For my non-med Tweeties

Let's talk about lungs

A story in GIFs

Many people think lungs are like two big balloons
To be fair they are often depicted that way

In truth, the lungs have lots of little 'air sacs' called alveoli where the action happens

AIr containing oxygen has to get from the mouth and nose to the alveoli

The gasses have to travel down a lot of tubes of decreasing size to get to the alveoli
The first is the trachea, windpipe, and then down bronchi and so on
The air passages look like an upside down tree

I like to use a London Underground analogy to explain some of this

Gasses like Oxygen are passengers
They move down tunnels to the platforms where they get on and off trains

The air passages are the Underground tunnels
The alveoli are the platforms

(stay with me)

The train tunnels are little blood vessels and the train carriages are red blood cells arriving to pick up the oxygen
(and let off the carbon dioxide but let us not get too confused)

There are a couple of thin walls the oxygen has to get across to get on the train

The wall of the alveolus (singular of alveoli)
And the wall of the blood vessel

Some airport trains have sets of glass doors on the platform to get through, as well as the doors of the train

In reality, there are no doors
The oxygen just squeezes across the walls moving from an area of lots of oxygen (the platform) to where there is less (the train)

Oxygen travels around the body on arterial trains, hoping off in the tissues where the platforms are emptier
(Carbon dioxide hops on in the tissues and travels back to the lungs to be breathed out - sorry, hate telling only half the story )

COVID can affect oxygen getting on the train in lots of ways

The alveoli can be flooded or blocked or collapse (can't get to the platforms)

The walls of the alveoli can be swollen and thickened and hard to traverse (doors won't open)

Blood clots can block the train tunnels and other parts of the system

(GIF may actually be deposits in the vessel wall but work with me here!)

Another big part of the problem on the train side is that the heart needs to pump to keep the blood flowing and the trains moving

COVID can affect the heart and slow the pump and hence slow the trains down

Hope that wasn't too confusing

When you hear:

Pulmonary oedema - the platforms are flooded

Fibrosis - tissues are stiff and thick, doors won't open, lungs can't expand and contract

Exudate -muck and debris in the air ways and alveoli making passages the platform difficult or impossible