Measured optical losses of Sc doped AlN waveguides

Although Sc doped AlN (ScAlN) has been used extensively in micro-electro-mechanical systems (MEMS) devices and more recently in optical devices, there have not been thorough studies of its intrinsic optical losses. Here we explore the optical losses of the Sc0.30Al0.70N waveguide system by observing racetrack resonator waveguide quality factors. Using a partial physical etch, we fabricate waveguides and extract propagation losses as low as 1.6 ± 0.3 dB/cm at wavelengths around 1550 nm, mostly dominated by intrinsic material absorption from the Sc0.30Al0.70N thin film layer. The highest quality factor of the resonators was greater than 87,000. The propagation loss value is lower than any value previously published and shows that this material can be broadly used in optical modulators without significant loss.

High index of suspicion: diagnosing a carotid-cavernous fistula

A woman in her 70s presented with acute bilateral retro-orbital headache, diplopia, chemosis and eye swelling. Ophthalmology and neurology were consulted after detailed physical examination and diagnostic workup including laboratory analysis, imaging and lumbar puncture. The patient was diagnosed with non-specific orbital inflammation and was started on methylprednisolone and dorzolamide-timolol for intraocular hypertension. The patient's condition improved slightly, but a week later, she developed subconjunctival haemorrhage in the right eye, which prompted investigation for a low-flow carotid-cavernous fistula. Digital subtraction angiography showed bilateral indirect carotid-cavernous fistula (Barrow type D). The patient underwent bilateral carotid-cavernous fistula embolisation. Her swelling improved considerably on day 1 after the procedure and her diplopia improved over the following weeks.

The German Quality Network Sepsis: Evaluation of a Quality Collaborative on Decreasing Sepsis-Related Mortality in a Controlled Interrupted Time Series Analysis

Background

Sepsis is one of the leading causes of preventable deaths in hospitals. This study presents the evaluation of a quality collaborative, which aimed to decrease sepsis-related hospital mortality.

Methods

The German Quality Network Sepsis (GQNS) offers quality reporting based on claims data, peer reviews, and support for establishing continuous quality management and staff education. This study evaluates the effects of participating in the GQNS during the intervention period (April 2016–June 2018) in comparison to a retrospective baseline (January 2014–March 2016). The primary outcome was all-cause risk-adjusted hospital mortality among cases with sepsis. Sepsis was identified by International Classification of Diseases (ICD) codes in claims data. A controlled time series analysis was conducted to analyze changes from the baseline to the intervention period comparing GQNS hospitals with the population of all German hospitals assessed via the national diagnosis-related groups (DRGs)-statistics. Tests were conducted using piecewise hierarchical models. Implementation processes and barriers were assessed by surveys of local leaders of quality improvement teams.

Results

Seventy-four hospitals participated, of which 17 were university hospitals and 18 were tertiary care facilities. Observed mortality was 43.5% during baseline period and 42.7% during intervention period. Interrupted time-series analyses did not show effects on course or level of risk-adjusted mortality of cases with sepsis compared to the national DRG-statistics after the beginning of the intervention period (p = 0.632 and p = 0.512, respectively). There was no significant mortality decrease in the subgroups of patients with septic shock or ventilation >24 h or predefined subgroups of hospitals. A standardized survey among 49 local quality improvement leaders in autumn of 2018 revealed that most hospitals did not succeed in implementing a continuous quality management program or relevant measures to improve early recognition and treatment of sepsis. Barriers perceived most commonly were lack of time (77.6%), staff shortage (59.2%), and lack of participation of relevant departments (38.8%).

Conclusion

As long as hospital-wide sepsis quality improvement efforts will not become a high priority for the hospital leadership by assuring adequate resources and involvement of all pertinent stakeholders, voluntary initiatives to improve the quality of sepsis care will remain prone to failure.

Ultrashort pulse written fiber Bragg gratings as narrowband filters in multicore fibers

We present the inscription of narrow-linewidth fiber Bragg gratings (FBGs) into different types of multicore fibers (MCFs) using ultrashort laser pulses and the phase mask technique, which can act as notch filters. Such filters are required, e.g., to suppress light emitted by hydroxyl in the Earth's upper atmosphere, which disturbs ground-based observation of extraterrestrial objects in the near infrared. However, the inscription into a commercially available seven-core fiber showed a quite large core-to-core deviation of the resonance wavelength of up to 0.45 nm. Two options are presented to overcome this: first, we present the photo-treatment of the FBGs to tune the resonance wavelength, which allows for sufficient resonance shifts. Second, adapted MCFs containing 12 cores, arranged on a circle, are fabricated. For this, two different fabrication procedures were investigated, namely, the mechanical drilling of the preform for a rod-in-tube version as well as a stack-and-draw approach. Both adapted MCFs yielded significant improvements with core-to-core wavelength variations of the FBGs of only about 0.18 nm and 0.11 nm, respectively, sufficient to fulfill the requirements for astronomical filter applications as discussed above.

Results from a real-time dosimetry study during left atrial ablations performed with ultra-low dose radiation settings

Background

Three-dimensional mapping systems and the use of ultra-low dose radiation protocols have supported minimization of radiation dose during left atrial ablation procedures. By using optimal shielding, scattered radiation reaching the operator can be further reduced. This prospective study was designed to determine the remaining operator radiation exposure during left atrial catheter ablations using real-time dosimetry.

Methods

Radiation dose was recorded using real-time digital dosimetry badges outside the lead apron during 201 consecutive left atrial fibrillation ablation procedures. All procedures were performed using the same X‑ray system (Siemens Healthineers Artis dBc; Siemens Healthcare AG, Erlangen, Germany) programmed with ultra-low dose radiation settings including a low frame rate (two frames per second), maximum copper filtration, and an optimized detector dose. To reduce scattered radiation to the operators, table-suspended lead curtains, ceiling-suspended leaded plastic shields, and radiation-absorbing shields on the patient were positioned in an overlapping configuration.

Results

The 201 procedures included 139 (69%) pulmonary vein isolations (PVI) (20 cryoballoon ablations, 119 radiofrequency ablations, with 35 cases receiving additional ablation of the cavotricuspid isthmus) and 62 (31%) PVI plus further left atrial substrate ablation.

Mean radiation dose measured as dose area product for all procedures was 128.09 ± 187.87 cGy ∙ cm² with a mean fluoroscopy duration of 9.4 ± 8.7 min. Real-time dosimetry showed very low average operator doses of 0.52 ± 0.10 µSv. A subanalysis of 51 (25%) procedures showed that the radiation burden for the operator was highest during pulmonary vein angiography.

Conclusion

The use of ultra-low dose radiation protocols in combination with optimized shielding results in extremely low scattered radiation reaching the operator.

[Young Respiratory Physicians in Germany - Current Situation and Future Perspectives]

BACKGROUND

 Demographic changes in the society and among doctors, as well as changing attitudes towards and norms of how living should be structured are creating challenges regarding the organization of work environment in the hospital. In addition, organization of medical training is increasingly being influenced by economic considerations as well as a high level of medical specialization. We asked young respiratory physicians how they assessed their current situation with respect to quality of medical training and organization of their work environment.

METHODS

 From September to November 2019, we performed an online survey adressing young respiratory physicians in Germany. Participants were recruited via three emails (baseline and reminders after 2 and 6 weeks) sent by the German Respiratory Society (DGP) and the German Union of Pulmonologists (BdP). The questionnaire consisted of a maximum of 62 questions. Apart from own questions that had been aligned with other questionnaires from similar surveys in other medical specialties, we also assessed the effort-reward ratio (ER ratio) based on the short version of the effort-reward imbalance questionnaire (16 questions).

RESULTS

 We recuited n = 224 participants (33.8 ± 4.5 years, 5.4 ± 2.9 years of medical training, 54.4 % female , 86.8 % with German nationality). A little under half of the interviewees (n = 103, 46 %) reported to be very or generally satisfied with their working conditions, while n = 60 (27 %) were unsure. The main reasons for not being satisfied were long working hours and high work-load, as well as a lack of streamlining the work environment in the hospital to the specific needs of doctors. Despite the fact that many participants were satisfied, a large majority (n = 166, 88.2 %) depicted an unfavorable effort-reward ratio imbalance (adjusted mean 1.89 ± 2.18).

CONCLUSION

 Compared to many other European countries and internationally, the German healthcare system offers high-quality patient care and a well-equipped work environment. Increasing demands in the health care sector, however, are leading to a gratification crisis that not only harms the health and work performance of doctors but is also leading to reduced attractiveness of the job that might possibly lead to the search for new fields of activity or migration. Respiratory medicine is a discipline of growing interest and motivating young doctors to secure the promotion of this discipline is increasingly important. Factors harming the growth of this discipline should be immediately addressed. The results of this survey might help leaders in the field to restructure the work environment and medical education according to the actual needs.

