cardiovascular stress testing in the laboratory. good general reference kamarck & lovallo (2003)...

Cardiovascular Stress Testing in the

Laboratory

Good general reference

Kamarck & Lovallo (2003)

Psychosomatic Medicine, 65, 9-21

Discusses;

CV reactivity stability over time

CV reactivity over different tasks

Types of tasks that are useful

Laboratory – Real life

Ideally we would measure cardiovascular reactions to stress in real life…..

However, this approach come with a number of problems

1.How do we know when people will experience stress?

2.What if we choose people under a lot of stress (e.g. caregivers)?

3.Will chronically stressed people be stressed all the time?

4.Why not recruit people who were stressed in the past?

5.Most importantly, CV measures still quite difficult to use in the field

•Portable or “ambulatory” BP and HR monitors

•Often bulky

•Visible to others

•For BP usually record periodically not continuously

Best option for real world events;

• Events that are stressful but not too upsetting

• Events that occur at predictable times

E.g. exams, driving tests, etc

• Standardised / timed

However, still problems;

• Limited in measures we can use

e.g. blood pressure cuff

• Critical not to distract people

• Still lots of confounds – e.g. smoking, caffeine

So what are your options?

•Aim -> Look at CV reactivity during stress

•Use an artificial laboratory stress task

Advantages;

• Complete experimental control

• Standardisation

• Task mixing (if interested in effects of stress on X)

• Can make sure CV measures working OK

What kind of tasks?

• Ethical considerations

• Demanding not traumatic

Ten most common lab stressors (in no order)

Reaction Time tasks

Respond to tone as fast as possible

Simple or choice versions

Public Speaking

Short period to prepare a speech

Typically fake job talk, defendant in court, etc

Audience / video camera

Mirror Tracing

Trace a complex shape

Using only mirror image

Usually distance / number correct in time allowed

Mental Arithmetic

Either backwards counting with large numbers

Or mentally solving rapidly presented maths problems

Stroop Task

Colour – word task

Name ink colours

Speeded test

RED

BLUE

YELLOW

GREEN

Cold Pressor Task

Hand /foot in iced water

1-2 mins (as long as possible)

Often painful

Distress Recall

Relive stressful event

Usually frustrating past events

Describing all the details

Video games

Tracking a target

Responding quickly

Parts requiring good hand-eye co-ordination

Raven’s Matrices

Visual logic puzzles

Must choose next in series

Often timed

Distressing Films

Passively watching nasty films

Car crashes, autopsy, childbirth, industrial accidents, horror films, etc

One of the best lab tasks

Combines public speaking and mental arithmatic;

The ‘Trier Social Stress Test’

Kirschbaum, Pirke, & Hellhammer (1993)

• Trier Social Stress Test

Part 1

Prepare

“Imagine you’ve applied for a job as a psychologist. In 5-10 minutes you will give a speech to the selection committee about why you would be good for this job.

You must speak for 5 minutes without notes and you will be audio and video-taped so we can analyse your body language.”

• Trier Social Stress Test

Part 2

Speech

‘The committee’ – 2-3 people

Microphone and video camera (switched on in silence).

Begin speech

Silence for >20 secs = “you still have time, please continue”

Further silence = questions

• Trier Social Stress Test

Part 3

Counting

“Thank you – we will now move onto a second task”

Count backwards (out loud) from 1687 in 13s

Quickly & accurately as possible

Mistake= start again

Committee still present

Camera / microphone still on

•Control task depends on your measure (BP, HR, cortisol, etc)

•Cortisol – quiet period at the start (before they know the nature of the task)

•BP/HR – quiet task at end (after a break) with similar demands but no stress

Debrief

•Participants told no recordings made

•Told task designed to elicit stress response and committee instructed to appear formal / unfriendly

Data from the lab (n=24)

BPM

50

60

70

80

90

100

110

120

130

Preparation Speech Maths Control

Individuals Average

BPM

50

60

70

80

90

100

110

120

130

Preparation Speech Maths Control

Data from the lab (n=24)

BPM

50

60

70

80

90

100

110

120

130

Preparation Speech Maths Control

Individuals Average

BPM

80

90

100

Preparation Speech Maths Control

Data from the lab (n=1)

High Speech Reactor High Maths Reactor

BPM

80

90

100

110

120

Preparation Speech Maths Control

BPM

80

90

100

110

120

Preparation Speech Maths Control

Data from the lab (n=1)

Non-Reactor

BPM

80

90

100

110

120

Preparation Speech Maths Control

The Trier task has been shown to elicit significant stress responses in

•Both males and females•Both children and adults•Both younger and older adults

•Kudielka, Buske-Kirschbaum, Hellhammer, & Kirschbaum. (2004) Psychoneuroendocrinology, 29, 83-98.

•NB – This paper is quite complicated – the main point to note is that they showed the Trier’s effectiveness in both genders, and all age groups.

Trier task = most effective laboratory task for inducing stress reactions (measured with cortisol)

Dickerson, S.S. & Kemeny, M.E. (2004) Psychological Bulletin, 130, 355-391 – READ ONLY ABSTRACT & DISCUSSION

Dickerson & Kemeny (2004) conclude Trier type tasks = effective because they include;

1.Social-evaluative threat (when other people may make negative judgements about the participant, or when poor performance would reveal a lack of ability)

2.Uncontrollability (when participant’s best efforts are not sufficient to prevent negative outcome)

To understand these last 2 references – need to know what the “HPA axis” is

HPA axis = Hypothalamic Pituitary-Adrenal Axis

Major part of the neuroendocrine system which controls the release of stress hormones

Under Stress, the HPA axis;

•Hypothalamus produces corticotrophin releasing hormone (CRH)

•CRH causes the Pituitary gland to release adrenocorticotrophin (ACTH)

•ACTH causes the Adrenal glands to release epinephrine (adrenaline), norepinephrine (noradrenaline) and cortisol (amongst other things)

These stress hormones help the body respond to threat by increasing HR and BP, diverting blood to muscles, speeding reaction time, releasing sugar to use as fuel, etc.

Worth remembering;

•Lab tasks aren’t perfect;

•Artificial

•Therefore lab reactivity may not relate directly to reactivity in real life (DJ to discuss)

In Summary

Measuring stress during real life events = sacrificing experimental control

Measuring stress in the laboratory = sacrificing ecological validity

Best strategy

•Combine both lab and field measures

•Use lab tasks with ecologically valid characteristics like the Trier

Any Questions

Dr Julia Hay

j.hay@abdn.ac.uk

Room B38, William Guild