1/THREAD
Ever wonder how someone could survive a lightning strike?
Let's learn how such an incredible feat is possible.
#medtwitter #tweetorial
Ever wonder how someone could survive a lightning strike?
Let's learn how such an incredible feat is possible.
#medtwitter #tweetorial
2/
Human religions and cultures have contemplated lightning for thousands of years, often assigning it divine significance.
Islam, Judaism, Hinduism, and Shinto have all addressed lightning in their liturgies; ancient mythologies from Greek gods to Mesoamerican and Chinese folklore have grappled with this natural event.
discovermagazine.com
Human religions and cultures have contemplated lightning for thousands of years, often assigning it divine significance.
Islam, Judaism, Hinduism, and Shinto have all addressed lightning in their liturgies; ancient mythologies from Greek gods to Mesoamerican and Chinese folklore have grappled with this natural event.
discovermagazine.com
3/
To understand the physics of lightning strikes, let's review a few basic terms and concepts.
Current (I) = amount of electricity flowing per second through a resistance circuit, measured in amperes or milliamperes (1 mA = 1/1000 of an ampere).
Voltage (V) = force pushing current to flow.
pubmed.ncbi.nlm.nih.gov
To understand the physics of lightning strikes, let's review a few basic terms and concepts.
Current (I) = amount of electricity flowing per second through a resistance circuit, measured in amperes or milliamperes (1 mA = 1/1000 of an ampere).
Voltage (V) = force pushing current to flow.
pubmed.ncbi.nlm.nih.gov
4/ (basic terms con't)
Resistor (R) = anything that restricts electric current flow
Insulator = substance with high resistance that does not conduct electricity well
pubmed.ncbi.nlm.nih.gov
Resistor (R) = anything that restricts electric current flow
Insulator = substance with high resistance that does not conduct electricity well
pubmed.ncbi.nlm.nih.gov
5/
Another key - if self-evident - concept to understand is that the amount of current flowing through the body after an electric shock determines its physical effects.
⚡️1 mA = barely felt
❤️🔥100 mA can lead to ventricular fibrillation
pubmed.ncbi.nlm.nih.gov
Another key - if self-evident - concept to understand is that the amount of current flowing through the body after an electric shock determines its physical effects.
⚡️1 mA = barely felt
❤️🔥100 mA can lead to ventricular fibrillation
pubmed.ncbi.nlm.nih.gov
6/
Lightning results from electrical charge differences within thunderclouds and between the cloud and the ground.
A typical lightning bolt carries a tremendous amount of electricity: up to 200 million mA.
britannica.com
Lightning results from electrical charge differences within thunderclouds and between the cloud and the ground.
A typical lightning bolt carries a tremendous amount of electricity: up to 200 million mA.
britannica.com
7/
Recall from tweet #4 that electrocution with only 20 mA of current can paralyze the respiratory musculature and be fatal, and 100 mA can cause ventricular fibrillation.
A lightning bolt can contain up to 10 MILLION times that much current.
So you might reasonably assume that lightning strikes are universally fatal...
Recall from tweet #4 that electrocution with only 20 mA of current can paralyze the respiratory musculature and be fatal, and 100 mA can cause ventricular fibrillation.
A lightning bolt can contain up to 10 MILLION times that much current.
So you might reasonably assume that lightning strikes are universally fatal...
8/
But they're not.
In fact, most lightning strikes are survived, with 'only' a 10-30% overall mortality (though up to ~75% of survivors are left w/ permanent sequelae).
How is it that most people struck by lightning manage to survive?
cdc.gov
But they're not.
In fact, most lightning strikes are survived, with 'only' a 10-30% overall mortality (though up to ~75% of survivors are left w/ permanent sequelae).
How is it that most people struck by lightning manage to survive?
cdc.gov
9/
A key clue actually relates to the clinical images from tweet #1, with the characteristic branching rash that can arise after lightning strikes, called Lichtenberg figures.
Here is another example, from a case where a man was struck by lightning outside his truck.
ncbi.nlm.nih.gov
A key clue actually relates to the clinical images from tweet #1, with the characteristic branching rash that can arise after lightning strikes, called Lichtenberg figures.
Here is another example, from a case where a man was struck by lightning outside his truck.
ncbi.nlm.nih.gov
10/
Lichtenberg figures represent the branching path of electrical charge through a material, anything from skin to wood to dust.
They're named for Georg Lichtenberg, an 18th century German physicist who discovered this physical property.
Lichtenberg figures represent the branching path of electrical charge through a material, anything from skin to wood to dust.
They're named for Georg Lichtenberg, an 18th century German physicist who discovered this physical property.
11/
More than just dramatic evidence of a person's electricity exposure, Lichtenberg figures actually reflect the reason that most people survive lightning strikes...
More than just dramatic evidence of a person's electricity exposure, Lichtenberg figures actually reflect the reason that most people survive lightning strikes...
12/
Due to its thick outer stratum corneum layer, the skin is an effective insulator and comprises >99% of the body's total electrical resistance.
So most of the lightning's current just flashes over the skin, rather than traveling through and damaging internal structures.
pubmed.ncbi.nlm.nih.gov
Due to its thick outer stratum corneum layer, the skin is an effective insulator and comprises >99% of the body's total electrical resistance.
So most of the lightning's current just flashes over the skin, rather than traveling through and damaging internal structures.
pubmed.ncbi.nlm.nih.gov
13/
One final caveat:
Water immersion or skin disruption bypasses the skin's electrical resistance and therefore degrades its ability to insulate.
This greatly increasing the chances that a lightning strike will be fatal.
pubmed.ncbi.nlm.nih.gov
One final caveat:
Water immersion or skin disruption bypasses the skin's electrical resistance and therefore degrades its ability to insulate.
This greatly increasing the chances that a lightning strike will be fatal.
pubmed.ncbi.nlm.nih.gov
14/SUMMARY
🌩️Lightning strikes have significant morbidity but 'only' a 10-30% mortality rate
🌩️The skin has high electrical resistance and acts as an insulator
🌩️This insulation helps prevent internal injury and leads to a characteristic Lichtenberg figure
rash
🌩️Lightning strikes have significant morbidity but 'only' a 10-30% mortality rate
🌩️The skin has high electrical resistance and acts as an insulator
🌩️This insulation helps prevent internal injury and leads to a characteristic Lichtenberg figure
rash
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