A&P Respiratory Question

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Hello. For some of the moderators on here, you've probably seen my questions pop up in the LVN/PN section. That would be because I am in LVN school here in SoCal. Anyway, I have a general question regarding A&P because our instructor staff have been less than knowledgeable and moreso confused in terms of their presentation of materials relating to internal structures of the Anatomy and Physiology. I've tried to turn to some of the resources on-line but can't seem to find much on the information. Our text does a real good job at confusing rather than educating - even with self study.

The questions that I have are:

The lungs - as they sit in the chest cavity - what surrounds the lungs? layers? and the "pressure" in those layers. This became an issue when our instructor started talking about pneumothorax and chest wounds. She couldn't remember if there was pressure in the cavities and whether they the pressures were positive or negative?

What is the normal pressure of lungs if there is no puncture - or injury?

If there is some type of injury like a GSW or rib puncture, where is the chest tube insertion site? In the puncture or away from it? This is because wound care became a heated issue between her and a combat medic.

Here is an equally pressing question that was posed by our book - but some of our more "learned" instructors are at odds with our new book:

Q: The patient with respiratory acidosis will demonstrate which of the following? (More than one answer may be correct.)

1. Disorentation

2. pH of less than 7.35

3. pH of more than 7.44

4. Rapid Respirations

(The Answer according to the book is 1,2,4)

But the puzzling thing is this - within the book they give an example of Respiratory acidosis as being a person who has O.D. on tranquilizers and the breath rate of the patient is slow and shallow. It is contradicted by their example of a person who just got into a car accident and is uninjured but is freaking out. The book says that with the rapid and short breaths the person is blowing out too much CO2 and therefore, the person is in Resp Alkalosis because of the loss of "Carbonic Acid".

Are there any resources out there that can clear this up - online or book wise. I need a "Neuro-crash cart" stat :bluecry1:

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Chest tube gets its own hole. In a combat situation where time is of the essense, I can understand going in the bullet hole, but in an ER a new hole will be created and I can guarantee that the field-placed tube would be moved.

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Specializes in ICU/Critical Care.

The patient in respiratory acidosis is not blowing off enough CO2 because they are hypoventilating. The patient with respiratory alkalosis is blowing off too much CO2 because they are hyperventilating. As for pressures, I think the lungs are positive pressure. If there is a pneumothorax, that creates negative pressure. I could be wrong. I can't exactly think straight because of the cold meds I'm taking. Someone please correct me if I am wrong.

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Specializes in RETIRED Cath Lab/Cardiology/Radiology.

Found a nice site explaining the physiology of the respiratory system.

http://people.eku.edu/ritchisong/RITCHISO//301notes6.htm

re: book examples of resp. acidosis:

slow, shallow respirations of OD pt = not getting rid of the CO2, so it builds up, causing the pH to become acidotic.

rapid respirations (the post-accident person who is freaking out) = pt blowing off too much CO2, goes into alkalosis (think hyperventilating: dizzy, faint)

I interpreted your one example to mean the person with respiratory acidosis will display signs in these ways (choose the right answer(s) ), NOT respiratory acidosis will be caused by these (choices listed).

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Specializes in ICU/Critical Care.

Here's another site about ABGs.

http://www.maagnursing.com/ABG/finished.php

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Placing a chest tube through a wound can lead to several complications.

First, who really knows where the wound goes. We try to place a chest tube in a specific area to prevent further damage. Too low, and you go in below the diaphgram and tube the adominal cavity, for example.

Next, the wound may not be the proper size. In addition, you generally need to place your fingers into the thoracic cavity prior to tube insertion. This is easier when you create a "custom" incision.

Finally, you risk harming yourself or the patient by blindly inserting a tube into a wound. Broken bones could be a problem for example.

The lungs are covered by a connective tissue known as the serosa. Actually, many other organs are covered with serosa as well. The serosa is a double layered membrane with serous fluid between the layers. The intrapleural pressure will nearly always be about 4 mm/Hg less than the pressure within the alveoli. This is actually needed, or the serosa would simply collapse and take the lung with it. This is what happens with a pneumothorax.

