Biomedical subjects
Publications and source records attributed to T Schreiber.
We report on an ytterbium-doped photonic-crystal-fiber-based chirped-pulse amplification system delivering 131 W average power 220 fs pulses at 1040 nm center wavelength in a diffraction-limited beam. The pulse repetition rate is 73 MHz, corresponding to a pulse energy of 1.8 microJ and a peak power as high as 8.2 MW.
We report on the rare-earth-doped fiber-based generation of nearly transform-limited 10-ps pulses based on self-phase-modulation-induced spectral compression. An ytterbium-doped low nonlinearity photonic crystal fiber is used as a gain medium. An average power of as much as 97 W at a repetition rate of 47 MHz, corresponding to a peak power as high as 200 kW, was obtained. Furthermore, efficient second-harmonic generation by application of this high-power laser source is discussed.
Fluorescence imaging of green fluorescent protein (GFP) may be used to locate proteins in live cells and fluorescence lifetime imaging (FLIM) may be employed to probe the local microenvironment of proteins. Here we apply FLIM to GFP-tagged proteins at the cell surface and at an inhibitory natural killer (NK) cell immunological synapse (IS). We present a novel quantitative analysis of fluorescence lifetime images that we believe is useful to determine whether apparent FLIM heterogeneity is statistically significant. We observe that, although the variation of observed fluorescence lifetime of GFP-tagged proteins at the cell surface is close to the expected statistical range, the lifetime of GFP-tagged proteins in cells is shorter than recombinant GFP in solution. Furthermore the lifetime of GFP-tagged major histocompatibility complex class I protein is shortened at the inhibitory NK cell IS compared with the unconjugated membrane. Following our previous work demonstrating the ability of FLIM to report the local refractive index of GFP in solution, we speculate that these lifetime variations may indicate local refractive index changes. This application of our method for detecting small but significant differences in fluorescence lifetimes shows how FLIM could be broadly useful in imaging discrete membrane environments for a given protein.
Open fractures are complex injuries affecting the integrity of bones and adjacent soft tissue. The therapeutic goals in dealing with open fractures should consist of primary osteosynthesis in conjunction with functional reconstruction of soft tissue. In a period over 2 years, 26 patients were treated with extensive trauma in an interdisciplinary approach. These patients suffered from open fractures type 2 and 3. All patients were treated by primary osteosynthesis, and temporary wound closure with V.A.C.-system. Definitive wound closure was achieved by day 31 after injury. In contrast to a review of the pertinent literature we report the successful free tissue transfer in 21 patients during the critical period between 72 hours and several months preceded by the use of V.A.C.-system for the temporary coverage of open wounds.
Efficient generation of 76-W average power of 400-fs pulses at 75-MHz repetition rate by use of a diode-pumped ytterbium-doped double-clad fiber-based chirped-pulse amplification system is demonstrated. The key element in the system is a diffraction grating compressor consisting of highly efficient transmission gratings in fused silica, allowing recompression at this high power level.
OBJECTIVES: The aim of this prospective study was to evaluate the vertical infraclavicular approach to the brachial plexus for the insertion of a catheter to achieve continuous analgesia in postoperative patients and patients with chronic upper limb pain. METHODS: The brachial plexus was identified using the technique described by Kilka et al. and a flexible catheter (diameter 0.85 mm) was introduced 3-5 cm into the perineural sheath via the punction cannula. Regional analgesia was achieved by intermittent injection of local anaesthetic agent. Placement of the catheter, duration and effectiveness of treatment, complications and reasons for catheter removal were recorded using a standard protocol. RESULTS: A total number of 226 plexus catheters were placed in 210 patients. Consecutive regional analgesia for at least 48 h was possible in 88%. Analgesia was sufficient in 76% of patients up to the time of catheter removal. The median (minimum-maximum) duration of catheterisation in the whole collective was 7 days (1-240) and 11 days in patients with chronic pain. Almost 30% of the patients were treated for 10 days or longer and 4.4% were treated for 1 month or longer. Major complications occurred in only three cases, while technical problems and minor complications (redness at puncture site) occurred in 10% of cases. CONCLUSIONS: The placement of an infraclavicular plexus catheter is a suitable method for pain management in the upper limb. This approach may have advantages in patients with severe injuries who cannot abduct the arm. Our results are encouraging in terms of catheterisation time, patient comfort and incidence of complications.
