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Biomedical subjects

A Schultz

Publications and source records attributed to A Schultz.

At least 19 recordsLinked to original sources
PubMed1992

Postural control in young and elderly adults when stance is perturbed: kinematics.

Increased postural sway and falling are associated with aging and are likely related to problems with postural control in the elderly. We investigated the motions of individual body segments in 24 healthy young adults and 15 healthy elderly adults (mean ages 26 and 72) in response to four tasks: (a) standing with feet flat on an anteriorly accelerating platform (Flat Translation); standing on a narrow beam support that was (b) stationary (Beam Standing) and (c) accelerating anteriorly (Beam Translation); and (d) standing on a rotatable but otherwise stationary springboard (Springboard Standing). An optoelectronic camera system was used to measure rotations of body segments, particularly regarding their maximum excursions, time to first rotation response, direction of initial rotation, and time to first rotation reversal. In general, larger rotation excursions were noted in the elderly compared to the young group, particularly in the Beam Standing and Beam Translation tasks, but the magnitude of rotation difference was small. All rotation magnitudes were well within the available ranges of motion of the body joints. In both excursion magnitudes and directions of initial rotation, the elderly showed greater variability than the young. In the Beam Translation task, the elderly group, compared to the young, tended to rotate their upper body segments more than in the Flat Translation task. These data suggest that healthy elderly adults with no apparent musculoskeletal or neurological impairments have small but consistent differences in postural control kinematics, particularly when more challenging conditions are presented. Moreover, these data provide the basis for biomechanical analyses of joint torques and other dynamic requirements of these responses.

Adult↗
PubMed1992

[Reduction of the number of recorded EEG channels for routine monitoring in the intensive care unit].

Monitoring patients in the intensive care unit with the aid of the conventional electroencephalogram employing a large number of recording channels is rather difficult, and can be laborious. This imposes limits on the routine application of this method. To investigate the possibility of developing a new monitoring device for easier application in the ICU, we aimed to establish whether the relevant information provided by a multi-channel EEG could be found in a subgroup of channels, thus reducing the number of channels required. Preferably those channels should be identified for use which are least contaminated by artefacts under routine conditions in the ICU. A total of 150 EEG recordings from the intensive care unit were inspected visually for the presence of artefacts. The derivations C3-P3 and C4-P4 proved to be least contaminated, at 35% and 39%, respectively. In these derivations visual assessment of the EEG was found to be impossible due to artefacts in only 4 and 5%, of all cases, respectively. A data set comprising 52 EEG segments with the fewest possible artefacts, was analysed using time series methods. On the basis of multivariate autoregressive processes, a measure was derived which describes the loss of information associated with a reduction in the number of EEG channels. The computation of the information loss for several channel combinations revealed that the derivations F3-C3, C3-P3 and A1-Cz represent a good compromise between information content, number of channels and frequency of artefacts. Practical experience shows that, at least for the control of sedation, a further reduction to a single channel should be possible.(ABSTRACT TRUNCATED AT 250 WORDS)

Artifacts↗
PubMed1992

Application of adjusted survival curves to renal transplant data.

An important means in the analysis of survival time data is the estimation and graphical representation of survival probabilities. In this paper unifactorial parametric and non-parametric survival curve estimators and two types of adjusted survival curves based on a parametric multifactorial approach are applied to renal transplant data. It is shown that the resulting survival curves can differ substantially. The unifactorial survival curves yield biased results in case of serious disequilibrium in the data. This drawback of the unifactorial methods has been overcome by the use of adjusted survival curves which take possible distortions in the data set into account. The benefits of adjusted survival curves in assessing potentially prognostic factors are elucidated by the application to data from renal transplantation.

Humans↗
PubMed1992

Testing the Gaussianity of the human EEG during anesthesia.

The Gaussian properties of human EEGs, which were measured over various stages of general anesthesia, were tested. The basis of the method was to describe the EEG signals by autoregressive models and to test the normality of the regression residuals with the Shapiro-Wilk statistic. The results show that in general the human EEG during anesthesia can be considered as a realization of a Gaussian stochastic process.

