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Quantifying Expert vs. Novice Skill In Vivo for Development of a Laryngoscopy Simulator
Nathan J. Delson*, Ph.D., Nada Koussa*, Randolph H. Hastings**, M.D, Ph.D., Matthew B. Weinger**, M. D.
University of California, San Diego - *Mechanical and Aerospace Engineering - **School of Medicine Veterans Administration San Diego Healthcare System
Laryngoscopy is used for Airway Intubation
The failure to establish the airway is a major cause of death and brain injury
Laryngoscopy is the most common technique for establishing an airway.
A laryngoscope is used to visualize the glottic opening to the lungs, and then an endotracheal tube is inserted into the trachea.
Experience makes the difference Experts succeed 99.9% Novices succeed 67% to 90%
Project Objectives
Long Term Develop realistic training simulator Provide guidance to trainee Quantitative assessment of trainee
Short Term Quantify expert skill and novice errors Measure relevant physical properties of airway in vivo
Expert Skill Acquisition
Instrument tools to measure: Sensory information used by expert Actions of expert
Collect data under a range of environments Range of patient anatomy
Quantify characteristics of expert actions and novice errorsIdentify physical properties of environment where interaction occurs
Instrumented Laryngoscope
•6 axis force/torque sensor (ATI)
•6 dof magnetic position sensor (Ascension)
Disassembled Assembled
Data Collection in the ORPosition Sensors
SkullAdam’s AppleJaw
ProtocolPatients undergoing AnesthesiaExpert and novice on same patientUse stylus to gather profile and calibration pointsGrade of view reported post procedure
Animation of Expert
Side ViewLaryngoscope in blueForce vector in redClick figure for animation
Data Interpretation is Preliminary
Variation between patients is large Some novices performed well Prior experience Easy patient anatomy
Number of procedures is low Data is presented as indication of method potential rather than definitive characterization of task
Laryngoscope placement seems more important than head position (for this
case!) Laryngoscope final position at maximum force for both expert and novice is very similar relative to the patient’s head anatomy
The expert tilted the head much more forward than novice. However, they both acquired the same grade view
Expert in blue, Novice in red at maximum force
Incorrect laryngoscope placement reduces grade view of novice
Expert in blue, Novice in red at maximum force
Expert vs. Novice in Head c.s.
Novice blade placement is too far into throat
VA_AB 17
Novice Expert
Max Force
75.2 N 43.8 N
Laryn Pitch at Max Y
-75.9o -60.2o
Distance Traveled
126 cm 51 cm
View Attained
Grade II Grade I
Expert vs. Novice in Head c.s.
VA_AB 12
Novice Expert
Max Force
24.2 N 24.9 N
Laryn Pitch at Max Y
-28.9o -26.0o
Distance Traveled
42 cm 75 cm
View Attained
Grade III Grade I
Novice blade placement is not far enough into throat
Expert vs. Expert in Head c.s.
VA_AB 10
Expert Expert
Max Force
34.9 N 35.4 N
Laryn Pitch at Max Y
-80.0o -70.4o
Distance Traveled
52 cm 84 cm
View Attained
Grade I Grade I
Both experts have similar blade placement and trajectory
Expert vs. Expert in Head c.s.
VA_AB 16
Expert Expert
Max Force
38.6 N 38.9 N
Laryn Pitch at Max Y
-85.7o -70.5o
Distance Traveled
85 cm 119 cm
View Attained
Grade I Grade I
Both experts have similar blade placement but vary trajectory at points
Expert vs Novice Comments
When novice blade placement differs from expert, grade view can be lower
Experts have similar blade placement locations on the same patient, although trajectories can vary in certain regions
regions of expertise can be defined
Region of Expertise can be Used to Identify Novice Error
Application of Robot Programming by Human Demonstration Obstacle avoidance example
Deviation from expert region would indicate error, allowing for real time guidance cues during training simulation
start
end
low variation corresponds tohigh precsion area
large variation corresponds tolow precsion requirment
Estimation of Physical Properties In Vivo
Advantages of Skill Acquisition Approach Contact forces are at ranges of interest and at locations of interest
Challenges Unlike probing, motion is not defined for tissue characterization Both sliding and compression occur
Sampling occurs at just a few tissue locations Tissue swelling may occur between procedures
Stiffness Estimation Method
Stiffness is approximated as single dimensional Stiffness is estimated during final loading and unloading when sliding is minimal
Stiffness calculation in head coordinate system estimates compliance of airway tissue
δF - K δX
Kload 41.93/ 50.3 =.833 N/mm
Kunload 32.28 /84.7 = 3.81 N/mm
Unloading occurs rapidly with smaller displacement, resulting in higher stiffness
Stiffness calculation in table coordinate system estimates overall head and neck resistance
δF - K δX
Kload 41.93/ 64.1 =.655 N/mm
Kunload 32.28 /125.6 =2.57N/mm
Stiffness is lower in table c.s. since motion includes head displacement
Stiffness Calculations in Same Patient for both Expert and Novice
Here expert placed blade less deep into the throat and attained same view as novice with lower force
Effective stiffness of expert is lower
Expert loading stiffness = .636 N/mmNovice loading stiffness = 1.29 N/mm
• Expert blade placement may be in “sweet spot” where stiffness is lower• Tissue swelling between procedures may also be a factor
Comments on Tissue Properties
Preliminary stiffness properties have been identified High nonlinearity observed in unloading Realistic simulator should mimic resistance to force (impedance) due to both tissue compliance and head/neck displacementSeparating sliding forces from compressive forces may allow for stiffness estimations at more regions
Future Direction
Comparison of stiffness properties to existing mannequins Add image capture Collect more expert vs expert data
Acknowledgments
Talla Farivar, Lance Feller, Anjali Godbole, William Green, Andrew Linn, and Nabyl Tejani
Society for Technology in AnesthesiaAnesthesia Patient Safety Foundation