Preventing barotrauma in deep-sea divers
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- Preventing barotrauma in deep-sea divers
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Preventing barotrauma in deep-sea divers
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[post_date] => 2025-01-09 07:55:06
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[post_content] => Practice Passage (Question 1-5)
*This passage is the property of Khan Academy and has been reformatted into an AAMC-style interface in their entirety by MedLife Mastery. MedLife Mastery does not endorse and is not an affiliate of Khan Academy.
In addition to decompression sickness, deep-sea divers must remain wary of injuries arising purely from mechanical forces that act on them as they ascend or descend significant depths. A common class of injuries, known as barotraumas, occur due to mechanical forces occurring within the body due to pressure gradients that occur inside and outside the body. Depending on the rate at which a diver ascends or descends, the fluid pressure inside their ears and other soft tissues may not have time to equilibrate with the external pressure, resulting in a difference in pressure that can cause mechanical strain in sensitive tissues.
In order to combat this effect, many dive suits, masks, and tanks are pressurized in order to combat the cumulative effects of pressure during the dive. However, because barotrauma can occur at depths as low as 20 meters, occasionally divers may fall victim because they did not wear adequate equipment for the depths that they attain. Particularly troubling are injuries occurring where most of the diver’s bodysuit was safely pressurized, but one component like a mask was not adequately pressurized, leading to pressure gradients across the body that can cause injury.
A diver has devised four different options for a dive to a depth of 40 meters over 90 minutes. For safety, she plans to maintain a fixed, positive buoyancy, and manually swim against their buoyancy in order to travel deeper. Her candidate diving procedures are illustrated in a depth versus time graph in Figure 1.
Note: The density of water is denoted by 𝝆 and the acceleration due to gravity is given by 𝒈
Figure 1: Four different dive procedures for a diver intending to dive 40 meters in 90 minutes.
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[questions] => Array
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[quiz_unique_key] => 578908434
[question] => Which of the following gives the difference in pressure between the surface and at dive depthＤ?
[value] => Array
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[answer] => 1
[description] => Reason for the Correct Answer:
Pressure should increase with increasing depth due to the added weight of the water.
All four answer choices have different units.
Only one of the four answer choices has units of (force)/(area).
Bernoulli’s equation gives the pressure at a depth D as 𝝆𝒈Ｄ.
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[answers] => Array
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[0] => Array
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[each_answer] => A. 𝝆𝒈Ｄ
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[1] => Array
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[each_answer] => B. 𝝆𝒈
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[2] => Array
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[each_answer] => C. 𝝆𝒈 / Ｄ
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[3] => Array
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[each_answer] => D. 𝝆𝒈Ｄ²
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[1] => Array
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[quiz_unique_key] => 3873426850
[question] => Which of the following symptoms could be a consequence of Pascal’s principle?
[value] => Array
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[answer] => 3
[description] => Reason for the Correct Answer:
Barotrauma arises due to the differences in pressure in different parts.
Pascal’s principle states that pressure is transmitted equally through a fluid in a sealed vessel.
When pressure is suddenly applied to the surface of the body, blood vessels can propagate that pressure to distant tissues via this effect.
Barotrauma in distant tissue may be a consequence of Pascal’s principle.
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[answers] => Array
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[0] => Array
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[each_answer] => A. Overstretching of tendons and ligaments during resurfacing.
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[1] => Array
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[each_answer] => B. Sudden cramping in muscle groups in the extremities and torso.
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[2] => Array
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[each_answer] => C. Barotrauma to a blood vessel distant from the part of the body that was exposed to pressure.
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[each_answer] => D. Gradual damage to muscle groups due to delayed diffusion of pressure into tissue.
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[2] => Array
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[quiz_unique_key] => 83407773
[question] => What is the buoyant force acting on the ascending diver’s body (mass 𝑴 and volume 𝑽)? (g is the standard acceleration due to gravity)
[value] => Array
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[answer] => 3
[description] => Reason for the Correct Answer:
The buoyant force does not include the separate contribution due to the diver’s weight.
Archimedes’ principle states that the buoyant force acting on an object is equal to the weight of the water the object displaces.
The total buoyant force on the diver is given by 𝝆 g V.
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[answers] => Array
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[0] => Array
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[each_answer] => A. 
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[1] => Array
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[each_answer] => B. M g
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[2] => Array
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[each_answer] => C. 𝝆 g V
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[3] => Array
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[each_answer] => D. (𝝆V + M)g
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[quiz_unique_key] => 2261298308
[question] => Which of the four diving procedures would be most effective in preventing barotrauma?
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[answer] => 4
[description] => Reason for the Correct Answer:
The danger of barotrauma comes from the rate of pressure change.
Pressure changes linearly with depth, and so pressurization rate corresponds to the slope of the curves in the graph.
The curved plots have very high slopes, either right at the beginning or right at the end of the dive.
The consistent diagonally sloped graph provides the best protection against barotrauma.
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[0] => Array
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[each_answer] => A. Choice A
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[1] => Array
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[each_answer] => B. Choice B
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[each_answer] => C. Choice D
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[3] => Array
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[each_answer] => D. Choice C
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[question] => Which of the diving protocols requires the diver to do the most work?
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[answer] => 2
[description] => Reason for the Correct Answer:
The net force acting on the diver is her buoyancy minus her weight, making the force she needs to exert constant during her dive.
Recall that the amount of work required to move between two points with equal gravitational potential is independent of the path taken between the two points.
All four diving procedures travel 30 m and thus all require the same amount of work.
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[0] => Array
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[each_answer] => A. Choice B
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[1] => Array
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[each_answer] => B. They all require equal work
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[2] => Array
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[each_answer] => C. They all require no work
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[3] => Array
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[each_answer] => D. Choices A and D
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[558253|1] => A
[558253|2] => C
[558253|3] => C
[558253|4] => D
[558253|5] => B
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Figure 1: