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The usual panic reaction can reduce the body’s sensitivity to temperature changes

The usual panic reaction can reduce the body’s sensitivity to temperature changes

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Summary: Panic-induced hyperventilation can reduce our ability to respond to environmental threats because it reduces the sensitivity of body temperature to changes.

source: University of Tsukuba

The fight-or-flight response evolved to protect us from predators, but it can sometimes cause us to overreact in modern life when we don’t face the same dangers as before.

Now, researchers in Japan have found that the general panic response can actually reduce our ability to deal with environmental threats.

In a study published this month in American Journal of Physiology – Regulatory, Integrative and Comparative Physiologyresearchers from the University of Tsukuba and Niigata University of Health and Welfare revealed that the change in blood gas caused by heavy breathing can reduce the body’s sensitivity to temperature changes.

When we encounter unexpected stressors in everyday life, such as acute pain or fear, the usual reaction is to start breathing faster. This response, called hyperventilation, often involves breathing faster than the body actually needs to deal with the perceived threat or danger.

“The purpose of hyperventilation during stress is not well understood, although it is thought to reduce sensitivity to the stressful stimulus,” said lead study author Dr. Tomomi Fujimoto.

“However, whether and how hyperventilation reduces sensitivity to temperature changes is still unclear.”

To investigate this, the researchers first tested sensitivity to temperature changes in young adults while they were breathing normally. They were then asked to breathe rapidly (hyperventilate), with or without adding carbon dioxide to the inhaled air, to simulate hypocapnia, which is the normal decrease in carbon dioxide that occurs with hyperventilation, or normocapnia, which is a normal carbon level of dioxide.

This response, called hyperventilation, often involves breathing faster than the body actually needs to deal with the perceived threat or danger. Image is in the public domain

“The results were striking,” explains Professor Takeshi Nishiyasu, corresponding author. “Local detection of warm and cool stimuli was blunted when subjects hyperventilated with hypocapnia but did not differ when hyperventilating with normocapnia.”

In addition, less blood flow to the brain is observed during hyperventilation with hypocapnia than during hyperventilation with normocapnia. Although reduced sensitivity to warm and cold stimuli was comparable on the forehead, detection of warm stimuli was unchanged on the forearm.

“These findings suggest that hyperventilation-induced hypocapnia, rather than hyperventilation per se, attenuates local skin heat perception, although changes in responses to warm stimuli may not be clearly perceived in some areas of the skin,” said Dr. r Fujimoto.

Given that hyperventilation with hypnocapnia reduces blood flow to the part of the brain that receives signals for thermal stimulation, it is plausible that this is the cause of blunted thermal perception.

Findings from this study suggest that hypocapnia may be a mechanism by which hyperventilation reduces sensitivity to stress while paradoxically reducing thermoregulatory behavior in severe hot and cold environments, which may contribute to heat stroke and accidental hypothermia.

About this neuroscience news

Author: Press office
source: University of Tsukuba
Contact: Press Office – University of Tsukuba
Image: Image is in the public domain

Original Research: Free access.
Hypocapnia attenuates local skin heat perception to innocuous warm and cool stimuli in normothermic resting humans” by Tomomi Fujimoto et al. American Journal of Physiology – Regulatory, Integrative and Comparative Physiology

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The usual panic reaction can reduce the body’s sensitivity to temperature changes

Summary

Hypocapnia attenuates local skin heat perception to innocuous warm and cool stimuli in normothermic resting humans

When a person is exposed to a stressful situation in their daily life, a common reaction is hyperventilation. Although the physiological significance of stress-induced hyperventilation remains uncertain, this response may blunt the perception of the stressful stimulus.

This study investigated the effects of voluntary hyperventilation and resulting hypocapnia on the local skin heat detection threshold in resting normothermic humans.

Local skin thermal detection thresholds were measured in 15 young adults (three female) under three breathing conditions: 1) spontaneous breathing (Control experiment), 2) voluntary hypocapnic hyperventilation (HH experience), and 3) voluntary normocapnic hyperventilation (NH trial). Local skin heat detection thresholds were measured using thermostimulators containing a Peltier element that were attached to the forearm and forehead.

The probe temperature was initially equilibrated with skin temperature, then gradually increased or decreased at a constant rate (±0.1 °C/s) until participants felt warm or cool.

The difference between the initial skin temperature and the local skin temperature at which the participant perceived warmth/coolness was scored as an index of local skin warmth/coolness detection threshold. Local detection of warm and cool stimuli did not differ between Control and NH trials, but was blunted in the HH trial compared with Control and NH trials, except for detection of warm stimuli on the forearm.

These findings suggest that hyperventilation-induced hypocapnia, rather than hyperventilation per se, attenuates local skin heat perception, although changes in responses to warm stimuli may not be clearly perceived in some skin regions (eg, forearm).


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