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Biomedical subjects

D Olsen

Publications and source records attributed to D Olsen.

At least 19 recordsLinked to original sources
PubMed2006

Decline eccentric squats increases patellar tendon loading compared to standard eccentric squats.

BACKGROUND: Recent studies have shown excellent clinical results using eccentric squat training on a 25 degrees decline board to treat patellar tendinopathy. It remains unknown why therapeutic management of patellar tendinopathy using decline eccentric squats offer superior clinical efficacy compared to standard horizontal eccentric squats. This study aimed to compare electromyography activity, patellar tendon strain and joint angle kinematics during standard and decline eccentric squats. METHODS: Thirteen subjects performed unilateral eccentric squats on flat-and a 25 degrees decline surface. During the squats, electromyography activity was obtained in eight representative muscles. Also, ankle, knee and hip joint goniometry was obtained. Additionally, patellar tendon strain was measured in vivo using ultrasonography as subjects maintained a unilateral isometric 90 degrees knee angle squat position on either flat or 25 degrees decline surface. FINDINGS: Patellar tendon strain was significantly greater (P<0.05) during the squat position on the decline surface compared to the standard surface. The stop angles of the ankle and hip joints were significantly smaller during the decline compared to the standard squats (P<0.001, P<0.05). Normalized mean electromyography amplitudes of the knee extensor muscles were significantly greater during the decline compared to the standard squats (P<0.05). Hamstring and calf muscle mean electromyography did not differ, respectively, between standard and decline squats. INTERPRETATION: The use of a 25 degrees decline board increases the load and the strain of the patellar tendon during unilateral eccentric squats. This finding likely explains previous reports of superior clinical efficacy of decline eccentric squats in the rehabilitative management of patellar tendinopathy.

Adult↗
PubMed2002

The application of quantitative oil streaking to the HeartQuest left ventricular assist device.

Methods of flow visualization using oil streaking are established techniques for investigating surface shear and near wall flow patterns. Recent studies have used an array of oil dots on a surface which form streaks when exposed to shear forces. This method is generally qualitative, but it is possible to make quantitative measurements of the shear if the oil streaks have been calibrated. This paper presents the application of a quantitative oil streak method to the HeartQuest left ventricular assist device (LVAD). An array of dots was applied to the top housing of the pump, yielding quantitative values for the shear and qualitative patterns of the near wall flow in that region. The results were used to locate regions likely to promote thrombosis, such as stagnation points or recirculation regions. Regions of high shear, where hemolysis might occur, also can be identified with this method. In addition to being an important design technique, quantitative oil streaking assisted in the verification of computational fluid dynamics results within the HeartQuest LVAD.

Cardiovascular Diseases↗
PubMed2001

Endovascular repair of AAA rupture 20 months after endoluminal stent-grafting.

PURPOSE: To demonstrate the feasibility of endovascular repair of a ruptured abdominal aortic aneurysm (AAA) previously treated with an endoluminal stent-graft. CASE REPORT: An 84-year-old man with a 9.5-cm AAA underwent endoluminal repair with an Endologix stent-graft, but a type I endoleak was detected postprocedurally. The patient was discharged and lost to follow-up. Twenty months later, he suffered an aneurysm rupture, which was repaired using endovascular techniques. Although he had a postoperative course complicated by aspiration pneumonia and renal failure, he recovered fully and was discharged from the hospital with no evidence of endoleak on the postprocedural imaging studies. CONCLUSIONS: Late ruptures after endoluminal AAA stent-grafting can be successfully treated with endovascular techniques.

Aged↗
PubMed2001

No BRCA1 germline mutation in a family with uterine papillary serous carcinoma: a case report.

