Valsalva and Eustachian tube

[Kiv]

I hope that this will not be answered using AI.

The starting premise is established as a certainty here:During the Valsalva maneuver, gas indeed moved through the Eustachian tube (ET) into the middle ear, and the middle ear pressure increased as a result of this gas transfer.

The question is solely this:Does it follow as a practical certainty that, at least in one single “frozen” moment during the Valsalva, there existed an uninterrupted gas-phase route / continuous gas cavity / air column from the pharynx to the middle ear, even if it were extremely narrow and short-lived?

Important Constraints:

• Do not address whether “air usually moves,” as that is already established as the premise.
• Do not address whether the ET was continuously open throughout the Valsalva; the question concerns only at least one single moment (a moment where time is frozen).
• Do not evade the question by stating that real-time imaging does not exist for every case; specifically evaluate what follows logically from the given premise.
• Do not pivot to swallowing, unless it is used only as a weak alternative model.
• Specifically evaluate the Valsalva maneuver, characterized by active overpressure in the nasopharynx, rather than the muscle-driven opening seen in swallowing.
• Take into account that McDonald’s cine-CT bolus/progressive opening model was based on a small, primarily swallow-oriented, and hypothetical dataset.
• Take into account that subsequent literature on the Valsalva maneuver leans toward the view that once the opening threshold is exceeded, a “continued column of air” is formed in the ET and that “most evidence suggests” the ET opens momentarily along its entire length.
• The question is not whether this is an absolute mathematical theorem in all possible biological worlds, but whether, given the premise, this is effectively the only credible explanation.

Please answer exactly this:Given the premise (i.e., that gas actually entered the middle ear via the ET during Valsalva), is it a practically certain conclusion that at least in one single moment, there was an uninterrupted pharynx–middle ear gas connection?

 

[weirdoguy]

I hope that this will not be answered using AI.

It is forbidden here on PF, so it won't. But I have no idea about what you wrote, so that's all I can say

 

[berkeman]

@Kiv -- is this question for schoolwork? What is the motivation for the question?

 

[Baluncore]

The question is solely this:Does it follow as a practical certainty that, at least in one single “frozen” moment during the Valsalva, there existed an uninterrupted gas-phase route / continuous gas cavity / air column from the pharynx to the middle ear, even if it were extremely narrow and short-lived?

No.
In some cases, when the ET contains a fluid, the fluid can move sufficiently to equilibrate pressure, without completely emptying the ET of the fluid. It comes down to a compression ratio; the volume of the inner ear, the volume of the ET, and the pressure difference.

 

[Kiv]

@Kiv -- is this question for schoolwork? What is the motivation for the question?

Not for school, for personal use

 

[berkeman]

Not for school, for personal use

Okay, fair enough. I've moved your thread from the Classical Physics forum to the Biology/Medical forum where it fits better.

The starting premise is established as a certainty here:During the Valsalva maneuver, gas indeed moved through the Eustachian tube (ET) into the middle ear, and the middle ear pressure increased as a result of this gas transfer.

Can you give a scientific/medical reference for this premise? Thanks.

 

[Kiv]

No.
In some cases, when the ET contains a fluid, the fluid can move sufficiently to equilibrate pressure, without completely emptying the ET of the fluid. It comes down to a compression ratio; the volume of the inner ear, the volume of the ET, and the pressure difference.

Thanks you for the perspective. However, I believe this model addresses a different scenario and bypasses the strict premise of the thought experiment.

First, a minor anatomical correction: the Eustachian tube connects to the middle ear (a gas-filled cavity), not the inner ear.

More importantly, the scenario you described is essentially a 'fluid piston' effect. In your model, a fluid plug moves up the tube, compressing the existing air in the cavity to equalize pressure without the plug clearing the tube. While perfectly valid in fluid mechanics for transferring pressure, it violates the core premise of my question: gas itself successfully transferred from Side A (nasopharynx) to Side B (middle ear).