Mid-German Sepsis Cohort (MSC): a prospective observational study of sepsis survivorship

PURPOSE

The Mid-German Sepsis Cohort (MSC) aims to investigate mid-term and long-term functional disabilities in sepsis survivors from intensive care unit (ICU) discharge until 1 year after. Secondary, post-acute mortality and morbidity, health-related quality of life and healthcare utilisation will be investigated.

PARTICIPANTS

The MSC comprises adult (aged ≥18 years) patients who were treated for (severe) sepsis or septic shock on ICU. The participants were recruited between 15 April 2016 and 30 November 2018 from five German centres. Three thousand two hundred and ten patients with sepsis were identified, of which 1968 survived their ICU stay and were eligible for enrolment in the follow-up cohort. Informed consent for follow-up assessment was provided by 907 patients (46.1% of eligible patients).

FINDINGS TO DATE

The recruitment of the participants for follow-up assessments and the baseline data collection is completed. Incidence of sepsis was 116.7 patients per 1000 ICU patients. In this cohort profile, we provide an overview of the demographics and the clinical characteristics of both the overall sepsis cohort and the ICU survivors who provided informed consent for follow-up assessment (907 out of 1968 ICU survivors (46.1%)).

FUTURE PLANS

The follow-ups are conducted 3, 6 and 12 months after ICU discharge. Another yearly follow-up up to 5 years after ICU discharge is pursued. Several cooperation and satellite projects were initiated. This prospective cohort offers a unique resource for research on long-term sequelae of sepsis survivors.

TRIAL REGISTRATION NUMBER

German Clinical Trials Registry (DRKS00010050).

Influence of pedestal diameter on mode instabilities in Yb/Ce/Al-doped fibers

In this paper we present numerical and experimental results revealing that the mode instability threshold of highly Yb-doped, Ce/Al co-doped pedestal fibers is affected by the size of the index-increased pedestal structure surrounding the core. An alternative preparation technology for the realization of large mode area fibers with very large Al-doped silica pedestals is introduced. Three different pedestal fiber design iterations characterized by low photodarkening were manufactured and tested in counter-pumped amplifier setups. Up to 1.9 kW continuous-wave output power of near-diffraction-limited beam quality (M² = 1.26) was achieved with an 18/200/420 µm fiber of very low NA = 0.042, limited only by the occurrence of mode instabilities.

Functional impairment assessed by the Barthel Index influenced outcomes after transcatheter aortic valve implantation

Objective. We investigated the influence of functional impairment assessed by the Barthel index (BI) on the three-month outcomes after transfemoral-transcatheter aortic valve intervention (TF-TAVI) under general anesthesia. Design. We included retrospectively analyzed 336 patients undergoing TAVI between January 2017 and January 2018 in central hospital, Bad Berka, Germany. All patients were followed up at three-month in our center's outpatient clinic. We stratified the patients according to the BI. Results. At baseline, 76 patients had a BI <80. Patients with a BI <80 were characterized by advanced age (80.6 ± 5.6 vs. 83 ± 4.1 years. p = .027), diabetes mellitus on insulin and higher surgical risk scores. A prior cerebral ischemic event was recorded more in patients with a BI ≥80. Regarding intermediate outcomes, three-month mortality was significantly higher in patients with a BI <80. Patients with a BI <80 developed significantly more postoperative cardiac decompensation, delirium and strokes. Patients with BI <80 had lower hemoglobin level preoperative and needed more blood transfusion postoperative. Other valve academic research consortiums (VARCs) complications were equally distributed in both groups. A BI <80 was associated with prolonged postoperative hospital stay and was an independent predictor of FT protocol failure (OR 4; CI 95% 1.3-11. p .02). Conclusions. A BI <80 is associated with increased mortality and risk of neurological events and cardiac decompensations after TF TAVI. A BI <80 is an independent predictor of failure in fast track TAVI.

Caloric consumption during early mobilisation of mechanically ventilated patients in Intensive Care Units

OBJECTIVE

To evaluate a) the magnitude of the increase in caloric consumption due to early mobilisation of patients with mechanical ventilation (MV) in Intensive Care Units (ICU) as part of routine care, b) whether there are differences in caloric consumption due to active or passive mobilisation, and c) whether early mobilisation in routine care would lead to additional nutritional requirements.

DESIGN

Prospective, observational, multi-centre study.

SETTING

Medical, surgical and neurological ICUs from three centres.

PATIENTS

Patients on MV in ICU who were mobilised out of bed as part of routine care.

