Why is bronchiectasis considered an obstructive, not restrictive disorder?

[Ven0m]

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Is it because the bronchioles are dilated, leaving more air inside the bronchioles at the end of each expiration?

 

[DrPicard]

Wide airways increase turbulence which offers greater resistance to air moving in and out.

(turbulence and diameter are directly related)

 

[Ven0m]

Wide airways increase turbulence which offers greater resistance to air moving in and out.

(turbulence and diameter are directly related)

Uhh.... I thought wide airways help increase air flow. Like when someone going through an asthma attack needs an inhaler to dilate their bronchioles/bronchi because they're constricted.

But I do know that there is excessive mucus lining the bronchi in bronchiectasis. Since the walls are damaged, it's harder to get the mucus out, so it just builds up, narrowing the airways. But then this would be both restrictive (difficulty filling lungs with air during inspiration) and obstructive (difficulty getting air out of the lungs during expiration). Yet bronchiectasis is still classified as an obstructive disease... I'm confused!!

 

[DrPicard]

If they get too wide it gets difficult getting air out since flow doesn't remain laminar. The air, instead of moving straight out, curls around in the airways.

The idea in vascular physiology is explained by Reynold's number. Not sure if the same term can be applied here, though.

 

[Transposony]

Uhh.... I thought wide airways help increase air flow. Like when someone going through an asthma attack needs an inhaler to dilate their bronchioles/bronchi because they're constricted.

But I do know that there is excessive mucus lining the bronchi in bronchiectasis. Since the walls are damaged, it's harder to get the mucus out, so it just builds up, narrowing the airways. But then this would be both restrictive (difficulty filling lungs with air during inspiration) and obstructive (difficulty getting air out of the lungs during expiration). Yet bronchiectasis is still classified as an obstructive disease... I'm confused!!

It's a functional obstruction. There is dilation of bronchi with loss of elastin, smooth muscle, and cartilage. So they are more "floppy" as compared to normal.
Also, the bronchi are not uniformly dilated since with repeated infection/inflammation there is always some element of patchy fibrosis leading to the dilation (cystic or saccular).
As @DrPicard said, the airways are dilated so the air doesn't flow through the bronchi that well.
Think of it being similar to atrial fibrillation where "eddies" leads to stagnation of blood in the atria leading to thrombus formation.
Another analogy : try to blow the same amount of air though a drinking straw and a paper towel roll.
You will be able to blow less air through the paper towel roll. And now if you add eddies to the equation you won't be able to make much air move through the paper towel roll.
Hope this helps.

 

[Ven0m]

It's a functional obstruction. There is dilation of bronchi with loss of elastin, smooth muscle, and cartilage. So they are more "floppy" as compared to normal.
Also, the bronchi are not uniformly dilated since with repeated infection/inflammation there is always some element of patchy fibrosis leading to the dilation (cystic or saccular).
As @DrPicard said, the airways are dilated so the air doesn't flow through the bronchi that well.
Think of it being similar to atrial fibrillation where "eddies" leads to stagnation of blood in the atria leading to thrombus formation.
Another analogy : try to blow the same amount of air though a drinking straw and a paper towel roll.
You will be able to blow less air through the paper towel roll. And now if you add eddies to the equation you won't be able to make much air move through the paper towel roll.
Hope this helps.

I understand your meaning, but my question was why is that considered obstructive, rather than restrictive? Is it harder to exhale out, but inspiration is normal?

 

[Transposony]

I understand your meaning, but my question was why is that considered obstructive, rather than restrictive? Is it harder to exhale out, but inspiration is normal?

What is your understanding of Restrictive lung diseases ?

 

[Ven0m]

Restrictive: decreased ability for lung to expand, facilitating airflow in
Obstructive: decreased ability for lung to recoil back, forcing air out

 

[Transposony]

Restrictive: decreased ability for lung to expand, facilitating airflow in

What do you mean by "facilitating airflow in" ?
Airflow in Restrictive lung diseases is normal, not increased.

 

[Ven0m]

What do you mean by "facilitating airflow in" ?
Airflow in Restrictive lung diseases is normal, not increased.

i meant to say that i thought restrictive means harder to get air in, while obstructive means harder to get air out

as in restrictive diseases, its harder to expand the lung, so its harder for air to flow in
and in obstructive diseases, its harder for all the air to come out, like in emphysema, where the alveoli have lost their elasticity, thus air remains in the alveoli and the alveoli remain distended with air.