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Biomedical subjects

I van der Tweel

Publications and source records attributed to I van der Tweel.

At least 37 records · Page 2Linked to original sources
PubMed1998

Re-breathing vs single-breath TLCO in patients with unequal ventilation and diffusion.

The single-breath (SB) method for determining the transfer factor for carbon monoxide (TLCO) is of limited value for the detection of diffusion disorders on the alveolar level, because the results are influenced by unequal distribution of ventilation and diffusion. The rebreathing method (RB) is thought not to be influenced by these inequalities. To the authors' knowledge, no study has measured both TLCORB and TLCOSB systematically and compared them with regard to the influence of unequal ventilation and diffusion. Therefore, the present study measured total lung capacity (TLC) as well as TLCO, both with the RB vital capacity method and the SB method, using the same apparatus in 10 healthy subjects and in 35 patients with chronic obstructive pulmonary disease (COPD). These patients are known to have increased unequal ventilation and diffusion in comparison with healthy subjects. In the healthy subjects, a small difference was found between TLC measured with the RB method (TLCRB) divided by the predicted value (TLCRB/pred) and TLCSB/pred (mean difference 0.07; SE = 0.02); no significant difference was found between TLCORB divided by the predicted value of TLCOSB (TLCORB/pred) and TLCOSB/pred. In the COPD patients, however, TLCRB/pred was larger than TLCSB/pred (mean difference 0.17; SE = 0.02) and TLCORB/pred was larger than TLCOSB/pred (mean difference 0.23; SE = 0.05). Multiple regression analysis revealed that in the COPD patients, 54% of the variance of the difference between TLCRB/pred and TLCSB/pred, and 76% of the variance of the difference between TLCORB/pred and TLCOSB/pred, were explained by parameters related to unequal ventilation and diffusion. In 25 of the 35 COPD patients, TLCOSB/pred was less than 0.8, whereas in 11 of these 25 patients, TLCORB/pred was more than 0.8. This difference was significant (P = 0.0005). In these 11 patients, the SB measurement resulted in the incorrect diagnosis of a diffusion disorder on the alveolar level. The RB method, however, never resulted in the diagnosis of a diffusion disorder when TLCOSB/pred was larger than 0.8. It is concluded that in a significant number of COPD patients, TLCOSB is below the normal range, whereas TLCORB is not below the normal range. This difference between TLCORB and TLCOSB is related to the combined effect of unequal ventilation and diffusion, and is of clinical importance for the detection of a diffusion disorder on the alveolar level.

Adult↗
PubMed1997

S-phase fraction, 5-bromo-2'-deoxy-uridine labelling index, duration of S-phase, potential doubling time, and DNA index in benign and malignant brain tumors.

Seventy-one histologically malignant brain tumors, 52 histologically benign brain tumors, and 14 cerebral metastases were characterized according to DNA content and proliferative capacity. DNA ploidy, DNA index (DI), S-phase fraction (SPF), 5-bromo-2'-deoxy-uridine (BrdUrd) labelling index (LI), duration of S-phase (Ts), and potential doubling time (Tpot) were assessed by flow cytometry (FCM). In histologically benign tumors, a high percentage of DNA diploid tumors and a low proliferative capacity in DNA diploid tumors were found. Histologically malignant tumors and cerebral metastases were both found to be characterized by a low percentage of DNA diploid tumors and a high proliferative capacity in DNA diploid tumors. The proliferative capacity of DNA aneuploid benign tumors and that of DNA aneuploid malignant tumors, however, appeared not to differ significantly. The number of DNA aneuploid tumors was small. Duration of S-phase was short (range 3.9-4.7 hr) and appeared not to differ between the three groups. From this, the observed differences in Tpot values should be accredited mainly to differences in LI. High-grade as well as low-grade gliomas both appeared to be characterized by malignant (FCM) features, i.e., 1) a high percentage DNA aneuploidy, 2) a high mean DI (for DI > 1), and 3) a high proliferative capacity.

