cnidae
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Hi, why do the to top of the lungs collapse during deco in the upright position opposed to the bottom of the lungs.
Why do the top of the lungs.....
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Interesting question...I'm looking forward to the responses....
a better way to phrase the question would be:
"Do the top of the lungs collapse during deco?"
"Do the top of the lungs collapse during deco?"
Dr Deco
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Dear Readers:
Lungs?
I must confess that I am stumped as to the origin of this question. I was of the impression that this was of importance only to those who studied pulmonary mechanics in space. I do not have much personal experience with lung research but will pass on what I know.
Slinky
The lung is often described as acting in a manner similar to the toy referred to as a Slinky. This little coil, if held in two separated hands, will be stretched the greatest at the top and will bunch together at the bottom. In a similar fashion, the lung will also have alveolar space greatest at the top and alveoli will be collapsed at the bottom (above the diaphragm). More blood will flow through the upper portion of the lung tissue and less through the bottom. There will not be a ventilation/perfusion mismatch.
This arrangement will be true whether the individual is standing on dry land or in the water. When immersed, the blood will be shifted from the legs towards the thoracic cavity.
In Space
In null gravity, the lung will open up and the ventilation will be more evenly distributed. Again think of the Slinky in no gravity, and how it would stretch. There is also the shift of fluid to the thorax and the rostral (= towards the head) shift of the diaphragm. I believe that I have this correct, as it was explained to me recently by Dr Kim Prisk, a pulmonary physiologist performing experiements on the Shuttle.
The external pressure does not determine the shape of the lungs as long as it is applied evenly across the whole of the body. Squeezing only the chest is a different matter.
Gas Exchange
The position of the Lungs, of the presence of gas bubbles, is seldom a limiting factor in gas exchange. The lungs have a very large reserve both for gas exchange and through put of blood even under heavy exercise. Muscle gas exchange is the limiting factor. The lungs are over designed, in that respect. As I would phrase it, God was in a good mood the day he designed lungs.
Dr Deco :doctor:
Lungs?
I must confess that I am stumped as to the origin of this question. I was of the impression that this was of importance only to those who studied pulmonary mechanics in space. I do not have much personal experience with lung research but will pass on what I know.
Slinky
The lung is often described as acting in a manner similar to the toy referred to as a Slinky. This little coil, if held in two separated hands, will be stretched the greatest at the top and will bunch together at the bottom. In a similar fashion, the lung will also have alveolar space greatest at the top and alveoli will be collapsed at the bottom (above the diaphragm). More blood will flow through the upper portion of the lung tissue and less through the bottom. There will not be a ventilation/perfusion mismatch.
This arrangement will be true whether the individual is standing on dry land or in the water. When immersed, the blood will be shifted from the legs towards the thoracic cavity.
In Space
In null gravity, the lung will open up and the ventilation will be more evenly distributed. Again think of the Slinky in no gravity, and how it would stretch. There is also the shift of fluid to the thorax and the rostral (= towards the head) shift of the diaphragm. I believe that I have this correct, as it was explained to me recently by Dr Kim Prisk, a pulmonary physiologist performing experiements on the Shuttle.
The external pressure does not determine the shape of the lungs as long as it is applied evenly across the whole of the body. Squeezing only the chest is a different matter.
Gas Exchange
The position of the Lungs, of the presence of gas bubbles, is seldom a limiting factor in gas exchange. The lungs have a very large reserve both for gas exchange and through put of blood even under heavy exercise. Muscle gas exchange is the limiting factor. The lungs are over designed, in that respect. As I would phrase it, God was in a good mood the day he designed lungs.
Dr Deco :doctor:
100days-a-year
Contributor
So Doc,without getting into the hor.vs.vert. deco thing it seems you are saying for deco purposes it has no perceptible effect on lung orientation?That the human lung is not the limiting factor,but the ability of gases to dissolve out of tissue into the blood is?This would seem logical then that the "slower tissues "would determine deco length independent of orientation but affected by temp,age,degree of saturation,workload etc...
Dr Deco
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Dear 100 days:
Thats it =-)
Unless we are talking about many, many bubbles in the lungs and exchange in fast compartments, the lungs are not limiting.
The critical factors are tissue saturation, hydration level, exercise level, and physical fitness.
Dr Deco :doctor:
Thats it =-)
Unless we are talking about many, many bubbles in the lungs and exchange in fast compartments, the lungs are not limiting.
The critical factors are tissue saturation, hydration level, exercise level, and physical fitness.
Dr Deco :doctor:
100days-a-year
Contributor
Thanx Doc,I'll still deco horizontally due to fact I'm usually weighted and trimmed to stay horizontal anyway.Thanx for makin' it clear tho.
I like that! Mind if I use it?
Brian1968,
Registered Respiratory Therapist
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