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Query: UMLS:C0085383 (hypocapnia)
 1,697 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Anxiety can induce hyperventilation, and the resultant hypocapnia and hypocalcaemia can lead to paraesthesiae and tetany. To define the nature of the disturbance created in peripheral nerve, the excitability of cutaneous and motor axons was monitored in 6 normal subjects requested to hyperventilate until paraesthesiae developed in the hands, face and trunk. This occurred when alveolar PCO2 (PACO2) had declined on average by 20 mmHg. Spontaneous EMG activity developed when PACO2 had declined by a further 4 mmHg. Changes in the excitability of cutaneous and motor axons were measured from changes in the compound action potentials evoked by stimulation of the median nerve at the wrist and recorded over the digital nerves of the index finger and over the thenar muscles, respectively. As PACO2 declined, the size of the compound sensory and muscle potentials evoked by a constant stimulus progressively increased, indicating an increase in axonal excitability. These changes occurred before paraesthesiae or tetany developed. In each subject there was a statistically significant inverse correlation between PACO2 and axonal excitability. Independent of this increase in axonal excitability, there was no significant change in the supernormal phase of the recovery cycle of cutaneous axons. Microneurographic recordings from the median nerve in 2 subjects revealed spontaneous bursting activity of cutaneous axons, perceived as paraesthesiae. It is concluded that the paraesthesiae and tetany induced by hyperventilation result solely from changes in the excitability of cutaneous and motor axons in the peripheral nerve, presumably due to an alteration in the electrical properties of the axonal membrane resulting from a reduced plasma [Ca2+]. The supernormal phase may entrain the ectopic discharge and thereby determine the maximal discharge frequency of impulses in ectopically generated trains, but does not otherwise contribute to the physiological disturbance.
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PMID:Paraesthesiae and tetany induced by voluntary hyperventilation. Increased excitability of human cutaneous and motor axons. 200 55

A 34-year-old woman with a recent history of a influenza-like illness and signs of bronchopneumonia presented with many of the features of acute epiglottitis, a condition which still carries a high mortality in adults. Urgent laryngoscopy and bronchoscopy under inhalational anaesthesia were negative. The results of arterial blood gases, taken when stridor was at its worst, revealed marked hypocapnia and respiratory alkalosis. We conclude that the resultant acute reduction of serum ionised calcium produced stridor as a result of tetany of the vocal cords. Similar cases from the literature and the role of emotional factors in the aetiology are discussed.
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PMID:Stridor in an adult. An unusual presentation of functional origin. 265 May 74

This experiment was undertaken to determine the connection between the breathing techniques practised in some methods of training for childbirth and the presence of certain undesirable side effects during labour. These symptoms, viz., dizziness, exhaustion, shortness of breath, "pins and needles", tremors and tetany, may be the result of hyperventilation and the ensuing hypocapnia (deficiency of CO2 in the blood) (Christophers, 1961).
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PMID:The effect of breathing techniques on the end-tidal percentage of carbon dioxide and its importance during labour. 2502 3

Hyperventilation can be a manifestation of anxiety that involves abnormally fast breathing (tachypnea) and an elevated minute ventilation that exceeds metabolic demand. This report describes a case of hyperventilation-induced hypocapnia resulting in tetany in a 16-year-old girl undergoing orthodontic extractions under intravenous conscious sedation. Pulse oximetry is the gold standard respiratory-related index in conscious sedation. Although the parameter has great utility in determining oxygen desaturation, it provides no additional information on respiratory function, including, for example, respiratory rate. In this case, we found capnography to be a very useful aid to monitor respiration in this patient and also to treat the hypocapnia.
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PMID:Tetany During Intravenous Conscious Sedation in Dentistry Resulting From Hyperventilation-Induced Hypocapnia. 2686 8