Isaac Luria

Microtubule nanospool formation by active self-assembly is not initiated by thermal activation

Biotinylated microtubules partially coated with streptavidin and gliding on a surface coated with kinesin motors can cross-link with each other and assemble into nanospools with a diameter of a few micrometres. The size distribution of these nanospools is determined, and it is shown with simulations of microtubule gliding that these spools are too small to be formed by thermally activated turns in the gliding direction (a Brownian ratchet mechanism). Instead, spool formation is primarily the result of two processes: pinning of gliding microtubules to inactive motors and simultaneous cross-linking of multiple microtubules.

Mixed simulators: Augmented physical simulators with virtual underlays

We introduce a taxonomy for mixed simulation focusing on mixed simulators with physical exteriors augmented with virtual underlays for practicing medical procedures such as central venous access (CVA). We used CT and MRI imaging and 3D printing to develop anatomically authentic mixed simulators, i.e., exact physical and/or virtual replicas of their human models. Embedded 6 DOF magnetic sensors monitor tracked instruments during simulated procedures, facilitating after action review or self-debriefing. We implemented automated scoring algorithms that include tracking and grading of near misses. After 28 anesthesia residents trained with the CVA simulator, incidence of pneumothorax and arterial puncture in the simulated environment dropped from 11 % to 7% and 13% to 7%, respectively.

Robot-assisted airway support: a simulated case.

Recent advances in telemedicine and robotically assisted telesurgery may offer advanced surgical care for the geographically remote patient. Similar advances in tele-anesthesia will be necessary to optimize perioperative care for these patients. Although many preliminary investigations into tele-anesthesia are underway, none involves remote performance of anesthesia-related procedures. Here we describe simulated robotically assisted fiberoptic intubations using an airway simulation mannequin. Both oral and nasal approaches to fiberoptic intubation were successful, but presented unique opportunities and challenges inherent to the robots design. Robotically assisted airway management is feasible using multipurpose surgical robotic systems.

Prevention of airway fires: do not overlook the expired oxygen concentration.

BACKGROUND: It is generally accepted that when an ignition source is used the inspired oxygen concentration (FIO2) should be <30% in the breathing circuit to help prevent airway fires. The time and conditions required to reduce a high O2% in the breathing circuit to <30% has not yet been systematically studied. METHODS: We evaluated the inspired and expired circuit oxygen concentration response times of an Aestiva Avance S/5 anesthesia machine to reach an FIO2 of <30% from a starting FIO2 of 100% and 60% after reducing the FIO2 to 21%. The circuit was connected to a human patient simulator which has a functional residual capacity of 2 L, total lung capacity of 2.8 L, an oxygen consumption of 200 mL/min, and respiratory quotient of 0.8. Fresh gas flow (FGF) inputs of 2 L/min and 5 L/min were chosen to represent a spectrum of typical clinical FGF rates. Minute ventilation was set at 4 L/min. Determining the requisite median time to reach an O2 concentration of <30% in the breathing circuit was the primary aim of the study. RESULTS: The median times (1st–99th percent confidence interval) required to achieve inspiratory and expiratory oxygen concentrations of <30% with the extended circuit configuration when starting at 60% for 5 L FGFs were 35 (32–36) and 104 (88–122) seconds, respectively. With 2 L FGF, these median times increased to 303 (291–313) and 255 (232–278) seconds, respectively. A shortened circuit configuration (P = 0.006) and higher FGF flow rate (P < 0.0001) were noted to be factors decreasing the median time required to achieve an oxygen concentration of <30%. CONCLUSIONS: Both inspired and expired circuit oxygen concentration may take minutes to decrease to <30% depending on circuit length, FGF rate, and starting circuit oxygen concentration. During the reduction in FIO2, the expiratory oxygen concentration may be >30% for a considerable time after the FIO2 is in a “safe” range. An increased expired oxygen concentration should also be considered an airway fire risk, and patient care protocols may need to be modified based on future studies.

Integrating conversational virtual humans and mannequin patient simulators to present mixed reality clinical training experiences

We integrated two simulators, a Virtual Patient (VP) system and a physical Human Patient Simulator (HPS) to create a mixed reality conscious sedation training environment. The VP system simulates clinical environments where learners conduct patient interviews. The HPS is a mannequin that models and simulates a wide array of clinical signs. The VP+HPS combination provides new capabilities specially suited for conscious sedation training. Future work will evaluate the efficacy of this MR simulation.

Intravenous Air: The Partially Invisible Phenomenon.

BACKGROUND:Air injection is carefully avoided during IV solution administration; however, ambient air is dissolved in all liquids used for intravenous (IV) therapy. A portion of this gas will come out of solution in the form of bubbles as the solution is warmed to body temperature in a fluid warming system and/or within the body. We sought to quantify the proportion of the gas theoretically dissolved in room temperature crystalloid and 4°C blood products that comes out of solution in the IV tubing on warming to 37°C. METHODS:Equilibrium-dissolved air calculations were performed for sodium chloride (0.9%), packed red blood cells, and fresh frozen plasma at various temperatures according to Henry’s Law. Outgassed gas volumes were experimentally measured for room temperature sodium chloride (0.9%) and 4°C blood products (packed red blood cells and fresh frozen plasma) warmed to 37°C during infusion into a body temperature water bath. The measured gas volumes were quantified as a fraction of the theoretical outgassing volumes required to maintain equilibrium saturation. RESULTS:Measured outgassed volumes in the IV tubing in milliliters of gas per liter of fluid were 1.4 ± 0.3 mL/L (n = 6) for sodium chloride (0.9%), 3.4 ± 0.2 mL/L (n = 6) for packed red blood cells, and 4.8 ± 0.8 mL/L (n = 6) for fresh frozen plasma when these fluids were warmed to body temperature from their respective starting temperatures. Theoretical outgassed gas volumes required to maintain equilibrium saturation for the same fluids and temperatures are 4.7 mL/L for sodium chloride (0.9%), 8.3 mL/L for packed red blood cells, and 10.9 mL/L for fresh frozen plasma. As a fraction of the theoretical outgassing volumes, the measured air volumes represented 30%, 41%, and 44%, respectively, for sodium chloride (0.9%), packed red blood cells, and fresh frozen plasma. Prewarming crystalloid solutions to 37°C before administration significantly reduced the outgassing. CONCLUSIONS:A significant and potentially clinically relevant amount of the resident dissolved gas in room temperature crystalloid, and 4°C packed red blood cells and plasma solutions comes out of solution on warming to body temperature. A nontrivial fraction of this outgassing is also expected to occur within the body circulation based on the results of this study. This can be substantially prevented by prewarming.

