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

____________________________________

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

___

____

____

____

____

___

____

____

____

____

___

____

____

____

____

___

____

____

____

____

+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