension over the past 100 years.

Pulmonary hypertension is a rare disease with a poor prognosis. It was first described in the late 19th century as a clinical-pathological syndrome characterised by obstruction of the small pulmonary arteries and right ventricular hypertrophy in patients presenting with severe dyspnoea and cyanosis. After the development of right heart catheterisation in the second half of the 20th century, it was found that many diseases could cause pulmonary hypertension, which is now recognised to be high blood pressure in the arteries that supply the lungs. In the 1960s, an epidemic of pulmonary hypertension caused by appetite suppressants initiated a systematic collection of information on pulmonary hypertension, leading to the first international classification of pulmonary hypertension. Increased understanding of the pathogenesis of the various forms of pulmonary hypertension has led to novel treatments and holds promise for the future.

Appetite Depressants↗
PubMed2005

[Pulmonary arterial hypertension due to the use of amphetamines as drugs or doping].

Pulmonary arterial hypertension (PAH) was diagnosed in three patients. All three had a history ofamphetamine consumption. The patients were a 48-year-old male drug addictwho had used intravenous amphetamine for more than 20 years, a 43-year-old man who had been administered intravenous amphetamines during a period of intensive cycling and a 34-year-old woman who regularly consumed amphetamine at dance festivals. All three patients received medicinal treatment. Amphetamines may lead to PAH due to the release of serotonin, which causes pulmonary vasoconstriction and the proliferation of smooth muscle cells. Due to the pathophysiology of amphetamine-induced PAH, other amphetamine derivatives such as methylenedioxymethamphetamine (ecstasy) and methylphenidate can be risk factors for PAH. These three cases show that PAH should be considered in patients who present with dyspnoea and a reduced exertion tolerance, and who are known to have a history of amphetamine use.

Adult↗
PubMed2004

Simulated hazards of loosing infection-free status in a Dutch BHV1 model.

A compulsory eradication programme for bovine herpesvirus 1 (BHV1) was implemented in the Netherlands in 1998. At the start of the programme, about 25% of the dairy herds were certified BHV1-free. Simulation models have played an important role in the decision-making process associated with BHV1 eradication. Our objective in this study was to improve understanding of model behaviour (as part of internal validation) regarding loss by herds of the BHV1-free certificate. Using a Cox proportional hazards model, the association between farm characteristics and the risk of certificate loss during simulation was quantified. The overall fraction of herds experiencing certificate loss amongst initially certified during simulation was 3.0% in 6.5 years. Factors that increased risk for earlier certificate loss in the final multivariable Cox model were higher 'yearly number of cattle purchased', 'farm density within a 1 km radius' and 'cattle density within a 1 km radius'. Qualitative behaviour of risk factors we found agreed with observations in field studies.

Animal Husbandry↗
PubMed2004

['Palm reading' as a diagnostic aid].

In four patients, a man aged 53, a woman aged 63 and two men aged 67 and 53 years, respectively, inspection of the hand led to the final diagnosis. In the first patient who presented with clubbing of the fingers and pulmonary hypertension, a small atrial septal defect was detected. The second patient had thick curved yellow nails and recurrent pleural effusions as part of this yellow nail syndrome. The third patient presented with clubbing and hypertrophic osteoarthropathy, a secondary complaint to adenocarcinoma of the lung. The fourth patient had increasing pulmonary hypertension as a secondary complaint to recurrent multiple pulmonary embolism from deep venous malformations of his right hand, arm and shoulder as a part of the Klippel-Trenaunay syndrome. These cases show that inspection of the hand may give a clue to the diagnosis.

Adenocarcinoma↗
PubMed2003

Electrical impedance tomography to measure pulmonary perfusion: is the reproducibility high enough for clinical practice?