Aneuploidy↗
PubMed1996

Comparison of one-sample two-sided sequential t-tests for application in epidemiological studies.

In epidemiological prospective cohort studies, exposure levels of cases with disease and disease-free control subjects can be measured by laboratory analysis of previously stored biological specimens. In such studies, a sequential t-test can be used for preliminary evaluations, at the expense of the smallest possible number of specimens, of whether a new aetiological hypothesis is worth further investigation or whether specimens should rather be spared to test other, more fruitful, hypotheses. For this purpose, we recently compared two sequential probability ratio tests (SPRTs), in which the log-likelihood ratio was either based on an approximation, or computed exactly, and which were adapted to account for various control-to-case matching ratios. The tests turned out relatively conservative, particularly in terms of the significance level achieved. In the present paper, we compare an SPRT for matched or paired data based on Rushton's approximation to the log-likelihood ratio with a profile log-likelihood method developed by Whitehead. The comparison is partly mathematical, and partly based on computerized simulations. Average sample size for a sequential test is already smaller than for the equivalent fixed sample test. Increasing the number of controls matched per case further reduces the average sample size necessary to come to a decision. We show that, irrespective of the number of controls per case, pre-specified levels of statistical power and significance are respected closely by Whitehead's method, but not by Rushton's SPRT. This last procedure can lead to a significant loss in power. Since, in addition, Whitehead's method has been implemented in a commercially available computer program (PEST), we conclude that this method can be preferred to the methods we described earlier. Moreover, compared with the method of Rushton, Whitehead's method has the advantage that it can also be applied to groupwise inspection of the data and that it can also be converted easily into a truncated procedure.

Breast Neoplasms↗
PubMed1996

A longitudinal study of maternal hemodynamics during normal pregnancy.

OBJECTIVE: To investigate the maternal hemodynamic changes that occur during normal pregnancy. METHODS: Serial hemodynamic investigations were performed throughout normal pregnancy by thoracic electrical bioimpedance monitoring in 50 healthy women. Analysis of variance with repeated measurements was used to evaluate the time course of a number of hemodynamic indies. RESULTS: The mean heart rate (+/- standard error [SE]) increased gradually from 87 +/- 2 beats per minute at 10-18 weeks' gestation to 92 +/- 1 beats per minute at 34-42 weeks' gestation. Mean arterial pressure decreased significantly after 14 weeks' gestation and increased significantly after 29 weeks' gestation. During the third trimester, mean cardiac output and mean stroke volume decreased, and mean systemic vascular resistance increased significantly. The course of cardiac output during the third trimester was not uniform in all women; it increased in nine and decreased in 41 women. A significantly higher mean cardiac output was found in nulliparous women compared with multiparous women (mean difference +/- SE 0.76 +/- 0.33 L/minute). The mean (+/- SE) cardiac output increased significantly from 6 (5.49 +/- 0.16 L/minute) to 12 weeks' postpartum (5.91 +/- 0.19 L/minute). CONCLUSION: Mean cardiac output and mean stroke volume decreased in late pregnancy. A significant difference in mean cardiac output was observed between nulliparous and multiparous women. Cardiac output usually, but not invariably, declined during the third trimester.

Adult↗
PubMed1996

Comparison of LysB28, ProB29-human insulin analog and regular human insulin in the correction of incidental hyperglycemia.