If we strictly enforce the given premise that the physical medium that entered the middle ear was gas, not a shifting liquid plug—does the conclusion hold? Is it physically possible for gas to travel from Side A to Side B via static overpressure without a continuous gas-phase lumen existing at some moment?"

 

[Kiv]

Okay, fair enough. I've moved your thread from the Classical Physics forum to the Biology/Medical forum where it fits better.


Can you give a scientific/medical reference for this premise? Thanks.

The premise is based on the standard physiological understanding of Eustachian tube ventilation. For example, McDonald et al. (2012), "New insights into mechanism of Eustachian tube ventilation based on cine computed tomography images", discusses how air traverses the ET to maintain middle ear pressure.

However, for the purpose of my question, I am asking you to accept this as a given premise (a thought experiment). I am not asking if it happens, but how the fluid dynamics must work if we observe that gas has indeed moved from the nasopharynx to the middle ear.

My goal is to understand the physical requirement of a continuous lumen in this specific successful scenario.

 

[Kiv]

Okay, fair enough. I've moved your thread from the Classical Physics forum to the Biology/Medical forum where it fits better.

I understand the biological context, but this is fundamentally a question of fluid dynamics and topology. I am not asking for clinical advice or biological functions, but rather the physical requirement for gas-phase continuity in a high-resistance flexible conduit. The biological terms are just the specific application of the model.

 

[pinball1970]

The starting premise is established as a certainty here:During the Valsalva maneuver, gas indeed moved through the Eustachian tube (ET) into the middle ear, and the middle ear pressure increased as a result of this gas transfer

Can you state where this comes from? The frame work of your question looks like Ai

 

[Baluncore]

First, a minor anatomical correction: the Eustachian tube connects to the middle ear (a gas-filled cavity), not the inner ear.

Sorry, I was asleep when I replied.

While perfectly valid in fluid mechanics for transferring pressure, it violates the core premise of my question: gas itself successfully transferred from Side A (nasopharynx) to Side B (middle ear).

Is it physically possible for gas to travel from Side A to Side B via static overpressure without a continuous gas-phase lumen existing at some moment?"

Yes, gas can travel from side A to side B, as bubbles, between multiple fluid pistons, without there being a continuous air path between the sides A and B. That could occur when the fluid entering the ET contained bubble envelopes, that created fluid pistons in the ET, as they were introduced.

Maybe you need to move, or reestablish, the goal posts, to preclude that possibly unwelcome scenario.

The way this question is worded, makes me feel like I am wearing a straitjacket, in an insane asylum.

 

[Kiv]

Sorry, I was asleep when I replied.


Yes, gas can travel from side A to side B, as bubbles, between multiple fluid pistons, without there being a continuous air path between the sides A and B. That could occur when the fluid entering the ET contained bubble envelopes, that created fluid pistons in the ET, as they were introduced.

Maybe you need to move, or reestablish, the goal posts, to preclude that possibly unwelcome scenario.

The way this question is worded, makes me feel like I am wearing a straitjacket, in an insane asylum.

This question was intentionally phrased with precision to avoid lengthy back-and-forth, the need for clarifying questions, or additional qualifiers. I am looking for responses based on definitive expertise regarding the exact question I initially presented.

I understand that a high volume of fluid could theoretically create discrete pistons or bubbles. However, to reach the core of the physics, let’s look at the standard physiological state where there is only a thin lubricating film of moisture—not enough volume to form liquid plugs across the lumen.

In this simplified, near-dry scenario, if we observe a gas volume V moving from A to B under static overpressure:

1. Is it physically possible for gas to transfer without an instantaneous, continuous gas-phase lumen existing from A to B at some point t_n?
2. Does fluid dynamics dictate that in a passive, high-resistance conduit, the critical opening pressure must result in a longitudinal breakthrough that creates a continuous path?

My question is specifically about the topological requirement of the tube during a successful gas transfer when significant fluid blockages are absent.

 

[Baluncore]

My question is specifically about the topological requirement of the tube during a successful gas transfer when significant fluid blockages are absent.

So you want to know: if an open tube that contains gas, without any liquid present, will be full of gas, from one end to the other. I think your question now fits the answer that you want.

 

[Kiv]

So you want to know: if an open tube that contains gas, without any liquid present, will be full of gas, from one end to the other. I think your question now fits the answer that you want.

I kindly request that only those who have a definitive answer to the question participate in this discussion. I am not referring to you specifically.
That is a significant oversimplification of the question. I am not asking about a permanently open tube; I am asking about the topological state of a collapsed, high-resistance elastic conduit (the ET) at the exact moment it transitions from closed to open under static overpressure.
The core of the physics problem is this:
When a gas volume moves through such a conduit during a Valsalva (mass transfer occurs), is it a physical necessity that at one discrete moment t_n, a continuous gas-phase lumen exists from end to end?

Or, to challenge the 'bolus' theories: Is it mechanically possible for a passive overpressure to move gas through this specific type of collapsed tube without ever creating a continuous longitudinal column at any single point in time?

I defined the system as having only a thin lubricating film specifically to address the physics of the tube's opening mechanism, rather than discussing large-scale fluid blockages. My question remains: is the continuous column a topological requirement for mass transfer in this scenario?

 

[Baluncore]

When you blow up a party balloon, the pressure is initially high, then falls as the balloon increases in radius.

The same may be true for the ET. It may naturally pinch off between the bubbles of air, with each bubble being at a different step in pressure. The bubbles then move along the tube, with the tube ahead opening, driven by the closing of the tube behind.
The question will come down to the construction of the tube. Is there any information on the orientation of elastic fibres in the outside wall of the tube?

When I swallow, I hear a click each time. That click seems to be a pressure step of air. If I hold that swallow position, I hear a continuous dull roar, which must be either the sound of muscle activity, or turbulent blood flow, reaching the thin end of my cochlea. If the connection was not shut off normally, I would be deafened to quiet speech, by the continuous roar.
It is as if the tube is closed at one end or the other, with equilibration of pressure switching momentary, averaging the pressure at each end. That might suggest the tube is rarely a continuous through passage. There would need to be two valves, one at each end.

 

[Kiv]

When you blow up a party balloon, the pressure is initially high, then falls as the balloon increases in radius.

The same may be true for the ET. It may naturally pinch off between the bubbles of air, with each bubble being at a different step in pressure. The bubbles then move along the tube, with the tube ahead opening, driven by the closing of the tube behind.
The question will come down to the construction of the tube. Is there any information on the orientation of elastic fibres in the outside wall of the tube?

When I swallow, I hear a click each time. That click seems to be a pressure step of air. If I hold that swallow position, I hear a continuous dull roar, which must be either the sound of muscle activity, or turbulent blood flow, reaching the thin end of my cochlea. If the connection was not shut off normally, I would be deafened to quiet speech, by the continuous roar.
It is as if the tube is closed at one end or the other, with equilibration of pressure switching momentary, averaging the pressure at each end. That might suggest the tube is rarely a continuous through passage. There would need to be two valves, one at each end.

I also usually or always hear a click when I swallow, and I can voluntarily click my Eustachian tubes (ET), but I assume this sound originates from the mucosal surfaces separating, not from the pressure equalization itself. Your analysis of a 'bubble train' and sequential valves is theoretically interesting, but in my view, it does not apply to a static Valsalva maneuver.

From the perspective of physics and topology, the problem is this:
In order for gas to move in 'segments' without a single momentary continuous connection, the tube would have to pinch shut air-tight immediately behind the gas.

In a Valsalva maneuver, the nasopharyngeal overpressure is continuous. What force would close the proximal or middle section of an elastic tube against that pressure while you are still blowing? This is, as I see it, a passive system.
If gas moves from point A to point B in an elastic conduit opened by passive overpressure, isn't it a mechanical necessity according to the laws of physics that there is at least one discrete moment in time when the conduit is open from end to end?
Without this momentary continuous lumen, mass transfer would require active pumping (like swallowing). In a Valsalva maneuver, the tube opens like a zipper: once it's open, it is open the entire way until the pressure differential equalizes.