How do ventilators work? - Alex Gendler

翻译人员: Lipeng Chen 校对人员: Yolanda Zhang

In the 16th century, Flemish physician Andreas Vesalius

十六世纪，弗拉芒医生 安德烈 · 维萨里（Andreas Vesalius）

described how a suffocating animal could be kept alive

描述了通过将管子插入气管 并向肺部吹入空气，

by inserting a tube into its trachea and blowing air to inflate its lungs.

让窒息的动物活下来的方法。

In 1555, this procedure didn’t warrant much acclaim.

在 1555 年，这种方式 并未得到多少认可。

But today, Vesalius’s treatise is recognized

但如今，维萨里的论述被认为是

as the first description of mechanical ventilation—

首次对于机械呼吸机的描述——

a crucial practice in modern medicine.

这是当代医学中一项重要的治疗手段。

To appreciate the value of ventilation,

要理解呼吸机的价值，

we need to understand how the respiratory system works.

我们需要了解呼吸系统是如何运作的。

We breathe by contracting our diaphragms, which expands our chest cavities.

我们通过收缩横膈膜来扩张胸腔呼吸。

This allows air to be drawn in, inflating the alveoli—

于是空气被吸进来，充满肺泡——

millions of small sacs inside our lungs.

肺泡是我们肺部成千上万的小囊。

Each of these tiny balloons is surrounded by a mesh of blood-filled capillaries.

每个这样的小球都被 充满血液的网状毛细血管包围着。

This blood absorbs oxygen from the inflated alveoli

血液从充气的肺泡中吸收氧气，

and leaves behind carbon dioxide.

并释放二氧化碳。

When the diaphragm is relaxed,

当横膈膜放松时，

the CO2 is exhaled alongside a mix of oxygen and other gases.

二氧化碳同氧气以及其他气体 一同被呼出体外。

When our respiratory systems are working correctly,

当我们的呼吸系统正常运作时，

this process happens automatically.

这一过程会自动发生，

But the respiratory system can be interrupted by a variety of conditions.

但是该过程也会因多种因素中断。

Sleep apnea stops diaphragm muscles from contracting.

睡眠窒息症会让横膈膜肌肉停止收缩。

Asthma can lead to inflamed airways which obstruct oxygen.

哮喘会导致气道发炎， 进而阻碍氧气的流通。

And pneumonia, often triggered by bacterial or viral infections,

肺炎——常常由细菌 或病毒感染引发——

attacks the alveoli themselves.

会攻击肺泡本身。

Invading pathogens kill lung cells,

外来病原体会杀死肺细胞，

triggering an immune response that can cause lethal inflammation

引发免疫反应，可能会导致致命的炎症

and fluid buildup.

和肺部积液。

All these situations render the lungs unable to function normally.

所有这些情况 都会让肺部无法正常运作。

But mechanical ventilators take over the process,

但是机械呼吸机替代了这一过程，

getting oxygen into the body when the respiratory system cannot.

在呼吸系统无法正常工作时 让氧气进入身体。

These machines can bypass constricted airways,

呼吸机可以绕过受阻的气道，

and deliver highly oxygenated air to help damaged lungs diffuse more oxygen.

传递富氧空气来帮助 受损的肺扩散更多氧气。

There are two main ways ventilators can work—

呼吸机有两种主要的工作方式——

pumping air into the patient’s lungs through positive pressure ventilation,

通过正压式呼吸 将空气冲入病人肺部，

or allowing air to be passively drawn in through negative pressure ventilation.

或通过负压式呼吸让空气被动吸入。

In the late 19th century,

十九世纪晚期的呼吸机技术

ventilation techniques largely focused on negative pressure,

主要为负压式呼吸，

which closely approximates natural breathing

这一过程模拟了自然呼吸，

and provides an even distribution of air in the lungs.

并保证了肺部均匀的空气分布。

To achieve this, doctors created a tight seal around the patient’s body,

为了实现这一目标，医生会 在病人身体周围构造密闭空间，

either by enclosing them in a wooden box or a specially sealed room.

比如将病人放在木盒 或特殊的密闭房间内。

Air was then pumped out of the chamber,

然后，空气从密室中被吸出，

decreasing air pressure, and allowing the patient’s chest cavity

降低气压，使得病人的胸腔

to expand more easily.

能更容易扩张。

In 1928, doctors developed a portable, metal device

在 1928 年，医生发明了 一种便携式金属装置，

with pumps powered by an electric motor.

气泵由电动机供能。

This machine, known as the iron lung,

这一装置，也就是俗称的“铁肺”，

became a fixture in hospitals through the mid-20th century.

成为了二十世纪中期 医院中的常备装置。

However, even the most compact negative pressure designs

但是，即使是最小巧的负压式呼吸机

heavily restricted a patient’s movement

也会大大限制病人的移动，

and obstructed access for caregivers.

妨碍看护人员的工作。

This led hospitals in the 1960’s to shift towards positive pressure ventilation.

这使得医院在六十年代 转而开始使用正压式呼吸机。

For milder cases, this can be done non-invasively.

对于较轻的病症，正压式呼吸 可以通过非侵入的方式实现。

Often, a facemask is fitted over the mouth and nose,

通常用面罩覆盖口鼻，

and filled with pressurized air which moves into the patient’s airway.

并将加压空气注入病人的气道。

But more severe circumstances

但对于更加严重的状况，

require a device that takes over the entire breathing process.

则需要能够接管整个呼吸过程的装备。

A tube is inserted into the patient’s trachea

一根管子会被插入病人的气管，

to pump air directly into the lungs,

向肺部直接打入空气，

with a series of valves and branching pipes

并通过一系列的气阀和支管

forming a circuit for inhalation and exhalation.

形成吸气和呼气的回路。

In most modern ventilators,

在最现代的呼吸机中，

an embedded computer system

内嵌的电脑系统

allows for monitoring the patient’s breathing and adjusting the airflow.

可以监控病人的呼吸，并调整气流。

These machines aren’t used as a standard treatment,

这些机器并不是常规治疗手段，

but rather, as a last resort.

而是最后的救命稻草。

Enduring this influx of pressurized air requires heavy sedation,

忍受加压空气的流入 需要大剂量的镇定剂，

and repeated ventilation can cause long-term lung damage.

而且重复的换气可能会导致 长期的肺部损伤。

But in extreme situations,

但在极端情况下，

ventilators can be the difference between life and death.

呼吸机就是生与死的差别。

And events like the COVID-19 pandemic

譬如新冠肺炎大流行的情况

have shown that they’re even more essential than we thought.

就证明了它们比我们想象的更重要。

Because current models are bulky, expensive,

因为现有的呼吸机模型笨重且昂贵，

and require extensive training to operate, most hospitals only have a few in supply.

还需要大量的训练才能安全操作， 大部分医院只配备了少量几台呼吸机。

This may be enough under normal circumstances,

这在一般情况下可能够用了，

but during emergencies, this limited cache is stretched thin.

但在紧急情况下， 这样的配置就捉襟见肘了。

The world urgently needs more low-cost and portable ventilators,

世界亟需更多廉价的便携式呼吸机，

as well as a faster means of producing and distributing

以及能够更快速的生产和分配

this life-saving technology.

这种救命技术的手段。