Panic and the Hypercapnic Alarm Response

[lermontov]

She says in the video that it came off in her hand -it sounds like she pulled off the inflator/deflator valve.from the hose.

so it wouldn't have made her heavier per se just no air to counteract at depth or any overweighting (other than dry suit) good lesson

 

[TONY CHANEY]

". . .Under normobaric and hyperbaric conditions, the single factor that limits the ability to increase ventilation is the rate at which gas can be exhaled from the lungs. The ability to exhale gas is reduced during hyperbaric and diving conditions. As gas density increases, increased effort is required to exhale gas (i.e.,it takes more work to move a heavier gas). . ."

So Kevrombo, if that is true then I guess we should do away with hyperbaric chamber therapy. I mean, why should we put someone with the bends in a hyperbaric environment where increased work of breathing would be increased? Yes, we as RRT’s do recognize density of gases and often use heliOx for severe bronchoconstriction as in asthma patients. Since you posted that I am a Respiratory Therapist which I am proud of, what makes you such an expert?
In order to help you out, CO2 is off gased via the lungs and not the metabolic track. So it is not a metabolic Co2 retention or what ever you call it. Feel free to PM me if you want some help in understanding ABG’s, CO2, DKA, etc. I do it for a living and you talk about it behind a keyboard! Here is me dropping the mic!!!!

 

[Kevrumbo]

". . .Under normobaric and hyperbaric conditions, the single factor that limits the ability to increase ventilation is the rate at which gas can be exhaled from the lungs. The ability to exhale gas is reduced during hyperbaric and diving conditions. As gas density increases, increased effort is required to exhale gas (i.e.,it takes more work to move a heavier gas). . ."

So Kevrombo, if that is true then I guess we should do away with hyperbaric chamber therapy. I mean, why should we put someone with the bends in a hyperbaric environment where increased work of breathing would be increased? Yes, we as RRT’s do recognize density of gases and often use heliOx for severe bronchoconstriction as in asthma patients. Since you posted that I am a Respiratory Therapist which I am proud of, what makes you such an expert?
In order to help you out, CO2 is off gased via the lungs and not the metabolic track. So it is not a metabolic Co2 retention or what ever you call it. Feel free to PM me if you want some help in understanding ABG’s, CO2, DKA, etc. I do it for a living and you talk about it behind a keyboard! Here is me dropping the mic!!!!

NO !!! This is about dynamic physiological in-water pressure immersion effects on a working diver -->NOT dry chamber hyperbaric oxygen therapy on a resting patient. . . !

• ". . .when inspired and alveolar PO2s are high and there are large volumes of oxygen in the lung relative to metabolic needs . . .divers could ventilate a lot less than they do and still remain well oxygenated. However, from the moment ventilation falls below that required to maintain alveolar (and therefore arterial) PCO2 at the desired level, then the alveolar and arterial PCO2 will begin to rise. It does not require divers to actually stop breathing . . .a period of relative “hypoventilation” will still cause CO2 accumulation (just a bit more slowly). This is a problem because, as most technical divers know, arterial CO2 levels do not have to rise much for the adverse effects to begin. " https://www.diversalertnetwork.org/files/Tech_Proceedings_Feb2010.pdf , p.12 "Respiratory Issues in Technical Diving"

 

[TONY CHANEY]

You are aware that all gases are independent of the the other gases.

“Gas Laws and Air Composition
Gas molecules exert force on the surfaces with which they are in contact; this force is called pressure. In natural systems, gases are normally present as a mixture of different types of molecules. For example, the atmosphere consists of oxygen, nitrogen, carbon dioxide, and other gaseous molecules, and this gaseous mixture exerts a certain pressure referred to as atmospheric pressure (Table 2). Partial pressure (Px) is the pressure of a single type of gas in a mixture of gases. For example, in the atmosphere, oxygen exerts a partial pressure, and nitrogen exerts another partial pressure, independent of the partial pressure of oxygen (Figure 1). Total pressure is the sum of all the partial pressures of a gaseous mixture. Dalton’s law describes the behavior of nonreactive gases in a gaseous mixture and states that a specific gas type in a mixture exerts its own pressure; thus, the total pressure exerted by a mixture of gases is the sum of the partial pressures of the gases in the mixture.” Don’t believe me then try diving with 36% NITROX with about 20% CO.
Noticed that you stated everything pertaining to respiratory and not metabolic.

 

[Kevrumbo]

You are aware that all gases are independent of the the other gases.

