{'fraction_non_alphanumeric': 0.027106227106227107, 'fraction_numerical': 0.020512820512820513, 'mean_word_length': 5.4739336492890995, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
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 (CO2), 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% CO2. In response to the remaining exposures, subjective and somatic symptoms of anxiety increased in a dose‐dependent manner. Unlike 5% and 25% CO2, 35% CO2 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% CO2 was seen when this dose was repeated after 1 week. A single breath of 35% CO2 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.