OBJECTIVE: To obtain clinically applicable data on the effects of regular human insulin and the LysB28,ProB29-human insulin analogue (lispro) on the correction of incidental hyperglycemia. RESEARCH DESIGN AND METHODS: The insulins were compared in a non-clamped randomized crossover study of 27 male IDDM patients. Hyperglycemia was induced by the withdrawal of the normal evening dose of insulin; the next morning patients fasted and received a single dose of study insulin according to a dosing nomogram. Blood glucose concentration and GR (a measure of glucose corrected for differences in administered insulin dose: GR = glucose concentration X BMI X insulin dose-1) were followed for 4 h. RESULTS: The time courses of blood glucose concentration and GR were significantly different after regular insulin in comparison with lispro (multiple analysis of variance, P < 0.001). At t = 120 min, glucose concentrations had decreased 1.4 mmol/l more with lispro than with regular insulin (95% confidence interval [CI] 0.6-2.3, P = 0.002). Similarly, GR had decreased 4.4 mol.kg.IU-1.m-5 more with lispro than with regular insulin (95% CI 2.6-6.2, P < 0.001). The overall difference in glucose values was 0.87 mmol/l (lispro < regular insulin, P = 0.036), and the overall difference in GR values was 1.96 mol.kg.IU-1.m-5 (lispro < regular insulin, P = NS). Unexpectedly, the intrinsic variability of GR was higher for lispro than for regular insulin. CONCLUSIONS: The more rapid action of lispro is an advantage in the correction of hyperglycemia, even though actual differences in glucose concentrations are smaller than suggested by previous clamped studies.

Adult↗
PubMed1996

Growth curves of Dutch children with Down's syndrome.

Two thousand and forty-five observations on height and weight were collected from 295 healthy Dutch children with Down's syndrome. In a cross-sectional analysis, means and standard deviations were calculated per age-class, and subsequently smoothed, resulting in age references between 0 and 20 years. Each child contributed only once in every age class. In a subgroup in whom more than four measurements were available before puberty, quadratic regression functions were determined on the basis of the full data set, as well as for individual children separately (54 boys and 25 girls). The average coefficients of the individual regression functions were almost identical to the coefficients of the regression line through all data, indicating that the reference curve for the mean height based on cross-sectional analysis adequately represents longitudinal growth during childhood. Dutch children with Down's syndrome are taller than their US peers (P50 equals P75) but more than 2 SD shorter than normal Dutch children. Above the age of 10 years, the mean weight for height is above the P90 of normal children.

Adolescent↗
PubMed1995

Use of cardiac index in pregnancy: is it justified?

OBJECTIVE: The aim of this study was to test the hypothesis that standardization of cardiac output in pregnancy by correcting for body surface area, and thus obtaining cardiac index, is justified. STUDY DESIGN: Cardiac output was determined by thoracic electrical bioimpedance monitoring in 78 pregnant women; recordings were made at 1-month intervals from the first antenatal visit and a further two were made during the sixth and twelfth weeks after delivery. In a separate group of 10 pregnant women, cardiac output was determined by Doppler echocardiography at 5, 10, 14, 25, and 35 weeks and at 12 weeks post partum. RESULTS: Irrespective of gestational age, the correlation between cardiac output and body surface area was poor, by either thoracic electrical bioimpedance monitoring (r = 0.15 to 0.39) or Doppler echocardiography (r = 0.00 to 0.29). Furthermore, strict proportionality between cardiac output and body surface area was in general not the best way of describing the (poor) relation between these two. CONCLUSION: Standardization of cardiac output in pregnancy by correcting for body surface area to compare cardiac performance between individuals and between groups of individuals is not justified.

Adult↗
PubMed1995

Does it make sense to use two internal thoracic arteries?

Retrospectively, the first 143 patients who were operated on with bilateral internal thoracic arteries (BITA group) were matched with 143 patients operated on with only one left internal thoracic artery anastomosed on the left anterior descending artery and additional vein grafts (LITA group) and followed up for a maximum of 8 years. At 5 years follow-up there were no significant differences in event-free survival between the groups. After 8 years, the overall survival was 96% and 92% (not significant [NS]), cardiac survival 99% and 97% (NS), angina-free cardiac survival 51% and 35% (NS), infarction-free cardiac survival 95% and 78% (NS), reintervention-free cardiac survival 87% and 88% (NS), and all cardiac event-free survival 49% and 31% (NS) for the BITA and LITA groups, respectively. The incidence of late pulmonary, wound, and other complications was comparable. Cox proportional hazards analysis showed that a higher left ventricular end-diastolic pressure and female sex were predictors of recurrent angina and late cardiac events. During this intermediate-term follow-up, the use of one or two internal thoracic arteries was of no value in predicting angina-free or cardiac event-free survival.

