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Biomedical subjects

R Hofstetter

Publications and source records attributed to R Hofstetter.

At least 19 recordsLinked to original sources
PubMed2002

[Effects of an optimized exercise therapy on physical performance of patients with cystic fibrosis].

Regular exercise training can increase the physical performance of patients with cystic fibrosis (CF). However, training is often hampered by negative factors such as infections, lack of time, etc. The aim of the present study was to investigate the effects of a 3-week-training-program performed under favourable conditions on physical performance and lung function of CF-patients: 17 patients daily trained at least 2,5 h under suspicious conditions at a sport hotel in Israel (Eilat). During the entire 3 weeks a comprehensive care was applied to the patients including intensive physical therapy and nutrition adapted to the individual demands. Testings of lung function and cycle ergometry ramp tests were performed a week before and after the training program. Additional control measurements were taken 7 months post training. After the 3-week-training vital capacity and FEV1 were increased by 7 % and 6 % (p > 0.05). The results of the cycle ergometry showed bigger and significant improvements in the maximal values of power (12 % - 20 %), oxygen uptake and ventilation. This findings were also valid for the submaximal exercise range indicated by a slower heart rate slope and a lower aerobic-anaerobic threshold. The present results suggest, that relatively large increases in physical performance can be obtained by short, but intensive exercise training including a comprehensive care.

Cystic Fibrosis↗
PubMed2001

[Navigation assisted by image conversion. An experimental study on pelvic screw fixation].

Within an experimental trial the new method of fluoroscopy based navigation was tested for percutaneous pelvic screw fixations. A regular C-arm was used and the navigation system developed by Medivision. In a first step appropriate C-arm projections were defined for five standardized screw positions. Then precision and fluoroscopy time of 60 screws in 6 artificial pelves were evaluated. For the sacroliacal screw in S1, S1 screw in S2, anterior column screw, posterior column screw and the supraacetabular ilium screw three to four appropriate projections were defined. These were all combinations of the known special pelvic views inlet/outlet and iliac/obturator. Using these standardized views the average fluoroscopy time was 6 seconds per screw. 51 screws (85%) were inserted correctly. In five cases there was a slight deviation without perforating the cortex, four times the cortex was perforated.

Acetabulum↗
PubMed2001

Correction of simple congenital heart defects in infants and children through a minithoracotomy.

BACKGROUND: Minimally invasive surgical techniques in pediatric cardiac surgery have evolved throughout the last 10 years. Advantages of minimally invasive procedures include excellent cosmetic results and superior postoperative outcome. However, safety of minimally invasive techniques has to be proven. METHODS: In 21 female infants and children, a right anterolateral thoracotomy was performed. Mean age was 7.1 years (0.5 to 16.6 years) and mean body weight was 20.8 kg (8.3 to 56 kg). The following defects were repaired: atrial septum defect type II (n = 14); partial atrioventricular septum defect (n = 3); partial anomalous pulmonary venous connection (n = 2); ventricular septum defect (n = 2); mitral valve insufficiency (n = 1); and resection of an embolized atrial septum defect occluder (n = 1). In two cases, aortic cross-clamping was performed by using a transthoracic clamp. In 5 patients, femoral cannulation was performed. Skin incisions were limited to 4 to 7 cm. RESULTS: There was no operative or late mortality. Mean operation time, bypass time, and aortic cross-clamp time were 138 (95 to 275), 72 (32 to 179), and 35 (12 to 120) minutes, respectively. Mean postoperative mechanical ventilation time, mean intensive care unit stay, and mean hospital stay were 3.9 hours (1 to 12 hours), 1.4 days (1 to 3 days), and 12 days (8 to 18 days), respectively. Postoperative complications included hemorrhage in 1 patient requiring surgical intervention. Mean follow-up period was 13.3 months (1 to 36 months). All patients were in New York Heart Association class I postoperatively. Trivial mitral insufficiency was evident in 1 patient operated for partial atrioventricular septum defect. CONCLUSIONS: A small right anterolateral thoracotomy as a minimally invasive technique in pediatric cardiac surgery is a safe and suitable alternative in the operative management of simple congenital heart defects. Cosmetic results are superior, however, improved postoperative outcome has to be proven.

Adolescent↗
PubMed2001

Novel computer-assisted fluoroscopy system for intraoperative guidance: feasibility study for distal locking of femoral nails.

OBJECTIVES: Orthopaedic procedures that use fluoroscopy require intraoperative mental navigation of the surgical tools in a three-dimensional space. Moreover, because of their reliance on real-time monitoring, such procedures are frequently associated with increased x-ray exposure. The goal of this study was to develop a computer-guided surgical navigation system based on fluoroscopic images that not only facilitates direction of surgical tools within anatomy, but also provides constant feedback without the need for radiologic updates. To evaluate the feasibility of the new technology, the authors used it on cases requiring distal locking of femoral nails. METHODS: The hardware components of the system include an instrumented C-arm, optoelectronic position sensor, stereotactic tools, and custom-made software. Computer integration of these devices permitted C-arm alignment assistance and real-time navigation control without constant x-ray exposure. The nails were locked in a variety of media, including plastic femurs, dry human femoral specimens, human cadavers, and one clinical case. Unreamed femoral nail sizes ranged from 9/340 to 12/400. Radiographs were taken to confirm that screws were positioned correctly, and fluoroscopic time associated with the locking procedure was recorded. RESULTS: All distal holes were locked successfully. In eight (11 percent) of seventy-six holes, the drill bit touched the canal of the locking hole, albeit with no damage to the nail and no clinical consequences. The fluoroscopy time per pair of screws was 1.67 seconds. CONCLUSIONS: The developed system enables the physician to precisely navigate surgical instruments throughout the anatomy using just a few computer-calibrated radiographic images. The total radiation time per procedure can be significantly reduced because additional x-ray exposure is not required for tool navigation.

Bone Nails↗
PubMed2000

Computer-assisted fluoroscopy-based reduction of femoral fractures and antetorsion correction.

OBJECTIVE: Intra-operative fluoroscopy is a valuable tool for visualizing underlying bone, implant, and surgical tool positions in orthopedics. It has brought about the minimally invasive surgical technique of intramedullar nailing to fix femoral shaft fractures. However, the limited field of view and two-dimensional property of fluoroscopic images aggravate intra-operative control of surgical parameters. The purpose of this article is to introduce a surgical navigation system based on fluoroscopy that provides missing information for the procedure of femoral fracture fixation. MATERIALS AND METHODS: Optoelectronic markers are placed on a surgical drill, involved bone fragments, the femoral nail, and the fluoroscope to track their positions. Projection properties of the fluoroscope are acquired through an initial precalibration. The relative positions of bone fragments, implants, and surgical tools are displayed superimposed simultaneously and in real time on multi-planar intra-operative fluoroscopic images. This is achieved by computer simulation of X-ray projections that have taken place with acquisition of the fluoroscopic images. In addition, a method has been developed that allows contactless measurement of three-dimensional anatomic landmarks, based on their representation in fluoroscopic images. In combination with optoelectronic tracking, this enables dynamic calculation of important surgical parameters such as femoral antetorsion. RESULTS: A pilot surgery showed that fracture reduction can benefit from the developed computer-assisted method. An in-vitro study on computer-assisted measurement of femoral antetorsion demonstrated the high degree of precision of this technique.

Bone Nails↗
PubMed2000

A new approach to computer-aided spine surgery: fluoroscopy-based surgical navigation.

A new computer-based navigation system for spinal surgery has been designed. This was achieved by combining intraoperative fluoroscopy-based imaging using conventional C-arm technology with free-hand surgical navigation principles. Modules were developed to automate digital X-ray image registration. This is in contrast to existing computed tomography- (CT) based spinal navigation systems, which require a vertebra-based registration procedure. Cross-referencing of the image intensifier with the surgical object allows the real-time image-interactive navigation of surgical tools based on one single registered X-ray image, with no further image updates. Furthermore, the system allows the acquisition and real-time use of multiple registered images, which provides an advanced multi-directional control (pseudo 3D) during surgical action. Stereotactic instruments and graphical user interfaces for image-interactive transpedicular screw insertion have been developed. A detailed validation of the system was performed in the laboratory setting and throughout an early clinical trial including eight patients in two spine centers. Based on the resulting data, the new technique promises improved accuracy and safety in open and percutaneous spinal surgery.