Anesthesia, General↗
PubMed1991

[Neurogenic pulmonary edema].

Neurogenic pulmonary oedema (NPE) is a recognized, serious, relatively uncommon, acute complication of cerebral insults of various types. Despite numerous animal experimental investigations and case reports, the pathological physiology is not yet elucidated. An acute cerebral insult with raised intracranial pressure is accompanied by violent activation of the sympathetic system and increase in the concentrations of circulating catecholamines. Probably, hydrostatic influences and altered capillary permeability both play roles in the pathogenesis. Acute increase in the total vascular surface in the lungs may also be contributory. Treatment includes intubation and positive pressure ventilation, diuretics, infusion of synthetic catecholamines, alpha-receptor blockades and reduction of raised intracranial pressure by hyperventilation and drainage of liquor. The optimal treatment of NPE is not yet established on account of insufficient knowledge of the pathological physiology.

Brain Injuries↗
PubMed1991

Identification of EEG patterns occurring in anesthesia by means of autoregressive parameters.

In EEG analysis an automatic pattern recognition is of interest. In this paper the usefulness of autoregressive parameters to classify EEG segments recorded during anesthesia is examined. Assuming that the AR parameters are multivariate normally distributed, parametric methods of discriminant analysis can be applied. The results show that AR parameters have high discriminating power and that the lowest error classification rate (smaller than 3%) is obtained by using quadratic discriminant functions. Consequently autoregressive parameters are efficient for classifying EEG segments into general stages of anesthesia.

Adult↗
PubMed1991

[Slowing down of the EEG during hypoventilation in emergence from anesthesia].

Electroencephalographic (EEG) recordings were made using a "Narkograph", which performs an automatic on-line interpretation of electroencephalographic data obtained during anesthesia. The EEG was classified into one of 13 stages from A (awake) to F (very deep narcosis). In 20 of roughly 600 patients EEG changes were observed that could not be explained by the effects of anesthetics. Slowing of the EEG occurred during the transition from controlled to spontaneous ventilation and disappeared after minute ventilation increased. The alterations seen during hypoventilation were similar to the effects of hypoxia described in the literature. During the slowing in the rough EEG, waves appeared that were very regularly formed and corresponded to sharp peaks in the power spectrum. These features are rather atypical of the effects of anesthetics such as thiopental, propofol, halothane, isoflurane, and enflurane and were not observed when patients went back to sleep after extubation. If depth of anesthesia is monitored by EEG recording, clinical circumstances should be taken into account because conditions such as hypoxia may cause alterations of the EEG that bear a resemblance to the effects of anesthetics.

Anesthesia Recovery Period↗
PubMed1991

[Can ventilation based on the principle of the iron lung act today as a substitute for or an alternative method to conventional forms of ventilation?].

A plastic lung working on the same principles as an iron lung has been developed at the Medical School in Hannover. Functional and practical tests were performed in a representative group of patients. Respirators support following the principles of an iron lung may be provided as a supplement or an alternative to existing artificial respirator therapy. The modern artificial respirators are superior to the plastic lung, which however, has advantages for particular indications: Respiratory therapy performed in a plastic lung is well tolerated by the patients. It requires specific skills which can easily be learned by the medical staff. Routine use certainly cannot be instituted before further technical improvement has been achieved; in particular the noise level should be reduced. The plastic lung is suitable for short-term ventilation (2-10 h); in view of the restricted nursing procedures possible, prolonged artificial respiration cannot be recommended. In conclusion, immediate postoperative ventilation is the area of application for the plastic lung. Several advantages are known: the endotracheal tube can be removed, there is no indication for sedative drugs, cardiac function and organ blood flow are positively influenced, mucolysis and lung expansion are adequate. A patient whose spontaneous respiratory activity is borderline benefits from short-term therapy, which can be repeated as necessary. Protracted artificial ventilation can be avoided. The gradual process of weaning from the ventilator following prolonged artificial respiration is facilitated by the use of a plastic lung. Plastic lung therapy is superior to other common methods of treating persistent atelectasis, because its mucolytic effects lead to expansion of the atelectatic lobe or segment.(ABSTRACT TRUNCATED AT 250 WORDS)

Equipment Design↗
PubMed1990

The Minnesota Clinical Comparison and Assessment Project.

