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Biomedical subjects

R Rohling

Publications and source records attributed to R Rohling.

16 recordsLinked to original sources
PubMed2005

Evaluating different radiology workstation interaction techniques with radiologists and laypersons.

This paper presents a new methodology for evaluating radiology workstation interaction features, using lay subjects to perform a radiology look-alike task with artificial stimuli. We validated this methodology by evaluating two different workstation interaction techniques with two groups of subjects: laypersons and radiologists, using a set of artificial targets to simulate the reading of a diagnostic examination. Overall, the results from the two groups of subjects performing the same tasks were very similar. Both groups showed significantly faster response times using a new interaction technique, and the mouse clicks for both groups were very similar, showing that all the subjects mastered the style of interaction in a similar way. The errors made by both groups were comparable. These results show that it is possible to test new workstation interaction features using look-alike radiological tasks and inexperienced laypersons, and that the results do transfer to radiologists performing the same tasks.

Computer Systems↗
PubMed2000

Intraoperative endogenous erythropoietin levels and changes in intravascular blood volume in healthy humans.

There is accumulating evidence of a relationship between changes in intravascular blood volume and endogenous erythropoietin (EPO) levels. In this study, eight healthy adult American Society of Anesthesiologists class-I patients due for prolonged elective surgery were randomised either to preoperative hypervolaemic haemodilution using hydroxyethyl starch, followed by intraoperative crystalloid infusion, or to standard intraoperative normovolaemic fluid balance management using crystalloids (control group). Electrolytes, creatinine, urea, osmolality, urine output and blood gases were monitored pre- and intraoperatively for 6 h, Comparable cardiopulmonary and renal homeostasis were maintained in both groups. We found that central venous pressure increased and EPO levels decreased, both significantly, in the hypervolaemic haemodilution group relative to controls. There were no significant intergroup changes in any other parameters. By controlling for other known determinants of EPO levels, our data indicate a relationship between EPO levels and changes in intravascular blood volume in humans, supporting the notion of EPO as a volume-regulated, and possibly volume-regulating, hormone.

Adult↗
PubMed1999

A comparison of freehand three-dimensional ultrasound reconstruction techniques.

Three-dimensional freehand ultrasound imaging produces a set of irregularly spaced B-scans, which are typically reconstructed on a regular grid for visualization and data analysis. Most standard reconstruction algorithms are designed to minimize computational requirements and do not exploit the underlying shape of the data. We investigate whether an approximation with splines holds any promise as a better reconstruction method. A radial basis function approximation method is implemented and compared with three standard methods. While the radial basis approach is computationally expensive, it produces accurate reconstructions without the kind of visible artefacts common with the standard methods. The other potential advantages of radial basis functions, such as the direct computation of derivatives, make further investigation worthwhile.

Algorithms↗
PubMed1999

Clinical investigation of a new combined pulse oximetry and carbon dioxide tension sensor in adult anaesthesia.

OBJECTIVE: To test the accuracy of a new combined oxygen saturation and cutaneous carbon dioxide tension (SPO2-PCO2) sensor in a routine adult clinical environment. This probe provides a non-invasive and continuous monitoring of the arterial oxyhaemoglobin saturation, arterial carbon dioxide tension and pulse rate at the ear lobe. The sensor is intended to measure both relevant respiration/ventilation parameters in one single probe. METHODS: Ten adult patients were consecutively studied during general anaesthesia. During the first 5 min after sensor placement at the ear lobe, arterial blood samples were drawn each minute. Carbon dioxide tension and oxygen saturation measurements were obtained simultaneously at 1-min intervals. After this period, patients were hyper-, normo- and hypoventilated. After 15 min at each setting, the simultaneously obtained cutaneous and arterial carbon dioxide tension values were compared. RESULTS: A total of 80 comparisons between ear lobe SpO2-PCO2 measurement, finger clip pulse oximetry and arterial blood gas values were analysed. Three minutes after sensor placement, there were no significant differences between ear probe (cutaneous) and arterial carbon dioxide tensions (p = 0.367). Comparison of arterial with cutaneous carbon dioxide values demonstrated an excellent linear correlation (r2 = 0.92), and showed a standard error of estimate (SDEE) of 0.26 kPa (1.95 mmHg) only. The mean difference was -0.08 kPa (-0.60 mmHg) with a limits of agreement range of -0.38 kPa to +0.22 kPa (-2.85 mmHg to +1.65 mmHg). Concerning oxygen saturation measurements, the absolute SpO2 value deviated 1% or less from standard pulse oximetry. CONCLUSIONS: During general anaesthesia, postoperative recovery and critical care treatment, both monitoring of oxygenation and ventilation is important. Since pulse oximetry estimates only arterial oxygen saturation, periodic blood sampling is still necessary to determine the patient's arterial carbon dioxide status. We could demonstrate that the difference between cutaneous and arterial PCO2 was clinically unimportant, and therefore we conclude that the two methods of estimating the patient's carbon dioxide status may be used interchangeably. Our results demonstrated that 3 min after sensor placement, the new SpO2-PCO2 sensor prototype proved to be a reliable tool for continuous non-invasive monitoring of oxygenation and ventilation.

