Using cognitive load theory to develop an emergency airway management curriculum: the Queen's University Mastery Airway Course (QUMAC).

Emergency airway management requires the simultaneous coordination of clinical reasoning and therapeutic interventions in the complex and time-sensitive setting of emergency resuscitation. The cognitive demand associated with these situations is invariably high and must be taken into consideration when designing training programs for this core professional competency. The four-component instructional design model (4C/ID), based on cognitive load theory, was used to develop a 1-year longitudinal airway management curriculum for Emergency Medicine residents. The simulation-based curriculum was designed with the goal of facilitating the construction and automation of schemas by individual residents in preparation for the high cognitive demand associated with emergency airway management in the clinical environment.

RéSUMé: La gestion des voies aériennes en urgence nécessite la coordination simultanée du raisonnement clinique et des interventions thérapeutiques dans le cadre complexe et sensible au temps de la réanimation d'urgence. La demande cognitive associée à ces situations est invariablement élevée et doit être prise en considération lors de la conception des programmes de formation pour cette compétence professionnelle essentielle. Le modèle de conception pédagogique à quatre composantes (4C/ID), fondé sur la théorie de la charge cognitive, a été utilisé pour élaborer un programme longitudinal de gestion des voies aériennes d'un an à l'intention des résidents en médecine d'urgence.

Surfactants and cloud droplet activation: A systematic extension of Köhler theory based on analysis of droplet stability.

The activation of aerosol particles to form cloud droplets, a necessary first step in cloud formation, controls much of the impact that aerosols have on clouds and climate. Recently, there has been a surge of interest in extending the Köhler theory of cloud droplet activation to include surface active (typically organic) as well as water-soluble (typically inorganic) aerosol components, but a systematic framework for doing this has yet to be developed. Here, we apply a droplet stability analysis to this end. Ideal and Szyszkowski-Langmuir surfactant models are analyzed to demonstrate the new approach, but the underlying theoretical framework is fundamental and model free. A key finding is that superficial densities at the cloud activation threshold (Köhler maximum) are significantly sub-monolayer, with fractional coverage ranging from 69% to 85% for the organic compounds and mixtures studied. The result, significant for model inventories of cloud condensation nuclei, is a weakening of the surfactant effect relative to expectations based on bulk sample measurements. Analytical results are obtained for the loci of Köhler maxima and applied to aerosol mixtures containing an arbitrary number of water-soluble and surfactant components.

Cognitive load theory as a framework for simulation-based, ultrasound-guided internal jugular catheterization training: Once is not enough.

OBJECTIVE: The main objective of this study was to use the principles of cognitive load theory to design a curriculum that incorporates a progressive part practice approach to teaching ultrasound-guided (USG) internal jugular catheterization (IJC) to novices. A secondary objective was to compare the technical proficiency of residents trained using this curriculum with the technical proficiency of residents trained with the current local standard of a single simulation session. METHODS: The experimental group included 16 residents who attended three 2-hour sessions of progressive part practice in a simulation lab. The control group included 46 residents who attended the current local standard of a single 2-hour simulation session just prior to their intensive care unit rotation. Technical proficiency was assessed using hand motion analysis and time to procedure completion. RESULTS: After three sessions, median scores for right hand motion (RHM) (34.5; [27.0-49.0]), left hand motion (LHM) (35.5; [20.0-45.0]), and total time (TT) (117.0 s; [82.7-140.0]) in the experimental group were significantly better than the control group (p<0.001). Results for eight experimental group residents who were assessed for retention at a later date revealed median scores for RHM (45.0; [32.0-58.0]), LHM (33.5; [20.0-63.0]), and TT (150.0 s; [103.0-399.6]), which were significantly better than those of the control group (p=0.01, p<0.01, and p=0.02, respectively). CONCLUSION: These results support multiple sessions of progressive part practice in a simulation lab as an effective competency-based approach to teaching USG IJC in preparation for the clinical setting.

