Hypocapnia

Hypocapnia or Hypocapnea, sometimes incorrectly called acapnia, is a state of reduced carbon dioxide in the blood. Hypocapnia usually results from deep or rapid breathing, known as hyperventilation. Hypocapnia is the opposite of hypercapnia.Even when severe, hypocapnia is normally well tolerated. However, hypocapnia causes cerebral vasoconstriction, leading to cerebral hypoxia and this can cause transient dizziness, visual disturbances, and anxiety. A low partial pressure of carbon dioxide in the blood also causes alkalosis , leading to lowered plasma calcium ions and nerve and muscle excitability. This explains the other common symptoms of hyperventilation —pins and needles, muscle cramps and tetany in the extremities, especially hands and feet.Hypocapnia is sometimes induced in the treatment of the medical emergencies, such as intracranial hypertension and hyperkalaemia.Because the brain stem monitors the level of blood CO₂ in blood to regulate breathing, hypocapnia can suppress breathing to the point of blackout from cerebral hypoxia. Self-induced hypocapnia through hyperventilation is the basis for the deadly schoolyard choking game. Deliberate hyperventilation has been unwisely used by underwater breath-hold divers to extend dive time but at the risk of shallow water blackout, which is a significant cause of drowning. (From the Wikpedia article Hypocapnia.)

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Recent Publications on Hypocapnia:
Estimating a modified Grubb's exponent in healthy human brains with near infrared spectroscopy and transcranial Doppler. The relationship between cerebral blood volume (CBV) and flow (CBF) has...	29th November, 2008	Department of Medical Physics and Bioengineering, University College	Physiol Meas. 2008 Nov 27;30(1):1-12. DOI Direct Link
Effect of picrotoxin on organism's resistance to acute severe hypoxia. Organism's resistance to acute severe hypoxia (3% O2) was studied after...	26th November, 2008	Laboratory for Pathophysiology, Institute of General Pathology and	Bull Exp Biol Med. 2008 Feb;145(2):177-80.
Respiratory alkalosis and primary hypocapnia in Labrador Retrievers participating in field trials in high-ambient-temperature conditions. OBJECTIVE: To determine whether Labrador Retrievers participating in field...	19th November, 2008	Department of Anatomy, Physiology, and Pharmacology, College of Veterinary	Am J Vet Res. 2008 Oct;69(10):1262-7. DOI Direct Link
Hypercapnia and hypocapnia in neonates. BACKGROUND: The arterial partial pressure of carbon dioxide (PaCO2)...	14th November, 2008	Department of Neonatology, Guangzhou Children's Hospital, Guangzhou	World J Pediatr. 2008 Aug;4(3):192-6. DOI Direct Link
Dyspnea from exercise in cold air is not always asthma. In the absence of other explanations, exercise-induced dyspnea is often...	13th November, 2008	Asthma and Allergy Research Group, Department of Respiratory Medicine and	J Asthma. 2008 Oct;45(8):705-9. DOI Direct Link
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Hypocapnia Clinical Trials:
Acceleration of Recovery From General Anesthesia - Efficacy of Isocapnic Hyperpnoea in Obese Patients Undergoing Isoflurane Anesthesia	Isoflurane Anesthesia

Hypocapnia Patents:
US Patent No.	Title
5716386	Non-invasive aortic impingement and core and cerebral temperature manipulation
6190872	Method for identifying and monitoring patients at risk for systemic inflammatory conditions and apparatus for use in this method
6192884	Method and apparatus for supplemental oxygen delivery
6296654	Non-invasive aortic impingement
6313155	Composition and method for treating macular disorders
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