Acute carbon dioxide exposure in healthy adults: evaluation of a novel means of investigating the stress response.
Acute hypercapnia was studied to assess its potential as a noninvasive and simple test for evoking neuroendocrine, cardiovascular and psychological responses to stress in man. A single breath of four concentrations of carbon dioxide (CO(2)), 5%, 25%, 35% and 50%, was administered to nine healthy volunteers in a randomized, single-blind fashion. Although no adverse effects occurred, most subjects were unable to take a full inspired vital capacity breath of 50% CO(2). In response to the remaining exposures, subjective and somatic symptoms of anxiety increased in a dose-dependent manner. Unlike 5% and 25% CO(2), 35% CO(2) stimulated significant adrenocorticotropic hormone and noradrenaline release at 2 min and cortisol and prolactin release at 15 min following inhalation. This same dose also provoked a significant bradycardia that was followed by an acute pressor response. No significant habituation of psychological, hypothalamic-pituitary-adrenal (HPA) or cardiovascular responses following 35% CO(2) was seen when this dose was repeated after 1 week. A single breath of 35% CO(2) safely and reliably produced sympathetic and HPA axis activation and should prove a useful addition to currently available laboratory tests of the human stress response.
Kaye
J
J
University Research Centre for Neuroendocrinology, Bristol Royal Infirmary, Bristol, UK. joey.kaye@health.wa.gov.au
Buchanan
F
F
Kendrick
A
A
Johnson
P
P
Lowry
C
C
Bailey
J
J
Nutt
D
D
Lightman
S
S
D000222:Adaptation, Physiological; D000324:Adrenocorticotropic Hormone / Q000097:blood / Q000187:drug effects; D000328:Adult; D001007:Anxiety / Q000097:blood / Q000175:diagnosis* / Q000209:etiology; D001919:Bradycardia / Q000097:blood; D002245:Carbon Dioxide / Q000097:blood; D004305:Dose-Response Relationship, Drug; D006801:Humans; D006935:Hypercapnia / Q000097:blood* / Q000139:chemically induced / Q000150:complications; D007320:Inspiratory Capacity / Q000502:physiology; D008297:Male; D009638:Norepinephrine / Q000097:blood; D011388:Prolactin / Q000097:blood / Q000187:drug effects; D012016:Reference Values; D016037:Single-Blind Method; D013312:Stress, Physiological / Q000097:blood / Q000175:diagnosis* / Q000209:etiology
D002245:Carbon Dioxide; D000324:Adrenocorticotropic Hormone; D011388:Prolactin; D009638:Norepinephrine