A unifying identity for the work of cluster formation in heterogeneous and homogeneous nucleation theory.

A unifying identity is derived relating the reversible work of cluster formation (W) and its molecular number content (n) and surface work (Φ) components, each ratioed to the corresponding values for a spherical capillary drop of critical size in classical nucleation theory. The result is a relationship that connects these ratios: fW = -2fN + 3fS, where fW = W/W*CNT, fN = n/n*CNT, and fS = Φ/Φ*CNT. Shown to generalize two early thermodynamic relationships of Gibbs, the new result is demonstrated here for Fletcher's model of heterogeneous nucleation, resulting in a unified treatment of condensation on flat and curved substrates and smooth passage to the homogeneous limit. Additional applications are made to clusters of non-critical as well as critical size and to a molecular-based extension of classical nucleation theory based on the Kelvin relation. The new identity serves as a consistency check on complicated theoretical expressions and numerical calculations and can be used to guide the construction of theory and interpretation of measurements.

Temperature Dependence in Heterogeneous Nucleation with Application to the Direct Determination of Cluster Energy on Nearly Molecular Scale.

A re-examination of measurements of heterogeneous nucleation of water vapor on silver nanoparticles is presented here using a model-free framework that derives the energy of critical cluster formation directly from measurements of nucleation probability. Temperature dependence is correlated with cluster stabilization by the nanoparticle seed and previously found cases of unusual increasing nucleation onset saturation ratio with increasing temperature are explained. A necessary condition for the unusual positive temperature dependence is identified, namely that the critical cluster be more stable, on a per molecule basis, than the bulk liquid to exhibit the effect. Temperature dependence is next examined in the classical Fletcher model, modified here to make the energy of cluster formation explicit in the model.  The contact angle used in the Fletcher model is identified as the microscopic contact angle, which can be directly obtained from heterogeneous nucleation experimental data by a recently developed analysis method. Here an equivalent condition, increasing contact angle with temperature, is found necessary for occurrence of unusual temperature dependence. Our findings have immediate applications to atmospheric particle formation and nanoparticle detection in condensation particle counters (CPCs).

Development and Evaluation of a Simulation-based Curriculum for Ultrasound-guided Central Venous Catheterization.

OBJECTIVE: To develop a simulation-based curriculum for residents to learn ultrasound-guided (USG) central venous catheter (CVC) insertion, and to study the volume and type of practice that leads to technical proficiency. METHODS: Ten post-graduate year two residents from the Departments of Emergency Medicine and Anesthesiology completed four training sessions of two hours each, at two week intervals, where they engaged in a structured program of deliberate practice of the fundamental skills of USG CVC insertion on a simulator. Progress during training was monitored using regular hand motion analysis (HMA) and performance benchmarks were determined by HMA of local experts. Blinded assessment of video recordings was done at the end of training to assess technical competence using a global rating scale. RESULTS: None of the residents met any of the expert benchmarks at baseline. Over the course of training, the HMA metrics of the residents revealed steady and significant improvement in technical proficiency. By the end of the fourth session six of 10 residents had faster procedure times than the mean expert benchmark, and nine of 10 residents had more efficient left and right hand motions than the mean expert benchmarks. Nine residents achieved mean GRS scores rating them competent to perform independently. CONCLUSION: We successfully developed a simulation-based curriculum for residents learning the skills of USG CVC insertion. Our results suggest that engaging residents in three to four distributed sessions of deliberate practice of the fundamental skills of USG CVC insertion leads to steady and marked improvement in technical proficiency with individuals approaching or exceeding expert level benchmarks.

Accuracy of instructor assessment of chest compression quality during simulated resuscitation.