Adult↗
PubMed1995

Landmark positioning on maxilla of cleft lip and palate infant--a reality?

In this study, we tested the precision of landmark positioning for a set of landmarks that can be used for the edentulous cleft lip and palate maxilla of the infant, by analyzing intraobserver and interobserver repositioning and measuring on a series of 121 (unilateral and bilateral) study casts. To date, no data on interobserver and only minimal data on intraobserver reproducibility are available. We found intraobserver reproducibility acceptable with total measurement errors ranging from 0.51 to 1.54 mm. Interobserver reproducibility was only slightly less with total measurement errors ranging from 0.63 to 1.57 mm. Total measurement errors were found to be relatively high for some variables. Both the intra- and interobserver analyses show insight into expected precision of landmark positioning during placement of these points on casts. A learning effect for precise positioning has been demonstrated in both analyses. The points with the highest precision overall are Q and Q', followed by the linear measurements PL and P'L'. Quality of regular study casts (impressions) is an important factor, with room for improvement. Reproducible landmark positioning on the cleft lip and palate infant's maxilla, can only be a reality if the quality of the cast is optimal and the investigator is experienced. Intraobserver and interobserver reproducibility are in the same range, which justifies the comparison of results from different studies and relieves future investigators of the need to have all measurements within a study conducted by the same investigator. Aspects of the biologic meaning of landmarks are also discussed.

Cephalometry↗
PubMed1994

Similar hospital morbidity with the use of one or two internal thoracic arteries.

The hospital morbidity and mortality of 100 patients operated with two internal thoracic arteries with or without additional vein grafts (BITA group) were compared with a matched group of 100 patients operated with one left internal thoracic artery (ITA) on the anterior descending artery with additional vein grafts (LITA control group). In each study group, 3% of the patients had diabetes mellitus. There was no statistical significant difference in hospital mortality (1% versus 0%), perioperative myocardial infarction (5% versus 1%), low cardiac output (3% versus 5%), rethoracotomy (1% versus 0%), lung complications (13% versus 13%), wound complications (8% versus 8%), other cardiac complications (26% versus 16%), other noncardiac complications (1% versus 4%), median duration of stay in the intensive care unit (1 versus 1 day), and mean duration of stay in the hospital (10.4 versus 10.8 days) between the groups. Logistic regression analysis showed that the number of ITAs used was not a predictor of complications. Thus, there is no difference between the BITA and LITA control group in hospital mortality and morbidity (in patients with a low incidence of diabetes). If an improvement in cardiac event-free and reoperation-free survival is to be expected, the use of both ITAs can be continued in similar patients.

Adult↗
PubMed1994

Reproducibility of estimated cardiovascular function by transthoracic bioimpedance cardiography in healthy volunteers.

In ten healthy volunteers, stroke index (SI), heart rate (HR), thoracic fluid conductivity (TFC) and index of contractility (IC) were estimated by transthoracic bioimpedance measurements (BoMed Noninvasive Continuous Cardiac Output Monitor, model 3, Revision 7 (NCCOM3-R7)). Intra- and inter-observer variability and the influence of time of day (morning or afternoon) were determined. The intra-observer variability was significantly smaller during the morning than during the afternoon. The mean differences +/- standard error between consecutive measurements for morning versus afternoon measurements were, respectively: SI, 0.8 +/- 1.2 vs. 4.6 +/- 1.2 ml/m2 (P = 0.057); HR, -1.0 +/- 0.6 versus -0.9 +/- 0.6 beats/min; TFC, -0.0 +/- 0.3 vs. 1.0 +/- 0.3 (= TFC x 1000.omega-1) (P = 0.031) and IC, -0.6 +/- 0.9 vs. 5.6 +/- 0.9 (= IC x 1000.s-1) (P = 0.001). The inter-observer variability for SI, HR, TFC and IC did not reach statistical significance. These data suggest that reproducible measurements can be obtained provided that only morning or afternoon measurements are compared. Since the reproducibility of measurements was better during the morning than during the afternoon, we recommend that measurements are performed in the morning.

