Summary: Panic-induced hyperventilation can reduce our ability to respond to environmental threats because it desensitizes body temperature to change.
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’re not facing the same dangers we once faced.
Now, Japanese researchers have discovered that a common panic reaction can actually reduce our ability to deal with environmental threats.
In a study published this month in the American Journal of Physiology – Regulatory, Integrative and Comparative Physiologyresearchers from the University of Tsukuba and the Niigata University of Health and Wellness found that a change in blood gases caused by intense breathing can desensitize the body to changes in temperature.
When we encounter unexpected stressors in daily life, such as sharp pain or fear, a common response is to start breathing quickly. 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,” says the study’s lead author, Dr. Tomomi Fujimoto.
“However, it remains unclear if and how hyperventilation reduces sensitivity to temperature changes.”
To explore this, the researchers first tested sensitivity to temperature changes in young adults while breathing normally. Next, they were instructed to breathe rapidly (hyperventilate), with or without the addition of carbon dioxide to their inspired air, to simulate hypocapnia, which is the normal decrease in carbon dioxide that occurs with hyperventilation, or normocapnia, which is a normal carbon dioxide level.
“The results were startling,” says Professor Takeshi Nishiyasu, corresponding author. “Local sensing of hot and cold stimuli was blunted when subjects hyperventilated with hypocapnia, but did not differ when they hyperventilated with normocapnia.”
Additionally, less blood flow to the brain was observed during hyperventilation with hypocapnia than during hyperventilation with normocapnia. Although reduced sensitivity to hot and cold stimuli is comparable on the forehead, sensing of hot stimuli is unchanged on the forearm.
“These results suggest that hyperventilation-induced hypocapnia, not hyperventilation per se, attenuates local skin thermal perception, although changes in responses to warm stimuli may not be clearly perceived at some areas. skin,” explains Dr. Fujimoto.
Since hyperventilation with hypnocapnia reduces blood flow to the part of the brain that receives thermal stimulation signals, it is plausible that this is the reason for the blunted thermal perception.
The results of this study suggest that hypocapnia may be a mechanism by which hyperventilation reduces stress sensitivity, while paradoxically attenuating thermoregulatory behavior in severe hot and cold environments, which may contribute to heat stroke and accidental hypothermia.
About this neuroscience research news
Original research: Open access.
“Hypocapnia attenuates local skin thermal perception to innocuous hot and cold stimuli in resting normothermic humans” by Tomomi Fujimoto et al. American Journal of Physiology – Regulatory, Integrative and Comparative Physiology
Hypocapnia attenuates local skin thermal perception to innocuous hot and cold stimuli in resting normothermic 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 unclear, this response may blunt perception of the stress-inducing stimulus.
This study investigated the effects of voluntary hyperventilation and resulting hypocapnia on the local skin thermal detection threshold in normothermic resting humans.
Local skin thermal detection thresholds were measured in 15 young adults (three women) under three respiratory conditions: 1) spontaneous breathing (control test), 2) voluntary hypocapnic hyperventilation (HH trial), and 3) voluntary normocapnic hyperventilation (NH test). Local skin thermal detection thresholds were measured using thermostimulators containing a Peltier element that were attached to the forearm and forehead.
The probe temperature was first equilibrated to skin temperature, then gradually increased or decreased at a constant rate (±0.1°C/s) until participants experienced warmth or the freshness.
The difference between the initial skin temperature and the local skin temperature at which the participant noticed warmth/coolness was assessed as an index of the skin’s local hot/cold detection threshold. Local detection of hot and cold stimuli did not differ between the control and NH trials, but was attenuated in the HH trial compared to the control and NH trials, except for the detection of hot stimuli on the forearm.
These results suggest that hyperventilation-induced hypocapnia, not hyperventilation per se, attenuates local skin thermal perception, although changes in responses to warm stimuli may not be clearly perceived at some skin areas. (for example, the forearm).