MEASUREMENTS AND MAIN RESULTS

Caloric consumption was assessed in 66 patients by indirect calorimetry at six time points: (1) lying in bed 5-10 min prior to mobilisation, (2) sitting on the edge of the bed, (3) standing beside the bed, (4) sitting in a chair, (5) lying in bed 5-10 min after mobilisation, and (6) 2 h after mobilisation. Differences in caloric consumption in every mobilisation level vs. the baseline of lying in bed were measured for 5 min and found to have increased significantly by: +0.4 (Standard Deviation (SD) 0.59) kcal while sitting on the edge of the bed, +1.5 (SD 1.26) kcal while standing in front of the bed, +0.7 (SD 0.63) kcal while sitting in a chair (all p < 0.001). Active vs. passive transfers showed a higher, but non-significant consumption. A typical sequence of mobilisation including sitting on edge of the bed, standing beside the bed, sitting in a chair (20 min) and transfer back into bed, would require an additional 4.56 kcal compared to caloric consumption without mobilisation.

CONCLUSIONS

Based on this data, routine mobilisation of MV patients in ICU increases caloric consumption, especially in active mobilisation. Nevertheless, an additional caloric intake because of routine mobilisation does not seem to be necessary.

Micro-fluorescence lifetime and spectral imaging of ytterbium doped laser materials

We present the application of a confocal fluorescence microscope to the analysis of Yb-doped solid-state laser materials, with examples of Yb-doped crystals, photonic crystal fibers and fiber preforms made with different manufacturing processes. Beside the fluorescence lifetime image itself, a microscopic spectral fluorescence emission analysis is presented and spatially resolved emission cross sections are obtained. Doping concentration and its distributions and other laser optical parameters are measured, which help to analyze manufacturing steps. Further properties like photodarkening and saturation are addressed.

Characterization of the seven-day course of pulmonary response following unilateral lung acid injury in rats

BACKGROUND

Aspiration of gastric acid is an important cause of acute lung injury. The time course of the pulmonary response to such an insult beyond the initial 48 hours is incompletely characterized. The purpose of this study was to comprehensively describe the pulmonary effects of focal lung acid injury over a seven day period in both directly injured and not directly injured lung tissue.

METHODS

Male Wistar rats underwent left-endobronchial instillation with hydrochloric acid and were sacrificed at 4, 24, 48, 96 or 168 h after the insult. Healthy non-injured animals served as controls. We assessed inflammatory cell counts and cytokine levels in right and left lung lavage fluid and blood, arterial oxygen tension, alterations in lung histology, lung wet-to-dry weight ratio and differential lung perfusion.

RESULTS

Lung acid instillation induced an early strong inflammatory response in the directly affected lung, peaking at 4-24 hours, with only partial resolution after 7 days. A less severe response with complete resolution after 4 days was seen in the opposite lung. Alveolar cytokine levels, with exception of IL-6, only partially reflected the localization of lung injury and the time course of the functional and histologic alterations. Alveolar leucocyte subpopulations exhibited different time courses in the acid injured lung with persistent elevation of alveolar lymphocytes and macrophages. After acid instillation there was an early transient decrease in arterial oxygen tension and lung perfusion was preferentially distributed to the non-injured lung.

CONCLUSION

These findings provide a basis for further research in the field of lung acid injury and for studies exploring effects of mechanical ventilation on injured lungs. Incomplete recovery in the directly injured lung 7 days after acid instillation suggests that increased vulnerability and susceptibility to further noxious stimuli are still present at that time.

Coherently combined 16-channel multicore fiber laser system

We present a coherently combined laser amplifier with 16 channels from a multicore fiber in a proof-of-principle demonstration. Filled-aperture beam splitting and combination, together with temporal phasing, is realized in a compact and low-component-count setup. Combined average power of up to 70 W with 40 ps pulses is achieved with combination efficiencies around 80%.

Single mode 4.3 kW output power from a diode-pumped Yb-doped fiber amplifier

We investigate the average power scaling of two diode-pumped Yb-doped fiber amplifiers emitting a diffraction-limited beam. The first fiber under investigation with a core diameter of 30 µm was able to amplify a 10 W narrow linewidth seed laser up to 2.8 kW average output power before the onset of transverse mode instabilities (TMI). A further power scaling was achieved using a second fiber with a smaller core size (23µm), which allowed for a narrow linewidth output power of 3.5 kW limited by stimulated Brillouin scattering (SBS). We mitigated SBS using a spectral broadening mechanism, which allowed us to further increase the output power to 4.3 kW only limited by the available pump power. Up to this power level, a high slope efficiency of 90% with diffraction-limited beam quality and without any sign of TMI or stimulated Raman scattering for a spectral dynamic range of higher than -80 dB was obtained.

Effect of a multifaceted educational intervention for anti-infectious measures on sepsis mortality: a cluster randomized trial

PURPOSE

Guidelines recommend administering antibiotics within 1 h of sepsis recognition but this recommendation remains untested by randomized trials. This trial was set up to investigate whether survival is improved by reducing the time before initiation of antimicrobial therapy by means of a multifaceted intervention in compliance with guideline recommendations.

METHODS

The MEDUSA study, a prospective multicenter cluster-randomized trial, was conducted from July 2011 to July 2013 in 40 German hospitals. Hospitals were randomly allocated to receive conventional continuous medical education (CME) measures (control group) or multifaceted interventions including local quality improvement teams, educational outreach, audit, feedback, and reminders. We included 4183 patients with severe sepsis or septic shock in an intention-to-treat analysis comparing the multifaceted intervention (n = 2596) with conventional CME (n = 1587). The primary outcome was 28-day mortality.

RESULTS

The 28-day mortality was 35.1% (883 of 2596 patients) in the intervention group and 26.7% (403 of 1587 patients; p = 0.01) in the control group. The intervention was not a risk factor for mortality, since this difference was present from the beginning of the study and remained unaffected by the intervention. Median time to antimicrobial therapy was 1.5 h (interquartile range 0.1-4.9 h) in the intervention group and 2.0 h (0.4-5.9 h; p = 0.41) in the control group. The risk of death increased by 2% per hour delay of antimicrobial therapy and 1% per hour delay of source control, independent of group assignment.

CONCLUSIONS

Delay in antimicrobial therapy and source control was associated with increased mortality but the multifaceted approach was unable to change time to antimicrobial therapy in this setting and did not affect survival.

Modal content measurements (S2) of negative curvature hollow-core photonic crystal fibers

We present modal content measurements (S²) of two different negative curvature hollow-core photonic crystal fibers: a kagome fiber and an ice cream cone fiber. Their sensitivity towards mode matching, bending and polarization is analyzed. For the kagome fiber, a higher order mode suppression of 17dB under optimal conditions was achieved, and for the ice cream cone fiber there was a suppression of up to 42dB. Polarization turned out to be a critical parameter for good higher order mode suppression in both fibers.

Libraries of Synthetic TALE-Activated Promoters: Methods and Applications

The discovery of proteins with programmable DNA-binding specificities triggered a whole array of applications in synthetic biology, including genome editing, regulation of transcription, and epigenetic modifications. Among those, transcription activator-like effectors (TALEs) due to their natural function as transcription regulators, are especially well-suited for the development of orthogonal systems for the control of gene expression. We describe here the construction and testing of libraries of synthetic TALE-activated promoters which are under the control of a single TALE with a given DNA-binding specificity. These libraries consist of a fixed DNA-binding element for the TALE, a TATA box, and variable sequences of 19 bases upstream and 43 bases downstream of the DNA-binding element. These libraries were cloned using a Golden Gate cloning strategy making them usable as standard parts in a modular cloning system. The broad range of promoter activities detected and the versatility of these promoter libraries make them valuable tools for applications in the fine-tuning of expression in metabolic engineering projects or in the design and implementation of regulatory circuits.

Narrow linewidth, single mode 3 kW average power from a directly diode pumped ytterbium-doped low NA fiber amplifier

We report on a newly designed and fabricated ytterbium-doped large mode area fiber with an extremely low NA (~0.04) and related systematic investigations on fiber parameters that crucially influence the mode instability threshold. The fiber is used to demonstrate a narrow linewidth, continuous wave, single mode fiber laser amplifier emitting a maximum output power of 3 kW at a wavelength of 1070 nm without reaching the mode-instability threshold. A high slope efficiency of 90 %, excellent beam quality, high temporal stability, and an ASE suppression of 70 dB could be reached with a signal linewidth of only 170 pm.

1009 nm continuous-wave ytterbium-doped fiber amplifier emitting 146 W

In this Letter, we demonstrate a single-mode continuous-wave fiber laser amplifier emitting 146 W of average output power at a wavelength of 1009 nm. The wavelength and bandwidth of the seed oscillator are defined by a pair of fiber Bragg gratings. The seed is amplified in a two-stage ytterbium-doped rod-type amplifier to 146 W with a high slope efficiency of 64%, showing excellent beam quality and stability throughout the experiment. The ASE suppression is as high as 63 dB.

Pilot study for compact microbeam radiation therapy using a carbon nanotube field emission micro-CT scanner

PURPOSE

Microbeam radiation therapy (MRT) is defined as the use of parallel, microplanar x-ray beams with an energy spectrum between 50 and 300 keV for cancer treatment and brain radiosurgery. Up until now, the possibilities of MRT have mainly been studied using synchrotron sources due to their high flux (100s Gy/s) and approximately parallel x-ray paths. The authors have proposed a compact x-ray based MRT system capable of delivering MRT dose distributions at a high dose rate. This system would employ carbon nanotube (CNT) field emission technology to create an x-ray source array that surrounds the target of irradiation. Using such a geometry, multiple collimators would shape the irradiation from this array into multiple microbeams that would then overlap or interlace in the target region. This pilot study demonstrates the feasibility of attaining a high dose rate and parallel microbeam beams using such a system.

METHODS

The microbeam dose distribution was generated by our CNT micro-CT scanner (100 μm focal spot) and a custom-made microbeam collimator. An alignment assembly was fabricated and attached to the scanner in order to collimate and superimpose beams coming from different gantry positions. The MRT dose distribution was measured using two orthogonal radiochromic films embedded inside a cylindrical phantom. This target was irradiated with microbeams incident from 44 different gantry angles to simulate an array of x-ray sources as in the proposed compact CNT-based MRT system. Finally, phantom translation in a direction perpendicular to the microplanar beams was used to simulate the use of multiple parallel microbeams.

RESULTS

Microbeams delivered from 44 gantry angles were superimposed to form a single microbeam dose distribution in the phantom with a FWHM of 300 μm (calculated value was 290 μm). Also, during the multiple beam simulation, a peak to valley dose ratio of ~10 was found when the phantom translation distance was roughly 4x the beam width. The first prototype CNT-based x-ray tube dedicated to the development of compact MRT technology development was proposed and planned based on the preliminary experimental results presented here and the previous corresponding Monte Carlo simulations.

CONCLUSIONS

The authors have demonstrated the feasibility of creating microbeam dose distributions at a high dose rate using a proposed compact MRT system. The flexibility of CNT field emission x-ray sources could possibly bring compact and low cost MRT devices to the larger research community and assist in the translational research of this promising new approach to radiation therapy.

Susceptibility to ventilator induced lung injury is increased in senescent rats

Introduction

The principal mechanisms of ventilator induced lung injury (VILI) have been investigated in numerous animal studies. However, prospective data on the effect of old age on VILI are limited. Under the hypothesis that susceptibility to VILI is increased in old age, we investigated the pulmonary and extrapulmonary effects of mechanical ventilation with high tidal volume (VT) in old compared to young adult animals.

Interventions

Old (19.1 ± 3.0 months) and young adult (4.4 ± 1.3 months) male Wistar rats were anesthetized and mechanically ventilated (positive end-expiratory pressure 5 cmH2O, fraction of inspired oxygen 0.4, respiratory rate 40/minute) with a tidal volume (VT) of either 8, 16 or 24 ml/kg for four hours.

Respiratory and hemodynamic variables, including cardiac output, and markers of systemic inflammation were recorded throughout the ventilation period. Lung histology and wet-to-dry weight ratio, injury markers in lung lavage and respiratory system pressure-volume curves were assessed post mortem. Basic pulmonary characteristics were assessed in non-ventilated animals.

Results

Compared to young adult animals, high VT (24 ml/kg body weight) caused more lung injury in old animals as indicated by decreased oxygenation (arterial oxygen tension (PaO2): 208 ± 3 vs. 131 ± 20 mmHg; P <0.05), increased lung wet-to-dry-weight ratio (5.61 ± 0.29 vs. 7.52 ± 0.27; P <0.05), lung lavage protein (206 ± 52 mg/l vs. 1,432 ± 101; P <0.05) and cytokine (IL-6: 856 ± 448 vs. 3,283 ± 943 pg/ml; P <0.05) concentration. In addition, old animals ventilated with high VT had more systemic inflammation than young animals (IL-1β: 149 ± 44 vs. 272 ± 36 pg/ml; P <0.05 - young vs. old, respectively).

Conclusions

Ventilation with unphysiologically large tidal volumes is associated with more lung injury in old compared to young rats. Aggravated pulmonary and systemic inflammation is a key finding in old animals developing VILI.

On the mode-locking mechanism of a dissipative- soliton fiber oscillator

We report on the generation of high-energy pulses in an all normal dispersion photonic-crystal fiber laser. Two mode-locking techniques with and without passive spectral filtering are studied both numerically and experimentally to address a roadmap for energy scaling. It is found that high-contrast passive modulation is a very promising mode-locking technique for energy scaling in dissipative-soliton laser. Moreover, this technique does not need any additional spectral filtering than the limited gain bandwidth to stabilize high-energy ultrashort pulses. The presented laser generates 110 nJ chirped pulses at 57 MHz repetition rate for an average power of 6.2 W. The output pulses could be dechirped close to the transform-limited duration of 100 fs.

