Preface
Depending on who you are, this blog might seem inflammatory - this is not my intention or aim. I aim to highlight a common misconception about the association between talking and breathing. This blog is meant for anyone who may see a person with shortness of breath or who may restrain someone (martial arts, law enforcement, emergency medical services, hospital personnel, or anyone else). I am aware that some restraints that are used at times are what you would refer to as a "blood choke" - which does not intentionally involve limiting a person's ability to breathe. I am specifically speaking about the act of limiting someone's ability to breathe by restricting the chest and abdomen. Restricting the chest and abdomen may be done unintentionally by applying your body weight to someone, keeping a person prone (chest to the ground), or not allowing someone to sit in a tripod position (sitting or standing forwards with hands-on knees).
With this said, let's get started.
“Help! I can’t breathe!”
“Of course you can breathe - you’re talking!”
How true is that statement? At first, it might seem like a rather simple question to answer - but there is actually a lot to unpack on this subject. We’ll need to start at the basics of how we produce sound and then how we exchange gas with the atmosphere. I’m going to attempt to write this blog in a way that people who are not medical professionals can understand it as well.
Phonation
Let’s first cover some of the basics of phonation (the ability to produce sound with our vocal cords).
Our vocal cords require air to pass by them for them to produce sound. Without air passing by our vocal cords, we have no ability to speak or produce any sound. So, if you can produce noise from your throat (phonate), you’re moving air past your vocal cords. You can check out this video and see how the vocal cords must be vibrated by the air passing by them to produce sound.
So... vocal cords don't work unless air passes by them! Well... that should settle it! I hope you all enjoyed the blog.
Not exactly, right? Armed with only this knowledge about how our vocal cords produce sound would be very dangerous. Why? The answer really comes down to understanding how we exchange gasses with the atmosphere and very little about how we produce sound.
Exchanging Oxygen and Carbon Dioxide
We all learned at some point that we take in oxygen from the atmosphere when we breathe in and that we breathe off carbon dioxide when we exhale. Both sides of this process are important - we must bring in oxygen and expel carbon dioxide for our bodies to function normally. This function of interacting with our environment is called gas exchange or respiration, but we could also simply call it breathing. But how far must airflow in and out of us to make this happen? Let’s take a look at the anatomy.
Those tiny air sacs at the top right of the picture are called alveoli (al-vee-oh-lie). Alveoli are the gas-exchanging units of the lungs. In fact, they are the only parts of the lungs that allow us to take in oxygen and exhale carbon dioxide. This means that air must travel past the mouth, nose, throat, trachea, bronchi, bronchioles, and then finally into the alveoli to participate in gas exchange with our blood. Once the air gets down to the alveoli, gasses exchange with our body's blood in something called the AC membrane (alveolar/capillary membrane) (Saladin et al., 2015). Air moves in and out in this manner to keep oxygen and carbon dioxide levels in the very narrow range that our body requires for normal function (Kacmarek et al., 2017).
Did you pick up on the subtle point in that last paragraph? Many people miss a very important concept when they learn about how the air travels through the lungs. What is it?
Dead Space
DEAD SPACE - sounds scary, right? What does it mean? Put simply, dead space is any area of the airway that has air in it but does not exchange gas with the atmosphere. So, which parts of the airway meet this definition?
Test yourself: Which of the following parts of the airway can have air in them but won’t exchange gas?
Mouth?
Nose?
Throat?
Trachea?
Bronchi?
Bronchiole?
Alveoli?
If you’re paying attention, you’ll conclude that every part of the airway is dead space, except the alveoli. This puts a very interesting requirement on the body - it must physically move a certain volume of air in and out to maintain proper balances of oxygen and carbon dioxide. Why? Because the air must overcome the dead space to make it all the way to the alveoli for oxygen delivery and then all the way back out to the atmosphere to get rid of the carbon dioxide (Kacmarek et al., 2017). Although dead space is a normal and expected hurdle to gas exchange, it must be kept in its proper percent, which is usually ~25% of what we breathe (Marino, 2014). The volume that must overcome our dead space is called our tidal volume. Let’s explore what this new term means as well!
Tidal Volume
Tidal volume is basically a way of describing each breath. “Tidal” means that it comes and goes. Think of the tide of the ocean - it comes and goes just like the air in our airways. “Volume” means that we are measuring it. We normally measure our tidal volume in milliliters (mL). Therefore, “tidal volume” is the air that comes and goes (measured in milliliters). Still with me?
That tidal volume must be larger than our dead space to exchange any meaningful amount of oxygen/carbon dioxide with the atmosphere. Read that again and make sure you understand that point before moving forward. If you can understand that statement, you’re almost to the point of understanding this whole concept and getting the answer to the question: “Does talking equal breathing?”
Volumes
We’ve alluded to the size of the tidal volume and the dead space, but we haven’t defined how large each one should be. All we know right now is that the tidal volume must be larger than the dead space to properly exchange gas with the atmosphere. This part requires a little math (don’t worry - I’ll do the math for both of us).
Your tidal volume is dependent on your height and sex, and so is your dead space. It is all based on something called your ideal body weight (IBW). How do we figure that out? It’s in kilograms, so if you’re not used to those, I’ll convert into pounds as well.
At 5 feet tall, a male gets a baseline of 50kg (110 lbs).
At 5 feet tall, a female gets a baseline of 45.5 kg (100 lbs).
Then, for every inch over 5 feet tall, we add 2.3 kg (~5lbs).
Examples:
A 6-foot-tall male is 12 inches over 5 feet tall, so the formula would go like this:
(12 x 2.3) + 50 = 77.6 kg (~171 lbs).