Adult↗
PubMed1994

Efficient use of biological banks for biochemical epidemiology: exploratory hypothesis testing by means of a sequential t-test.

In view of recent advances in molecular and biochemical epidemiology, there is growing interest in the creation of biological banks of blood, urine, tissue, or other biological specimens collected from participants in prospective cohort studies. The existence of biological banks may make it possible to study a multitude of etiologic hypotheses, by comparing biochemical parameters measured in the biological specimens of subjects who will eventually develop the disease of interest ("cases") and of control subjects, using a nested case-control or a case-cohort design. In practice, however, the amount of biological material available per subject (in particular, that of cases) will limit the number of hypotheses that can be tested. The present paper discusses the use of a sequential t-test which, compared with an analogous fixed sample procedure, will on average require fewer biological specimens before a given study hypothesis can be accepted or rejected. The sequential test should thus facilitate an early decision on whether a new hypothesis is worth further investigation, while avoiding wasting too much biological material on testing hypotheses that may eventually prove unfruitful. If the test reveals an exposure difference of interest, the study may be extended so that relevant epidemiologic effect measures can be estimated more accurately.

Biological Specimen Banks↗
PubMed1994

Rebreathing TLCO versus single breath TLCO at different degrees of unequal ventilation.

The influence of unequal ventilation on the differences between the rebreathing (RB) and the single breath (SB) measurement of the transfer factor of the lung for carbon monoxide (TLCO) was investigated. An apparatus was developed which measured both TLCORB and TLCOSB. Unequal ventilation increases with lung volume, caused by the combined effect of increasing ratio of total volume to RV from apex to basis, the fact that apex inspires before basis and asymmetric intra-acinar branching patterns. Therefore measurements were done at three different values of inspired volume (VI) in 10 normal subjects. To separate the effects of gas mixing and diffusion, residual volume (RV) was measured by He dilution in addition to TLCO. We found that RV and TLCO increase with increasing VI. The increase is larger with RB. We also found that RVRB is larger than RVSB at the three values of VI. TLCORB is smaller than TLCOSB except at vital capacity (VC). We concluded from the different behavior of RVRB and RVSB as a function of VI that the SB measurement increasingly underestimated RV with increasing unequal ventilation. This is also reflected in the measurement of TLCOSB. From the different behavior of TLCORB and TLCOSB as a function of VI we concluded that TLCORB was smaller than TLCOSB when unequal ventilation was minimal. This is caused by the smaller mean alveolar volume during RB. But increasing unequal ventilation causes an increasing underestimation with the SB method, resulting in TLCOSB being equal to TLCORB at VC.

Adult↗
PubMed1993

[Complications following axillary dissection for breast carcinoma].

Axillary dissection in breast cancer is performed to stage the tumor and to obtain regional tumour control. It is associated with some morbidity. Recently mention was made of post-axillary dissection pain of the arm following damage to one or more of the intercostobrachial nerves. In the University Hospital of Utrecht a radical axillary dissection is routinely performed for breast cancer with transection of the sensory intercostobrachial nerve(s). To evaluate the inherent morbidity of this operation, we interviewed and examined 71 women (75 axillae) who had undergone an axillary dissection for carcinoma of the breast between January 1987 and January 1990. In almost all cases a sensory deficit was present in the axilla and/or arm. In 23 patients (26 sides; 35%) there was pain in the arm, always in the innervation area of the intercostobrachial nerves. One-third of these cases had a NRS score of 5 or higher, indicating moderate to severe pain. Seroma and lymphedema were found in 21 patients. In 6 shoulders abduction was reduced to 90 degrees. The several complaints were non-invalidating to 48 patients, slightly invalidating to 13 and moderately invalidating to 10 patients. At present, histological examination of the axillary nodes is still the best way to detect metastases, and it has implications for adjuvant therapies. The results of this study indicate that routinely sacrificing the intercostobrachial nerves during axillary dissection may result in annoying sensory changes and that efforts should be made to preserve one or two of these nerves during the operation.