High power narrow-band fiber-based ASE source

In this paper we describe a high power narrow-band amplified spontaneous emission (ASE) light source at 1030 nm center wavelength generated in an Yb-doped fiber-based experimental setup. By cutting a small region out of a broadband ASE spectrum using two fiber Bragg gratings a strongly constrained bandwidth of 12±2 pm (3.5±0.6 GHz) is formed. A two-stage high power fiber amplifier system is used to boost the output power up to 697 W with a measured beam quality of M2≤1.34. In an additional experiment we demonstrate a stimulated Brillouin scattering (SBS) suppression of at least 17 dB (theoretically predicted ~20 dB), which is only limited by the dynamic range of the measurement and not by the onset of SBS when using the described light source. The presented narrow-band ASE source could be of great interest for brightness scaling applications by beam combination, where SBS is known as a limiting factor.

Spectral beam combination of fiber amplified ns-pulses by means of interference filters

In this paper we introduce a simple scheme to spectrally combine four single beams using three low-cost dielectric interference filters as combining elements. 25 ns pulses from four independent and actively Q-switched fiber seed-sources are amplified in a single stage fiber-amplifier. Temporally and spatially combined 208 W of average power and 6.3 mJ of pulse energy are obtained at two different repetition frequencies. A detailed analysis of beam quality as well as the thermal behavior of the combining elements is carried out and reveals mutual dependency.

Oxygenation during one-lung ventilation with propofol or sevoflurane

60 patients, ASA I-III, underwent one-lung ventilation for open or video-assisted thoracic surgery randomized either with intravenous anesthesia with propofol or with inhalational anesthesia with 1 MAC sevoflurane. Propofol was titrated during one-lung ventilation to achieve a mean arterial pressure of 75-80 mmHg. Blood gas analyses, hemodynamic and respiratory parameters were measured during two-lung ventilation at the beginning of the surgical procedure and 10 min, 20 min and 30 min after start of one-lung ventilation. At all time points, hemodynamic and respiratory parameters were comparable in both groups. Oxygenation did not differ between groups at comparable mean arterial blood pressures.

Average power of 1.1 kW from spectrally combined, fiber-amplified, nanosecond-pulsed sources

We report on spectral combination of four high repetition rate 5 ns pulsed Yb-doped fiber amplifiers at 1 microm wavelength. The output beam is spatially and temporally superposed by use of an all-reflective diffraction grating. 1.1 kW average power and 220 microJ pulse energy were extracted with a combining efficiency of 99%.

2 kW incoherent beam combining of four narrow-linewidth photonic crystal fiber amplifiers

We report on beam combining of four narrow-linewidth fiber amplifier chains, running at different wavelengths and each delivering 500 W optical output power. The main amplifier stage consists of a large mode area photonic crystal fiber. The four output beams of the amplifier chains are spectrally (incoherent) combined using a polarization-independent dielectric reflective diffraction grating to form an output beam of 2 kW continuous-wave optical power with good beam quality (M(2)x = 2.0, M(2)y = 1.8).

Effects of Arginine Vasopressin on Oxygenation and Haemodynamics during One-Lung Ventilation in an Animal Model

In a case of arterial hypotension during one-lung ventilation, haemodynamic support may be required to maintain adequate mean arterial pressure. Arginine vasopressin, a potent systemic vasoconstrictor with limited effects on the pulmonary artery pressure, has not been studied in this setting. Twelve female pigs were anaesthetised and ventilated and arterial, central venous and pulmonary artery catheters were inserted. A left-sided double lumen tube was placed via tracheostomy and one-lung ventilation was initiated. The animals were in the left lateral position, with the left lung ventilated and right lung collapsed. Respiratory and haemodynamic values were recorded before and during a continuous infusion of arginine vasopressin sufficient to double the mean arterial pressure. The arginine vasopressin caused a decrease in cardiac output (3.8±1.1 vs. 2.7±0.7 l/min, P <0.001) and mixed-venous oxygen tension (39.1±5.8 vs. 34.4±5 mmHg, P=0.003). Pulmonary artery pressure was unchanged (24±2 vs. 24±3 mmHg, P=0.682). There was no effect of the arginine vasopressin on arterial oxygen tension (226±106 vs. 231±118 mmHg, P=0.745). However, there was a significant decrease in shunt fraction (28.3±6.2 vs. 24.3±7.8%, P=0.043) and a significant proportional increase in perfusion of the ventilated lung (78.8±9.5 vs. 85.5±7.9%, P=0.036). In our animal model of one-lung ventilation, doubling mean arterial pressure by infusion of arginine vasopressin significantly affected global haemodynamics, but had no influence on systemic arterial oxygen tension.