OBJECTIVES: The transpulmonary double indicator method uses intra- and extravascular indicators to calculate cardiac output, intrathoracic blood volume, global end-diastolic volume, and extravascular lung water content. Since lung perfusion may be of importance during these measurements, we studied the effects of pulmonary blood flow occlusion on measurements obtained with this method. SETTING: Experimental animal facility of a University department. METHODS AND INTERVENTIONS: In seven pigs, the branch of the pulmonary artery perfusing the lower and middle lobe of the right lung was occluded. Measurements before, during, and after the occlusion were made with a pulmonary artery catheter and a commonly used transpulmonary double indicator catheter and device. MEASUREMENTS AND RESULTS: Occlusion of the right lower and middle lobe branch of the pulmonary artery increased mean pulmonary pressure (before occlusion: 24+/-1, during occlusion: 32+/-2, after reopening 25+/-1 mmHg; P<0.05), increased right ventricular end-diastolic volume (172+/-34, 209+/-21, 174+/-32 ml, respectively; P<0.05), decreased intrathoracic blood volume (998+/-39, 894+/-48, 1006+/-49 ml, respectively; P<0.05), and decreased extravascular lung water (7.2+/-0.5, 4.2+/-0.4, 6.9+/-0.4 ml/kg, respectively; P<0.05) without causing significant changes in cardiac output. All changes were reversible upon reopening the vessel. CONCLUSIONS: These data show that the transpulmonary double indicator method may underestimate extravascular lung water and right ventricular preload when the perfusion to parts of the lung is obstructed.
We introduce a method to clean uncorrelated deterministic and stochastic noise components from time series. It combines recently developed techniques for nonlinear projection with properties of the wavelet transform to extract noise in state space. The method requires that time series are generated by a dynamical system which is at least approximately deterministic and that they are recorded together with a reference signal. Its efficiency was tested on both simulated signals and measured magnetic fields of the heart. Convincing results are obtained even at low signal-to-noise ratios.
The MULTI-LINK (ML) stent is a novel second generation coronary stent. The ACS MultiLink Stent Clinical Equivalence in De Novo Lesions Trial (ASCENT) randomized 1,040 patients with single, de novo native vessel lesions to treatment with the ML stent or the benchmark Palmaz-Schatz (PS) stent, to demonstrate that the ML stent was not inferior to (i.e., equivalent or better than) the PS stent in terms of target vessel failure by 9 months. Successful stent delivery was achieved in 98.8% versus 96.9% of patients, with a slightly lower postprocedural diameter stenosis (8% vs 10%, p = 0.04), and no difference in 30-day major adverse cardiac events (5.0% vs 6.5%) for the ML stent versus the PS stent. The primary end point of target vessel failure at 9 months was seen in 15.1% of ML-treated patients versus 16.7% of PS-treated patients, with the ML proving to be equal or superior to the PS stent (p <0.001 by test for equivalency). In a prespecified subset, angiographic restudy showed a nonsignificant trend for reduced ML restenosis (16.0% vs 22.1%). Thus, the ML stent showed excellent deliverability and acute results, with 9-month clinical and 6-month angiographic outcomes that were equivalent or better than the PS stent.
Mechanical rotational atherectomy with the Rotablator is widely used for percutaneous coronary revascularization, but the ideal debulking strategy remains unknown. The purpose of this study was to compare the immediate and late results after Rotablator using two treatment strategies: Large burrs (burr/artery ratio of >0.7) to achieve maximal debulking (lesion debulking strategy) or small burrs (burr/artery ratio < or = 0.7) to modify lesion compliance (lesion modification strategy). Two hundred twenty-two patients at six centers were prospectively enrolled in this study and randomly assigned to large (n = 104 patients with 118 lesions) or small (n = 118 patients with 136 lesions) burrs. The primary endpoint was final diameter stenosis at the end of the procedure, and secondary endpoints included inhospital angiographic and clinical complications, and target lesion revascularization at 6 months. Baseline demographic and angiographic characteristics were similar. There were no differences in procedural success, the extent of immediate lumen enlargement, inhospital ischemic complications, or late target vessel revascularization. However, compared with small burrs, patients randomized to large burrs were more likely to experience serious angiographic complications (5.1% vs. 12.7%, P < 0.05) immediately after atherectomy. This study suggests that a routine lesion modification strategy employing small burrs (burr/artery ratio < or = 0.7) achieves similar immediate lumen enlargement and late target vessel revascularization compared with a more aggressive debulking strategy (burr/artery ratio >0.7), but with fewer angiographic complications.