OBJECTIVES: The 2010 American Heart Association Guidelines stress the importance of high quality cardiopulmonary resuscitation (CPR) as a predictor of survival from cardiac arrest. However, resuscitation training is often facilitated and evaluated by instructors without access to objective measures of CPR quality. This study aims to determine whether instructors experienced in the area of adult resuscitation (emergency department staff and senior residents) can accurately assess the quality of chest compressions as a component of their global assessment of a simulated resuscitation scenario. METHODS: This is a prospective observational study in which objective chest compression quality data (rate, depth, and fraction) were collected from the simulation manikin and compared to subjective instructor assessment. Data were collected during weekly simulation training sessions for residents, medical students, and nursing students. RESULTS: We included data from 24 simulated resuscitation scenarios assessed by 1 of 15 instructors. Subjective assessment of chest compression quality identified an adequate compression rate (100-120 compressions per minute) with a sensitivity of 0.17 (confidence interval [CI] 0.02-0.32) and specificity of 0.06 (CI -0.04-0.15), adequate depth (>50 mm) with a sensitivity of 0 and specificity of 0.38 (CI 0.18-0.57), and adequate fraction (>80%) with a sensitivity of 1 and a specificity of 0.25 (CI 0.08-0.42). CONCLUSION: Instructor assessment of chest compression rate, depth, and fraction demonstrates poor sensitivity and specificity when compared to the data from the simulation manikin. These results support the use of objective and technologically supported measures of chest compression quality for feedback during resuscitation education using simulators.

How we developed a comprehensive resuscitation-based simulation curriculum in emergency medicine.

Over the past decade, simulation-based education has emerged as a new and exciting adjunct to traditional bedside teaching and learning. Simulation-based education seems particularly relevant to emergency medicine training where residents have to master a very broad skill set, and may not have sufficient real clinical opportunities to achieve competence in each and every skill. In 2006, the Emergency Medicine program at Queen's University set out to enhance our core curriculum by developing and implementing a series of simulation-based teaching sessions with a focus on resuscitative care. The sessions were developed in such as way as to satisfy the four conditions associated with optimum learning and improvement of performance; appropriate difficulty of skill, repetitive practice, motivation, and immediate feedback. The content of the sessions was determined with consideration of the national training requirements set out by the Royal College of Physicians & Surgeons of Canada. Sessions were introduced in a stepwise fashion, starting with a cardiac resuscitation series based on the AHA ACLS guidelines, and leading up to a more advanced resuscitation series as staff became more adept at teaching with simulation, and as residents became more comfortable with this style of learning. The result is a longitudinal resuscitation curriculum that begins with fundamental skills of resuscitation and crisis resource management (CRM) in the first 2 years of residency and progresses through increasingly complex resuscitation cases where senior residents are expected to play a leadership role. This paper documents how we developed, implemented, and evaluated this resuscitation-based simulation curriculum for Emergency Medicine postgraduate trainees, with discussion of some of the challenges encountered.

Examination of Learning Trajectories for Simulated Lumbar Puncture Training Using Hand Motion Analysis.

OBJECTIVES: A prospective cohort study was conducted using hand motion analysis (HMA) to assess the acquisition and retention of technical proficiency among first-year medical students learning the lumbar puncture (LP) skill in a simulated setting. METHODS: Twenty-five subjects attended three or four simulation sessions at 6-week intervals. The initial session consisted of an introduction to the procedure and a baseline HMA assessment. This was followed by a session involving deliberate practice and evaluation using HMA. Subject HMA metrics were followed over time and compared to performance benchmarks to determine the volume of practice required to achieve and maintain technical proficiency in the simulated setting. Performance benchmarks were derived from the assessment of experts using HMA. RESULTS: Subject baseline metrics were significantly different from expert (p < 0.01). At the outset of session 2, none of the subjects achieved the performance benchmarks. At the outset of sessions 3 and 4, 40 and 60% of subjects, respectively, demonstrated retention of technical proficiency. However, there was evidence of significant skill erosion between sessions (p < 0.01). The mean number of practice attempts required to achieve technical proficiency declined between sessions. Regression analysis indicated that there was a significant training effect for all students (overall negative slopes) over time. When examining the group as a whole, the speed at which students reached the expert benchmark was not significantly associated with number of practices in the first three sessions, although for some individuals these factors did appear associated. A total of 76% of subjects retained technical proficiency by session 4 and required a mean of 14 practices (range = 5 to 19). CONCLUSIONS: These results show that the majority of students require three to four sessions of deliberate practice to achieve a sustainable level of proficiency in the LP procedure. There is considerable variation in learning progression and retention of technical proficiency. These results have important implications for the design and resource requirements of a competency-based medical education program targeting LP training.

