Pleural Space [HD]

Summary

Dr. Ricardo Gonzalez Rafi and Jody Chapman explore the pleura and pleural space in this informative video. They explain the pleura's role in regulating lung pressure and the function of pleural fluid, which normally contains 8-10 mL per side in an adult, providing lubrication during breathing. The script delves into the mechanics of pleural fluid absorption and the consequences of pleural effusion, such as lung compression and shortness of breath, caused by disruptions in the pleural space. Clinical examples include effusions due to heart failure, tumors, and pneumonia, highlighting the impact of various diseases on pleural fluid dynamics.

Takeaways

• 📚 The pleura is a continuous membrane of cells that folds over itself at the apex and base of each lung.
• 🌐 The pleural space is a potential space between the parietal pleura (lining the chest wall) and the visceral pleura (lining the lungs).
• 🛠 The pleural space helps regulate pressure during breathing and provides lubrication for the lungs and chest wall as they move against each other.
• 💧 The pleural space typically contains 8-10 milliliters of fluid per side in an average-sized adult, serving as a lubricant for the pleural surfaces.
• 🧬 Pleural fluid is a clear plasma filtrate originating from small capillaries in the chest wall, containing solutes like sodium chloride, bicarbonate, glucose, and small amounts of protein.
• 🔬 Pleural fluid has equivalent glucose concentrations to serum but slightly higher concentrations of albumin and bicarbonate, resulting in an alkaline pH of about 7.6.
• 🔄 The pleural fluid provides mechanical coupling between the pleural surfaces, allowing for the transmission of forces and sliding during the breathing cycle.
• 💉 Pleural fluid is absorbed primarily through the mesothelial cells of the visceral pleura and exits via microscopic uni-directional valves known as lymphatic stoma in the parietal pleura.
• 🚫 A pleural effusion occurs when there is too much fluid in the pleural space, disrupting the mechanical coupling and causing the lung to pull away from the chest wall.
• 🏥 Clinical examples of pleural effusions include conditions that increase hydrostatic pressure (like heart failure), tumors obstructing lymphatic drainage, and inflammation from pneumonia.
• 🛑 A trapped lung occurs when the lung physically pulls away from the chest wall due to conditions like inflammatory, infectious, or neoplastic changes, leading to pleural effusion.

Q & A

What is the pleura and what is its function?

The pleura is a continuous membrane of cells that folds over onto itself at the apex and base of each lung. It functions to help regulate the pressure inside and outside the lungs during breathing and provides lubrication for the pleural surfaces as they slide against each other during the breathing cycle.

What is the pleural space and where is it located?

The pleural space is a potential space between the parietal pleura, which lines the inside of the chest wall, and the visceral pleura that lines the lungs. It is where the two pleural membranes fold upon themselves.

How much fluid is normally present in the pleural space?

The pleural space is estimated to hold between eight and ten milliliters of fluid per side in an average-sized adult man.

What is pleural fluid and what substances does it normally contain?

Pleural fluid is a clear plasma filtrate that originates from small capillaries in the chest wall and contains small solutes like sodium chloride, bicarbonate, glucose, and small amounts of protein including albumin. It also contains macrophages, lymphocytes, and mesothelial cells.

What is the normal pH of pleural fluid and why is it alkaline?

The normal pH of pleural fluid is approximately 7.6, which is alkaline due to the increased bicarbonate concentration compared to serum.

How does the pleural space provide mechanical coupling during breathing?

The fluid in the pleural space provides mechanical coupling between the two pleural surfaces, allowing instantaneous transmission of perpendicular forces between them, similar to how a damp glass coaster sticks to the bottom of a glass.

Where does pleural fluid come from and how is it absorbed?

Pleural fluid originates from plasma filtrate drawn by a pressure gradient from the subpleural capillaries in the chest wall. It is primarily absorbed through the mesothelial cells of the visceral pleura and exits the space through microscopic unidirectional valves known as lymphatic stoma found in the parietal pleura.

What happens when there is too much fluid in the pleural space, causing a pleural effusion?

When there is too much fluid, it disrupts the mechanical coupling between the chest wall and the lung, causing the lung to pull away from the chest wall. This can lead to shortness of breath and a feeling of fullness in the chest, as the lung tissue becomes compressed and alveoli are electively reduced.

What are some clinical examples of conditions that can cause a pleural effusion?

Conditions such as heart failure, which increases hydrostatic pressure leading to fluid accumulation; tumors in the lung or chest wall obstructing lymphatic drainage; and pneumonia, which increases capillary permeability, can all cause pleural effusions.

What is a trapped lung and how does it relate to pleural effusion?

