Don't hold your breath: anoxic convulsions from coupled hyperventilation-underwater breath-holding.
نویسندگان
چکیده
The Medical Journal of Australia ISSN: 0025729X 7 June 2010 192 11 663-664 ©The Medical Journal of Australia 2010 www.mja.com.au Lessons from Practice he seizure-like activity that occurred in the two university students was probably convulsions secondary to cerebral hypoxia induced by breath-holding. Anoxic convulsions result from interruption of the oxygen supply to metabolically active neurones, particularly in the cerebral cortex. They may be regarded as a brainstem-release phenomenon in which primitive movements can occur, particularly multifocal arrhythmic myoclonic jerks. They can result from voluntary breath-holding, such as cyanotic breath-holding of early childhood. Swimmers often hyperventilate before breath-holding to reduce the urge to breathe from hypercapnia. This may result in prolonged breath-holds with consequent hypoxaemia. Loss of consciousness may ensue without forewarning because the respiratory stimulus from hypoxaemia is weak and easily overridden. Vigorous exercise, such as underwater swimming, may exacerbate hypoxia by increasing oxygen consumption. These factors are likely to result in syncope occurring late in the dive, as in our two cases. Hyperventilation-induced hypocapnia is known to constrict cerebral vasculature and may contribute to syncope. In addition, the Valsalva manoeuvre can cause syncope during the early stages of a breath-hold dive, probably by reducing cerebral blood perfusion further as a result of decreased cardiac output from reduced thoracic venous return. This may be a cause of early syncope before hypoxia and hypercapnia have occurred, but the Valsalva effects may still be operative late in the dive. When Student 1 stood up at the end of his dive, the change in posture would have impaired venous return even more, and may have triggered the anoxic convulsions. Breath-hold practitioners are often skilled male swimmers who are not closely watched by lifeguards. Loss of consciousness underwater can lead to drowning. A report of 58 cases of syncope during underwater swimming and diving found that all victims were known to be good swimmers or divers and the victims were almost exclusively men (56 cases). Victims were often involved in a competition in which they wanted to “beat” someone else’s or their own underwater distance record. The number of fatalities in that particular medical case series was high (23 cases). Anecdotal observations suggest that underwater breath-holding is a relatively common practice in Australia. The practice is particularly dangerous if coupled with prior hyperventilation. This report provides further evidence that hyperventilating before breath-holding should be discouraged. Swimming pool authorities should be made aware of the potentially dangerous consequences, as should, arguably, children and adults undergoing basic swimming training.
منابع مشابه
3D late gadolinium enhancement in a single prolonged breath-hold using supplemental oxygenation and hyperventilation.
PURPOSE To evaluate the feasibility of three-dimensional (3D) single breath-hold late gadolinium enhancement (LGE) of the left ventricle (LV) using supplemental oxygen and hyperventilation and compressed-sensing acceleration. METHODS Breath-hold metrics [breath-hold duration, diaphragmatic/LV position drift, and maximum variation of R wave to R wave (RR) interval] without and with supplementa...
متن کاملBreath-holding and the sensations due to chemical and mechanical stimuli to breathing.
EVERY medical student and, indeed, every schoolboy knows that it is possible to hold the breath for a longer time with lungs fully inflated than at a smaller lung volume, and that the breath-holding time can also be prolonged by hyperventilation beforehand. This prolongation is possible because the onset of the unpleasant sensations which arise during breath-holding is delayed. Thus both mechan...
متن کاملSourcebook of Laboratory Activites in Physiology The ins and outs of breath holding: simple demonstrations of complex respiratory physiology
Skow RJ, Day TA, Fuller JE, Bruce CD, Steinback CD. The ins and outs of breath holding: simple demonstrations of complex respiratory physiology. Adv Physiol Educ 39: 223–231, 2015; doi:10.1152/advan.00030.2015.—The physiology of breath holding is complex, and voluntary breath-hold duration is affected by many factors, including practice, psychology, respiratory chemoreflexes, and lung stretch. ...
متن کاملThe ins and outs of breath holding: simple demonstrations of complex respiratory physiology.
The physiology of breath holding is complex, and voluntary breath-hold duration is affected by many factors, including practice, psychology, respiratory chemoreflexes, and lung stretch. In this activity, we outline a number of simple laboratory activities or classroom demonstrations that illustrate the complexity of the integrative physiology behind breath-hold duration. These activities requir...
متن کاملA Comparison of the Physiological Responses to Underwater Arm Cranking and Breath Holding Between Synchronized Swimmers and Breath Holding Untrained Women
Exercise and breath holding in the water such as that performed in the sport of synchronized swimming may evoke the physiological consequences of the diving response. The purpose of this study was to investigate the physiological responses of breath holding during underwater arm cranking in synchronized swimmers who are trained in breath holding and compare these responses to untrained women. E...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- The Medical journal of Australia
دوره 192 11 شماره
صفحات -
تاریخ انتشار 2010