Efforts to quantify and improve the effectiveness and efficiency of health care services are critical to the health care system in the United States. Essential components of these efforts are clinician involvement and support and reliable clinical information systems. Organized medicine and the hospital industry in Minnesota have initiated and funded the Minnesota Clinical Comparison and Assessment Project (MCCAP) to begin to document, compare, and improve health care services. Through MCCAP, a forum, comprising leaders in the Minnesota health care community, oversees efforts to collaboratively identify and address quality of care. In addition, MCCAP will adapt guidelines for specific conditions/procedures, collect hospital-level data on clinical practices in the state relative to those conditions/procedures, and provide feedback so that physicians can evaluate their practice and modify it, if necessary, to improve quality of care.

Clinical Competence↗
PubMed1990

[Complications of intravenous therapy with peripheral indwelling catheter].

Intravenous fluid replacement via a peripheral catheter harbours several risks. The study presented emphasizes that about 50% of the patients show complications during the first days after positioning of an intravenous line. Women patients have been affected more often than male patients. Small catheters positioned in a major vessel away from a joint in the forearm, yield the best results. Peripheral lines should be removed within 8 to 12 hours after surgical procedures, when early symptoms are observed. Complications can be avoided by following these recommendations.

Catheterization, Peripheral↗
PubMed1990

[Postoperative ventilation in the "iron lung"].

Postoperative artificial ventilation by using an endotracheal tube may cause a pulmonary infection. A possibly necessary permanent sedation and relaxation may result in an additional danger for the patient. The principle of the "iron lung" represents an alternative to endotracheal artificial respiration, which applies especially to endangered patients who are under postoperative artificial respiration. After an abdominal operation five patients have been extubated and artificially respirated by using the "iron lung" principle while not being able to breath by themselves. The degree of the sedation was monitored both intraoperatively and postoperatively using an automatic EEG classification. The performance spectrum of the respiratory curve enabled very early detection of the onset of spontaneous respiration.

Abdomen↗
PubMed1990

[Pelvic tilt and leg length discrepancy].

Pelvic obliquity caused by leg length discrepancy is a problem facing patients with a wide variety of conditions. It is the degree of discrepancy and the growth pattern of the legs that usually govern treatment decisions, with the cause of the discrepancy having little influence. We analyzed the results recorded in 345 patients with pelvic obliquity caused by leg length inequality operated on between 1969 and 1989. In 146 patients a shortening procedure was done and in 199 patients a lengthening procedure. Biological bone growth stimulation did not prove to be predictable and effective in 65 cases. In 134 patients and 138 segments a distraction procedure was performed. In 26 segments the technique was according to Wagner; in 37 cases the Ilizarov fixator was used and in 75 the Orthofix device. Excellent results were obtained in 65% and good results in 23%; the condition became worse in 12%. Analysis of the results justifies the use of epiphysiodesis, shortening osteotomies and bone lengthening according to the biological principles investigated by Ilizarov in the presence of well-defined indications outlined in this report. Patients with a discrepancy of up to 2-3 cm are treated conservatively by shoe lift. For patients with a leg length inequality of 3-5 cm, epiphysiodesis or shortening osteotomy is still a good indication although lengthening procedures can also be performed. Discrepancies between 5 and 15 cm are treated mainly by lengthening operations. New lengthening techniques such as corticotomy and callus distraction, as well as new external fixation systems like Orthofix and Ilizarov, have made bone lengthening a less risky, easier, and more effective procedure. In a growing child, careful clinical and radiological assessment and repeated analysis of past growth in order to predict future growth can provide an exact plan for effective treatment, which often consists of bone lengthening, combined with shortening procedures on the contralateral side to establish leg length equality even in cases when there is 20 cm difference. Surgical treatment can be especially gratifying when anatomical, cosmetic and functional symmetry is restored and a lifetime of shoe lifts, braces or prostheses can be avoided.