A possible clinical application of electrical impedance tomography (EIT) might be to monitor changes in the pulmonary circulation, provided the reproducibility of the EIT measurement is adequate. The purpose of this study was threefold: the intra- and inter-investigator variability of repeated measurements was investigated. Three different regions of interest (ROI) were analysed to assess the optimal ROI. Twenty-four healthy subjects and six patients were included. The Sheffield applied potential tomograph (DAS-01P, IBEES, Sheffield, UK) was used. Electrodes were attached by investigator A, and duplicate EIT measurements were performed. After detachment and 45 min of rest, the protocol was repeated by another investigator B, and afterwards by the initial investigator A. Three ROIs were analysed: whole circle, 'inner half circle' and contour. The mean difference in impedance changes between observers is presented in arbitrary units (AU) +/- SD. Finally, the influence of age, body composition and sex on the EIT result was examined. For the contour ROI, the mean difference for the intra-investigator situation was -1.44 x 10(-2) +/- 18.45 x 10(-2) AU (-0.7 +/- 9.0%), and was 5.46 x 10(-2) +/- 21.66 x 10(-2) AU (2.7 +/- 10.8%) for the inter-investigator situation. The coefficient of reproducibility of the intra- and inter-investigator reproducibility varied between 0.89 and 0.97 for all ROIs (P < 0.0001). There is a relation between impedance change and age (correlation coefficient r = -0.63, P < 0.01 for contour ROI), and between impedance change and body mass index (BMI) (r = -0.53, P < 0.05). We found a significant difference in mean impedance change between groups of males and females. In conclusion, EIT results are highly reproducible when performed by the same investigator as well as by two different investigators.

Adolescent↗
PubMed2003

Epoprostenol therapy for primary pulmonary hypertension after rejection of a single donor lung.

Before prostacyclins became available, lung or heart/lung transplantation was the only effective treatment for patients with primary pulmonary hypertension (PPH) who deteriorated under supportive medical treatment. Unfortunately, acute and chronic rejections occur in a large number of cases, limiting the average survival to 4.5 yrs. A female patient, age 35 yrs, was diagnosed with PPH and underwent single lung transplantation. Despite aggressive immunosuppressive therapy, the patient had several episodes of acute rejection. Eventually, chronic rejection with bronchiolitis obliterans developed. After 5 yrs, the donor lung was no longer functional. The patient was in New York Heart Association (NYHA) class 4, had a 6-min walking distance of 50 m and a resting arterial oxygen tension (Pa,O2) of 9.8 kPa (74 mmHg) when using 3 L x min(-1) of oxygen. Epoprostenol treatment was started and the patient showed remarkable improvement. After 17 months the patient was NYHA class 2, walked 503 m in 6 min and had a resting Pa,O2 of 10.9 kPa (82 mmHg) without supplemental oxygen. In this patient, treatment with epoprostenol was effective after rejection of a single donor lung transplanted for primary pulmonary hypertension.

Adult↗
PubMed2002

Epoprostenol-induced pulmonary vasodilatation in patients with pulmonary hypertension measured by electrical impedance tomography.

Electrical impedance tomography (EIT) has been proposed as a method to monitor dynamic changes in the pulmonary vascular bed. In this study we examined the validity of EIT in the measurement of pulmonary vasodilatation in eight patients with primary and secondary pulmonary hypertension when given the vasodilating agent epoprostenol (Flolan). Therefore, catheterization of the pulmonary artery was performed in the ICU and the cardiac output was measured by means of the Fick method. The pulmonary vascular resistance (PVR) and mean pulmonary arterial pressure (mPAP) were determined. Epoprostenol was given in increasing doses to test reversibility of pulmonary hypertension. The maximum test dose was 12 ng kg(-1) min(-1). During each step simultaneous EIT (DAS-01 P Portable Data Acquisition System, Sheffield, England) measurements were performed with the 16 electrodes equidistantly positioned in the third intercostal space. The maximal systolic impedance change, relative to end-diastole, deltaZperf, was chosen as a measure of pulmonary perfusion. The impedance change between baseline and highest tolerable epoprostenol concentration was compared with the change in PVR. The mean PVR (dyn s/cm5) decreased from 636 (+/-399) to 366 (+/-242); p < 0.01. DeltaZperf (in arbitrary units) for the whole patient group increased from 901 (+/-295) x 10(-3) to 1082 (+/-472) x 10(-3) (p<0.05). Only one patient showed a reduction in pulmonary artery pressure >20%, which is defined as significant vasodilatation. A strong relationship was found between the impedance changes and the change in PVR and mPAP in the patient with a significant vasodilatation on epoprostenol. From these results we conclude that EIT is a reliable method to measure blood volume changes due to pharmacologically induced vasodilatation in the pulmonary bed.

Adult↗
PubMed2001

[Sinusitis as a major cause of fever in intubated patients].