A 5’ 6” female is 6 inches over 5 feet tall, so the formula would go like this:
(6 x 2.3) + 45.5 = 59.3 kg (~130 lbs)
Now that we have our ideal body weight, what do we do with it? First, let’s figure out how we get an average tidal volume from our ideal body weight, then we can figure out our dead space after that (Kacmarek et al, 2017).
We normally move tidal volumes (the size of your breath) at approximately 7ml / kg of ideal body weight. Let’s go back to our two example patients from above:
Examples:
A 6’ male was 77.6 kg, so multiplying by 7 gets us a tidal volume of 534.2 mL tidal volume.
A 5’6” female was 59.3 kg, so multiplying by 7 gets us a tidal volume of 415.1 mL of tidal volume.
What’s yours?
These, of course, are just averages. If we’re extremely relaxed, our tidal volume may go down a little, perhaps to 5 or 6 mL/kg of IBW. If we’re stressed, exercising, or have a high metabolic demand, our tidal volume may increase by a large degree - perhaps even doubling or tripling (Kacmarek et al, 2017).
Alright, now that we know how to find our average tidal volume, how do we figure out how much volume our dead space takes up? Remember, our tidal volume has to be larger than our dead space volume to move air effectively.
To find our dead space volume, we multiply our ideal body weight in kilograms by 2 (Chang, 2018). Let’s again use our two examples from above and see what we come up with.
Examples:
A 6’ male was 77.6 kg, so multiplying by 2 gives us a dead space volume of 155.2 mL of dead space volume.
A 5’6” female was 59.3 kg, so multiplying by 2 gives us a dead space volume of 118.6 mL of dead space volume.
Now that we have some volumes for dead space and tidal volume, we can do some comparisons.
Alveolar tidal volume
When our 6’ male from above inhales a tidal volume of 550 mL, how much actually makes it to his alveoli? Or how about our 5’6” female? All we have to do to figure that out is look at the tidal volume and subtract off our dead space.
Examples:
For the 6’ male, we would take the dead space of 150 mL off of the ~550 mL tidal volume to end up with 400 mL.
For the 5’6” female, we would take the dead space of 115 mL off of the tidal volume of ~415 mL to end up with 300 mL.
This ‘leftover’ volume that actually goes to the alveoli to exchange fresh air is called our alveolar tidal volume (because it’s the air that actually makes it to the alveoli to perform gas exchange) (Chang, 2018).
As long as our tidal volume exceeds our dead space volume, we move fresh air into the alveoli. But, what happens if our tidal volume is equal to, or barely larger than, our dead space volume?
This is where we really have to put all of these concepts together.
Putting it all together
Suppose my dead space is about 150 mL, but for some reason, I can’t take a deep breath in - perhaps I'm extremely exhausted, being crushed by someone, or even both. Maybe I’m moving 150-200 mL breaths at the most. At this volume of air movement, I can still phonate - I might even be able to let out some pretty loud noises. However, the air that is being used to pass by my vocal cords is not enough to maintain normal oxygen or carbon dioxide levels in my body. In fact, when our tidal volume becomes the same as our dead space volume, we are effectively suffocating even though we are moving air in and out of our lungs.
This is the same reason why we can’t have a super long snorkel. Snorkels are like adding dead space to our airways. If you tried to use a snorkel that had more dead space volume than you could overcome with your tidal volume, you would suffocate even though you were taking in very large breaths. Also, if we have a very large metabolic demand for some reason, just overcoming our dead space a little bit won’t do the trick - we need to maintain huge alveolar tidal volumes to feed our body oxygen and get rid of carbon dioxide. See the point? It’s all about adequately overcoming our dead space to get fresh air into our alveoli (Kacmarek et al, 2017).
This final illustration shows how we can simply be re-breathing our own stale air over and over again if our tidal volume is not larger than our dead space. Is air passing by the vocal cords? Yes. Can they speak? Yes. Are they oxygenating and ventilating? Absolutely not.
I hope this blog helped you to understand the relationship between gas exchange and phonation. Clearly, the ability to talk does not mean that someone is breathing (if by breathing you mean the essential act of getting fresh air into their alveoli).
If you understand these facts, you might avoid ever having to hear these words:
‘Your honor, my defendant says that they know for a fact the patient could breathe because the patient was talking.’
Peer Review:
Kristin Ireland, RRT, EMT
As a Respiratory Therapist, the above concepts are not just empirically true but scientifically proven. In the field of respiratory care, we see these concepts expressed through laboratory values and clinical settings where we see many people with shortness of breath. People may express that they can breathe, but demonstrate their inability to truly defeat dead space and oxygenate adequately enough to preserve life. While managing ventilators, we must take into account the increased amount of dead space, much like the snorkel comparison. I would like to add that the anatomy of the airways where the flow of tidal volumes takes place, decrease in diameter. Every section of the airway will become smaller and smaller as the air travels to the alveoli. Terminating the flow and exchanging oxygen and carbon dioxide in diameters as small as 0.5mm. To attempt to pull in a tidal volume through decreasing diameters requires a profound amount of energy that is is fueled by the oxygen we breathe in the first place. So, when we are not getting enough oxygen to those gas exchange units, but still expending energy to drive air movement, the result is pure exhaustion and failure to breathe. This is further exacerbated if someone has a decreased ability to expand their chest, due to reasons such as increased body mass index, fluid in the lungs, or someone putting their body weight on someone else.
References
Kacmarek, R., Stoller, J., Heuer, A., Chatburn, R. & Kallet, R. (2017). Egan's fundamentals of respiratory care. St. Louis, Missouri: Elsevier.
Chang, D. (2018). Respiratory care calculations. Middletown.
Marino, P. (2014). Marino's The ICU book. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins.
Saladin, K., Sullivan, S. & Gan, C. (2015). Anatomy & physiology: the unity of form and function. New York: McGraw-Hill Education.
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