The purpose of the study was to examine BRCA1 germline mutation and its relationship to BRCA1 expression in two patients, a mother and a daughter, both diagnosed with uterine papillary serous carcinoma (UPSC). DNA was screened for BRCA1 and BRCA2 germline mutations common in the Jewish population (185delAG, 5382insC, and 6174delT) by PCR-based assay and with a protein truncation test (PTT) to detect mutation in exon 11 of BRCA1 and exons 10 and 11 of BRCA2. BRCA1 expression in fixed tumor tissues was assessed by immunocytochemistry (IHC). No germline mutation in either BRCAI or BRCA2 gene was found in the two patients. Both samples showed reduced levels of BRCAI expression. Taken together, these results suggest that undetected or unscreened for germline mutation may be associated with occurrence of this rare tumor type in two members of the same family. Alternatively, an epigenetic mechanism such as BRCA1 promoter hypermethylation may be responsible for reduced expression of BRCA1 in the absence of DNA mutations.

Aged↗
PubMed2000

Incidence and significance of pneumomediastinum after laparoscopic esophageal surgery.

BACKGROUND: Pneumomediastinum can be a sign of esophageal perforation. During laparoscopic esophageal surgery, the mediastinum is exposed to carbon dioxide gas under pressure that can cause pneumomediastinum. METHODS: Forty-five patients undergoing laparoscopic esophageal procedures had erect, inspiratory, single-view chest radiographs (CXR) performed in the recovery room (RR). Patients with extraabdominal gas underwent daily erect, inspiratory, single-view CXR until resorption of the gas or discharge from the hospital. Insufflation time and pressure were recorded, and morbidity was evaluated. Results are expressed as mean +/- SEM. RESULTS: Twenty-five men (56%)and 20 women (44%) aged 33.0 +/- 2.9 years underwent 10 Heller myotomies (22.2%), 27 Nissen fundoplications (60.0%), six Toupet fundoplications (13.3%), and two paraesophageal hernia repairs (4.4%). Twenty-four patients (53.3%) had normal CXR in RR, and 21 (46.7%) had extraabdominal gas. Eighteen (85.7%) of the 21 had pneumomediastinum, three (14.3%) had pneumothorax, and 12 (57.1%) had subcutaneous emphysema in RR. Sixteen of these 21 remained hospitalized and had repeat CXR on postoperative day 1. Of these 16, five (31.3%) had normal CXR, 11 (68.8%) had pneumomediastinum, and seven (43.8%) had subcutaneous emphysema. There were no esophageal perforations and no chest tube insertions, and there was no morbidity related to pneumomediastinum. CONCLUSION: Pneumomediastinum is observed frequently following laparoscopic esophageal operations and often persists past 24 h. After these operations, pneumomediastinum is not necessarily indicative of esophageal perforation. In this group, it caused no clinically significant events that altered the course of the patients.

Adolescent↗
PubMed2000

Surgical wound morbidity in an austere surgical environment.

Surgical wound morbidity was analyzed for a U.S. military field hospital deployed to the Republic of Haiti in support of Operation New Horizons 1998. The purpose of the analysis was to determine if procedures performed in the field hospital had greater infectious risks as a result of the environment compared with historical reports for traditional hospital or clinic settings. Acceptable historical infection rates of 1.5% for clean surgical cases, 7.7% for clean contaminated cases, 15.2% for contaminated cases, and 40% for dirty cases have been noted. There were 827 operations performed during a 6-month period, with the majority of patients assigned American Society of Anesthesiologists Physical Status Classification class I or II. The distribution of these cases was: 72% clean cases, 5% clean contaminated cases, 4% contaminated cases, and 19% dirty cases. The overall wound complication rate was 3.6%, which included 5 wound infections, 11 wound hematomas, 8 superficial wound separations, and 6 seromas. The infectious morbidity for clean cases, the index for evaluation of infectious complications, was 0.8%, well within the accepted standards. There were two major complications that required a return to the operating room: a wound dehiscence with infection in an orchiectomy, and a postoperative hematoma with airway compromise in a subtotal thyroidectomy. There were no surgical mortalities. The infectious wound morbidity for operations performed in the field hospital environment was found to be equivalent to that described for the fixed hospital or clinic settings. No special precautions were necessary to ensure a low infection rate. The safety for patients undergoing elective surgical procedures has been established. Further training using these types of facilities should not be limited based on concerns for surgical wound morbidity.

Adolescent↗
PubMed1999

Motor feedback physiological control for a continuous flow ventricular assist device.

