Post on 27-Aug-2018
Induction of ConsciousnessPart 1 of 2: +Gz-Time Relationships
Disclosure Information84rd AsMA Annual Scientific Meeting
Typ Whinnery
I have no financial relationships to disclose.
I will not discuss off-label use and/or investigational use in my presentation.
The opinions or views expressed in this presentation are those of the authors and do not necessarily reflect the opinions and recommendations of the FAA.
11stst acceleration-induced acceleration-induced loss and loss and recoveryrecovery of of consciousness episodeconsciousness episode
19031903MaximMaxim’s Captive Flying’s Captive Flying MachinesMachines
G-LOC at +6.87GzG-LOC at +6.87Gz ROC at +3.0GzROC at +3.0Gz
Head (1919)Head (1919)
Sopwith TriplaneSopwith Triplane G-LOC at +4.5G - +4.6GzG-LOC at +4.5G - +4.6Gz
The unconsciousness mustThe unconsciousness musthave lasted about 20 secondshave lasted about 20 seconds
ROC = 20sROC = 20s
11stst in-flight Loss and in-flight Loss and RecoveryRecovery of consciousness episodeof consciousness episode
“… a flier may become unconscious when making a turn at terrific speed.”
“Anemia of the brain causes faintness and unconsciousness immediately.”
“Is it possible to maintain a speed so great that the anemia produced will be so markedand so prolonged that recovery will not takerecovery will not take place?place?”
ROC =ROC =
Historical QuotationsHistorical QuotationsLOC and LOC and ROCROC fromfrom 1924 1924
∞∞
Founder of the Aero Medical Association Founder of the Aero Medical Association 19291929
““The answer is probablyThe answer is probably yes yes.”.”
No previously developed curvesNo previously developed curves
? ? ?? ? ?There are There are significant challenges significant challenges associated with development of associated with development of recovery of consciousness curvesrecovery of consciousness curves
A definitive answer to BauerA definitive answer to Bauer’s question!’s question!
Recovery of Consciousness CurvesRecovery of Consciousness Curves
Recovery of Consciousness CurvesRecovery of Consciousness Curves
The Significant ChallengesThe Significant Challenges
- Lack of adequate data - Lack of adequate data
- Lack of analysis: Emphasis on prevention- Lack of analysis: Emphasis on prevention
- Inadequate descriptions even when Inadequate descriptions even when LOC data available.LOC data available.
- No relationship between unconscious time - No relationship between unconscious time and Max –G of the exposureand Max –G of the exposure
- Safety trumps the exposure profiles- Safety trumps the exposure profiles
Recovery of Consciousness CurvesRecovery of Consciousness Curves
The starting point (Unconsciousness)The starting point (Unconsciousness)is less precise than that for is less precise than that for consciousness…. When developingconsciousness…. When developingLoss of Consciousness Curves.Loss of Consciousness Curves.
CompletelyConsciousness
CompletelyUnconsciousness
The Significant ChallengesThe Significant Challenges
+Gz+Gz
G-LOCG-LOC
G-ROCG-ROC
CompletelyConsciousness
Available RangeAvailable Range
G-LOCG-LOC
Required RangeRequired Range
Too slow: Prolonged IschemiaToo slow: Prolonged Ischemia
Too fast: Centrifuge limits/Study DesignToo fast: Centrifuge limits/Study Design
ToleranceTolerance
Because there are important Because there are important operational, safety, and theoretical operational, safety, and theoretical applications for the applications for the Recovery of Consciousness Curves Recovery of Consciousness Curves
We accepted the We accepted the 66 challenges challengesin our experimental development of in our experimental development of these curves and found even more! these curves and found even more!
Dataset:Dataset: 889889 G-LOC episodes- G-LOC episodes- 763 763 ROC episodesROC episodesAcceleration data repository spanning Acceleration data repository spanning 8 8 yearsyears723723 individuals ( individuals (7474 with more than one G-LOC) with more than one G-LOC)
Subjects:Subjects: All healthy humansAll healthy humans 1. Fighter pilots (Centrifuge +Gz training)1. Fighter pilots (Centrifuge +Gz training) 2. Experimental subjects2. Experimental subjects 3. Students in aeromedical courses3. Students in aeromedical courses 4. Aircrew undergoing medical evaluation4. Aircrew undergoing medical evaluation
Acceleration profiles:Acceleration profiles:
1. Gradual onset runs (GOR)1. Gradual onset runs (GOR)
2. Rapid onset runs (ROR)2. Rapid onset runs (ROR)
3. Simulated aerial combat maneuvers (SACM)3. Simulated aerial combat maneuvers (SACM)
4. Complex runs (tracking task, variable)4. Complex runs (tracking task, variable)
Centrifuges:Centrifuges:
1. USAF School of Aerospace Medicine1. USAF School of Aerospace Medicine2. Naval Air Development Center2. Naval Air Development Center
Configuration (Varied – All combinations included):Configuration (Varied – All combinations included):Subjects sitting: 15-30 tilt seatSubjects sitting: 15-30 tilt seatRelaxed, performing anti-G straining maneuvers,Relaxed, performing anti-G straining maneuvers,with and without anti-G suit combinationswith and without anti-G suit combinations
Common Outcomes:Common Outcomes:
1. G-LOC 1. G-LOC →→ ROC ROC
2. No adverse events2. No adverse events
MAXG:MAXG: +Gz-level at which G-LOC occurred. +Gz-level at which G-LOC occurred.
