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Self-induced syncope: the fainting lark: Difference between revisions
Self-induced syncope: the fainting lark (view source)
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[[File:FaintingLark_Fig1.jpg | thumb | | [[File:FaintingLark_Fig1.jpg | thumb | right | 300px | Fig 1. Continuous monitoring of changes in finger blood pressure, end-tidal CO2 and cerebral blood flow velocity induced by the fainting lark in a 55 year old male. After a very short period of lightheadedness (grey area), the subject blacked out and fainted.]] | ||
The figure documents the precipitous and deep fall in arterial pressure and cerebral blood flow in one of the authors (WW) <cite>Wieling</cite>. The subject briefly (2-3 s) lost consciousness preceded by an extreme short period of light-headedness and black out. Note the overshoot in blood pressure after lying down. | The figure documents the precipitous and deep fall in arterial pressure and cerebral blood flow in one of the authors (WW) <cite>Wieling</cite>. The subject briefly (2-3 s) lost consciousness preceded by an extreme short period of light-headedness and black out. Note the overshoot in blood pressure after lying down. | ||
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== Editor's comments == | == Editor's comments == | ||
The fainting lark combines the effects of systemic arterial hypotension induced by acute vasodilatation of the lower limbs (the combination of standing up and the post-ischemic effect of squatting) and decreased cardiac output (effects of arising and raised intrathoracic pressure) and cerebral vasoconstriction induced by hypocapnia (due to hyperventilation) <cite>Howard</cite>. The high cerebral venous pressure induced by straining can be expected to play an important adjunctive role in the effectiveness of the fainting lark to induce fainting <cite>Gastaut</cite>. The fainting lark can trigger syncope in almost anyone. Myoclonic jerks directly after falling down are observed in the majority of the subjects engaged <cite>Howard</cite><cite>Lempert</cite>. | The fainting lark combines the effects of ''systemic arterial hypotension'' induced by acute vasodilatation of the lower limbs (the combination of standing up and the post-ischemic effect of squatting) and decreased cardiac output (effects of arising and raised intrathoracic pressure) and ''cerebral vasoconstriction'' induced by hypocapnia (due to hyperventilation) <cite>Howard</cite>. The high cerebral venous pressure induced by straining can be expected to play an important adjunctive role in the effectiveness of the fainting lark to induce fainting <cite>Gastaut</cite>. The fainting lark can trigger syncope in almost anyone. Myoclonic jerks directly after falling down are observed in the majority of the subjects engaged <cite>Howard</cite><cite>Lempert</cite>. | ||
Other manoeuvres that are applied to induce syncope are the mess trick <cite>Howard</cite> recently described as suffocation roulette <cite>Shlamovitz</cite>. During the latter trick subjects are instructed to take a deep breath and a companion grasps the subject unexpectedly from behind around the chest and squeezes it as hard as he can. The subject automatically closes his glottis, the intrathoracic pressure is raised and the subject faints. This is liable be done as entertainment, usually with the effects of alcohol added to the mechanical effects. Self-induced fainting is reported to be safe, but injuries may occur by falling. Moreover, severe complications and even death have been described <cite>Murphy</cite><cite>Rumball</cite><cite>Chow</cite>. | Other manoeuvres that are applied to induce syncope are the mess trick <cite>Howard</cite> recently described as suffocation roulette <cite>Shlamovitz</cite>. During the latter trick subjects are instructed to take a deep breath and a companion grasps the subject unexpectedly from behind around the chest and squeezes it as hard as he can. The subject automatically closes his glottis, the intrathoracic pressure is raised and the subject faints. This is liable be done as entertainment, usually with the effects of alcohol added to the mechanical effects. Self-induced fainting is reported to be safe, but injuries may occur by falling. Moreover, severe complications and even death have been described <cite>Murphy</cite><cite>Rumball</cite><cite>Chow</cite>. | ||
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== References == | == References == | ||
<biblio> | <biblio> | ||
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#Rumball pmid=13975507 | #Rumball pmid=13975507 | ||
#Chow pmid=12899159 | #Chow pmid=12899159 | ||
<biblio> | </biblio> | ||