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Old 02-23-2012
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Default I just cantr understand this

in one Q in uworld , it says that airway resisitance in medium sized and small bronchioles first 1-10 generation is greater than airway resistance in upper airways (nasal passages) and also greater than the resistance in small bronchioles ??
is that mean that resisitance is first increase then decrease
can anyone clarify???
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  #2  
Old 02-23-2012
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Yes, this one is kinda weird.

I am not sure if I understand this one completely, but I imagine lungs to be like a balloon - it has very narrow opening, so its hard for all the air to go through this opening, but once it passes the narrow part - there is low resistance to go further...
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Old 02-23-2012
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What's the Q ID? Maybe I can look it up...
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in the Q there is graph and it (as i understood)that resistance first little in upper airways then increase (then decrease again) and the last part what I am not sure of and cant explain it??
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Old 02-23-2012
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Airway resistance in the repiratory tract us as follows:

Increases until the level of the large bronchi, and then steadily decreases as you approach the terminal bronchioles.

I had this graph on a test somewhere, i hope my explanation is enough to visual the graph.
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Quote:
Originally Posted by d_wiqed View Post
What's the Q ID? Maybe I can look it up...

I am not sure which one but I read the notes if I will find which one i will post it, but that is the explanation u world gave
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Ok! I haven't encountered that question yet. Maybe if I come across it one of these days or if someone finds the Q Id, I'll see if I can explain it. I'll just pm you or get back to this thread.
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Old 02-23-2012
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its a concept, if its a narrow radius there is more resistance. That being said, you can think that the bronchiole has more resistance because of its small radius , but remember the generations of bronchiole, many divisions, making it easier for air to divide its resistance.

So, main bronchus, more resistance, terminal bronchili less resistance.

Be aware if they mention small airway disease, that might turn the curve upside down.
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Old 02-23-2012
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Quote:
Originally Posted by LatinGeorge View Post
its a concept, if its a narrow radius there is more resistance. That being said, you can think that the bronchiole has more resistance because of its small radius , but remember the generations of bronchiole, many divisions, making it easier for air to divide its resistance.

So, main bronchus, more resistance, terminal bronchili less resistance.

Be aware if they mention small airway disease, that might turn the curve upside down.

To elaborate wht latingeorge explained:


While a single smaller airway has more resistance compared to a larger airway, the resistance to flow depends on the number of parallel pathways, therefore, large and med airways provide much more resistance to flow than NUMEROUS smaller airways (you could use the flow in parallel equation here, parallel is 1/r1 + 1/r2...)

if plotted on a graph the pressure should start high in the main trachea, peak at the bronchus and taper as we reach the bronchioles

AND to top it, the resistance decrease as lung volume increases ... so the airways distal the 2ndary bronchus will distend as the lung inflates leading to wider airways which leads to decreased resistance.

phew!
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Old 02-23-2012
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Also... remember the surfactant, helps to reduce the resistance in the alveoli...
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Old 02-24-2012
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You guys seem to have a fair idea of the situation for. (That's why really appreciate this forum)

Just to give it a final polishing; I'll quote a line from wikipedia -
"Resistance is greatest at the bronchi of intermediate size, in between the fourth and eighth bifurcation."

Just to reinforce this information with a fascinating fact - The NVBS (normal vesicular breath sounds) we hear by keeping the stethoscope on various areas of the chest is produced in this zone of maximum airway resistance. The sound waves thus produced are then carried by the lung substance to to the chest well where the steth is kept.
The original sound produced is a so called white noise having multiple frequencies ranging from 200-2000. This coarse sound has a so called "bronchial" quality. But the while it's passage through the lung architecture, the lower frequencies are filtered out and we perceive the NVBS.
Now in case of lung consolidation; a bypass path created for the breath sounds to pass directly to the chest wall (without getting filtered by the lung architecture). Hence the all important auscultatory finding of bronchial breath sounds in Pneumonia.

Hope that was of some use.
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Old 02-24-2012
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Quote:
Originally Posted by Dr. Mexito View Post
Also... remember the surfactant, helps to reduce the resistance in the alveoli...
Surfactant only helps in reducing surface tension.. it has nothing to do with airway resistance.

Also as rightly mentioned in many of the post above the till the the respiratoty bronchioles distribute the resistance among themselves thus reducin individual resistance levels..
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Old 02-24-2012
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Quote:
Originally Posted by manusharma1406 View Post
Surfactant only helps in reducing surface tension.. it has nothing to do with airway resistance.

Also as rightly mentioned in many of the post above the till the the respiratoty bronchioles distribute the resistance among themselves thus reducin individual resistance levels..
So... A child with a collapsed alveoli wouldn't have an increase in the airway resistance?
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Quote:
Originally Posted by Dr. Mexito View Post
So... A child with a collapsed alveoli wouldn't have an increase in the airway resistance?
BRS physiology..

Factors that change airway resistance:
a. contraction or relaxation fo bronchial smooth muscle
b. lung volume
c. viscosity or density of inspired gas

LUNG VOLUME: alters airway resistance because of the radial traction exerted on the airways by surrounding lung tissue.

high lung volumes = greater traction, less resistance
low lung volumes = less traction, increase resistance even to the point to collapse.

"Surfactant maintains the openness of alveoli and terminal conducting airways, and thereby promotes normal blood gas levels and low airway resistance."
http://chestjournal.chestpubs.org/co...133/4/975.full
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Old 02-24-2012
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Alveoli.have a very important role in lung compliance.not airway resistance.. High surface tension means u need more pressure per unit volume increase thus reduced compliance of the lungs.. Not airway resistance.. I'll find a reference to back this up...
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