A trapped lung occurs when certain conditions cause the lung to become unexpanded, physically pulling away from the chest wall and creating an imbalance of pressure that favors increased filtration of fluid into the pleural space, leading to pathologic pleural effusion.

Can pleural effusions occur even when pleural mechanics are normal?

Yes, pleural effusions can occur when fluid formation within the thorax and absorption are intact, but excess fluid entry occurs via non-physiologic routes, such as peritoneal dialysis fluid entering the pleural space via diaphragmatic defects in liver disease.

Outlines

00:00

😀 Introduction to Pleura and Pleural Space

Dr. Jody Chapman and Dr. Ricardo Gonzalez Rafi introduce the pleura as a continuous membrane of cells that folds over itself, lining the chest wall and lungs. The pleural space, located between the parietal and visceral pleura, is a potential space that helps regulate lung pressure during breathing. It contains a small amount of fluid, estimated at 8-10 milliliters per side in an average-sized adult, which serves as a lubricant for the pleural surfaces as they slide against each other during the breathing cycle. Pleural fluid is normally a clear plasma filtrate, containing solutes like sodium chloride, bicarbonate, glucose, and small amounts of protein, including albumin. It also contains cells like macrophages, lymphocytes, and mesothelial cells in low numbers. The pleural space's mechanics involve the fluid providing mechanical coupling, allowing the transmission of forces between the pleural surfaces, similar to how a damp glass coaster sticks to a glass surface.

05:01

😨 Pleural Effusion and Its Causes

The second paragraph delves into pleural effusion, a condition where an excess of fluid accumulates in the pleural space, disrupting the mechanical coupling and causing the lung to pull away from the chest wall. This can lead to reduced lung expansion, shortness of breath, and a feeling of chest fullness. The paragraph discusses various mechanisms that can lead to pleural effusion, such as increased hydrostatic pressure in heart failure, tumor obstruction of lymphatic drainage, and increased capillary permeability due to inflammation or infection. Examples include transudative effusions in heart failure, exudative effusions due to tumors, and parapneumonic effusions in pneumonia. The concept of a 'trapped lung' is introduced, where conditions like inflammatory or neoplastic changes can encase the lung, leading to pleural effusion. Lastly, the paragraph touches on scenarios where pleural mechanics are intact, but pleural effusion occurs due to non-physiological fluid entry, such as peritoneal dialysis fluid entering the pleural space in liver disease.

Keywords

💡Pleura

The pleura refers to a continuous membrane of cells that folds over onto itself, enveloping the lungs. It is crucial for the respiratory system as it helps in the expansion and contraction of the lungs during breathing. In the video, the pleura is described as having two layers: the parietal pleura, which lines the inside of the chest wall, and the visceral pleura, which adheres to the lungs.

💡Pleural Space

The pleural space is the potential space between the parietal and visceral pleura. It is filled with a small amount of fluid that serves as a lubricant, allowing the lungs and chest wall to move smoothly against each other during the breathing cycle. The script explains that this space is estimated to hold between eight and ten milliliters of fluid per side in an average-sized adult man.

💡Pleural Fluid

Pleural fluid is a clear plasma filtrate that originates from small capillaries in the chest wall. It contains solutes like sodium chloride, bicarbonate, and glucose, as well as small amounts of protein, including albumin. The script mentions that pleural fluid has a slightly higher concentration of albumin and bicarbonate compared to serum, resulting in an alkaline pH of about 7.6 under normal conditions.

💡Mechanical Coupling

Mechanical coupling in the pleural space refers to the interaction between the two pleural surfaces facilitated by the pleural fluid. It is likened to a glass coaster sticking to the bottom of a damp glass, where the thin film of fluid creates a partial vacuum that allows the surfaces to cling together while still sliding against each other during breathing. This concept is central to understanding the normal functioning of the pleural space.

💡Starling Forces

Starling forces, also known as pressure-related forces, describe the movement of fluid across the capillary walls into the pleural space. The script explains that during breathing, the recoil of the lungs creates a negative pressure in the pleural space, drawing plasma filtrate from the subpleural capillaries in the chest wall into the pleural space, maintaining the fluid volume in equilibrium.

💡Lymphatic Stoma

Lymphatic stoma are microscopic, unidirectional valves found in the parietal pleura. They allow the exit of pleural fluid from the pleural space. The script mentions that these stoma stretch during inspiration, facilitating the passage of cells and cell debris, playing a role in the absorption of pleural fluid.

💡Pleural Effusion

A pleural effusion occurs when there is an abnormal accumulation of fluid in the pleural space. The script discusses several mechanisms that can lead to pleural effusions, such as increased hydrostatic pressure in heart failure, obstruction of lymphatic drainage by tumors, or increased permeability of lung and chest wall capillaries due to inflammation or infection.

💡Transudate

Transudate is a type of pleural fluid that has a low protein content. In the context of the script, it is mentioned as the nature of fluid found in pleural effusions caused by conditions like heart failure, where increased pressure leads to pulmonary flooding and fluid accumulation in the pleural space.

💡Inflammation

Inflammation is a biological response to harmful stimuli and is mentioned in the script as a cause for pleural effusions. It can increase the permeability of the lung and chest wall capillaries, allowing fluid to leak into the pleural space. An example given is parapneumonic effusion, which occurs in the setting of infectious pneumonia.

💡Trapped Lung

A trapped lung is a condition where the lung becomes unexpanded and physically pulls away from the chest wall, disrupting the normal pleural mechanics. The script explains that this can occur due to inflammatory, infectious, or neoplastic changes that encase the lung surface, leading to an imbalance of pressure and the formation of a pathologic pleural effusion.

💡Diaphragmatic Defects

Diaphragmatic defects refer to abnormalities or openings in the diaphragm that can allow fluid from other areas, such as peritoneal acidic fluid in liver disease, to enter the pleural space. The script mentions this as a non-physiologic route for pleural effusion formation in cases of liver cirrhosis.

Highlights

Introduction of the pleura as a continuous membrane of cells that folds over itself at the apex and base of each lung.

Definition of the pleural space as the potential space between the parietal and visceral pleura.

Explanation of the pleural space's role in regulating lung pressure during breathing.

Description of pleural fluid as a clear plasma filtrate providing lubrication for the pleural surfaces.

Estimation of pleural fluid volume, holding between 8-10 milliliters per side in an average-sized adult.

Composition of pleural fluid including small solutes, glucose, and proteins like albumin.

Mechanical coupling in the pleural space allowing transmission of forces between pleural surfaces.

Comparison of mechanical coupling to a damp glass coaster sticking to a glass surface.

Origin of pleural fluid from plasma filtrate drawn by pressure gradient in the pleural space.

Absorption of pleural fluid through the mesothelial cells of the visceral pleura and lymphatic stoma.

Discovery of fluid absorption via electrolyte coupling through mesothelial surfaces of both pleural layers.

Impact of pleural effusion on mechanical coupling and lung function, leading to shortness of breath.

Examples of conditions causing pleural effusion, such as heart failure and increased hydrostatic pressure.

Role of tumors in obstructing lymphatic drainage and causing pleural fluid accumulation.

Inflammation and infection increasing capillary permeability, leading to pleural effusion in pneumonia.

Concept of trapped lung and its relation to inflammatory, infectious, or neoplastic changes causing pleural effusion.

Existence of pleural effusion with intact pleural mechanics due to non-physiological fluid entry routes.

Example of peritoneal acidic fluid entering the pleural space in liver disease as a cause of pleural effusion.

