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Doctor Answers Lung Questions From Twitter

Pulmonologist Dr. Ravi Kalhan answers the internet's burning questions about our lungs. What happens to your lungs if you vape? How do our lungs know the difference between oxygen and carbon dioxide? How much snot can your lungs hold? Does lung cancer only happen because of smoking? Dr. Kalhan answers all these questions and much more! Director: Lisandro Perez-Rey Director of Photography: Francis Bernal Editor: Louville Moore Expert: Dr. Ravi Kalhan Line Producer: Joseph Buscemi Associate Producers: Paul Gulyas; Brandon White Casting Producer: Nick Sawyer Camera Operator: Eric Brouse Audio: Sean Paulsen Production Assistant: Ryan Coppola Post Production Supervisor: Alexa Deutsch Post Production Coordinator: Ian Bryant Supervising Editor: Doug Larsen Additional Editor: Paul Tael Assistant Editor: Justin Symonds

Released on 05/23/2023


I'm pulmonologist Dr. Ravi Kalhan.

Let's answer some questions from Twitter.

This is Lung Support.

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@jwaizen asks, If you vape, what your lungs look like.


Normally a lung looks like this.

There's a black, which is air

inside the lung, and it looks really clear.

So if you vape

and you are unlucky and get vaping-associated lung injury,

inflammation happens and the air sacs fill up with stuff.

So this white stuff

in this X-ray really is the injury caused by vaping.

So this means there's fluid inside the air sacs.

You can't move oxygen and carbon dioxide through fluid.

They're gases.

It makes it hard to breathe

because the air can't move in and out of your lungs

and exchange the oxygen for carbon dioxide.

@gvybi asks, How do lungs know

what's oxygen and what's carbon dioxide?

So the lungs don't know what's oxygen and carbon dioxide.

The air comes in through the windpipe,

gets spread out throughout the lung in a bunch of air sacs.

Each air sac has a blood vessel going by it,

so the gas moves from inside the air sacs in the lung

into the blood where it attaches to hemoglobin

that's job is to carry oxygen.

It's really avid for oxygen.

And then the carbon dioxide, which is higher

in the blood than it is

in the air that's inside the lung, diffuses out.

@haris_a1 asks, Can lungs be transplanted?

They sure can.

Lung transplants are done mostly for chronic lung diseases

like pulmonary fibrosis, cystic fibrosis,

or COPD, chronic obstructive pulmonary disease.

To get a lung transplant, you have to go on a bypass machine

and then they actually remove a lung,

cutting off the windpipe and reattaching the windpipe,

and put in a new set of lungs.

But you've gotta be pretty, pretty, pretty sick

to get a lung transplant.

@NeimanMarcusEsq asks, I wonder what bad lungs sound like?

I'm in the doctor's office with good sounding lungs

so I wanna know how bad lungs sound.

When you go to the doctor, they put on their stethoscope

and they, you know, very doctorly, start listening

in the back, side to side, bottom.

When we say lungs sound good,

that means we can hear air moving in and out of the lungs

without making any extra noises.

One of the most common things we hear is wheezing.

It sounds like this.

[muffled wheezing]

That whistling noise

on the way out means that there's resistance

to air moving through the windpipes.

We hear this sound, wheezing, pretty commonly with asthma,

sometimes with COPD.

Because of narrowing of the windpipes, people can wheeze.

Another thing we listen for is crackles.

They sound like this.


Crackles occur when there's stuff in the air sacs.

So if there's fluid

in the air sacs, that creates a crackling noise

when it inflates.

That can be created by heart failure,

blood backing up into the lungs

from the heart 'cause the heart isn't pumping well.

It can be created by pneumonia

when fluid fills up areas of the lung,

and those are usually what we call fine crackles.

There also can be something called coarse crackles.

[coarse crackling]

Coarse crackles occur when there's pulmonary fibrosis,

or scarring in the lungs.

@yoseiyume asks, Honestly WTF is COPD?

Like what.

C O P D is the most common lung disease.

It occurs mostly in smokers

and it sometimes gets called emphysema.

The lung is normally rubbery and elastic.

It's like made up of tons of balloons,

and if you take a balloon and you blow air into it...

[balloon hissing]

And when you take the air and let go, so air fills the lung,

it comes out super easily and fast.

With emphysema, the lung loses its elasticity,

so it gets like this grocery bag.

Air can go into it, and then someone has to breathe in again

'cause you gotta keep breathing, right?

So more air goes in and then it just stays there,

and then more air goes in and it just stays there.

Imagine taking a breath in and then taking another breath in

and then taking another breath in without air coming out

fully after each breath, and then getting up

and trying to like go up a flight of stairs.

It's pretty uncomfortable to move around

with air stuck in your lungs.

@artsetsufree asks, How much snot can your lungs hold?

The lung capacity, like the amount

of volume in someone's lungs, can be anywhere

from three to five liters.