The response of a continuous flow magnetic bearing supported ventricular assist device, the CFVAD3 (CF3) to human physiologic pressure and flow needs is varied by adjustment of the motor speed. This paper discusses a model of the automatic feedback controller designed to develop the required pump performance. The major human circulatory, mechanical, and electrical systems were evaluated using experimental data from the CF3 and linearized models developed. An open-loop model of the human circulatory system was constructed with a human heart and a VAD included. A feedback loop was then closed to maintain a desired reference differential pressure across the system. A proportional-integral (PI) controller was developed to adjust the motor speed and maintain the system reference differential pressure when changes occur in the natural heart. The effects of natural heart pulsatility on the control system show that the reference blood differential pressure is maintained without requiring CF3 motor pulsatility.

Algorithms↗
PubMed1999

Biologic attachment of an allograft bone and tendon transplant to a titanium prosthesis.

An Achilles tendon allograft with its bony insertion was used to bridge a Titanium implant, containing an endoprosthetic tendon anchor, and the sheep biceps muscle. Twelve sheep were operated on unilaterally and followed up clinically and histologically for 2, 4 (n = 2), 8, and 12 months (n = 4). Full function of the front limb was regained after 8 to 12 weeks. There were no signs of mechanical loosening at all times. The morphologic changes at the bone block and implant fixation site were an initial revascularization of the allograft bone, which was observed at 2 months and enhanced at 4 months but occurred without any evidence of bone remodeling. This was changed in all specimens taken at 8 and 12 months where intensive new bone development, remodeling, and bone ingrowth in the titanium implant was found. Bone mass was shifted significantly to the tendon insertion half of the bone block because of a creeping substitution of the cancellous allograft bone and bone ingrowth to the implant. Overall bone mass slightly decreased with time but resorption of allograft bone outweighed new bone development only at lesser loaded areas. Transplantation of a bone and tendon allograft to an implant resulted in a revitalized, mechanically stable, and biologically anchored compound.

Achilles Tendon↗
PubMed1998

High-level expression of eukaryotic polypeptides from bacterial chromosomes.

Attractive economics and short development timelines have often been cited as reasons for using bacteria to express eukaryotic proteins on a commercial scale. Nevertheless, routine techniques for bacterial expression of heterologous proteins are beset by a variety of technical and legal difficulties. In particular, the use of plasmids to express foreign proteins, popular promoter systems, protein fusion partners, and histidine tags and the recovery of proteins from inclusion bodies are affected by a host of issued patents. Chromosomally encoded leaderless fusions (CELF) offer a variety of technical and legal advantages over existing bacterial expression systems. In this study, we show that CELF can be used to produce a wide assortment of eukaryotic proteins at 10-liter fermentation scale.

Bacteriophage T7↗
PubMed1998

Performance of a continuous flow ventricular assist device: magnetic bearing design, construction, and testing.

A new centrifugal continuous flow ventricular assist device, the CFVAD III, which is fully magnetic bearing suspended, has been developed. It has only one moving part (the impeller), has no contact (magnetic suspension), is compact, and has minimal heating. A centrifugal impeller of 2 inch outer diameter is driven by a permanent magnet brushless DC motor. This paper discusses the design, construction, testing, and performance of the magnetic bearings in the unit. The magnetic suspension consists of an inlet side magnetic bearing and an outlet side magnetic bearing, each divided into 8 pole segments to control axial and radial displacements as well as angular displacements. The magnetic actuators are composed of several different materials to minimize size and weight while having sufficient load capacity to support the forces on the impeller. Flux levels in the range of 0.1 T are employed in the magnetic bearings. Self sensing electronic circuits (without physical sensors) are employed to determine the impellar position and provide the feedback control signal needed for the magnetic bearing control loops. The sensors provide position sensitivity of approximately 0.025 mm. A decentralized 5 axis controller has been developed using modal control techniques. Proportional integral derivative controls are used for each axis to levitate the magnetically supported impeller.

Algorithms↗
PubMed1997

Bile duct injuries during laparoscopic cholecystectomy.