Because sinusitis is usually clinically silent in intubated patients, it is not widely appreciated as an important source of infection and fever in critically ill patients. Three such patients, two men aged 22 and 36 years, and a woman aged 50 years, suffered from respiratory insufficiency due to pneumonia. The course of the disease was determined by the sinusitis, which did not resolve during antibiotic therapy of the pneumonia, notwithstanding the fact that the causative micro-organism was susceptible to the antibiotics administered, and that both the tracheal and gastric tubes were led through the mouth instead of the nose. Flushing of the sinuses caused the fever to disappear and led to recovery of the patients. An aggressive approach to diagnose sinusitis in the intubated patient with fever in the intensive care unit is needed. A maxillary sinus lavage and culture, followed by treatment with specific antibiotics should be an integral part of the diagnosis and treatment in these patients. Surgery is indicated in the event of persistent sepsis.

Adult↗
PubMed2001

Impaired left ventricular filling due to right ventricular pressure overload in primary pulmonary hypertension: noninvasive monitoring using MRI.

OBJECTIVE: To analyze the effect of primary pulmonary hypertension (PPH) on cardiac function using MRI. METHODS: In 12 patients (9 women; age range, 30 to 56 years), the diagnosis of PPH had been established by catheterization (mean +/- SD pulmonary artery pressure [PAP] was 56 +/- 8 mm Hg). With breath-hold cine MRI, a series of short-axis images was acquired covering the whole left ventricle (LV) and right ventricle (RV). The curvature, defined as 1 divided by the radius of curvature in centimeters, was calculated for the septum and the LV free wall in early diastole. Leftward ventricular septal bowing (LVSB) is denoted by a negative curvature. For the LV and the RV, the end-diastolic volume (EDV), stroke volume (SV), and volumetric filling rate were calculated. The control subjects were all healthy (n = 14; 11 women; age range, 20 to 57 years). RESULTS: In the patients, LVSB was quantified in early diastole by the septal curvature of - 0.14 +/- 0.07 cm(-1), and the septal to free-wall curvature ratio of - 0.42 +/- 0.21. LV EDV and LV SV correlated negatively with diastolic PAP (p = 0.004 and p = 0.04, respectively). In patients vs control subjects, RV SV was reduced (52 +/- 12 mL vs 82 +/- 11 mL, p < 0.0001); LV peak filling rate was smaller (2.2 +/- 0.7 EDV/s vs 3.3 +/- 0.5 EDV/s, p < 0.001); LV EDV was smaller (81 +/- 23 mL vs 117 +/- 19 mL, p = 0.001); and LV SV was smaller (49 +/- 18 mL vs 83 +/- 13 mL, p < 0.0001). CONCLUSION: In PPH, RV pressure overload leads to LVSB and reduced RV output. By decreased blood delivery, LV filling is reduced, which results in decreased LV SV by the Frank-Starling mechanism.

Adult↗
PubMed1999

Non-invasive evaluation of left ventricular function by means of impedance cardiography.

BACKGROUND: Simple, accurate, continuous non-invasive cardiac monitoring during the peri- and postoperative periods for patients at risk of cardiac failure would be very useful. Electrical impedance cardiography (EIC) has been proposed as an accurate method for non-invasive measurement of cardiac function. However, in recent years the accuracy of EIC in stroke volume (SV) measurement has been questioned and this prevented global acceptance of the method. Beside SV, EIC is capable of measuring several other left ventricular contractility indices, which are measured directly from the impedance signal. The aim of this study was to compare these variables with the echocardiographically derived left ventricular wall motion score (WMS) as the reference method. METHODS: In a group of eight coronary artery disease patients we performed a pharmacologically (dobutamine) induced stress test. Echocardiographic and impedance cardiographic recordings were performed simultaneously during four levels of dobutamine infusion. WMS was derived from the simultaneously displayed four-stage echocardiographic image. RESULTS: Analysis of variance showed that the majority of indices changed significantly during the test. Direct correlation with the wall motion score gave very satisfactory results over all stages with the RZ time (r = 0.75, P < 0.001) and Heather index (r = -0.78, P < 0.001). Other correlations were substantially lower. CONCLUSION: The Heather index has to be preferred as indicator of the left ventricular performance. Since EIC is capable of giving continuous information of the left ventricular performance, it might be a valuable method for peri- and postoperative monitoring.

Adrenergic beta-Agonists↗
PubMed1999

Noninvasive measurement of cardiac output: two methods compared in patients with mitral regurgitation.