Offset Rate:Offset Rate: MAXG - 1 over the time from leaving MAXG - 1 over the time from leaving MAXG to time for reachingMAXG to time for reaching Base G.Base G.
ABSINCAP:ABSINCAP: Absolute incapacitation period.Absolute incapacitation period. Time from onset of LOC to ROC.Time from onset of LOC to ROC.The period of The period of “unconsciousness.”“unconsciousness.”
LOC:LOC: Identified (defined) by sudden muscle relaxation (facial, extremities, and torso), loss of postural tone, loss of response, loss of performance of a required task, and/or abrupt change in facial expression (eye fixation, staring, blank expression).
ROC:ROC: Identified (defined) by recovery of muscle tone (facial, extremities, and torso), return of postural tone, response, and/or abrupt change in facial expression (purposeful eye movement, return of expression).
ROC less certainty than LOCAgreement between trained
observers was ± 1.0 s± 1.0 s
ABSINCAP for the entire population ABSINCAP for the entire population consisting of 763 recovery ofconsisting of 763 recovery of
consciousness episodes consciousness episodes
10.39 ± 5.09 s10.39 ± 5.09 s
763 G-ROC episodes763 G-ROC episodes
+Gz-levels: +2.5 to +11.7 GzOffset rates: 0.171 to 7.76 G/sABSINCAP: 1 to 38 s
Recovery of Consciousness EnvelopeRecovery of Consciousness Envelope
+Gz-level +Gz-level vsvs ABSINCAP ABSINCAP
+Gz-level +Gz-level vsvs ABSINCAP ABSINCAP
+Gz-level +Gz-level vsvs ABSINCAP ABSINCAP
Recovery of Consciousness CurvesRecovery of Consciousness Curves
The +Gz-exposure profiles (Safety)The +Gz-exposure profiles (Safety) - Canadian Forces LOC Study- Canadian Forces LOC Study
G-offset rate G-offset rate vsvs ABSINCAP ABSINCAP
Means for Offset RangesMeans for Offset Ranges
G-offset rate G-offset rate vsvs ABSINCAP ABSINCAP
MeansMeans
13.6114.13
9.479.899.349.069.448.488.638.028.548.137.47ABSINCAP IndependentABSINCAP Independent
of Offset Rate ≥ 1.0G/s of Offset Rate ≥ 1.0G/s
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Recovery of Consciousness CurvesRecovery of Consciousness Curves
MinimumMinimum Time for recovery Time for recoverySafetySafety R&DR&D7.47s
Operational ApplicationsOperational Applications
Offset rates ≥ 1.0G/s Offset rates ≥ 1.0G/s
Mean: 10.4sOverall MeanOverall Mean
G-LOCG-LOC G-ROCG-ROC
SymmetrySymmetry
≥≥1.0Gz1.0Gz
Onset=OffsetOnset=Offset
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+Gz-exposure+Gz-exposure
10.0 ± 3.3 s10.0 ± 3.3 s
Induction of unconsciousness
1.0 G/s1.0 G/s
(LOCINDTI)(LOCINDTI)
10.4 ± 5.1 s10.4 ± 5.1 s
Induction of consciousness
1.0 G/s1.0 G/s
(ABSINCAP)(ABSINCAP)
Consciousness CurvesConsciousness Curves
LOCLOC = = ROCROC
Functional Functional Buffer PeriodBuffer Period
Recovery Recovery Buffer PeriodBuffer Period
Theoretical ApplicationsTheoretical Applications
Neurological MechanismsNeurological Mechanisms
Onset IschemiaOnset Ischemia To LOCTo LOC MaintainMaintainConsciousnessConsciousness
Return Blood FlowReturn Blood Flow To ROCTo ROC Maintain Maintain Unconsciousness Unconsciousness
Recovery of ConsciousnessRecovery of Consciousness
Treat – Remove CancerTreat – Remove Cancer
Treat – RemoveTreat – Remove UnconsciousnessUnconsciousness
MedicineMedicine
Prevent CancerPrevent Cancer
Prevent LOCPrevent LOC
AerospaceAerospace MedicineMedicine
Induction of ConsciousnessInduction of Consciousness
DonDon’t Give Up’t Give Up
DonDon’t Give Up’t Give Up
Appreciation to my co-authors for the assistance and encouragementAppreciation to my co-authors for the assistance and encouragement
Especially to Dr. E. M. Forster I am indebted to her for allowing me toEspecially to Dr. E. M. Forster I am indebted to her for allowing me towork with her all my high school and college years; for her patience andwork with her all my high school and college years; for her patience andher influence on my life. her influence on my life.
Offset Rate Data AnalysisOffset Rate Data Analysis
Descriptive StatisticsDescriptive Statistics
+Gz-level Data Analysis+Gz-level Data Analysis
Non-normal Data DistributionNon-normal Data Distribution
Curve Fitting (LOESS)Curve Fitting (LOESS)
Offset Rate Data AnalysisOffset Rate Data Analysis
Methods to Define Methods to Define Time to Induce ConsciousnessTime to Induce Consciousness
1. ROC 1. ROC vsvs Offset Rate Curve Offset Rate Curve Vary the offset rateVary the offset rate
2. ROC 2. ROC vsvs +Gz-level Curve +Gz-level CurveTake subjects well above toleranceTake subjects well above tolerance
BOTH INCREASE RISKBOTH INCREASE RISK
Recovery of Consciousness CurvesRecovery of Consciousness Curves
Mean = Complete LOCMean = Complete LOCMin = Almost LOCMin = Almost LOC
Quantifying the Ischemic InsultQuantifying the Ischemic Insult