Voluntary Respiratory Control and Cerebral Blood Flow Velocity upon Ice-Water Immersion
| Autor: | Teit Mantoni, Bo Belhage, Jakob Højlund Rasmussen, Frank Christian Pott |
|---|---|
| Rok vydání: | 2008 |
| Předmět: |
Adult
Male Respiratory rate Ultrasonography Doppler Transcranial Poison control Hypothermia Risk Factors medicine.artery Immersion Hyperventilation Heart rate medicine Humans Tidal volume Analysis of Variance Physical Education and Training business.industry Ice Public Health Environmental and Occupational Health Adaptation Physiological Cold Temperature Cerebral blood flow Cerebrovascular Circulation Anesthesia Middle cerebral artery Respiratory Mechanics Reflex Female medicine.symptom business |
| Zdroj: | Aviation, Space, and Environmental Medicine. 79:765-768 |
| ISSN: | 0095-6562 |
| DOI: | 10.3357/asem.2216.2008 |
| Popis: | INTRODUCTION: In non-habituated subjects, cold-shock response to cold-water immersion causes rapid reduction in cerebral blood flow velocity (approximately 50%) due to hyperventilation, increasing risk of syncope, aspiration, and drowning. Adaptation to the response is possible, but requires several cold immersions. This study examines whether thorough instruction enables non-habituated persons to attenuate the ventilatory component of cold-shock response. METHODS: There were nine volunteers (four women) who were lowered into a 0 degrees C immersion tank for 60 s. Middle cerebral artery mean velocity (CBFV) was measured together with ventilatory parameters and heart rate before, during, and after immersion. RESULTS: Within seconds after immersion in ice-water, heart rate increased significantly from 95 +/- 8 to 126 +/- 7 bpm (mean +/- SEM). Immersion was associated with an elevation in respiratory rate (from 12 +/- 3 to 21 +/- 5 breaths, min(-1)) and tidal volume (1022 +/- 142 to 1992 +/- 253 ml). Though end-tidal carbon dioxide tension decreased from 4.9 +/- 0.13 to 3.9 +/- 0.21 kPa, CBFV was insignificantly reduced by 7 +/- 4% during immersion with a brief nadir of 21 +/- 4%. DISCUSSION: Even without prior cold-water experience, subjects were able to suppress reflex hyperventilation following ice-water immersion, maintaining the cerebral blood flow velocity at a level not associated with impaired consciousness. This study implies that those susceptible to accidental cold-water immersion could benefit from education in cold-shock response and the possibility of reducing the ventilatory response voluntarily. Language: en |
| Databáze: | OpenAIRE |
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