Computerized training system for ultrasound-guided lumbar puncture on abnormal spine models: a randomized controlled trial.

PURPOSE: A randomized controlled trial was carried out to determine whether Perk Tutor, a computerized training platform that displays an ultrasound image and real-time needle position in a three-dimensional (3D) anatomical model, would benefit residents learning ultrasound-guided lumbar puncture (LP) in simulation phantoms with abnormal spinal anatomy. METHODS: Twenty-four residents were randomly assigned to either the Perk Tutor (P) or the Control (C) group and asked to perform an LP with ultrasound guidance on part-task trainers with spinal pathology. Group P was trained with the 3D display along with conventional ultrasound imaging, while Group C used conventional ultrasound only. Both groups were then tested solely with conventional ultrasound guidance on an abnormal spinal model not previously seen. We measured potential tissue damage, needle path in tissue, total procedure time, and needle insertion time. Procedural success rate was a secondary outcome. RESULTS: The needle tracking measurements (expressed as median [interquartile range; IQR]) in Group P vs Group C revealed less potential tissue damage (39.7 [21.3-42.7] cm(2) vs 128.3 [50.3-208.2] cm(2), respectively; difference 88.6; 95% confidence intervals [CI] 24.8 to 193.5; P = 0.01), a shorter needle path inside the tissue (426.0 [164.9-571.6] mm vs 629.7 [306.4-2,879.1] mm, respectively; difference 223.7; 95% CI 76.3 to 1,859.9; P = 0.02), and lower needle insertion time (30.3 [14.0-51.0] sec vs 59.1 [26.0-136.2] sec, respectively; difference 28.8; 95% CI 2.2 to 134.0; P = 0.05). Total procedure time and overall success rates between groups did not differ. CONCLUSION: Residents trained with augmented reality 3D visualization had better performance metrics on ultrasound-guided LP in pathological spine models.

The development and validation of hand motion analysis to evaluate competency in central line catheterization.

OBJECTIVES: Traditionally, technical skills proficiency has been assessed by direct observation. While direct observation and feedback are essential components in technical skills learning, they demand considerable investment of faculty time, and as an assessment tool, direct observation is inherently subjective and has been criticized as unreliable. The purpose of this study was to determine if quantitative electromagnetic motion tracking is feasible and can discriminate between experts and nonexperts during simulated ultrasound (US)-guided insertion of a central venous catheter (CVC) guidewire. METHODS: Ten nonexperts (junior emergency medicine residents) and 10 experts (critical care fellows or attending physicians) were recruited. Electromagnetic sensor probes were used to capture hand motion during an US-guided internal jugular cannulation on a standardized manikin. Hand, US, and needle motion were analyzed for the following metrics: total path length, total time, translational movements, and rotational movements. Subjects were also videotaped and evaluated using a modified, validated global rating scale (GRS) by a blinded expert. RESULTS: There was a significant difference in almost all examined motion parameters between experts and nonexperts. Experts took 66% less time (50.2 seconds vs. 148.7 seconds, p < 0.001) and had significantly less right-hand and US motion (total path length and translational and rotational movements). Left-hand total path length was the only parameter that was not significantly different between groups. Concurrent validity of motion parameters was established by strong correlations (r2 > 0.74) to a previously published, modified GRS. CONCLUSIONS: Electromagnetic hand and instrument motion analysis is technically feasible for assessing competence in US-guided insertion of a CVC guidewire in a simulation setting. In showing that it discriminates between the performances of nonexperts and experts, this study has provided evidence for construct validity. It also shows excellent correlation with a modified version of a previously validated GRS, providing evidence of concurrent validity.