Automated, real-time fresh gas flow recommendations alter isoflurane consumption during the maintenance phase of anesthesia in a simulator-based study.

BACKGROUND: The Low Flow Wizard (LFW) provides real-time guidance for user optimization of fresh gas flow (FGF) settings during general inhaled anesthesia. The LFW can continuously inform users whether it determines their FGF to be too little, efficient, or too much, and its color-coded recommendations respond in real time to changes in FGF performed by users. Our study objective was to determine whether the LFW feature, as implemented in the Dräger Apollo workstation, alters FGF selection and thereby volatile anesthetic consumption without affecting patient care. METHODS: To reduce potentially confounding variables, we used a human patient simulator that consumes and exhales volatile anesthetics. Standard monitoring was provided for the patient initially with invasive arterial blood pressure added after anesthetic induction. In this within-group study, each of 17 participants acted as his or her own control. Each participant was asked to anesthetize an identical simulated patient twice using a Dräger Apollo workstation, first with the LFW feature disabled and subsequently enabled. The volatile anesthetic was isoflurane. Both simulation runs were set up to have similar time durations for the different phases of anesthesia: induction, incision, and maintenance. Emergence was not simulated. The isoflurane vaporizer was weighed before and after each simulation run on a digital scale to verify total computed volatile liquid anesthetic consumption. In addition, the product of FGF (reported by the Apollo) times the isoflurane volumetric concentration (sampled by a multigas analyzer at the equivalent of the FGF hose for the Apollo) was integrated over time to obtain isoflurane consumption rate (on-the-fly anesthetic consumption rate measurement). RESULTS: The maintenance isoflurane consumption rate and FGF were significantly lower with the LFW display enabled than without (P = 0.005). The mean reduction in FGF was 53.6% (95% confidence interval, 39.2%–67.9%). There was no significant difference in alveolar isoflurane concentration (P = 0.13 for differences <0.1%). The isoflurane consumption measurement closely matched the consumption measured via the digital scale. CONCLUSIONS: Our data in a simulated anesthetic suggest that enabling the display of FGF efficiency data by the LFW results in a median percent reduction in volatile liquid anesthetic consumption rate of 53.2%. Since the lower limit of the 95% confidence interval for the median is 39.4%, this finding is likely to translate into cost savings and less waste anesthetic gas generated in the clinical setting and released into the atmosphere.

A mixed-reality part-task trainer for subclavian venous access.

Introduction Mixed-reality (MR) procedural simulators combine virtual and physical components and visualization software that can be used for debriefing and offer an alternative to learn subclavian central venous access (SCVA). We present a SCVA MR simulator, a part-task trainer, which can assist in the training of medical personnel. Methods Sixty-five participants were involved in the following: (1) a simulation trial 1; (2) a teaching intervention followed by trial 2 (with the simulator’s visualization software); and (3) trial 3, a final simulation assessment. The main test parameters were time to complete SCVA and the SCVA score, a composite of efficiency and safety metrics generated by the simulator’s scoring algorithm. Residents and faculty completed questionnaires presimulation and postsimulation that assessed their confidence in obtaining access and learner satisfaction questions, for example, realism of the simulator. Results The average SCVA score was improved by 24.5 (n = 65). Repeated-measures analysis of variance showed significant reductions in average time (F = 31.94, P < 0.0001), number of attempts (F = 10.56, P < 0.0001), and score (F = 18.59, P < 0.0001). After the teaching intervention and practice with the MR simulator, the results no longer showed a difference in performance between the faculty and residents. On a 5-point scale (5 = strongly agree), participants agreed that the SCVA simulator was realistic (M = 4.3) and strongly agreed that it should be used as an educational tool (M = 4.9). Conclusions An SCVA mixed simulator offers a realistic representation of subclavian central venous access and offers new debriefing capabilities.

Sub‐millimeter Size Sensors for Measurements in Cryogenic Turbulence

Classical turbulence research is advancing by utilizing MEMS temperature and pressure fluctuation sensor technology. Turbulence research at cryogenic temperatures has many advantages over the classical approach, such as extreme stability of control parameters and very high Reynolds numbers in small apparatus. However, changes in material properties from room temperature to 1 K (and below) make most sensors unusable at low temperature. A new type of thermistor, incorporating a Ge‐film deposited on a GaAs substrate, has been designed. It provides high sensitivity in the range of 20 mK to 5 K. In this paper, the design and characteristics of these sensors is discussed, and experimental data from three thermistors is presented. Progress on a miniature pressure transducer is also described.