Normal pressures will vary and depend on inspiration versus exhalation. Remember a standard atmosphere is about 760 mm/Hg. So, pressures will relate to atmospheric pressure and will depend on the phase of the respiratory cycle.

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Ok....I think I know about most of this stuff except maybe the combat portion.

What surrounds the lungs is the visceral outside) and parietal (inside) Pleura.....the area between them is the pleural space. The pressure under normal circumstances is negative when compared to the lungs and outside the chest wall. A puncture of the space will result in a abnormal pressure equalization and the lung will go down.

As others have mentioned pressure is expressed as relative to that of the atmosphere which is the 760 number.....so at rest (to atmosphere) it's 0 (=atmospheric pressure) negative for inspiration and positive for expiration. A larger thoracic cavity makes for a larger negative pressure which is what happens during inspiration. I'd say choice B is true kinda although really it should be less than 7.4

I don't know jack about combat stuff but I'd guess using the same hole would be an emergency/temporary thing. Previous poster's rationale made sense to me.

As for the multiple choice question: I think it's a lousy question. Respiratory acidosis can come in various degrees. Not going to get fancy with mixed cause stuff but in general if the Ph is less than 7.40 and the CO2 exceeds the high normal reference value, the diagnosis is respiratory acidosis-----a slightly hypercap. but well oxygenated patient is not necessarily going to be disoriented. Choice C is definately/always wrong since 7.44 is greater than 7.4 and so the patient has alkalosis not acidosis. And finally I would expect the rapid breather to blow off CO2 making them less not more acidotic. So shoot....I don't get the book's answers at all. Would have failed I guess.lol

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The book says that with the rapid and short breaths the person is blowing out too much CO2 and therefore, the person is in Resp Alkalosis because of the loss of "Carbonic Acid".

CO2 binds with H2O and forms carbonic acid, hence the inverse relationship between pH and CO2. In most places the acceptable range for CO2 is 35 - 45 mmHg resulting in a normal pH of 7.35 - 7.45. As previously posted, pleural pressure must be negative compared to alveolar pressure, otherwise atelactasis will occur. Ever hear the term "sucking chest wound"? Upon inspiration pleural pressure becomes more negative, and if open (tramatic/surgicaly) air will be "sucked" into pleural space. In this case a chest tube is used to maintain negative pleural pressure. That example really drove it home for me. As far as the multiple choice question goes, answers 1.2.4 can be correct. Remember, tachypnea does not equal hyperventilation, hypopnea does not equal hypoventilation, and ventilation is not oxygenation.

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Re: A&P Respiratory Question

I believe the visceral layer of the lungs lies closer to the organs or innermost portion of the lungs which would be (inside) which would be closer to the bronchioles, alveoli etc. and the parietal layer of the lungs lie closer to the rib cage or the outermost portion of the lungs?

Hope that helps!

Neem

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CO2 binds with H2O and forms carbonic acid, hence the inverse relationship between pH and CO2. In most places the acceptable range for CO2 is 35 - 45 mmHg resulting in a normal pH of 7.35 - 7.45. As previously posted, pleural pressure must be negative compared to alveolar pressure, otherwise atelactasis will occur. Ever hear the term "sucking chest wound"? Upon inspiration pleural pressure becomes more negative, and if open (tramatic/surgicaly) air will be "sucked" into pleural space. In this case a chest tube is used to maintain negative pleural pressure. That example really drove it home for me. As far as the multiple choice question goes, answers 1.2.4 can be correct. Remember, tachypnea does not equal hyperventilation, hypopnea does not equal hypoventilation, and ventilation is not oxygenation.

Yeah, I read the post again. I think without much A&P, the way the book and the instructors seem to be articulating is quite confusing. I think it is important that people undestand PH is "per hydrogen." We are actually talking about the hydrogen ion H+, when considering PH. CO2 does not contain hydrogen; however, much of our CO2 is transported as bicarbonate ions (HCO3-) in plasma. You do not loose carbonic acid per say, carbonic acid is unstable and will want to dissociate into hydrogen ions and bicarbonate ions. This is where you get the hydrogen when talking about PH.

This process is reversed in the lungs. carbon dioxide must be liberated from bicarbonate so we can get rid of it. So, bicarbonate ions bind with hydrogen ions to make cabonic acid. The carbonic acid is quickly split into CO2 and H2O, and the CO2 can be released.

