Summary: Hyperventilation caused by shock can cause changes in body temperature, which can reduce our ability to respond to environmental threats.
Source: University of Tsukuba
The fight-or-flight response evolved to protect us from predators, but it can sometimes cause us to overreact when faced with the same dangers we face in modern life.
Now, researchers from Japan have found that the normal panic response reduces our ability to cope with environmental hazards.
In a study published this month, American Journal of Physiology: Control, Integrative and Comparative PhysiologyResearchers at the University of Tsukuba and Niigata University of Health and Welfare have found that blood gas changes caused by vigorous breathing can cause the body to cool down.
When we face unexpected stressors in our daily lives, such as acute pain or fear, a normal response is to breathe quickly. This response involves breathing faster than the body needs to cope with the threat or danger, known as hyperventilation.
“The purpose of the increase in blood pressure during stress is not well understood, although it is thought to reduce sensitivity to the stress stimulus,” said Dr. Tomomi Fujimoto, who led the study.
However, it is still not clear whether and how the increase in blood pressure reduces susceptibility to temperature changes.
To explore this, the researchers first tested young adults’ sensitivity to temperature changes while breathing normally. They were then asked to breathe rapidly with or without adding carbon dioxide to the inspired air, to simulate hypocapnia, which is a normal decrease in carbon dioxide caused by hyperventilation, or normocapnia, which is normal carbon dioxide. Dioxide level.
“The results were amazing,” said co-author Professor Takeshi Nishiyasu. “Distinguishing between hot and cold stimuli in the environment is blurred when subjects are hypocapnically cooled, but do not differ when normocapnically hyperventilated.”
In addition, less blood flow to the brain was observed during hyperventilation with hypocapnia than with hyperventilation with normocapnia. Although reduced sensitivity to hot and cold stimuli was comparable across the forehead, detection of hot stimuli was unchanged across the forehead.
“These findings suggest that hyperventilation-induced hypocapnia, hyperventilation per se, reduces the perception of local skin temperature, although changes in the response to warm stimuli cannot be clearly seen in some areas of the skin,” said Dr. Fujimoto.
Because hyperventilation with hypnocapnia reduces blood flow to the part of the brain that receives thermal stimulus signals, it is plausible that this accounts for blunted thermal perception.
The findings of this study suggest that hypocapnia may be a mechanism by which hyperventilation reduces susceptibility to stress, paradoxically impairing thermoregulatory behavior in extreme hot and cold environments, which may contribute to heat stroke and sudden hypothermia.
So neuroscience research news
Author: Press office
Source: University of Tsukuba
Contact: Press Office – University of Tsukuba
Image: The image is in the public domain.
Preliminary study: Open Access.
“Hypocapnia impairs the perception of local skin temperature to normal resting temperature to non-injurious hot and cold stimuli in humans.” by Tomomi Fujimoto et al. American Journal of Physiology: Control, Integrative and Comparative Physiology
look up
Draft
Hypocapnia impairs the perception of local skin temperature to normal resting temperature to non-injurious hot and cold stimuli in humans.
When a person experiences a stressful situation in their daily life, the usual reaction is hyperventilation. Although the physiological significance of stress-induced hyperventilation is uncertain, this response may reduce awareness of stress-inducing stimuli.
This study investigated the effect of voluntary hyperventilation and consequent hypocapnia on the detection level of ambient skin temperature in normothermic resting humans.
Ambient skin temperature detection thresholds were measured in 15 young adults (three women) under three breathing conditions: 1Spontaneous breathing (control test), 2) voluntary hypocapnic hyperventilation (HH test), and 3) voluntary normocapnic hyperventilation (NH test). Local skin temperature detection thresholds were measured using Peltier element thermostats attached to the forehead and forehead.
The temperature of the probe is equal to the skin temperature at the beginning, and then gradually increases or decreases at a constant rate (±0.1 °C/s) until the participants feel hot or cold.
The difference between the initial skin temperature and the surrounding skin temperature is an index of the degree of skin heat/cold detection at which the participant perceives heat/cold. Local detection of warm and cold stimuli did not differ between control and NH trials, but in the HH trial compared to control and NH trials, except for detection of warm stimuli in the upper arm.
These findings suggest that hyperventilation-induced hypocapnia, hyperventilation per se, impairs the perception of local skin temperature, although changes in responses to warm stimuli cannot be clearly seen in some skin areas (eg, forearm).