Assessment of lumbar puncture skill in experts and nonexperts using checklists and quantitative tracking of needle trajectories: implications for competency-based medical education.

UNLABELLED: CONSTRUCT: With the current shift toward competency-based education, rigorous assessment tools are needed for procedurally based tasks. BACKGROUND: Multiple tools exist to evaluate procedural skills, each with specific weaknesses. APPROACH: We sought to determine if quantitative needle tracking could be used as a measure of lumbar puncture (LP) performance and added discriminatory value to a dichotomous checklist. Thirty-two medical students were divided into 2 groups. One group was asked to practice an LP once (single practice [SP]) and the other 5 times (multiple practice [MP]). Experts (attending ER physicians, senior ER residents, and a junior anesthesia resident) were used as comparators. Medical students were assessed again at 1 month to assess skill retention. Groups were assessed performing an LP with an electromagnetic tracking device that allows the needle's 3-dimensional movements to be captured and analyzed, and a dichotomous checklist. RESULTS: Quantitative needle metrics as assessed by electromagnetic tracking showed a decreasing trend in needle movement distance with practice and with experience. The SP group made significantly more checklist mistakes initially as compared to the MP group (1.2 vs. 0.3, p <.05). At 1 month, there was a significant increase in both groups' mistakes (SP 3.4 vs. MP 1.3, p =.01). No correlation existed between individuals' needle motion and checklist mistakes. CONCLUSIONS: These findings suggest that quantitative needle tracking identifies students who struggle with needle insertion but are successful at completing the dichotomous checklist.

Communication: kinetics of scavenging of small, nucleating clusters: first nucleation theorem and sum rules.

Despite recent advances in monitoring nucleation from a vapor at close-to-molecular resolution, the identity of the critical cluster, forming the bottleneck for the nucleation process, remains elusive. During past twenty years, the first nucleation theorem has been often used to extract the size of the critical cluster from nucleation rate measurements. However, derivations of the first nucleation theorem invoke certain questionable assumptions that may fail, e.g., in the case of atmospheric new particle formation, including absence of sub-critical cluster losses and heterogeneous nucleation on pre-existing nanoparticles. Here, we extend the kinetic derivation of the first nucleation theorem to give a general framework to include such processes, yielding sum rules connecting the size dependent particle formation and loss rates to the corresponding loss-free nucleation rate and the apparent critical size from a naïve application of the first nucleation theorem that neglects them.

Feasibility of real-time workflow segmentation for tracked needle interventions.

Computer-assisted training systems promote both training efficacy and patient health. An important component for providing automatic feedback in computer-assisted training systems is workflow segmentation: the determination of what task in the workflow is being performed. Our objective was to develop a workflow segmentation algorithm for needle interventions using needle tracking data. Needle tracking data were collected from ultrasound-guided epidural injections and lumbar punctures, performed by medical personnel. The workflow segmentation algorithm was tested in a simulated real-time scenario: the algorithm was only allowed access to data recorded at, or prior to, the time being segmented. Segmentation output was compared to the ground-truth segmentations produced by independent blinded observers. Overall, the algorithm was 93% accurate. It automatically segmented the ultrasound-guided epidural procedures with 81% accuracy and the lumbar punctures with 82% accuracy. Given that the manual segmentation consistency was only 84%, the algorithm's accuracy was 93%. Using Cohen's d statistic, a medium effect size (0.5) was calculated. Because the algorithm segments needle-based procedures with such high accuracy, expert observers can be augmented by this algorithm without a large decrease in ability to follow trainees in a workflow. The proposed algorithm is feasible for use in a computer-assisted needle placement training system.

