Suffocation - Quickly

Asphyxia is a condition in which the body lacks oxygen, which is necessary for life, for some reason. When this causes death, it is called death by asphyxia. Asphyxia is written in English as asphyxia, and its origin is from the Greek aphtha and sphyzo, which means to palpitate. Asphyxia is caused by ventilation-related disorders in pulmonary (external) breathing, or blood flow-related disorders in tissue (internal) breathing, but in legal medicine, it refers to ventilation failure (pulmonary respiratory disorder) caused by mechanical obstruction of air breathing (external pressure on the nose and mouth, neck, or thorax, obstruction or narrowing of the airway due to impaction of a foreign body or liquid). Hanging or strangulation, which is a case where pressure is applied to the neck from the outside, is a well-known form of asphyxiation in society, and hanging in particular accounts for the majority of recent suicides. Drowning, airway obstruction or narrowing due to a foreign object (such as mochi rice cakes, dentures, or toys), being trapped in an airtight container such as a refrigerator, sudden death while playing with paint thinner using a plastic bag, sudden worsening of bronchopneumonia or asthma, or clinical respiratory failure due to a tumor around the airway are also examples of asphyxiation. These types of asphyxiation are accompanied by hypoxemia and hypercapnia, and the interaction between these causes labored breathing (dyspnea) in the early stages, followed by convulsions, and then a state of asphyxiation leading to irreversible breathing cessation. The heart continues to beat for about 15 minutes after breathing stops. The risk values ​​for arterial blood oxygen and carbon dioxide (carbon dioxide) partial pressures that result in death are approximately 25 and 80 (normally, in healthy adults, the arterial blood oxygen partial pressure is around 95 and the carbon dioxide partial pressure is around 37), and resuscitation is possible if the risk values ​​(before the asphyxiation stage) are reached. Organ-specific responses to asphyxiation at the tissue level are seen, with the brain experiencing a faster decline in oxygen availability and a shift to anaerobic metabolic processes than other organs. In acute asphyxiation (time to death within 15 minutes) such as by hanging or airway obstruction, the pathophysiological process of asphyxiation is prominent, but in chronic or protracted asphyxiation, where asphyxiation occurs gradually, the pathophysiological process of asphyxiation slows down as the body adapts. In asphyxiated bodies, dark red fluid blood, congestion in the internal organs (especially the lungs), and tiny bleeding points (hematochezia) under the mucous membrane and serosal membrane are seen.

[Akiko Sawaguchi]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

生命の維持に必要な酸素が、なんらかの原因で生体に欠乏する状態をいい、この結果、死亡すると窒息死とよぶ。英語でasphyxiaと書き、その語源はギリシア語の欠性辞aと、動悸(どうき)を打つの意のsphyzoからなる。窒息は肺（外）呼吸の換気側障害、または組織（内）呼吸の血流側障害に起因するが、法医学的には、空気呼吸の機械的阻害（鼻口部や頸(けい)部、または胸郭の外部からの圧迫、異物嵌入(かんにゅう)や液体浸入による気道の閉塞(へいそく)・狭窄(きょうさく)など）に基づく換気不全（肺呼吸障害）をいう。いわゆる「首をつって、あるいは絞められて」といった、外部からの圧迫が頸部に加わった縊首(いしゅ)や絞首は社会的によく知られた窒息であり、とくに縊首は最近の自殺の過半数を占める。溺死(できし)、異物（餅(もち)、義歯、玩具(がんぐ)など）による気道閉塞・狭窄、冷蔵庫などの密閉器内閉じ込め、ビニル袋を用いたシンナー遊び中の急死も窒息であり、気管支肺炎や喘息(ぜんそく)の急激な悪化、あるいは気道周囲の腫瘍(しゅよう)による臨床的な呼吸不全も窒息に相当する。これらの窒息は、低酸素血症、高炭酸ガス血症を合併し、その相互作用で、初期には努力性呼吸（呼吸困難）、ついでけいれんを発現して、その後、仮死状態から不可逆性に呼吸が停止する。心臓は呼吸停止後も15分前後拍動する。死の転帰をとる動脈血酸素と炭酸ガス（二酸化炭素）分圧の危険値は約25と80（通常、健康成人では動脈血酸素分圧95前後、炭酸ガス分圧37前後）であり、この危険値前（仮死期前）ならば蘇生(そせい)が可能である。組織レベルでの窒息の応答には、臓器による特異性がみられ、脳は他臓器よりも酸素利用能の低下、嫌気的代謝過程への移行が速い。絞首や気道閉塞などの急性窒息（致死時間15分以内）では窒息の病態生理学的経過が顕著であるが、徐々に窒息に陥る慢性ないし遷延性窒息では、生体の順応で窒息の病態生理学的経過は緩行する。窒息死体では暗赤色流動性血液、内臓（とくに肺）のうっ血、粘・漿(しょう)膜下の微小出血点（溢血(いっけつ)点）をみる。

［澤口彰子］

出典　小学館　日本大百科全書(ニッポニカ)日本大百科全書(ニッポニカ)について　情報 | 凡例