Adult↗
PubMed1997

[Life support for homeostasis in organ donors].

The main goal of intensive care of potential organ donors includes the maintenance of the organs' function with respect to their integrity after transplantation. Profound disturbances of cardiovascular, respiratory and endocrinological function may lead to early organ loss. Therefore, comprehensive therapy is required from the onset of brain death. The major dysfunctions and therapeutic goals in organ donors are summarized on the basis of current literature and our own findings.

Brain Death↗
PubMed1997

Three-dimensional spatial compounding of ultrasound images.

One of the most promising applications of 3-D ultrasound lies in the visualization and volume estimation of internal 3-D structures. Unfortunately, the quality of the ultrasound data can be severely degraded by artefacts and speckle, making automatic analysis of the 3-D data sets very difficult. In this paper we investigate the use of 3-D spatial compounding to reduce speckle. We develop a new statistical theory to predict the improvement in signal-to-noise ratio with increased levels of compounding, and verify the predictions empirically. We also investigate how registration errors can affect automatic volume estimation of structures within the compounded 3-D data set. Having established the need to correct these errors, we present a novel reconstruction algorithm which uses landmarks to register each B-scan accurately as it is inserted into the voxel array. In a series of in vitro and in vivo trials, we demonstrate that 3-D spatial compounding is very effective for improving the signal-to-noise ratio, but correction of registration errors is essential.

Algorithms↗
PubMed1997

The effect of intravenous iron on the reticulocyte response to recombinant human erythropoietin.

We studied the effect of intravenous (i.v.) administration of 200 mg of iron sucrose following an i.v. bolus injection of recombinant human erythropoietin (r-HuEPO; 300 U/kg body weight) in seven subjects and compared it with seven subjects treated with r-HuEPO alone. Reticulocytes, serum erythropoietin (EPO) and ferritin levels were studied at baseline and daily for the following 8 d. Use of i.v. iron abolished the marked reduction in serum ferritin observed with r-HuEPO administration. Although the total number of reticulocytes was not affected by i.v. iron administration, the reticulocyte Hb content and retHb (a measure in g/l of the Hb contained in all reticulocytes) were increased in the i.v. iron/r-HuEPO group compared with the group who received r-HuEPO alone. Therefore i.v. iron significantly potentiates the haemopoietic response to r-HuEPO in normal subjects.

Adult↗
PubMed1996

Radial artery tonometry: moderately accurate but unpredictable technique of continuous non-invasive arterial pressure measurement.

Radial artery tonometry provides continuous measurement of non-invasive arterial pressure (CNAP) by a sensor positioned above the radial artery. An inflatable upper arm cuff enables intermittent oscillometric calibration. CNAP was compared with invasive radial artery pressure recordings from the opposite wrist in 22 high-risk surgical patients with an inter-arm oscillometric mean arterial pressure difference < or = 10 mm Hg. Oscillometric, tonometric and invasive digital pressure values, and invasive and CNAP waveforms were obtained by the same instrument (Colin BP-508). Correlation coefficients (r) of invasive vs oscillometric values (n = 481 pairs) were 0.83, 0.90 and 0.92, and mean absolute errors of oscillometry were 7.6, 4.7, and 2.6 mm Hg for systolic, diastolic and mean arterial pressures, respectively. Correlation was poor for systolic (r = 0.80), diastolic (r = 0.77) and mean (r = 0.84) invasive vs CNAP values (n = 1375). Compared with oscillometry, mean absolute errors of 15.2, 10.9 and 9.4 mm Hg for systolic, diastolic and mean CNAP, respectively, were significantly (P < 0.001) higher. Mean prediction errors of CNAP, compared with invasive values, were -5.8 (SD 14.2) mm Hg for systolic, +7.2 (8.3) mm Hg for diastolic and +3.9 (8.8) mm Hg for mean arterial pressure. Individual patient accuracy of CNAP was assessed as good (individual prediction error < or = 5 (8) mm Hg and individual absolute error < or = 10 mm Hg) in seven patients, as acceptable (< or = 10 (12) and < or = 15 mm Hg) in 11 patients, and as inadequate in four of 22 patients. Individual accuracy of oscillometry was good or acceptable in all 22 patients. The trend in CNAP changes (difference between consecutive measurements) was sufficiently accurate during induction of anaesthesia, as only 47 (7.6%), 14 (2.3%) and 27 (4.4%) of 616 systolic, diastolic and mean CNAP values differed by more than 10 mm Hg of invasive pressure trends. We conclude that: intermittent oscillometry provides accurate arterial pressure monitoring; CNAP measurements offer a reliable trend indicator of pressure changes during induction of anaesthesia and may be considered an alternative to invasive pressure measurements, should arterial cannulation be difficult in an awake patient; and accuracy of absolute CNAP values is only moderate and unpredictable, thus radial artery tonometry should not replace invasive monitoring in high-risk patients during major surgical procedures.