A 42-year-old male with a history of chronic alcoholism was admitted to the department of otolaryngology with acute respiratory insufficiency and generalised cyanosis due to a respiratory obstruction by a large tumour of the hypopharynx. Because of the size and location of the tumour and the risk of bleeding, orotracheal intubation by direct laryngoscopy was considered almost impossible. To improve oxygenation cricothyroidal punction and oxygen insufflation was done immediately and SpO2 increased from 56% to 82%. Awake fiberoptic nasotracheal intubation was performed under topical anaesthesia, then general anaesthesia was induced and controlled ventilation was started. After surgical tracheotomy the patient was transferred to an intensive care unit and 12 h later the patient was discharged from the ICU.
BACKGROUND: Deficits in quality of postoperative pain management are not caused by the complexity of the medical problem or shortage of suitable drugs but by difficulties in organization and hospital structures. Moreover, there is no consensus on how to measure the quality of pain management. Quality management programs consist of strategies to overcome such difficulties and to increase quality continuously. This study reports the implementation of a quality management program to improve postoperative pain management at a university hospital. METHODS: An interdisciplinary task force consisting of nursing staff, anesthesiologists, surgeons, and members of the hospital pharmacy was set up. This task force interviewed patients and performed an analysis of current deficits (phase 1). Then, primary and secondary outcome parameters were defined to measure quality of pain management, and strategies were defined to implement improvements (phase 2). These referred to aspects of organization, standardization, and responsibility. One of the main intentions was the involvement of nursing staff. After implementation (phase 3), a second analysis was performed (phase 4). This was followed by a continuous assessment of parameters indicating quality of procedures and results which were fed back to all participants (phase 5). RESULTS: After implementation of the program (phase 4), significantly more patients reported no or mild (NRS < 4) postoperative pain (40.2% vs 30.1%) compared to phase 1. Also, patients' satisfaction with pain therapy improved significantly. The proportion of patients without pain treatment decreased by one-third. Opioids were given more frequently and more often intravenously. In contrast, the proportion of i.m. injections decreased from 20% to 5%. Continuous assessment of up to now more than 4,900 patients helped to identify possible reasons for problems and to maintain overall quality of pain management. DISCUSSION: Tools of quality management consisting of deficit analysis, definition of outcome parameters, implementation of improving strategies, post-intervention analysis and continuous feed-back may be successfully used to improve postoperative pain therapy. Changes in organization of medical management seem to be more important than medical or technical aspects. Similar strategies might be used to increase quality of other medical procedures.
OBJECTIVE: The aim of this follow-up study was to find out if severely injured patients with multiple organ failure (MOF) show any organotopic sequelae in the late course. Additionally the occupational rehabilitation result as well as the reasons for a poor occupational result were investigated. METHODS: A total of 50 MOF patients with an injury severity of 45.3 +/- 2.1 PTS points were followed up 4.9 +/- 0.3 years after trauma. In order to show any organotopic sequelae, patients were examined and laboratory tests for the function of the lungs (function test, Horovitz-quotient), liver (bilirubin, GOT, bleeding time), and kidnies (creatinine, urea) were performed. The functional (locomotion and neurological system) and occupational rehabilitation results as well as the reasons for a poor occupational result were analysed. RESULTS: The clinical examination as well the functional and laboratory tests showed mainly normal results but in in 25% of the patients a significantly decreased range of motion of the elbow, hip, knee and ankle joint was found. The "return to work rate" was 64%. Reasons for a poor occupational result were the severity of head injury, a decreased range of motion of the hip joint and general physical fitness. CONCLUSIONS: Severely injured patients who survive MOF during their intensive care treatment, show no sequelae of organ failure. The occupational rehabilitation results were excellent with a "return to work rate" of 64% which was dependent on the severity of head injury, a decreased range of motion of the hip joint and general physical fitness.
INTRODUCTION: Increasing life expectancy is associated with an increase of geriatric fractures such as intracapsular femoral neck fractures. Their treatment by arthroplasty imposes a significant burden on our health care system. METHODS: In an open clinical study we investigated the complication rate of a less expensive and less invasive, femoral head saving operative procedure. Between June 1997 and June 2000, 205 intracapsular femoral neck fractures of elderly patients (mean age 78.1 +/- 11.8 years) were fixed with cannulated screws. RESULTS: Seventy-seven percent were displaced fractures and 15.6% were impacted Garden I fractures. Reoperation after internal fixation occurred in 38 patients. The most frequent cause of reoperation was secondary arthroplasty due to redisplacement (14x), femoral head necrosis (10x) and non-union (7x). Implant removal (4x), wound hematoma (1x) and femoral head penetration by screws (2x) were other causes for reoperation. CONCLUSION: Less invasive cannulated screw fixation of intracapsular femoral neck fractures should be considered as a treatment option, because it is a smaller and less expensive operation than prosthetic replacement. Adequate reduction and screw placement, however, are a prerequisite for successful outcome.
