@mar%nbarwood
DrMar%nBarwoodPhD,FHEA,FRSS
ReaderinPhysicalAc%vityandHealth
AccidentalColdWaterImmersion:theeffectofextremeanxietyonthevic%mandrescuer
Drowning Statistics
400-1000 accidental deaths by drowning
372,000+ in World Health Organisation
Report
Water temperature and lack of swimming skills are
implicated
SafeRefugeisCloseby…
• 67%ofdrowningsoccurinstrongswimmers• 55%occurwithin3mofsaferefuge(i.e.land)Source:HomeOfficeReport(1977):Reportoftheworkingpartyonwatersafety.HMSO,London
Advice Embedded in National Water Safety Campaign…
Source: Barwood et al., (2011) Int J Aq Res Edu, 5: 147-163 & Barwood et al., (2016) Physiol & Behav, 154:83-89
Initial Responses: Cold Shock Summary
Respiratory
Gasp Response
Inspiratory Shift
Hyperventilation
Decreased Breath Hold Time
Difficulty in breathing
Muscle spasm (“Tetany”) Cardiovascular
Peripheral Vasoconstriction
Tachycardia
Noradrenaline/Adrenaline
(Stress Hormones)
Hypertension
Increased Cardiac Workload
Arrhythmias
A threat to otherwise healthy individuals: 90% of cases
A threat to unhealthy individuals (underlying CV disorder): 10% of
cases
ImmersionScenarios1.Member
ofthepublic
Riskto:65million
2.RescuePersonnel/Occupa%onexposure
Riskto:1million+
3.WaterSports
Par%cipant
Riskto:14million
4.Clinicalpopula%ondepression/anxiety
Riskto:1in6;10.8million
Experimental Set-Up
• Ethically approved studies • Measurement of Cold Shock
Response (fc, fR, Vt, VE & Anxiety) • Standardised duration (7-min),
rate and depth • Water temperature controlled (+/-
0.5°C) • CWI = 15°C WWI = 35°C
Standard Immersion
Scenario 1 Memberofthepublic
Riskto:65million
Results • Acute anxiety
significantly increased the magnitude and duration of the CSR
MAGNITUDE: Heart rate only (9-12 b.p.m-1 higher)
DURATION: Sustained higher heart rate; Ventilation higher by 5.4 L.min-1
Applied Significance: Increased risk of drowning to all
Scenario 2 Results
• Acute anxiety significantly lower
after repeated exposure to scenario
Applied Significance: Possible reduced rate of aspiration of water to
the lungs
RescuePersonnel/Occupa%onexposure
Riskto:1million+ Anxiety lowered, tidal
volume reduced (1.27 L.min-1 vs 1.11 L.min-1
Scenario 2
VS
Sea Water Fresh Water
Lethal Dose: 22.ml.kg-1;
1.65 L for AVG 75 kg person
Lethal Dose: 44.ml.kg-1; 3.30L for AVG 75 kg person
Theoretically: If sea water entered the lungs unimpeded at lethal dose would be achieved after 78 seconds vs 90 seconds
Stress, Appraisal and Coping
Lazarus RS, Folkman S. Stress, appraisal, and coping. New York: Springer Publishing Company; 1984:141-78.
Life Threatening
Survival Training
or Safety Behaviour
Advice
Scenario 3 Benefits of Habituation
of the CSR? • Habituation: A diminished response to a stimulus of the
same magnitude
3.WaterSportsPar%cipant
Riskto:14million
Mean[SD]heartrate(HR)andrespiratoryfrequency(fR)inthefirst30secondsofCWIacross5habituaUonimmersionsinahabituaUononlygroup(HAB)andahabituaUonwithpsychologicalskillsgroup(H-PST);n=20,*(p<0.05).FromBarwoodetal.,(2007),AviatSpaceEnvironMed78:1029-1034.
Habituation of the CSR
Less voluntary control
Some voluntary control
*
*
Scenario 3 Results
3.WaterSportsPar%cipant
Riskto:14million
Magnitude: HR 12 bpm-1
higher
Duration: Sustained increase across immersion
Applied Significance: Habituation partially reversed. Increased
cardiovascular strain; 10% at risk
Scenario 4: What if Anxiety is ever present?
Fig. Experimental Design
Challenge: How can we induce a sustained increase in anxiety?
Deception about water temperature
Punitive maths task; extend immersion for incorrect response
No difference in CSR
Scenario 4 Results
• Habituation was prevented/delayed by
repeated anxiety. • Even when anxiety
levels were not manipulated the CSR
did not subside
4.Clinicalpopula%ondepression/anxiety
Riskto:1in6;10.8million
Stress, Appraisal and Coping
Lazarus RS, Folkman S. Stress, appraisal, and coping. New York: Springer Publishing Company; 1984:141-78.
Life Threatening
Cold Shock
Response Predictors
Future Directions
Finding: Pre-Immersion
Anxiety Levels Predict CSR Components
Future Directions: New Model of CSR
Perceptual Component Attentional Component
Thermal physiological Pathways
Neurophysiological Responses to Stress
Applied Significance
Summary • Scenario 1: Acute anxiety increases the magnitude and duration of the CSR
in unhabituated individuals increasing the risk of drowning to any (anxious) immersed individual.
• Scenario 2: Repeated exposure to the immersion scenario (e.g. in rescue personnel) reduces the magnitude and duration of the ventilatory (depth) component of the CSR which may be beneficial on CWI through a perceptual habituation.
• Scenario 3: Acute anxiety partially reverses the heart rate component of the CSR thereby increasing the cardiovascular strain on immersion which may increase the risk of drowning in a minority of individuals.
• Scenario 4: In repeated anxious individuals (possibly chronic & clinical populations) CSR habituation does not take place potentially increasing the risk of drowning in these individuals.
• Anxiety is integral to the CSR. • We are developing a new integrated of the CSR before and after
habituation to account for the perceptual, attentional, thermal physiological and neurophysiological components that influence the response.
Ques%ons?