Bone Screws↗
PubMed2000

Uncontrolled reoxygenation by initiating cardiopulmonary bypass is associated with higher protein S100 in cyanotic versus acyanotic patients.

BACKGROUND: The systemic reoxygenation injury produced by initiating cardiopulmonary bypass (CPB) in infants with cyanotic heart disease may be associated with cerebral dysfunction and injury. Increased protein S100 (S100) serum levels may indicate cerebral and blood brain barrier damage as well as inflammatory changes, therefore serving to quantify these changes. The present clinical study assessed S100 in cyanotic patients undergoing CPB with normoxic versus hyperoxic paO2 in acyanotic cases and in controls without CPB. METHODS: 43 patients with congenital heart disease aged 5 days to 15 years (mean 4.4 years) were enrolled consecutively and divided in four groups: (1) Cyanotic infants undergoing controlled normoxic reoxygenation on CPB (n = 12), (2) cyanotic infants undergoing uncontrolled hyperoxic reoxygenation on CPB (n = 9), (3) acyanotic infants operated with CPB (n = 16) and (4) patients operated without CPB (n = 6). Blood samples were collected after induction of anesthesia (A), up to 4 hours after surgery (B) and at postoperative day one (C). RESULTS: Preoperative S100 serum levels [microg/l] in all groups were below clinical relevance. S100 increased markedly after surgery in groups 1 and 2. Differences in postoperative S100 levels were significant between groups 1 (0.45 +/- 0.13) and 3 (0.35 +/- 0.09; p = 0.018), between groups 2 (1.41 +/- 0.47) and 3 (p = 0.01), and between groups 2 and 4 (0.29 +/- 0.09; p = 0.045). There were no significant differences in postoperative S100 levels (B) between groups 1 and 2 (p = 0.05), groups 1 and 4 (p = 0.05), or groups 3 and 4 (p = 0.93). CONCLUSION: Uncontrolled hyperoxic reoxygenation on CPB for surgical correction of congenital heart defects is associated with higher S100 levels in cyanotic infants as compared to acyanotic patients undergoing comparable operations.

Adolescent↗
PubMed1999

Fluoroscopy as an imaging means for computer-assisted surgical navigation.

OBJECTIVE: Intraoperative fluoroscopy is a valuable tool for visualizing underlying bone and surgical tool positions in orthopedic procedures. Disadvantages of this technology include the need for continued radiation exposure for visual control, and cumbersome means of alignment. The purpose of this article was to highlight a new concept for a computer-assisted freehand navigation system that uses single intraoperatively acquired fluoroscopic images as a basis for real-time navigation of surgical tools. MATERIALS AND METHODS: Optoelectronic markers are placed on surgical tools, a patient reference, and the fluoroscope to track their position in space. Projection properties of the fluoroscope are acquired through an initial precalibration procedure using a tracked radiopaque phantom grid. Corrections are applied to compensate for both the fluoroscope's image intensifier distortions and the mechanical bending of the C-arm frame. This enables real-time simulation of surgical tool positions simultaneously in several single-shot fluoroscopic images. In addition, through optoelectronically tracked digitization of a target viewpoint, the fluoroscope can be numerically aligned at precise angles relative to the patient without any X-ray exposure. RESULTS: This article shows the feasibility of this technology through its use in cadaver trials to perform the difficult task of distal locking of femoral nails.

Bone Nails↗
PubMed1999

Transvenous closure of patent ductus arteriosus with Ivalon plugs. Multicenter experience with a new technique.