UNLABELLED: We studied whether inhaled nitric oxide (NO) would improve arterial oxygen tension (PaO(2)) and reduce the occurrence of oxygen saturation of hemoglobin (O(2)Hb) < 90% during one-lung ventilation (OLV). One-hundred-fifty-two patients were ventilated either with or without NO (20 ppm) with an inspired fraction of oxygen (FIO(2)) of either 0.3, 0.5, or 1.0 during OLV. Anesthesia was induced and maintained with propofol, remifentanil, and rocuronium IV, and lung separation was achieved with a double-lumen tube. During OLV, we set positive end-expiratory pressure at 5 cm H(2)O, peak pressure at 30 cm H(2)O, and end-tidal CO(2) at 30 mm Hg. The nonventilated lung was opened to room air and collapsed. During OLV, three consecutive measurements were performed every 10 min. The operated lung was temporarily ventilated if pulse oximetric saturation (SpO(2)) decreased to < 91%. SpO(2) <9 1% occurred in 2 of the 152 patients. SpO(2) overestimated O(2)Hb by 2.9% +/- 0.1%. NO failed to improve oxygenation or alter occurrence of O(2)Hb < 90% during OLV across all time points and all levels of FIO(2). Increasing FIO(2) increased oxygenation and decreased occurrence of O(2)Hb < 90% (P: < 0.001). At FIO(2) = 1, PaO(2) was higher (P < 0.01) and O(2)Hb < 90% rate tended to be lower (P = 0.1) during right versus left lung ventilation. PaO(2) was higher in patients undergoing pneumonectomy and lobectomy than in those undergoing metastasectomy or video-assisted operations (P < 0.05). IMPLICATIONS: Inhaled nitric oxide failed to improve oxygenation during one-lung ventilation. Oxygenation during one-lung ventilation was improved with increasing levels of FIO(2) during ventilation of the right versus the left lung and with increasing pathology of the nonventilated lung.
UNLABELLED: During one-lung ventilation (OLV), hypoxic pulmonary vasoconstriction (HPV) reduces venous admixture and attenuates the decrease in arterial oxygen tension by diverting blood from the nonventilated lung to the ventilated lung. In vitro, desflurane and isoflurane depress HPV in a dose-dependent manner. Accordingly, we studied the effects of increasing concentrations of desflurane and isoflurane on pulmonary perfusion, shunt fraction, and PaO(2) during OLV in vivo. Fourteen pigs (30-42 kg) were anesthetized, tracheally intubated, and mechanically ventilated. After placement of femoral arterial and thermodilution pulmonary artery catheters, a left-sided double-lumen tube (DLT) was placed via tracheotomy. After DLT placement, FIO(2) was adjusted at 0.8 and anesthesia was continued in random order with 3 concentrations (0.5, 1.0, and 1.5 minimal alveolar concentrations) of either desflurane or isoflurane. Differential lung perfusion was measured with colored microspheres. All measurements were made after stabilization at each concentration. Whereas mixed venous PO(2), mean arterial pressure, cardiac output, nonventilated lung perfusion, and shunt fraction decreased in a dose-dependent manner, PaO(2) remained unchanged with increasing concentrations of desflurane and isoflurane during OLV. In conclusion, increasing concentration of desflurane and isoflurane did not impair oxygenation during OLV in pigs. IMPLICATIONS: In an animal model of one-lung ventilation, increasing concentrations of desflurane and isoflurane dose-dependently decreased shunt fraction and perfusion of the nonventilated lung and did not impair oxygenation. The decreases in shunt fraction are likely the result of anesthetic-induced marked decreases in cardiac output and mixed venous saturation.
An information theoretic measure is derived that quantifies the statistical coherence between systems evolving in time. The standard time delayed mutual information fails to distinguish information that is actually exchanged from shared information due to common history and input signals. In our new approach, these influences are excluded by appropriate conditioning of transition probabilities. The resulting transfer entropy is able to distinguish effectively driving and responding elements and to detect asymmetry in the interaction of subsystems.
We discuss how nonstationarity in observed time series data due to pronounced fluctuations of system parameters can be resolved by making use of embedding techniques for scalar data. If a D-dimensional deterministic system is driven by P slowly time dependent parameters, a (D+P)-dimensional manifold has to be reconstructed from the scalar time series, which is done by an m>2(D+P)-dimensional time delay embedding. We show that in this space essential aspects of determinism are restored. We demonstrate the validity of the idea heuristically, for numerical examples and for human speech data.