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Specializes in med/surg, telemetry, IV therapy, mgmt.

all the following information is from human body: an illustrated guide to every part of the human body and how it works and from my own clinical knowledge and background working with chest tubes on a stepdown unit.

what is the normal pressure of lungs if there is no puncture - or injury?

760mmhg

what surrounds the lungs? layers?

the lungs are surrounded by the pleural membranes which consist of two layers surrounding the lung tissue. the two membranes are separated by a lubricating fluid that allows them to slide around during the act of breathing.

and the "pressure" in those layers?

the act of breathing involves the diaphragm which is a muscle. when the diaphragm contracts, the size of the chest cavity increases and pressure in the chest cavity and pleural space (the area between the two pleural membranes) drops creating a negative pressure. in order to equalize the pressure in the lungs and pleural space with the pressure of the outside atmosphere, air is drawn into the lungs--this is
inspiration.
when the diaphragm relaxes, the size of the chest cavity decreases and pressure in the chest cavity and pleural space rises creating a positive pressure. in order to equalize the pressure in the lungs and pleural space with the pressure of the outside atmosphere, air is exhaled from the lungs--this is
expiration.

this became an issue when our instructor started talking about pneumothorax and chest wounds. she couldn't remember if there was pressure in the cavities and whether they the pressures were positive or negative?

with normal inspiration and expiration air does not get into the pleural space
at all
. with a traumatic injury such as a gsw or rib puncture a hole in the pleura allows air to enter the pleural space and that air has no way to exit so it begins to accumulate in the pleural space. now you have a pneumothorax. if there is also bleeding going on and the blood is spilling into and collecting in the pleural space you also get a hemothorax. these can be seen on x-ray. the danger? they are taking up chest space that the lungs normally need in order to fill with air. as a pneumothorax or hemothorax enlarges, the amount of air that the lungs can take in on inspiration and expiration gets restricted since the diaphragm keeps on doing its job if it has been unimpaired. not enough air = not enough oxygen (hypoxia) = build up of carbon dioxide in the blood = decreased amount of oxygen available in the blood and your patient goes into acidosis.

when the pleural space and lung are punctured it
creates a doorway for air to enter the
pleural space
. this creates what the emt people call a "sucking wound". the pleural space, and the lungs if they too have been punctured, will pull atmospheric air in when the diaphragm contracts. the problem is that when the diaphragm relaxes, there is no escape for the air that has gone into the pleural space. the immediate treatment is quite simple really: you put an airtight seal over the chest wall wound if you can. a plastic bag at the accident site works wonders! in hospitals you'll see all kinds of occlusive dressings used--usually adaptic which has petroleum jelly on it. this stops the pneumothorax from getting any larger from the outside. however, the pneumothorax can still enlarge from air going inside the lungs and getting into the pleura from an internal pleural tear, so the patient needs relief of the pneumothorax asap.

if there is some type of injury, where is the chest tube insertion site? in the puncture or away from it?

the chest tube is inserted so that it lies between the two layers of the pleura. it creates an exit site for any air and blood that has collected in the pleural space.

the docs will look at an x-ray of the patient's lung and determine where the best placement will be that will be the most efficient to remove what is causing the problem. if air needs to be removed, chest tube placement will be higher and more anterior in the pleural space since air is lighter than most fluid and tends to rise; if blood and pus need to be removed, chest tube placement will be lower and more posterior in the pleural space since blood and other body fluids tend to pool in dependent areas. the area of injury that caused the hole to the pleura in the first place is either repaired and sutured surgically or covered with some sort of occlusive dressing to prevent any further atmospheric air from entering. internal pneumothoraxes from injury during needle punctures will eventually seal up on their own.

there are weblinks on fluids, acidosis and alkalosis around post #24 or 25 on a sticky thread with anatomy links around post #45

this site has chest tube information:

i hope the combat medic and the instructor didn't get into a slugfest. nothing is worth getting into a big argument over.

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Specializes in SNF.

The chest goes into the pleural space, not into the lung.

Inspiration causes negative pressure in the lungs.

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