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ELI-PGY5 t1_iu4vi1s wrote

Reply to comment by Existing_Thought5767 in Does the cerebral spinal fluid of people with Alzheimer's have a notably different pH from 'normal' people's? by wrhollin

It’s not really the right answer. Because we test the pH of bodily fluids pretty regularly, and it’s clinically useful. Just not useful in CSF in standard practice, and it definitely not a standard test in Alzheimer’s.

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NergalMP t1_iu536tk wrote

It’s clinically useful because pH outside the normal range is indicative of a significant problem. Mammalian physiology operates in a pretty narrow pH range with many processes maintaining it.

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ELI-PGY5 t1_iu56p3o wrote

  1. pH changes in bodily fluids are often clinically useful
  2. I don't really care about pH in CSF.
  3. I doubt it's a good test for Alzheimers, as we would presumably all be doing it if a $20 investigation could detect the condition. The linked article isn't very relevant to everyday clinical medicine.
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NergalMP t1_iu5l91f wrote

Sorry, I meant it can be clinically useful outside the specific CSF/Alzheimer’s question. I’m sure it’s irrelevant to that.

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MeshColour t1_iu54qhd wrote

We test blood oxygen level pretty regularly too, which is also clinically useful?

That's unrelated to the fact that for a healthy person that it should not vary

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Existing_Thought5767 t1_iu5gzml wrote

It is 100% the right answer. Just because you are checking pH in blood doesn’t mean it suppose to change when you get sick or something. As people in this have said .2 pH is the most change you will see in the human body, anything more than that change you body literally cannot function. Cells would be destroyed very quickly.

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ELI-PGY5 t1_iu5i898 wrote

That’s gibberish. pH of blood changes in specific disease states. Checking blood pH is a common, useful pathology test.

As for 0.2 = “cells destroyed very quickly” “body would literally not function” - you’re exaggerating. A drop of 0.2 (7.4 to 7.2) would not even count as a severe acidosis.

So I rate your comment 3.2% the right answer, not 100%.

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Daguvry t1_iu5zvmw wrote

Run blood gases all the time working in Respiratory. That's how we monitor correct vent settings and most COPD patients on BIPAP. I can swing blood pH by more than .2 in less than hour with tidal volumes and respiratory rates.

Out of control diabetics can get really low pH values but that's a metabolic issue, not a respiratory issue. I've seen plenty of diabetics under 7.0 pH where the normal pH values are 7.35-7.45

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ELI-PGY5 t1_iu7lm1h wrote

Yeah, I was think of a guy I saw recently with DKA, pH 6.9, not crisp but his cells were also not all dead.

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gasdocscott t1_iu8ox4x wrote

I've treated patients with pH less than 6.7 (or lower- the gas machine doesn't go lower). Often DKA, which is remarkably responsive to treatment even at those extremes.

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