Mantoni Teit, Belhage Bo, Pedersen Lars M, Pott Frank C
Bispebjerg Hospital Research Unit for Anaesthesia and Intensive Care, Copenhagen, Denmark.
Aviat Space Environ Med. 2007 Apr;78(4):374-6.
Near-drowning incidents and drowning deaths after accidental immersion in open waters have been linked to cold shock response. It consists of inspiratory gasps, hyperventilation, tachycardia, and hypertension in the first 2-3 min of cold-water immersion. This study explored the immediate changes in cerebral blood flow velocity (Vmean) during cold-water immersion since cold shock induced hyperventilation may diminish Vmean and lead to syncope and drowning.
There were 13 male volunteers who were lowered into a 0 degrees C immersion tank for 30 s. Vmean in the middle cerebral artery (MCA) was measured together with ventilatory parameters and heart rate before, during, and after immersion.
Within seconds after immersion in ice water, heart rate increased from 74 +/- 16 to 107 +/- 18 bpm (mean +/- SD; p < 0.05). Immersion was associated with a marked elevation in respiratory rate (from 16 +/- 3 to 38 +/- 14 breaths x min(-1)) and tidal volume (883 +/- 360 to 2292 +/- 689 ml). The end-tidal carbon dioxide tension decreased from 38 +/- 4 to 26 +/- 5 mmHg and MCA Vmean dropped by 43 +/- 8%. Signs of imminent syncope (drowsiness, blurred vision, loss of responsiveness) were shown by two subjects (MCA Vmean dropped 62% and 68%, respectively).
Following ice-water immersion, hyperventilation induced a marked reduction in MCA Vmean to a level which has been associated with disorientation and loss of consciousness.
意外浸入开放水域后的近乎溺水事件和溺水死亡与冷休克反应有关。它包括在冷水浸入的最初2 - 3分钟内出现吸气性喘息、通气过度、心动过速和高血压。由于冷休克引起的通气过度可能会降低平均脑血流速度（Vmean）并导致晕厥和溺水，本研究探讨了冷水浸入过程中脑血流速度的即时变化。
13名男性志愿者被放入0摄氏度的浸浴槽中30秒。在浸入前、浸入期间和浸入后，测量大脑中动脉（MCA）的Vmean以及通气参数和心率。
浸入冰水后数秒内，心率从74±16次/分钟增加到107±18次/分钟（平均值±标准差；p<0.05）。浸入与呼吸频率（从16±3次/分钟增加到38±14次/分钟）和潮气量（从883±360毫升增加到2292±689毫升）的显著升高有关。呼气末二氧化碳分压从38±4毫米汞柱降至26±5毫米汞柱，MCA的Vmean下降了43±8%。两名受试者出现了即将晕厥的迹象（嗜睡、视力模糊、反应丧失）（MCA的Vmean分别下降了62%和68%）。
冰水浸入后，通气过度导致MCA的Vmean显著降低至与定向障碍和意识丧失相关的水平。