In search for the origin of the less reliable cardiac output (CO) estimations by means of electrical impedance cardiography (EIC), the authors hypothesized that cardiac valve pathology might be one of the reasons. Twenty-six patients were examined by means of echo Doppler (ED) and EIC. The cardiac valve status was obtained by means of echocardiography and color Doppler flow, while CO was obtained by means of both methods. Seventeen patients had no valve pathology (nVP) while nine patients had mild to moderate mitral regurgitation (MVR). The overall correlation between the calculation of CO by means of the two methods was good (r = 0.85, p < 0.001, mean difference and standard deviation: 0.20+/-0.74 L/min), while there was no significant difference between the paired values. After division into an nVP and an MVR population, the results showed an even closer agreement between the CO values in the nVP population (r = 0.88, p < 0.001, mean difference and standard deviation: 0.15+/-0.68 L/min). Furthermore, significant differences were found in the first derivative of the impedance (dZ/dt) signals of these groups. Although the agreement between ED and EIC was slightly lower in the MVR population, EIC reliably estimated CO, even in case of MVR. The impedance signal itself gave an indication for the existence of MVR.

Adult↗
PubMed1999

Electrical impedance tomography in the assessment of extravascular lung water in noncardiogenic acute respiratory failure.

STUDY OBJECTIVES: To establish the value of electrical impedance tomography (EIT) in assessing pulmonary edema in noncardiogenic acute respiratory failure (ARF), as compared to the thermal dye double indicator dilution technique (TDD). DESIGN: Prospective clinical study. SETTING: ICU of a general hospital. PATIENTS: Fourteen ARF patients. INTERVENTIONS: In order to use the TDD to determine the amount of extravascular lung water (EVLW), a fiberoptic catheter was placed in the femoral artery. MEASUREMENTS AND MAIN RESULTS: Fourteen consecutive ARF patients receiving mechanical ventilation were measured by EIT and TDD. EIT visualizes the impedance changes caused by the ventilation in two-dimensional image planes. An impedance ratio (IR) of the ventilation-induced impedance changes of a posterior and an anterior part of the lungs was used to indicate the amount of EVLW. For the 29 measurements in 14 patients, a significant correlation between EIT and TDD (r = 0. 85; p < 0.001) was found. The EIT reproducibility was good. The diagnostic value of the method was tested by receiver operator characteristic analysis, with 10 mL/kg of EVLW considered as the upper limit of normal. At a cutoff level of the IR of 0.64, the IR had a sensitivity of 93%, a specificity of 87%, and a positive predictive value of 87% for a supranormal amount of EVLW. Follow-up measurements were performed in 11 patients. A significant correlation was found between the changes in EVLW measured with EIT and TDD (r = 0.85; p < 0.005). CONCLUSION: We conclude that EIT is a noninvasive technique for reasonably estimating the amount of EVLW in noncardiogenic ARF.

Acute Disease↗
PubMed1998

An epidemiological and economic simulation model to evaluate the spread and control of infectious bovine rhinotracheitis in The Netherlands.

Bovine herpesvirus type I (BHV1), causing infectious bovine rhinotracheitis (IBR), was introduced in the Netherlands in 1971. In 1993, about 42% of the dairy cows had antibodies against BHV1. In the future, stricter requirements are anticipated regarding the health status of exported breeding cows and material. To support policymakers in their decisions on IBR eradication, a simulation model was developed in which the epidemiological and economic consequences of various control strategies were evaluated. This paper describes the model and provides an overview of some important outcomes. In the model, dairy herds were classified into different disease states based on (1) the reproduction ratio of the disease (R, defined as the number of secondary cases caused by one infectious animal) (2) the within-herd prevalence, within each value of R and (3) the expected number of infectious animals in an infectious herd within each prevalence range. The dynamic transition probability of a herd going from one state to another per week depends on direct contacts between animals, and other contacts such as transmission through fomites, indirect transmission through other species, airborne transmission and minor disease-specific routes such as venereal or iatrogenic transmission. Five control strategies, including both a voluntary vaccination program and a compulsory vaccination program for all dairy herds were evaluated. A voluntary vaccination program with 50% participation is not expected to lead to eradication of IBR. It appears that compulsory vaccination would be necessary to reach an IBR-free status.

Animals↗
PubMed1998

Influences of lung parenchyma density and thoracic fluid on ventilatory EIT measurements.