Mucus is produced by the cells that line the windpipes.

If someone has allergies, right,

and they inhale a bunch of pollen,

their nose starts running and dripping

and their lungs can produce stuff and they start coughing,

and to protect against that reaction, it creates fluid

or a film along the lining of the lungs so that the exposure

to that stuff goes down.

@bless_bottle asks, Does anyone have studies

of #cannabis inhalation effect on the lungs?

Trying to gauge long-term damage,

how it compares to smoking cigarettes

and whether vaping really reduces risk.

It's been known for some time

that smoking marijuana causes less injury

to the lungs than smoking tobacco cigarettes.

People smoke fewer joints historically

than they do cigarettes in a day.

It's also true

that marijuana itself is what we call a bronchodilator,

so it relaxes the muscle in the windpipes and opens them up

a little bit so people temporarily can breathe easier

if they get cannabis in their lungs.

Now, the problem is vape juice

doesn't just have pure cannabis in it.

It has all sorts of other things

and you heat it up and it causes long-term problems

because all the other stuff gets in the lungs

and causes damage to the wind pipes and air sac.

@cattlegoth asks, I've been thinking about alveoli

too much lately.

I just want to know what they feel like.

Are they soft like roe

or is there firmness like a ripe berry?

I think maybe the best way to think

about the lung is like a sponge.

Not really firm like a raspberry.

So the lung has a main branch, that's this Y here,

and then it branches into millions of tiny branches.

At the end of each branch

is a tiny air sac called an alviolus.

Then the whole thing is surrounded

by like a Saran Wrap called the pleura.

which holds the whole thing together.

@jinxeptor asks, Why is cold air so hard on lungs?

Well, cold air triggers reactions in things, right?

It's hard on skin, it makes your eyes water.

You breathe in, cold air hits your windpipes,

can really irritate them.

In people with asthma, it can cause an asthma flare-up.

It can cause wheezing and real trouble breathing.

So what should people do about that?

Well, breathing through your nose is better than breathing

through your mouth.

When you breathe through your nose,

the air gets warmed up and humidified

before it goes into the lungs.

Or when it's really cold,

people, especially with asthma, but probably

everybody who gets sensitive to cold air,

should wear a scarf

or a mask or something that allows the air to get warmed

before they breathe in.

@emilycblz asks, How do I train my lungs to not asthma?

You can't really train your lungs to not have asthma.

You can avoid the things that trigger your asthma.

So if you're allergic to cats, get rid of your cat.

So when asthma's acting up, there's inflammation

inside the windpipes, and when there's inflammation

inside the windpipes, they get narrowed and filled up

with mucus and phlegm so air can't move in and out,

and then the muscles around the windpipe actually spasm

and squeeze the windpipe shut.

So the best way to deal

with asthma is to use an inhaled antiinflammatory medicine.

A lot of people have asthma.

10% to 15% of people in the United States have asthma.

Their inhaler may have a bronchodilator,

something called albuterol

or rescue medicine that opens up their windpipes.

Most people with asthma who have significant symptoms

should be on an antiinflammatory inhaler,

an inhaled corticosteroid which lowers the inflammation,

so they don't need this rescue bronchodilator.

@AlexanderMcCoy 4 asks, Is there any truth

to the urban legend that smokers do better than non-smokers

in high altitude rucks, because their lungs are used to it?

There is no truth to that.

Smokers do not do better at altitude.

In fact, lots do worse because they might have COPD

or other things that impair their oxygen in their lungs.

There's lower oxygen pressure at higher altitudes,

which means there's less oxygen available

to transfer to the lungs.

One of the adaptations that the body makes

after it's been at high altitude is to make more hemoglobin.

The oxygen-carrying capacity of the blood goes up.

Athletes sometimes train

at high altitude to improve their hemoglobin

so that they are capable of carrying more oxygen

when they are at sea level.

@yoyo_yelena asks, Curious, what does covid do to lungs?

Does it fill them with fluid?

The x-rays look horrible but I have no clue what they mean.

When covid was causing the pandemic

and people were dying everywhere, it caused pneumonia.

So this is what covid can look like in the lung.

This one has worse pneumonia on the left side

and not as bad on the right side.

This area right here, this white stuff,

it's filled up, socked in, we call it consolidation.

It has bacteria, immune cells, white blood cells,

things that are trying to fight an infection.

I betcha this person got really sick,

had a low blood oxygen level,

and was having a really hard time breathing.

Why some people with covid caught a runny nose

and other people got pneumonia and died, we don't know.

Some people are just more vulnerable,

like if you have diabetes, if you smoke cigarettes or vape,

you're probably more vulnerable to infections.

@watrcoolr asks, How does a pulse oximeter

measure the blood oxygen levels

without actually taking blood?

So this pulse oximeter you can wear

on your finger shoots infrared light from one side

and has a sensor on the other,

and you've gotta put it on a part of thin skin.