Adult↗
PubMed1993

[Risk factors for the development of recurrences in patients with breast carcinoma without axillary lymph node metastases].

The influence of a number of risk factors on development of tumour recurrence was studied retrospectively in a group of breast cancer patients without axillary lymph node metastases, all treated identically and with long follow-ups. Of 71 patients all data could be retrieved. This group had a median duration of follow-up of five years. Thirteen patients (18.3%) had had a recurrence of carcinoma after a median disease-free period of 41 months (range 3-124 months). These patients at the time when breast cancer was diagnosed had had a lower median age than patients who had remained free of tumour recurrence, 48 (40-70) as against 59.5 (30-81) years. Factors having a statistically significant prognostic importance for recurrence of tumour were age at the time of diagnosis of breast carcinoma, histological tumour grade and nuclear DNA content. Identifying groups of patients with a higher or lower risk of tumour recurrence appears possible by combination of risk factors. Although patients with breast cancer without axillary lymph node metastases are supposed to have a favourable prognosis, there appear to exist subgroups with a raised risk for development of a recurrence. These groups might be prime candidates for prospective randomized studies of the usefulness of adjuvant therapy.

Adult↗
PubMed1993

Incidence and management of benign anastomotic stricture after cervical oesophagogastrostomy.

Benign anastomotic stricture after transhiatal oesophagectomy and gastric tube reconstruction constitutes a major problem. From August 1988 to April 1991, 81 patients were followed after cervical oesophagogastrostomy. Twenty-four patients (30 per cent) developed a benign anastomotic stricture 3-23 (median 8) weeks after operation. Poor vascularization of the gastric tube, determined during operation, and postoperative anastomotic leakage were statistically significant risk factors for stricture formation. Symptoms related to stricture were often typical and were confirmed by endoscopy and/or radiography. Radiography did not yield information additional to that obtained from endoscopy. Strictures were treated in the outpatient clinic by dilatation with Savary dilators. Repeated dilatation completely alleviated dysphagia in 20 of the 24 patients (83 per cent). In ten patients dilatations could be discontinued after a median of 8 (range 1-17) sessions. Dilatation was continued until the end of follow-up in nine patients or until death from recurrent disease in five. No complications of dilatation were seen.

Adult↗
PubMed1993

Selenium and the risk of postmenopausal breast cancer in the DOM cohort.

Selenium has been claimed to have chemo-preventive properties. However, data showing that in humans selenium levels are already decreased prior to diagnosis of breast cancer were not available. Such information is mandatory before oral selenium supplementation in the primary prevention of (breast) cancer in humans is acceptable. This question of a 'preventive-potential' of selenium was evaluated in a case-control study nested in a cohort, because this design allows determination of the time-order of preceding selenium levels and subsequent cancer risk. The cohort consisted of 5577 women aged 55-70 years from the DOM project, a population based breast cancer screening program in the Netherlands. Instrumental Neutron Activation Analysis was used to measure the selenium content of toenail clippings. The 69 cases of breast cancer found during follow-up after screening. represent 'recent' tumours since all women had a negative screening mammogram 3-5 years previously. No decreased selenium levels, as measured in nail clippings from the big toes, could be detected in cases-to-be, either when compared to 4 age matched controls per case or when compared with a random control group drawn from the entire cohort. On the contrary, a tendency for slightly higher selenium levels among 'future' cancer cases was observed. As to the sensitivity of detecting differences in selenium by nail clippings, lower selenium could be detected in nails of current smokers. The smoking-related decrease in nail selenium level was of the same order as the differences between breast cancer cases and controls, but was independent of the breast cancer risk.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