Ventilatory impedance changes can be measured by electrical impedance tomography (EIT). Several studies have pointed out that the ventilatory-induced impedance change measured over the lungs shows a linear relationship with tidal volume. However, EIT measures the ventilatory impedance changes relative to a reference. Therefore, changes in the reference due to lung parenchyma destruction (increase of thoracic impedance) or lung water (decrease of thoracic impedance) might influence ventilatory EIT measurements. A study was designed to evaluate the influence of the density of lung parenchyma and the thoracic fluid content on ventilatory EIT measurements. Eleven emphysema patients with a variable degree of lung parenchyma destruction, nine haemodialysis patients with general fluid overload and ten healthy subjects were measured. The impedance changes were measured with the subject in the supine position breathing a constant tidal volume of 1 litre starting at the maximum end-expiratory level. In the emphysema group a significantly lower impedance change between ins- and expiration was found in comparison with the healthy subjects (11.6 +/- 6.4 AU l-1 versus 18.6 +/- 4.2 AU l-1, p < 0.05), whereas the haemodialysis group showed a significantly larger impedance change between ins- and expiration before haemodialysis (30.5 +/- 13.1 AU l-1, p < 0.05). A significant decrease in ventilation-induced impedance change during dialysis was found (30.5 +/- 13.1 AU l-1 versus 21.4 +/- 8.6 AU l-1, p < 0.01). Furthermore, a significant correlation between lung function parameters, which indicate the severity of lung parenchyma destruction, and the measured impedance change was found in emphysema patients. From these results it can be concluded that the density of lung parenchyma and the thoracic fluid content have a serious impact on the ventilation-induced impedance change.

Adult↗
PubMed1998

Pulmonary perfusion measured by means of electrical impedance tomography.

Electrical impedance tomography (EIT) is a recent imaging technique based on electrical impedance, offering the possibility of measuring pulmonary perfusion. In the present study the influence of several pulmonary haemodynamical parameters on the EIT signal were investigated. First, the influence on the systolic wave of the EIT signal (delta Zsys) of stroke volume, large pulmonary artery distensibility (both assessed by means of MRI) and the extent of the pulmonary peripheral vascular bed in 11 emphysematous patients (reduced peripheral vascular bed) and 9 controls (normal peripheral vascular bed) was investigated. Second, the influence of hypoxic pulmonary vasoconstriction on delta Zsys was examined in 14 healthy subjects. Finally, the origin of the diastolic wave was examined in three patients with atrioventricular dissociation. Multiple regression analysis showed that delta Zsys was only dependent on the variable emphysema (p < 0.02), but not dependent on stroke volume (p < 0.3) or pulmonary artery distensibility (p > 0.9). The mean value of delta Zsys for emphysematous patients (131 +/- 32 arbitrary units (AU)) was significantly lower (p < 0.001) than in the control group (200 +/- 39). In the group of healthy subjects delta Zsys decreased significantly (p < 0.001) during hypoxia (193 +/- 38 AU) compared with rest measurements (260 +/- 62 AU). The absence of the diastolic wave in the cardiological patients suggests the influence of reverse venous blood flow on the EIT signal. It is concluded that volume changes in the small pulmonary vessels contribute significantly to the EIT signal. Moreover, the hypoxia induced decrease in delta Zsys indicates the potential of EIT for measuring pulmonary vascular responses to external stimuli.

Aged↗
PubMed1998

Ventilation and perfusion imaging by electrical impedance tomography: a comparison with radionuclide scanning.

Electrical impedance tomography (EIT) is a technique that makes it possible to measure ventilation and pulmonary perfusion in a volume that approximates to a 2D plane. The possibility of using EIT for measuring the left-right division of ventilation and perfusion was compared with that of radionuclide imaging. Following routine ventilation (81mKr) and perfusion scanning (99mTc-MAA), EIT measurements were performed at the third and the sixth intercostal level in 14 patients with lung cancer. A correlation (r = 0.98, p < 0.005) between the left-right division for the ventilation measured with EIT and that with 81mKr was found. For the left-right division of pulmonary perfusion a correlation of 0.95 (p < 0.005) was found between the two methods. The reliability coefficient (RC) was calculated for estimating the left-right division with EIT. The RC for the ventilation measurements was 94% and 96% for the perfusion measurements. The correlation analysis for reproducibility of the EIT measurements was 0.95 (p < 0.001) for the ventilation and 0.93 (p < 0.001) for the perfusion measurements. In conclusion, EIT can be regarded as a promising technique to estimate the left-right division of pulmonary perfusion and ventilation.

Adult↗