RATIONALE AND OBJECTIVE: The authors assess the clinical efficacy of transvenous closure of patent ductus arteriosus (PDA) with a new plug consisting of Ivalon foam and a platinum/iridium frame with four aortic and two pulmonary nitinol struts. The most widely used devices for transcatheter treatment of PDA (Porstmann plug, Rashkind umbrella, Botallo occluder, coils) have specific limitations inherent to their design (e.g., transarterial approach, residual shunts, limited retrieval). METHODS: Between 1994 and 1997, PDA closure was attempted in 33 children and 67 adolescents and adults in 7 clinical centers; PDA diameter was 2 to 11 mm. Plug diameter was 6 to 20 mm, and 8 to 16 F venous sheaths were used for insertion. RESULTS: Placement was successful in 98% (with a single plug in 88%, and a second or third plug in 10%) and unsuccessful in 2%. Plugs were retrieved after malpositioning in 12 of 12 patients and after pulmonary embolization in 2 of 3 patients. One patient underwent surgery for removal of an embolized plug. Complete PDA closure was proved by aortography and color Doppler echocardiography in 85% (40 of 43 patients with a PDA 2-3.9 mm, 30 of 36 patients with a PDA 4-5.9 mm, and 15 of 21 patients with a PDA 6-11 mm). During a median follow-up interval of 16 months, there were no complications (infection, hemolysis, fracture, embolization). CONCLUSION: The new plug device can be used successfully in patients with a PDA diameter up to 11 mm. Further investigations are underway to determine the definite clinical value of this technique.

Adolescent↗
PubMed1998

[The method of computer-assisted orthopedic surgery based on two-dimensional fluoroscopy: the principles of action].

Surgical instruments play a major role in orthopedic surgery; usually they are controlled visually at the operation. In certain situations additional device to control instrument is needed. The aim of this paper is to present theoretical foundations, create prototype and give initial assessment of computer assisted orthopedic surgery system. Two-dimensional fluoroscopy was the base for system functioning. Lab tests and first applications in the operating room are presented. Precision of the system found allows for its use in orthopedic surgery with television monitoring.

Bone Diseases↗
PubMed1997

[A new system for transvenous occlusion of persistent ductus arteriosus].

An Ivalon-plug (PDA-plug) has been developed for transvenous closure of patent ductus arteriosus. It can be introduced into the ductus through standard venous sheaths with a diameter of 8-16 French. The plug is fixed in its target position by means of four distal (aortal) and two proximal (pulmonary) nitinol struts. In case of malpositioning the system can be pulled back into and retrieved through the sheath. In animal experiments endothelialization of the implanted material was demonstrated. PDA-closure was attempted in 58 patient; the procedure was successful in 57 cases; a residual ductal flow was present in eight patients. During a follow-up of up to 24 months there were no complications.

Adolescent↗
PubMed1995

Service utilization and costs of care for severely mentally ill clients in an intensive case management program.

OBJECTIVE: The study evaluated the effects of an intensive case management model on clients' use of inpatient and outpatient psychiatric care and on the costs of care. METHODS: Ninety clients of a county mental health system who were frequent users of inpatient services were randomly assigned to either an intensive case management group, a traditional case management group, or a control group who received no particular services. Outcome variables measured over a two-year period were number of units used by clients and costs of inpatient care in county and private facilities and various types of outpatient care, including day treatment and use of an emergency psychiatric unit. RESULTS: Clients who received intensive case management had fewer inpatient days and reduced overall costs for mental health services. CONCLUSIONS: Assertive outreach and intensive case management can reduce hospitalizations of clients who are frequent users of inpatient care and can reduce overall mental health care costs. Mental health consumers employed as case management aides can play an important role in the delivery of mental health services, particularly with frequent users of inpatient care.

Adolescent↗
PubMed1994

Syntactic complexity in Spanish narratives: a developmental study.

Syntactic complexity in the movie retellings of 77 school-age Spanish-speaking children was examined using a structural constituent analysis. The results demonstrated developmental differences in the length of T-units, index of subordination, use of relative clauses, and prepositional phrases. There were also differences in the length of T-units, use of nominal clauses, and adverbial phrases across Spanish language groups. The analysis underscores the significance of subordination as a cohesive device and as an indicator of narrative proficiency.

