What to do when you get stuck in the subway

Avoid panic, reduce breathing rate, avoid excess body consumption

When trapped in a confined environment, avoiding panic is the first principle, and the second is to reduce all unnecessary physical activities

What to do when you get stuck in the subway

The heavy rains in Zhengzhou and other places in Henan that started on July 19 have attracted the attention of the people across the country. Especially, the heavy rains on July 20 caused people to be trapped in the subway, which is even more worrying. In the end, although most of the trapped people successfully escaped, 12 people were still killed.

When people encounter torrential rain disasters outdoors and urban and rural public areas, they need to pay attention to the knowledge of avoidance: 1. Look for stable high ground; 2. Avoid entering dangerous areas, such as river embankments, underground parts of buildings, subways, underground culverts, and underground passages , Old buildings, hillsides, under trees, near billboards, etc.; 3. Avoid using transportation; 4. Stay away from electric facilities; 5. Save electricity, ensure the ability to contact the outside world, and reduce communication consumption.

Of course, in the face of sudden disasters, in many cases people are often unable to move to a safe place in time, and it is easy to fall into a confined or relatively confined environment and encounter danger. Such as flooded buildings, power failure elevators, flooded subways, crossings, bridges and culverts.

In a narrow, confined or relatively confined space, the risk factors are very complex, and common ones include hypoxia, oxygen enrichment, toxic pollutants, leakage, high temperature, low temperature, and high humidity. It is very necessary for each of our citizens to master some knowledge of self-help prevention in such situations.

01  Hypoxia is graded, chest tightness, shortness of breath does not mean suffocation

Trapped in a confined or relatively confined space, the most important fatal factor is suffocation caused by hypoxia, and confined spaces caused by heavy rain have other special characteristics. Under normal circumstances, the space itself is in an atmospheric environment, but in a relatively closed space, due to poor ventilation, the oxygen concentration will slowly and continuously drop.

Decreased oxygen concentration is bound to cause hypoxia, but hypoxia is also graded, and it is not fatal as soon as hypoxia. In medicine, the arterial blood oxygen partial pressure is an important indicator to assess whether the human body has hypoxia and its degree. At sea level atmospheric pressure and in a quiet state, the normal value of the partial pressure of the arterial blood sample is 80-100mmHg (10.6-13.3kPa).

When the partial pressure of oxygen in arterial blood is lower than 60mmHg, it is medically defined as respiratory failure. At this time, the body is often in a state of deoxygenation. When the partial pressure of the arterial blood sample is 50-60mmHg, the central nervous system will produce a decrease in concentration, orientation, and intelligence. The respiratory system will produce symptoms of chest tightness, dyspnea, and increased respiratory rate. The circulation will cause increased heart rate and blood pressure. High performance, the digestive system will have symptoms of loss of appetite.

If the arterial blood oxygen partial pressure is lower than 50mmHg, that is, under severe hypoxia, the human body will experience changes in consciousness, such as lethargy, delirium, coma, and even induce malignant arrhythmia, leading to sudden death of the patient.

A general hypoxic state will only lead to weakened mental activity, prone to symptoms such as fatigue, dizziness, chest tightness, and shortness of breath. A short-term hypoxic state does not pose a fatal risk to healthy people.

When the human body feels slight chest tightness in a confined space, it does not necessarily mean that the body is in a severe hypoxia state, and it does not necessarily cause serious consequences. The trapped person does not need to be overly nervous. Moreover, the degree of hypoxia is related to the body’s compensatory capacity. If the body’s oxygen consumption can be reduced and the compensatory capacity can be improved, often important tissues and organs will not cause serious hypoxic damage.

Especially in such a closed environment caused by heavy rain, the rate of hypoxia damage will be slower. This type of environment is generally temporarily formed due to structural reasons. In many cases, it is not completely isolated from the atmospheric environment. With continuous oxygen supply, the rate of decrease of oxygen concentration will be slower than that of a truly confined space.

Hypoxia is indeed dangerous, but it should be understood that hypoxia is graded, and chest tightness and shortness of breath are not necessarily fatal. However, if the body’s oxygen consumption increases due to mental panic caused by mild hypoxia, it will further worsen the body’s hypoxia and exacerbate the damage caused by hypoxia.

02  Hypoxia is dangerous, but panic is more dangerous

In fact, in most cases, panic is a more dangerous factor than hypoxia in a confined space.

In a relatively confined space, the horror and emotional tension caused by the darkness, closure, and various oppressive environments of the trapped will stimulate the body’s sympathetic nerves, resulting in faster heart rate, faster metabolism, and increased body oxygen consumption. In a relatively oxygen-deficient environment, the body’s hypoxia state worsens, and symptoms such as dyspnea and suffocation further aggravate tension. In this state, a person may make a variety of uncomfortable escape actions due to panic, resulting in trauma and secondary infection.

At the same time, the overactive sympathetic nerves will act on the vascular smooth muscle of the whole body, causing the vascular smooth muscle to contract, releasing angiotensin to cause vasoconstriction and increasing blood pressure. Under stress, it will also increase the oxygen consumption of tissues and organs, cause stress secretion of endocrine function, induce immune system activation, and redistribute blood, body fluids and other fluid volumes under the action of the nerve-endocrine-immune regulatory network. The body balance of patients with underlying diseases is disrupted.

Disruption of the body balance of healthy people will further aggravate the symptoms of hypoxia, and if the trapped person has basic diseases, such as coronary heart disease, hypertension, bronchial asthma, chronic obstructive pulmonary disease, mental illness, etc., then the disruption of body balance will lead to The symptoms of the underlying disease are aggravated, and even lead to disturbances in the electrical activity of the heart, directly inducing arrhythmia and even sudden cardiac death.

03  Do not panic, do not move, do not Luanhan

Hypoxia and panic. To deal with these two main fatal factors in a confined space, people should try their best not to panic, move, and shout.

Being trapped in a confined or relatively confined environment, the most important thing is not to break down mentally. First of all, you should keep calm, properly adjust your breathing according to the environment, take a deep breath, reduce your breathing rate, relax your tension, carry out psychological construction, and avoid panic. Check the personal supplies, transfer the power bank (power supply), mobile phone (communication, lighting) and other help-seeking tools to the jacket pocket to ensure the ability to call for help.

Then observe the environment, avoid harmful substances, such as toxic substances, dust, harmful pollutants, sharp objects, etc., to assess the possibility of breaking through the space barriers. If there is difficulty in self-rescue, and it is difficult to quickly escape from a narrow space or a relatively closed environment, try to avoid dangerous areas that are not strong, and look for supports that can lean on or help share the weight of the body to save energy. After finding a temporarily safe place, you should reduce your activity, reduce oxygen consumption, reduce your body’s energy consumption, and save more calories to prevent your body from losing temperature.

If you shout at will, your oxygen consumption is huge and you will lose a lot of energy. Call for help, such as tool percussion, while conserving energy as much as possible and reducing energy consumption. If the communication is still valid, call, SMS, WeChat , Weibo , and release distress messages by all means.

In short, when trapped in a confined or relatively confined environment, avoiding panic is the first principle. Because if you fall into a panic, no matter how much self-help knowledge you learn, it will be useless. The second is to avoid excess body consumption. Reduce breathing rate and reduce all unnecessary physical activities . At this time, we need to actively “lie down.” To achieve the above two points, for ordinary people without any professional rescue knowledge and ability, it is the best plan to successfully support the arrival of rescue.

(The author, Guo Nan, is the head of the ICU district of Dongzhimen Hospital, Beijing University of Chinese Medicine, chief physician; editor: Yu Le)

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