Perk Tutor: an open-source training platform for ultrasound-guided needle insertions.

Image-guided needle placement, including ultrasound (US)-guided techniques, have become commonplace in modern medical diagnosis and therapy. To ensure that the next generations of physicians are competent using this technology, efficient and effective educational programs need to be developed. This paper presents the Perk Tutor: a configurable, open-source training platform for US-guided needle insertions. The Perk Tutor was successfully tested in three different configurations to demonstrate its adaptability to different procedures and learning objectives. 1) The Targeting Tutor, designed to develop US-guided needle targeting skills, 2) the Lumbar Tutor, designed for practicing US-guided lumbar spinal procedures, and (3) the Prostate Biopsy Tutor, configured for US-guided prostate biopsies. The Perk Tutor provides the trainee with quantitative feedback on progress toward the specific learning objectives of each configuration. Configurations were implemented through simple rearrangement of hardware and software components, attesting to the modularity and ease of configuration. The Perk Tutor is provided as a free resource to enable research and development of educational programs for US-guided intervention.

The effect of augmented reality training on percutaneous needle placement in spinal facet joint injections.

The purpose of this study was to determine if augmented reality image overlay and laser guidance systems can assist medical trainees in learning the correct placement of a needle for percutaneous facet joint injection. The Perk Station training suite was used to conduct and record the needle insertion procedures. A total of 40 volunteers were randomized into two groups of 20. 1) The Overlay group received a training session that consisted of four insertions with image and laser guidance, followed by two insertions with laser overlay only. 2) The Control group received a training session of six classical freehand insertions. Both groups then conducted two freehand insertions. The movement of the needle was tracked during the series of insertions. The final insertion procedure was assessed to determine if there was a benefit to the overlay method compared to the freehand insertions. The Overlay group had a better success rate (83.3% versus 68.4%, p=0.002), and potential for less tissue damage as measured by the amount of needle movement inside the phantom (3077.6 mm(2) versus 5607.9 mm(2) , p =0.01). These results suggest that an augmented reality overlay guidance system can assist medical trainees in acquiring technical competence in a percutaneous needle insertion procedure.

Reversible uptake of water on NaCl nanoparticles at relative humidity below deliquescence point observed by noncontact environmental atomic force microscopy.

The behavior of NaCl nanoparticles as a function of relative humidity (RH) has been characterized using non-contact environmental atomic force microscopy (e-AFM) to measure the heights of particles deposited on a prepared hydrophobic surface. Cubic NaCl nanoparticles with sides of 35 and 80 nm were found to take up water reversibly with increasing RH well below the bulk deliquescence relative humidity (DRH) of 75% at 23(∘)C, and to form a liquid-like surface layer of thickness 2 to 5 nm, with measurable uptake (>2 nm increase in particle height) beginning at 70% RH. The maximum thickness of the layer increased with increasing RH and increasing particle size over the range studied. The liquid-like behavior of the layer was indicated by a reversible rounding at the upper surface of the particles, fit to a parabolic cross-section, where the ratio of particle height to maximum radius of curvature increases from zero (flat top) at 68% RH to 0.7 ± 0.3 at 74% RH. These observations, which are consistent with a reorganization of mass on the solid NaCl nanocrystal at RH below the DRH, suggest that the deliquescence of NaCl nanoparticles is more complex than an abrupt first-order phase transition. The height measurements are consistent with a phenomenological model that assumes favorable contributions to the free energy of formation of a liquid layer on solid NaCl due both to van der Waals interactions, which depend partly upon the Hamaker constant, A(film), of the interaction between the thin liquid film and the solid NaCl, and to a longer-range electrostatic interaction over a characteristic length of persistence, ξ; the best fit to the data corresponded to A(film)= 1 kT and ξ = 2.33 nm.