That's why we put it on our finger or our earlobe.

Hemoglobin, when it has oxygen attached

to it, has a certain configuration, and when it doesn't

have oxygen attached to it,

it has a different configuration.

That influences how much light gets absorbed.

And then the sensor in the pulse oximeter

can then calculate how much blood oxygen there is based

on that confirmation of hemoglobin.

A normal blood oxygen level is like 95% or higher.

It's dangerous if it's below 90%.

That's when I think we should really pay attention.

@ireojima asks, I'm sorry,

but how is mouth to mouth even real?

Like how am I not just exhaling carbon dioxide

into your lungs instantly killing you?

Scientists explain this.

So it's not mainly carbon dioxide.

What we breathe in, remember, is mostly nitrogen.

The atmosphere is mostly made up of nitrogen.

It's about 21% oxygen,

and then some small portion of carbon dioxide.

So when you breathe out there's a little more carbon dioxide

than what's in the air, but it's not 100% carbon dioxide.

It's still more like the air we breathe in

than anything else.

@paisleymoths asks, Like do lungs have muscles?

Can I train myself to be like able

to hold my breath longer than anyone?

The diaphragm is outside the lung.

It goes downward, the lung opens up.

So those muscles can be trained

and you can make those muscles stronger

and breathe more efficiently to some extent.

But the lungs themselves don't have muscles

that generate breathing.

One of the reasons people who train can hold

their breath longer is they're in better shape,

so all their muscles in their body demand less oxygen

and produce less carbon dioxide so their lungs

don't have to do as much work to keep those muscles fueled.

Sometimes people who have operations

or are in the hospital get a gadget

called an incentive spirometer where you're told

to breathe in and make these balls go up.

The reason for that is people who are lying

in bed don't breathe deeply, and then if that happens, areas

of the lung can end up without air in them

called atelectasis, and we wanna prevent that

'cause areas of the lung

without air in them are prone to developing pneumonia.

And one of the ways we prevent that is forcing people

to breathe deeply using one of these machines.

@bphesq asks, Which is worse for your lungs,

vaping or smoking?


Smoking we've known forever to be bad,

and vaping is newer and we don't know how bad,

but I'm a lung doctor so I think inhaling anything

but air is bad for your lungs.

The lungs can recover from some injuries.

The things that are caused by the environment

like smoking cigarettes causing COPD or emphysema

or pulmonary fibrosis, which is scarring in the lungs,

those things don't heal.

We have treatments that stop them from getting worse,

but we don't have a way to just fix it

and make it act like you were never exposed to that problem

and the lung never got damaged in the first place.

@iwasrightonce asks, Why TF do lungs

have an uneven number of lobes?

What's up with that?

Well, the reason is is that the left lung

has to make space for the heart

because the heart sits in the left side of the chest.

There are three lobes on the right, upper, middle, lower,

and two lobes on the left.

@deepak_rajgor asks, Does lung cancer happen

only because of smoking?

Lung cancer's most common cause is smoking,

but there are a lot

of people who don't smoke who get lung cancer.

There's one exposure that's well known to cause lung cancer,

and that's radon exposure.

Around the country, people's basements

can have a lot of radon,

and home tests are available to test for radon.

And radon is clearly associated

with lung cancer when it's present in someone's house.

A lot of young women seem to get lung cancer

who didn't smoke.

We have no idea why that is.

They get a type

of lung cancer that's often called an adenocarcinoma.

Maybe they had secondhand smoke exposure in the home,

maybe there's a genetic factor, but it's pretty scary

that non-smokers still get lung cancer

at a pretty significant rate.

@farazmunshi asks, How long before AI can label lung cancer

better than a certified radiologist?

The automated tools on CAT scans are coming soon

and will be really helpful.

One of the things where I think they'll be super helpful

are the things we can't see.

You know, a CAT scan's a picture

and it has various densities of images

and we can't see every density on a CAT scan,

but there might be parts

of the lung that are starting to have abnormalities

that we can't see visually that a machine could detect.

And in that sense, AI would be huge, right?

And figure out whether that person

needs some enhanced surveillance or things to keep an eye on

to see whether they get cancer.

@estoyArTo_ asks, How TF do lungs collapse?

Like do they just get tired or something?

They don't get tired.

Usually they get injured and it causes the lung to collapse

and causes what we call a pneumothorax.

Getting stabbed or shot or having something go

through the chest wall can puncture the lung.

So there's two sets of pleura.

There's a layer of Saran Wrap

that's holding all those alveoli together,

and then there's a layer against the chest wall,

and there's a space between the lungs and the ribcage.

If you pop the balloon, poke a hole in the Saran Wrap,

air can escape from inside the lung to outside of the lung.

That builds pressure and the lung can collapse.

It doesn't have enough pressure

inside the lung to stay open, so it deflates.

So those are all the questions for today.

Lots of good ones.

Thanks for watching Lung Support.

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