@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?