The four-dimensional stress test: psychological, sympathetic-adrenal-medullary, parasympathetic and hypothalamic-pituitary-adrenal responses following inhalation of 35% CO2

Wetherell, Mark, Crown, Anna, Lightman, Stafford, Miles, Jeremy, Kaye, Joey and Vedhara, Kavita (2006) The four-dimensional stress test: psychological, sympathetic-adrenal-medullary, parasympathetic and hypothalamic-pituitary-adrenal responses following inhalation of 35% CO2. Psychoneuroendocrinology, 31 (6). pp. 736-747. ISSN 0306-4530

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Abstract

Background

Hypercapnia is a threat to homeostasis and results in neuroendocrine, autonomic and anxiogenic responses. The inhalation of carbon dioxide (CO2) may, therefore, provide a good paradigm for exploring the pathways by which stress can lead to increased susceptibility to ill-health through physiological and psychological stress reactivity. The current study was designed, therefore, to assess the psychological and physiological responses to the inhalation of CO2.

Methods

Healthy participants (N=24) inhaled a single vital capacity breath of a mixture of CO2 (35%) and oxygen (65%). Blood pressure and heart rate were recorded for 5 min before and after the test and blood and saliva samples were taken immediately before and 2, 10, 20 and 30 min post-inhalation for the measurement of noradrenaline, salivary and serum cortisol and salivary α amylase. In addition, psychosomatic symptoms were recorded immediately before and after the test. The same protocol was repeated 4–6 weeks later at the same time of day.

Results

A single inhalation of CO2 increased blood pressure, noradrenaline, salivary α amylase and psychosomatic symptoms, but decreased heart rate at both testing sessions. Analyses of salivary cortisol data revealed that 70% of the sample could be reliably classified as either responders (i.e. demonstrated a post-CO2 cortisol increase) or non-responders (i.e. responded with a decrease or no change in cortisol following CO2) at both test sessions. Responders also perceived the test to be more aversive than non-responders.

Conclusions

Inhalation of 35% CO2 reliably stimulated the key mechanisms involved in the human stress response. The inter-individual differences in the reactivity of the hypothalamic–pituitary–adrenal axis were also related to differences in the perception of the test.

Item Type:	Article
Additional Information:	Published online 18-4-2006 ahead of print.
Uncontrolled Keywords:	Carbon dioxide inhalation; 35% CO2 stress test; HPA and SAM axes; Stress reactivity; Parasympathetic activation
Subjects:	C800 Psychology
Department:	Faculties > Health and Life Sciences > Psychology
Depositing User:	EPrint Services
Date Deposited:	18 Dec 2008 12:17
Last Modified:	12 Oct 2019 16:28
URI:	http://nrl.northumbria.ac.uk/id/eprint/3407

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