'Air hunger' is the
sensation of the urge to
breathe. It is usually caused by the detection of high levels of
carbon dioxide in the blood by sensors in the
carotid sinus and is one of the body's
homeostatic mechanisms to ensure proper oxygenation. Natural chemicals in the blood such as
adrenalin can also induce an urge to breathe by a separate pathway. Insufficient
pulmonary minute ventilation, a sustained breath-hold, constriction of the
alveoli of the lungs as in
asthma or high ambient levels of carbon dioxide in the air breathed can cause air hunger resulting in a respiratory distress condition characterized by
dyspnea, labored breathing or gasping. Air hunger can be very distressing and triggers strong reactions to restore breathing.
In
mammals (with the notable exception of
seals and some burrowing mammals) the breathing reflex is triggered by excess of carbon dioxide rather than lack of
oxygen, so
asphyxiation progresses in oxygen-deprived environments, such as storage vessels purged with nitrogen or helium balloons, without the victim's experiencing air hunger.
References
★ Banzett, Robert.
Hunger for Air: from Afferent Input to Cerebral Cortex. ''www.hsph.harvard.edu''. URL last accessed
February 26 2006.
★ Banzett, Robert.
DYSPNEA RESEARCH LAB Publications
★ Dunn, Katharine.
Waiting to Inhale
★ Gracely, Richard.
Dyspnea and Pain: Similarities and Contrasts Between Two Very Unpleasant Sensations. ''http://www.ampainsoc.org''. URL last accessed
February 26 2006.
★
PET images reveal brain's response to hunger for air