Adult↗
PubMed1995

Comparison of relative accuracy between a mechanical and an optical position tracker for image-guided neurosurgery.

An essential component in the execution of image-guided surgery is a hand-held probe whose spatial position is tracked during the procedure and displayed on a three-dimensional operative workstation. This paper describes an experiment performed in order to compare the accuracy of a mechanically linked pointing device (FARO surgical arm) and an optical position tracker (OPTOTRAK) against a "gold standard."

Image Processing, Computer-Assisted↗
PubMed1995

Effects of single-dose oral ranitidine and sodium citrate on gastric pH during and after general anaesthesia.

The effects on gastric pH of the H2-receptor antagonist ranitidine (R) with 0.3 molar (M) sodium citrate (SC) as an oral effervescent and those of plain SC were studied in 25 patients scheduled for elective surgery. Following induction of general anaesthesia, the gastric contents were evacuated via a nasogastric tube, and a pH electrode was placed in the stomach. Then, eight patients received R 300 mg plus SC dose (Group R300), ten received R 150 mg plus SC dose (Group R150), and seven received 50 ml SC alone (Group SC). The drugs were administered orally in a double-blind fashion, and the gastric pH was recorded continuously over a period of 24 hr. Mean (range) baseline pH values were 1.2 (0.8-1.8), 1.3 (1.0-1.8), and 1.2 (0.9-1.6) in the R300, R150, and SC groups, respectively (P = NS among groups). These values increased to 7.0 (6.2-7.5), 6.9 (6.3-7.3), and 4.9 (1.9-7.3), respectively, at emergence from anaesthesia (P < 0.05 for R300 vs SC and R150 vs SC). Two minutes after administration of R300 and R150, a mean (range) gastric pH of 6.8 (5.8-7.5), and 5.6 (1.2-7.0), respectively, was reached, and remained above 2.5 for 14 hr (P = NS). Plain SC increased the gastric pH within two minutes to a mean of 6.8 (6.7-7.0), and maintained it above 2.5 for six hours (P < 0.05 for R300 vs SC at 8, 10, 12, and 14 hr after induction).(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1995

The time course of gastric pH changes induced by omeprazole and ranitidine: a 24-hour dose-response study.

The time-course of the effects of single-dose acid-reducing therapy in surgical patients is not known. Therefore, a prospective, randomized trial compared the effects of single-dose administration of omeprazole or ranitidine on gastric pH in 52 patients undergoing lower abdominal surgery. The two drugs were administered intravenously in random fashion after placement of a gastric electrode for continuous 24-h pH monitoring In patients receiving omeprazole 20 mg (n = 13) and 40 mg (n = 13), gastric pH > or = 2.5 was achieved after a median of 80 (range 15-269) min and 40 (6-102) min (P = not significant [NS]), whereas in those receiving ranitidine 25 mg (n = 13) and 50 mg (n = 13), this pH was reached after a median of 32 (15-82) and 44 (16-84) min, respectively (P = NS). Over the first 24 h postoperatively, gastric pH remained less than 2.5 for a significantly longer time (1060 min vs 611 min), and more than 4.0 for a significantly shorter time (240 min vs 780 min) after omeprazole 20 mg than after ranitidine 50 mg. There were no other significant differences among treatment groups regarding the duration of gastric pH less than 2.5, between 2.5 and 4.0, and more than 4.0. In all treatment groups, the gastric pH returned to the baseline value of < 2.0 within 18 h. We conclude that when it is desired that gastric pH be more than 4.0 for at least 3 h, a single dose of ranitidine 25 mg or 50 mg should be administered 30-45 min prior to induction of anesthesia.

