First Aid: Why People Die

I’ve had the opportunity to talk with a variety of medics, both in the military and civilian world. From EMTs, paramedics, ER doctors, special operators, fire fighters and first responders, and sometimes I ask why they chose their profession.

Some are in the medical field because they fell into it. But often, the answer I get for why they do such a difficult job is because at some point in their life, they witnessed a life-threatening injury and didn’t know what to do about it.

That feeling of helplessness while they watched someone, maybe someone they loved, struggle to stay alive drove them to pursue their profession. They wanted, badly, to help, but didn’t know where to begin.

They saw paramedics or firefighters sweep onto the scene and handle the emergency with a calm and confident demeanor, and each of them wanted to be able to do the same.

The thought of a medical emergency is something most people find daunting, and overwhelming, and for good reasons that aren’t hard to understand.

Fortunately, however, keeping someone alive isn’t as difficult as you may think. Yes, trauma doctors and nurses go to school for many years to learn their trade. But stabilizing a casualty until they can be transported to these professionals is surprisingly simple.

Why People Die

I’ve found I learn a new skill more efficiently when I understand the most basic theories behind it. Learning how to do a thing less difficult when you know why you’re doing it and what’s being accomplished.

Basic first aid is remarkably easy and only complicated by the fear and uncertainty associated with the emergency. We can dispel a large portion of the panic and instill a confidence in our abilities when we learn this one major rule.

Death primarily occurs because of a lack of oxygen.

Basic Human Anatomy

  1. When we breath in, oxygen enters our lungs and is transferred to our blood, oxygenating it.
  2. The heart then pumps the blood through the arteries around the body to all the tissues and vital organs which is called “perfusion,” and allows them to stay alive. This oxygenated blood is bright red in color.
  3. The blood deposits oxygen to the tissues and picks up CO2 (Carbon Dioxide), returns to the heart where it is transferred to the lungs and the CO2 is expelled on expiration. The CO2 rich blood is dark red or dark purple in color.

Why O2 is Important

The cells in your body require a steady flow of oxygen in order to stay alive. If there is any interruption in the transportation of oxygen to the cells, death follows soon after.

 If the injured party is maintaining a steady flow of oxygen, they will remain stable. A breakdown in any of the systems that bring in and distribute O2 throughout the body leads to death.

  • The Brain

Starting at the top and working our way down, if there is a significant head injury, the brain is no longer sending signals for the vital organs, like the heart, lungs, and blood vessels to maintain adequate levels of oxygen.

  • Airway

Since people use their mouth, nose and lungs to take in oxygen, anything like trauma, burns, or allergies that restrict the airway leads to insufficient O2 and death.

  • The Circulatory System

This includes all your veins, arteries, and blood which picks up oxygen from the lungs and transports it around the body. Not enough blood in your body means not enough O2 is being delivered. Shock causes the vessels to relax and expand (dilate) all at once and blood pressure drops to the point where oxygen is not delivered quickly enough to keep cells alive. Like a garden hose that suddenly expands into a fire hose, and the jet of water becomes only a trickle.

  • Heart

If the heart isn’t working well enough to move oxygenated blood around the body, cells die. When someone dies from a heart attack, the heart attack itself didn’t kill them, the lack of O2 did because the heart isn’t moving blood. One of the more well known injuries relating to combat trauma is the “sucking chest wound,” or, tension pneumothorax.

Most people think that the reason a sucking chest wound is dangerous is because the lungs are compromised. While this is a contributing factor, the real reason for its danger is the increased pressure inside the chest cavity that builds to the point where the heart is compressed and is unable to move large enough quantities of blood to keep the casualty alive.


Now that we know the primary danger to a person with a life-threatening injury, all we need to do is monitor the body systems responsible for delivering the oxygen needed to stay alive.

Combat medics, and now civilian medics, use the M.A.R.C.H algorithm to help them remember which body systems to focus on first.

M – Major Bleeding

This is first on the list because it’s the most dangerous and easiest to prevent. Since we know that blood carries oxygen around the body, we need to make sure they don’t have an injury reducing the amount of available blood.

This is why direct pressure on any life-threatening bleeding is the top priority. You may not be able to completely stop to flow of blood, but hopefully you can reduce it long enough for someone to bring you a tourniquet, and keep as much blood in the body as possible, to get the oxygen where it needs to go.

A – Airway

Without a clear airway, the blood is not being oxygenated.

R – Respiration

The lungs are the mechanism in which a person collects O2 and if the casualty is unable to take good quality and regular breaths, they will expire. The medic or first responder needs to ensure their casualty is breathing well to ensure stability.

C – Circulation

This step is a careful sweep of the casualty to make sure no major bleeds have been missed since keeping blood in the body is the easiest and most preventable way to stabilize the casualty’s supply of life-giving oxygen.

H – Head Injury/Hypothermia

In combat, head injuries are last because there isn’t much you are going to be able to do to assist the casualty in a battlefield environment. With multiple casualties, those with devastating wounds such as head trauma are skipped and resources are dedicated to those casualties who have a better chance for survival. When time and resources allow, those skipped, or “triaged” casualties are reassessed.

Head injuries and especially spinal cord injuries to vital nerve bundles can trigger a sudden relaxing (dilation) of blood vessels. Blood stops moving around the body and the casualty dies from a lack of O2 even though all other body systems are working just fine.

Hypothermia is the primary concern here. Low body temperature can set in after a significant loss of blood and can also reduce the bloods ability to clot, making it more likely they will die from a lack of blood, and thereby a lack of O2.

As you can see each one of the steps of the MARCH algorithm is really just a focus on maintaining a steady flow of oxygen to the most important body tissues.

With this information at our disposal, the first responder will be better equipped to make use of one of the most important keys to survival: thinking outside the box.

Medics are trained to make the most of the very limited resources they have available, and great pride is taken in being able to effectively improvise and develop creative solutions to complex problems.

We can do this better by understanding that the reason why trauma is so dangerous is because of the casualty’s decreased ability to provide adequate oxygen to their tissues.


  1. Daryl Salley on April 8, 2020 at 3:25 pm

    I am a natural Prepper and have always had an interest in learning First Aid. I have taken a a course through our local EMT service and was certified but felt it was geared mostly to industrial, and office medical emergencies. Online courses like yours are so valuable to those of us who want to be prepared. I’ve learned far more online about things like gunshot trauma, and outdoor medical emergencies than through certification classes. Thank you very much for this info. It’s the first time anyone has explained the concept of oxygenation and why it is so important. Looking forward to your next lesson.

    • Brian McLaughlin on April 9, 2020 at 3:57 pm

      Thanks Daryl! I appreciate the feedback. Glad I could pass along helpful information. In case you haven’t already, check out our training video series which goes into more depth about emergency trauma medicine.

      Brian McLaughlin

Leave a Comment