Child Language↗
PubMed1991

Determination of left atrial area and volume by cross-sectional echocardiography in healthy infants and children.

Part 1 of the study measured the end-systolic and end-diastolic left atrial (LA) areas and volumes in 30 children through sector echocardiography, and compared these values with those obtained with biplane angiocardiography. A strong correlation exists between the LA area in the frontal plane as determined by apical (r greater than 0.91) and subcostal (r greater than 0.98) echocardiography on the one hand and by angiocardiography on the other. However, there is a slight underestimation of the LA area by the apical 4-chamber view. LA volume as determined by subcostal sector echocardiography in the frontal and sagittal plane also correlated well with LA volume calculated with biplane angiocardiography (r greater than 0.97). Part 2 of the study determined LA areas and volumes in 74 healthy newborns and infants by echocardiography and related them to body weight and body surface area, thus obtaining normal values for this age group. The relation of the LA area and volume measurements in newborns and infants to body weight or surface area was best described by a linear function. The mean of the percentage of systolic-diastolic area diminution was 53 +/- 6% for the apical 4-chamber view and 50 +/- 4% for the subcostal 4-chamber view. LA ejection fraction determined by the subcostal biplane volume measurements was 62 +/- 7% (mean +/- standard deviation). These values were independent of body weight or surface area.

Angiocardiography↗
PubMed1991

Identification of correlates of physical activity among Latino adults.

127 Latino adults responded to a survey concerning physical activity. Respondents over-represented well educated and middle class Latinos. Subjects reported a mean of 48 minutes/week of walking for exercise. This sample reported less than two episodes per week of vigorous physical activity, again below the recommended 3/wk needed to insure cardiovascular fitness. We expect more representative samples to engage in less physical activity. Stepwise multiple regression analyses were conducted using 24 variables based on Social Learning Theory. A multiple R of 0.66 accounted for over 27% of the variance in walking for exercise (p less than 0.001). Older adults, those with a history of childhood injury, and those who reported friend support were more likely to walk for exercise. Respondents who participated in physical activity during childhood and adolescence (including formal physical education in school) and, paradoxically, those who had models for exercise in childhood were less likely to walk for exercise. A multiple R of 0.75 accounted for 43% of the variance in vigorous physical activity and reached significance (p less than 0.001). Self-efficacy, friends' support, childhood physical activity, and eating a heart healthy diet were positively related to vigorous activity. These results suggest that different correlates influence walking versus vigorous activity, and that correlates of physical activity are different for Latinos compared to Anglos. The findings emphasize the need for larger scale investigations of the determinants of activity within the Latino population.

Attitude to Health↗
PubMed1991

Surgery for critical congenital aortic stenosis during the first three months of life.

Open commissurotomy for critical aortic stenosis has been performed in a consecutive series of 28 neonates and infants below 3 months of age (average age 1 month) including 5 patients with severe organic mitral valve disease in need of concomitant correction. In the majority of cases, aortic stenosis was due not only to fused commissures but also to excessive immature valve tissue protruding into the valve area. Therefore a technique of extended commissurotomy has been adopted resecting such nodules responsible for a secondary level stenosis. All operations were done under deep hypothermia (17 degrees C), circulatory arrest (33 +/- 11 min) and cardioplegia using the Bretschneider solution (35-50 ml/kg). Hospital mortality was 18% (5) including 1 infant dying at 2 months of thrombosed mitral prosthesis inserted at a secondary operation. Severe organic mitral valve disease proved to be the only significant risk factor for early mortality. During the follow-up period of up to 10 years (average 5 years), 1 child with a hypoplastic left heart died and 2 children had to undergo reoperation for residual and recurrent stenosis, respectively. Actuarial survival for the present series is 78% at 10 years while reoperation free survival for the aortic valve is 64%. It is concluded that careful and if necessary extended open commissurotomy still represents the method of choice in this age group. Alternative methods such as transventricular or percutaneous dilatation did not show a lower risk until now and long-term results are not convincing as yet.

Actuarial Analysis↗