Abdomen↗
PubMed1990

[Preservation of homeostasis following the onset of brain death].

One of the main problems faced by transplantation medicine is the lack of suitable donor organs. The success of organ transplantation depends on the quality of the organ to be transplanted. The initial function of the transplant depends on the quality of preparation. The aim of efforts after brain death is to maintain the morphological and functional integrity of the donor organ in situ. At our clinic, all potential organ donors undergo direct arterial pressure measurement and many receive a Swan-Ganz catheter. Catecholamine administration--varied on the basis of the hemodynamic parameters--is not associated with an impairment of organ function. Electrolyte determinations at 2-hour intervals and close laboratory controls are obligatory. These intensive-care measures are necessary because of the occurrence of severe metabolic and hemodynamic imbalances. A partly transient diabetes insipidus is the most frequent homeostatic disorder. In addition, severe electrolyte imbalances, disturbed glucose utilization and hypotension may be observed. Our investigations on the plasma concentration course of thyroid hormones, ACTH and cortisol after the onset of brain death suggest that the secretion of pituitary hormones is maintained until total necrosis of the pituitary gland occurs 30 to 40 hours later. The detection of circulating ADH up to 24 hours after the onset of brain death, despite the angiographically confirmed cessation of cerebral circulation, suggests that there may be a residual perfusion of hypothalamus and pituitary. The blood levels of epinephrine, norepinephrine and dopamine measured in brain-dead patients not receiving catecholamines were in part considerably above the reference level. Our data suggest that vigorous intensive care management increases the number and quality of organs suitable for transplantation and reduces to a minimum the incidence of premature organ losses.

Brain Death↗
PubMed1988

[Is cerebral panangiography unnecessary in determining brain death?].

UNLABELLED: The diagnosis of brain death, i.e. death of cortex and brainstem, can be established by neurologic examination only if there is no intoxication, sedative therapy, or hypothermia. In the latter cases, until now only cerebral panangiography can establish the diagnosis. We investigated, whether in these cases cerebral perfusion scintigraphy (CPS) in combination with brainstem auditory evoked potential (BAEP) can replace CPA for establishing the diagnosis. METHODS: 40 patients, treated in our interdisciplinary ICU because of primary or secondary brain lesions and in whom determination of brain death by neurological examination was contraindicated, were subjected to the following procedure: When coma was diagnosed, brainstem reflexes were examined. If negative, an atropine-test was done and this being negative, apnea-testing was performed. If apnea was positive, BAEP, CPS and CPA were performed. The results of BAEP and CPS were compared with the results of CPA. RESULTS: In 38 patients with suspected brain death the first examination showed complete correspondence between BAEP and CPS on one hand and CPA on the other hand (Table 3). In patient No. 39, CPS as well as CPA showed minimal supratentorial circulation, whereas BAEP were negative as was circulation in the fossa posterior. In patient No. 40 as well CPS and CPA showed minimal supratentorial circulation. Brainstem testing with BAEP was negative although CPA showed minimal brainstem perfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain↗
PubMed1988

[Auditory evoked potentials in determining brain death].

Until now, in hypothermic patients, patients under barbiturate therapy etc. brain death can only unequivocally be determined by cerebral panangiography. We evaluated in 41 patients, whether panangiography can be substituted by recording of brain stem auditory evoked potentials in combination with cerebral perfusion scintigraphy. Our results demonstrate, that even if no potential except wave I can be recorded, a minimal intracranial perfusion may exist, so that by definition the patient is not dead. During the course of our investigations we found one patient, in whom disappeared auditory evoked potentials recovered. So we conclude, that the recording of auditory evoked potentials is only an adjunct in determination of brain death, not an objective method as is cerebral panangiography. But recording of auditory evoked potentials is helpful in excluding brain death in certain patients.

Brain Death↗
PubMedDate not supplied

Anesthesia in a patient with acute respiratory insufficiency due to relapsing polychondritis.

We report on a male patient with advanced relapsing polychondritis (RP), who was hospitalized for an ophthalmologic intervention. He had to undergo a tracheostomy with general anesthesia due to respiratory decompensation. RP is a rare systemic, inflammatory, and destructive disease of the cartilaginous structures leading to multiple functional disorders in the affected organs. Involvement of the tracheobronchial tract may cause severe respiratory problems and even life-threatening respiratory insufficiency. Treatment consists of corticoids, chemotherapy, antirheumatics, and surgical intervention. Anesthesiologic management requires careful preoperative evaluation of vital organ functions, in particular respiration, so that the anesthetic approach can be tailored to the individual needs of each patient.

Acute Disease↗