Behaviorally Inhibited Individuals Exhibit Greater Minute Ventilation and Breathing Frequency Than Non‐Inhibited Individuals When Breathing 4.5% CO2

Abstract

Behavioral inhibition (BI) is a temperament in which an individual tends to avoid unfamiliar situations or environments. Individuals with high BI are more vulnerable to developing an anxiety disorder, such as Post‐Traumatic Stress Disorder (PTSD), when placed under stressful conditions. Behaviorally inhibited individuals learn faster and are slower to stop the response to a stimulus (Sheynin, 2005; Servatius, 2008). Our lab over the past several years has been investigating the relationship between a respiratory stress response to 4.5% CO2 and BI. BI is characterized by avoidance behavior, which is an active response aimed to reduce fear of a certain stimulus. In this study, a computer game was used as an aversive stimulus to detect BI. 4.5% CO2 was applied as a mild respiratory stimulant to detect any differences in those with BI compared to those without. One indication of PTSD is avoidance behaviors. 4.5% CO2 decreases the pH of the blood, hence causing an increase in frequency of breathing (fbr), tidal volume (VT), and inspired minute ventilation (VI). We hypothesize that individuals with high BI will exhibit greater increases in all parameters of breathing compared to individuals with low BI. The 4.5% CO2 was obtained by mixing room air with pure CO2 in a Tissot Spirometer and was validated using an Oxygraph O2 and CO2 analyzer. The mixed gas was then delivered from a 100 liter gas bag attached to a breathing tube attached to a Hans Rudolph two‐way nonrebreathing valve. The subjects placed the two‐way valve attached to a mouthpiece into their mouths and then had a nose clip placed over their noses to created a tight seal between the breathing gas bags and the participants. BI and non‐BI individuals were separated based on Adult Measure of Behavioral Inhibition (AMBI) and Retrospective Measure of Behavioral Inhibition (RMBI). Heart rate and respiratory data were collected using a BioPac computer data collection system while breathing room air and 4.5% CO2. In BI individuals, we observed a 35.9% (+/−33.3) increase in minute ventilation and a 32.4% (+/−32.1) increase in breathing frequency (n=4). In non‐BI individuals, we observed a −6.4% (+/−18.3) decrease in minute ventilation and a −15.1% (+/−2.9) decrease in breathing frequency (n=2). We observed no difference in tidal volume or heart rate for either group. In conclusion, individuals who scored high on the BI test have a greater response to a respiratory stimuli. Our future studies will include cortisol measurements by analyzing saliva samples taken before and after the test.Support or Funding InformationCarthage College Research and Development Grants