BACKGROUND: With the introduction of laparoscopic cholecystectomy, an increase in the incidence of bile duct injury two to three times that seen in open cholecystectomy was witnessed. Although some of these injuries were blamed on the "learning curve," many occurred long after the surgeon had passed his initial experience. We are still seeing these injuries today. METHODS: To better understand the mechanism behind these injuries, in the hope of reducing the injury rate, 177 cases of bile duct injury during laparoscopic cholecystectomy were reviewed. All records were studied, including the initial operative reports and all subsequent treatments. Videotapes of the procedures were available for review in 45 (25%) of the cases. All X-ray studies, including interoperative cholangiograms and ERCPs, were reviewed. RESULTS: The vast majority of the injuries seen in this review (71%) were a direct result of the surgeon misidentifying the anatomy. This misidentification led to ligation and division of the common bile duct in 116 (65%) of the cases. Cholangiograms were performed in only 18% (32 patients) of cases, and in only two patients was the bile duct injury recognized as a result of the cholangiogram. Review of the X-rays showed that in each instance of common bile duct ligation and transection in which a cholangiogram was performed the impending injury was in evidence on the X-ray films but ignored by the surgeon. CONCLUSIONS: From this review, several conclusions can be drawn. First and foremost, the majority of bile duct injuries seen with laparoscopic cholecystectomy can either be prevented or minimized if the surgeon adheres to a simple and basic rule of biliary surgery; NO structure is ligated or divided until it is absolutely identified! Cholangiography will not prevent bile duct injury, but if performed properly, it will identify an impending injury before the level of injury is extended. And lastly, the incidence of bile duct injury is not related to the laparoscopic technique but to a failure of the surgeon to translate his knowledge and skills from his open experience to the laparoscopic technique.

Adult↗
PubMed1996

Laparoscopic discectomy with anterior interbody fusion of L5-S1.

BACKGROUND: A laparoscopic approach to the spine for the performance of a minimally invasive discectomy was first described in 1991. Since that time, a number of approaches to laparoscopic discectomy have appeared in the literature. Although these reports demonstrate the ability to approach the spine through a laparoscopic technique, they do not address the issues of loss of disc space, lumbar instability, and the need for interbody fusion. METHODS: Described is a technique of laparoscopic discectomy with interbody fusion that has been performed successfully in 75 patients. Although a carbon fiber implant was utilized to aid in the fusion process, the technique can equally be performed using donor bone as the interbody support. In the 75 patients attempted, 73 procedures were successfully completed via the laparoscopic approach. One patient was converted to an open anterior approach due to extensive pelvic adhesions from prior surgery. A second patients procedure was aborted after the diagnostic laparoscopy demonstrated dense presacral scarring from a previous gynecological procedure. RESULTS: There were no major complications in the series. Two patients with high riding bladders sustained bladder lacerations that were recognized and repaired with simple suture closure. There were no bowel injuries, and more importantly, no major vessel injury. The patients were discharged from the hospital on an average within 36 hours, with a return to work averaging between 2-4 weeks depending on the patients type of work. Using a modified pain score for evaluation, post operative pain was reduced by 75%. CONCLUSIONS: From this study, it is concluded that laparoscopic discectomy with interbody fusion is not only feasible, but appears to give good results with follow up extending out beyond two years. Issues regarding the use of carbon fiber cages vs. bone and indications of the procedure are independent of the laparoscopic approach and are addressed extensively in the orthopedic literature. It can be concluded that when there is surgical indication for L5-S1 discectomy, that a laparoscopic approach with interbody fusion may become the procedure of choice.

Diskectomy↗
PubMed1996

Quantitative 1D saturation profiles on chalk by NMR.

Quantitative one-dimensional saturation profiles showing the distribution of water and oil in chalk core samples are calculated from NMR measurements utilizing a 1D CSI spectroscopy pulse sequence. Saturation profiles may be acquired under conditions of fluid flow through the sample. Results reveal that strong saturation gradients exist in chalk core samples after core floods, due to capillary effects. The method is useful in analysis of corefloods, e.g., for determination of capillary pressure functions.

Calcium Carbonate↗