Predictability and perceived control during 5.5% CO 2-enriched air inhalation in high and low anxious subjects

Abstract

Predictability of type of symptoms and perceived control were manipulated during placebo-controlled inhalation of 5.5% CO 2-enriched air in a group of high and low trait anxious subjects. Overall, high anxious subjects had more complaints, more state anxiety, and breathed faster than low anxious subjects. CO 2 inhalation produced more complaints, more state anxiety, faster breathing, and larger minute ventilation than placebo. Perceived control increased the level of complaints during CO 2 inhalation compared to placebo and raised the respiration frequency of low anxious subjects. Across high and low anxious subjects, control raised the respiration frequency to a CO 2 challenge, but only when this came first and not when placebo had preceded the CO 2 inhalation. High anxious subjects tend to respond strongly in terms of minute ventillation in conditions of minimal information and control, when they were first challenged with a CO 2 mixture. Moreover, they tend to continue this breathing pattern when subsequently breathing regular air. On the other hand, with placebo first, and/or with sufficient information and control, their minute ventillation dropped considerably, even below the level of low anxious subjects.