Adolescent↗
PubMed1990

[The effects of ketamine on the electroencephalogram--typical patterns and spectral representations].

In 40 female patients aged between 17 and 79 years, the pre- and intraoperative EEG was recorded and processed by personal computer. For induction of general anesthesia patients received between 2 and 3 mg/kg ketamine i.v. within 30 s. In the phase of diminished ketamine effects enflurane was given in addition. Activity in the theta band was observed in all patients during general anesthesia, and in 30% there were complexes. These complexes differ in their spectral content of burst suppression patterns. Under effect of ketamine nearly all patients showed fast beta waves in the EEG. It is proposed that the spectral domain of EEG evaluations be enhanced to an upper limit of 45 Hz.

Adolescent↗
PubMed1989

[Atelectasis treatment by ventilatory support using an iron lung].

Total atelectasis of the left lung occurred in a 61-year-old woman after several weeks ventilator-assisted breathing following an operation for ileus, when the tracheal cannula was removed. It was quickly replaced and artificial ventilation resumed. But despite daily bronchoscopic suction for three weeks the patient's state failed to improve (vital capacity 39%, arterial pO2 47 mm Hg, pCO2 37 mm Hg). Mechanical ventilation with an "iron lung" was therefore instituted over a six month period, at first for two hours daily (as an in-patient) and then weekly (as out-patient). During this time her condition and general state clearly improved. On re-hospitalization to remove the tracheal cannula her vital capacity was 75%, pO2 78 mm Hg and pCO2 38 mm Hg.

Carbon Dioxide↗
PubMed1989

Prevention of urethral stricture formation after transurethral resection of the prostate: a controlled randomized study of Otis urethrotomy versus urethral dilation and the use of the polytetrafluoroethylene coated versus the uninsulated metal sheath.

Stricture formation after transurethral prostatectomy was studied in a randomized clinical trial including 185 patients. The patients were allocated to either a 2-day urethral catheter-dilation or internal Otis urethrotomy and to an operation with either a polytetrafluoroethylene coated or an uninsulated metal resectoscope. Urethral stricture was defined as an obstruction resulting in a maximum urine flow rate of less than 15 ml. per second and not permitting the passage of a 21F cystoscope. The frequency of urethral strictures was significantly lower after Otis internal urethrotomy (4 per cent) than after a 2-day urethral catheter dilation (16 per cent). The incidence of stricture formation was similar in patients operated on with a polytetrafluoroethylene coated (8 per cent) and with an uninsulated metal (12 per cent) resectoscope sheath. The incidence of stricture formation was unrelated to age, duration of preoperative and postoperative catheterization, operating time and presence of urinary tract infection.

Aged↗
PubMed1989

Genetic characterization of FLA, the cat major histocompatibility complex.

The major histocompatibility complex (MHC) of the domestic cat (termed FLA) has been refractile to genetic and serological definition largely because of repeated failure to detect cytotoxic antibodies in multiparous cats or to elicit antibody following allogeneic lymphocyte immunization. We have developed a protocol for producing cytotoxic alloantisera in the cat following rejection of multiple surgical skin grafts. Of 59 cats subjected to grafting, 13 produced lymphocytotoxic antisera which had varying specificities among a panel of outbred cat cells. A population cluster analysis of the 13 alloantisera permitted the identification of six clusters of overlapping FLA specificities. Serological analysis of cells from 12 cat kindreds led to the definition of 24 allogeneic haplotypes, which segregate as a single Mendelian complex. Feline FLA antisera were characterized as class I or class II specific by immunoprecipitation of FLA gene products on lymphocyte cell surfaces. Abundant antigenic polymorphisms for both class I and class II MHC determinants were discovered, a result consistent with precedence in other species and the common expectation of the adaptive value of MHC variation. Development of feline MHC typing reagents and the definition of haplotypes for the cat hold promise for experimental analysis of valuable feline models for virus-induced immune deficiencies.

Animals↗