Passively mode-locked single-polarization microstructure fiber laser

The generation of high-power and stable ultra-short pulses from a passively mode-locked purely normal dispersion fiber laser is reported using the unique combination of a photonic crystal fiber featuring single-polarization, single-mode, and low nonlinearity with a high modulation depth semiconductor saturable absorber mirror. The environmentally-stable, self-starting fiber laser generates 1.6 W of average power at a repetition rate of 63 MHz, corresponding to a pulse energy of 25 nJ. The emitted pulses are positively chirped with a pulse duration of 3.7 ps. They are compressible down to a near transform-limited duration of 750 fs. Numerical simulations are in good agreement with the experimental results.

Low-dose intravenous midazolam reduces etomidate-induced myoclonus: a prospective, randomized study in patients undergoing elective cardioversion

BACKGROUND

Myoclonic movements are a common problem in unpremedicated patients during induction of anesthesia with etomidate.

METHODS

In a double-blind fashion, 40 patients (ASA physical status III-IV) scheduled for elective cardioversion were randomly assigned to receive either 0.015 mg/kg midazolam or placebo 90 s before the injection of 0.3 mg/kg etomidate. Myoclonic movements and sedation were recorded on a scale between 0 and 3. Pulse oximetry, noninvasive arterial blood pressure, and heart rate were recorded during the study period.

RESULTS

Two patients (10%) in the midazolam group had myoclonic movements after the administration of etomidate, whereas 10 of the 20 patients (50%) receiving placebo experienced such movements (P = 0.006). No other differences were found between the groups; in particular, there was no difference in recovery 5 min after the administration of etomidate.

CONCLUSIONS

IV midazolam 0.015 mg/kg administered 90 s before induction of anesthesia with etomidate is effective in reducing myoclonic movements and does not prolong recovery in unpremedicated patients after short procedures.

Experimental and numerical study of pulse dynamics in positive net-cavity dispersion modelocked Yb-doped fiber lasers

We report on environmentally stable mode-locked Yb-doped all-fiber lasers operating in the wave-breaking-free and stretched-pulse regime. The compact linear cavity is constructed with saturable absorber mirror directly glued to the fibers end-facet as nonlinear mode-locking mechanism and chirped fiber Bragg grating for dispersion management, thus, without any free-space optics. In the wave-breaking-free regime the laser generates positively-chirped pulses with a pulse duration of 15.4 ps. These pulses are compressed to 218 fs in a hollow-core photonic bandgap fiber spliced to the output port. Adaptation of dispersion management has led to operation in the stretched-pulse regime, where a parabolic spectral profile is obtained as well. In this regime pulses are compressible to 213 fs. Numerical simulations are presented which confirm the wave-breaking-free and stretched-pulse evolution inside the fiber laser cavity. Both regimes are compared in terms of pulse quality.

Percutaneous transtracheal emergency ventilation with a self-made device in an animal model

BACKGROUND

Special equipment for emergency percutaneous transtracheal ventilation is often not immediately available. We used a self-made device consisting of a three-way stopcock connected between a G-15 transtracheal airway catheter and an oxygen supply in a simulated 'cannot intubate, cannot ventilate' scenario and tested the hypothesis that the effectiveness of the device depends on the body weight of the experimental animals.

METHODS

With approval of the local animal protection committee, two groups of six pigs each with a body weight of 21 +/- 2 and 36 +/- 6 kg, respectively, were tracheally intubated and mechanically ventilated after induction of anesthesia. Hemodynamic monitoring included cardiac output and arterial, central venous and pulmonary artery pressures. An emergency transtracheal airway catheter was inserted into the trachea and a situation of partial expiratory airway obstruction was created. Each animal was ventilated for 15 min via the transtracheal airway catheter with the self-made device (FiO(2) 1.0 at an oxygen flow of 15 l x min(-1); respiratory rate of 60 min(-1); I/E ratio approximately 1:1).

RESULTS

Whereas satisfactory oxygenation was achieved in all animals, sufficient ventilation was obtained only in the lightweight animals.

CONCLUSIONS

Adequate oxygenation could be provided by jet-like transtracheal ventilation with a simple self-made device using easily available materials. Sufficient ventilation depends on the body weight of the animals.