Transcripts

hi my name is Jody Chapman and I'm here

with dr. Ricardo Gonzalez Rafi to give

you an inside look into the pleura and

the pleural space

what is the pleura exactly the pleura is

a continuous membrane of cells that

folds over onto itself at the apex at

the base of each lung

what is the pleural space well the

pleural space is a potential space

that's between the parietal pleura that

lines the inside of the chest wall and

the visceral pleura that lines the lungs

as the two pleural membranes fold upon

themselves what are the functions of the

pleura in the pleural space the pleural

space it helps regulate the pressure

inside and outside the lungs during

breathing it is thought that the fluid

in the space that provides lubrication

for the pleural surface is on the lungs

and the chest wall as they slide against

each other during the breathing cycle

how much fluid is in the pleural space

this virtual space is estimated to hold

between eight and ten milliliters of

fluid per side and an average-sized

adult man so it's not very much fluid

and under normal circumstances that

amount is held at a pretty fairly

constant volume what is plural fluid

what kind of substances would you find

in it normally pore fluid is a very

clear plasma filtrate if you will which

originates from small capillaries in

chest wall and it contains small solutes

like sodium chloride bicarbonate also

contains glucose as well as the small

amounts of protein including albumin and

when compared with serum pleural fluid

actually has their equivalent

concentrations of glucose but it has

slightly higher concentrations of

albumin and by car

in fact the increased bicarbonate

concentration results in an alkyl otic

pH of about seven point six under normal

conditions plural fluid also contains

macrophages lymphocytes and mesothelial

cells that are exfoliated from the

pleura and these are also found in

pleural fluid in low numbers under

normal circumstances generally under

1700 cells per cubic millimeter one of

the mechanics of the pleural space how

does it work the fluid in the pleural

space provides mechanical coupling

between the two pleural surfaces and it

actually allows instantaneous

transmission of perpendicular forces

between them what exactly do you mean by

mechanical coupling the mechanism of

mechanical coupling is similar to that

which occurs say when a glass coaster

sticks to the bottom of a slightly damp

glass you have a thin film of fluid

between the two smooth surfaces and and

this creates a partial vacuum that

forces the two surfaces to cling to one

another yet allows the two surfaces to

slide against each other

a similar situation occurs between the

two chloral surfaces during breathing as

the lungs expand and contract woman's

chest cavity

where does pleural fluid come from you

know for a very long time we weren't

exactly certain how this came about the

during breathing the recoil of the lungs

creates a negative pressure in the

pleural space especially towards the

apex of the lung and plasma filtrate is

drawn by a pressure gradient from the

sub pleural capillaries in the chest

wall and this fluid passes through the

mesothelial cells of the parietal pleura

into the pleural space by what are

called Starling or pressure related

forces so the volume of fluid in the

pleural space is maintained in

equilibrium under normal circumstances

so such that fluid inflow is proximate

to fluid absorption from the pleural

space how it's plural fluid absorbed

pleural fluid is primarily absorbs

through the mesothelial selling of the

visceral pleura fluid also exits the

space to these microscopic uni

directional valves that are in the

parietal pleura and they're known as a

lymphatic stoma and these lymphatic

stoma are really only found on the

parietal pleura the stoma stretch during

inspiration and allow cells and cell

debris and other particulate products

through it's been recently discovered

that fluid absorption from the pleural

space also occurs as a result of what's

called electrolyte coupling through the

mesothelial surfaces of both the

parietal pleura and the visceral pleura

we've gone over normal pleural fluid

mechanics when you have too much fluid

it's called a pleural effusion what

mechanics are broken when there's a

pleural effusion the sent film of fluid

between the parietal and visceral

pleural surface is it creates a partial

vacuum of negative pressure which forces

the surfaces of the pleura to cling to

one another if you have too much fluid

under pathologic circumstances this

disrupts the mechanical coupling between

the chest wall and the lung and the

pleural surface is no longer cling

together so the lung actually pulls away

from the chest wall

and this increased fluid into thoracic

cavity reduces the vital capacity of the

lung to fully expand during expiration

and this can lead to shortness of breath

and on occasion a feeling of fullness in

the chest the lung tissue in turn

becomes compressed by the effusion

causing an elective of the alveoli and

reduce ventilation to to the areas of

the lung that are being compressed could

you give me some examples of where you

would clinically see a pleural effusion

one mechanism of pleural effusion

formation is that it's caused by

conditions that increase hydrostatic

pressure in the case of heart failure

you have increased left ventricular

natural pressures which caused a back

pressure on the capillaries in the lung

and therefore you get interstitial

pulmonary flooding and this causes fluid

movement and accumulation by

transmutation into the pleural space the

nature of this fluid is that it's a very

low protein content and as such it's

usually referred to as a transudate

another example is when there's a tumor

in the lung or chest wall that's another

mechanism of pathologic formation of

pleural effusions and pleural effusion

can form as a result of impairment of

the lymphatic drainage a tumor in the

lung or in the chest wall can can

mechanically obstruct the thoracic

lymphatics causing a pleural fluid

accumulation by decreasing the rate of

absorption of pleural fluid that

normally occurs in cases of pneumonia

you commonly see pleural effusions what

causes an effusion in that case

inflammation can increase the

permeability or the leakiness of the

lung and the chest wall capillaries as a

result of inflammation and/or infection

so you write a classic example of this

mechanism of pleural fluid information

is Parana Monica fusion in the setting

of an infectious pneumonia you can have

an effusion when there's an unexplored

lung what is a trapped lung certain

conditions can cause the lung to become

unexpanded ballif you will in which case

the lung physically pulls away from the

chest wall causing an imbalance of

pressure which favours increased

filtration of fluid into the pleural

space and formation of pathologic

pleural effusion you can have

inflammatory infectious or neoplastic

changes which can encase the lung

surface leading to a trap lung with

subsequent formation of plural effusion

there are cases when there's a pleural

effusion and the pleural mechanics are

fine nothing's wrong with them where is

that fluid coming from that's correct

there are certain circumstances in which

the fluid formation within the thorax

and the absorption are intact there's

nothing wrong but the mechanism of

pleural effusion formation can occur as

a result of excess fluid entry via what

I would say are non physiologic routes

and the typical example of this can be

seen when peritoneal acidic fluid enters

the pleural space via defects in the

diaphragm in the setting of liver

disease such as cirrhosis I think

looking at these mechanisms from the

different perspectives that we've talked

about really helps conceptualize how

different disease processes can affect

plural flu information and I think it

helps the clinician conceptualize the

whole process better

you