“Gas Laws and Air Composition
Gas molecules exert force on the surfaces with which they are in contact; this force is called pressure. In natural systems, gases are normally present as a mixture of different types of molecules. For example, the atmosphere consists of oxygen, nitrogen, carbon dioxide, and other gaseous molecules, and this gaseous mixture exerts a certain pressure referred to as atmospheric pressure (Table 2). Partial pressure (Px) is the pressure of a single type of gas in a mixture of gases. For example, in the atmosphere, oxygen exerts a partial pressure, and nitrogen exerts another partial pressure, independent of the partial pressure of oxygen (Figure 1). Total pressure is the sum of all the partial pressures of a gaseous mixture. Dalton’s law describes the behavior of nonreactive gases in a gaseous mixture and states that a specific gas type in a mixture exerts its own pressure; thus, the total pressure exerted by a mixture of gases is the sum of the partial pressures of the gases in the mixture.” Don’t believe me then try diving with 36% NITROX with about 20% CO.
Noticed that you stated everything pertaining to respiratory and not metabolic.

Look, in terms of respiratory physiology and Carbon Dioxide generation in the immersed hyperbaric environment:

• "Causes of increased CO2 production: Carbon dioxide is produced as a waste product of metabolism and must be eliminated. . . Fundamentally [other than a rebreather scrubber failure], the only cause of increased CO2 production is increased work. Thus, exercise results in production of more CO2 whereas rest should reduce it. . . when CO2 rises, respiration will be stimulated, and when CO2 falls, respiratory drive will be reduced. The only point that requires emphasis in regard to diving is that breathing itself requires work and results in production of CO2. When a diver breathes dense gas, and/or if the underwater breathing apparatus imposes significant degrees of resistance, then the work of breathing can be a significant contributor to CO2 production and in some scenarios may be virtually all that the diver is capable of doing. . . We don’t notice the work of breathing under normal circumstances because we are well adapted to the normal demands. However, it is important in diving because it can be increased by immersion, the use of underwater breathing equipment and by increases in gas density. Though perhaps stating the obvious, the diver’s ability to respond to increases in work of breathing is not unlimited. The corollary is that respiratory muscle exhaustion or failure to respond to increased work demand for any reason will result in inadequate ventilation (“hypoventilation”) and an increase in arterial CO2. . ." (https://www.diversalertnetwork.org/files/Tech_Proceedings_Feb2010.pdf ,Ibid.)

If you cannot ventilate and expel this metabolically generated CO2 efficiently enough, you will degenerate into a hypercapnic vicious cycle condition. The only solution is to cease the physical work causing it and to remain on a known good source of breathing gas (subject to ppO2 and MOD limitations), trying to relax with full inspiratory/expiratory lung ventilations in order to regain normal homeostatic respiration physiology.

 

[Dan]

Sounds like @Dr Simon Mitchell needs to referee this boxing match

 

[Dan]

....Don’t believe me then try diving with 36% NITROX with about 20% CO.
Noticed that you stated everything pertaining to respiratory and not metabolic.

Don’t understand how 20% CO is brought up in the discussion. You’ll be dead in less than 3 minutes with 1.28% CO. Even 0.16% CO can kill you in < 2 hours, according to Carbon monoxide poisoning - Wikipedia

Physics (Dalton’s Law) has little to do with how your body & brain react to the gas composition in the ambient gas you are breathing in and the dissolved gas composition in your blood.

 

[GJC]

Back to the original post.

Excellent video for everyone to watch to see how a short of breath diver will (and won't) respond to you.

Key points to remember when you feel short of breath:

STOP moving your arms and legs and relax (don't tense) your muscles. This reduces CO2 production and makes it easier to blow off the excess CO2 you have accumulated.

TAKE SOME SLOW DEEP BREATHS, exhaling completely with each breath. This moves the most CO2 out of the lung spaces allowing the fastest movement of CO2 from the bloodstream into the lungs.

The problem is that short of breath divers (and drowning swimmers) don't want to stop moving because they want to get out of the water and they don't want to exhale completely because that makes them sink. CO2 rises, O2 decreases until they lose conciousness.

THINK about what needs to be done next.
-Get positive buoyancy (if you're on the surface or sinking) by inflating the BCD or dropping weight.
-Switch regulators or to a different tank if you might have a mechanical problem or are out of air.
-Get in a horizontal, not vertical position. When vertical, it is harder to breath because the water pressure on your chest and abdomen is greather than the pressure at your head where the air is coming from.

 

[Kevrumbo]

Sounds like @Dr Simon Mitchell needs to referee this boxing match

It's covered all here in his good and often cited presentation below. . .

(Go to 2:20 mark for a quick two minute overview, otherwise the entire hour long lecture clearly explains the respiratory physiology of CO2 and Diving):

 

[Kevrumbo]

Back to the original post.
Excellent video for everyone to watch to see how a short of breath diver will (and won't) respond to you. . .

Understandable looking at the second video of the original post (the novice diver's panicked ascent; I sincerely hope she did not embolize). . .

The truly frightening and sobering part is in the first video: the cave diver initially could not realize the danger or comprehend the teammates telling her that the dome room air was "bad" and to instead breath her regulator, and how quickly the panic of "air starvation" hypercapnia can overcome even the best faculties and instincts of an experienced cave diver & instructor.