Why would Restrictive Lung Disease make exhaling difficult?

[sameeralord]

Restricitive air way disease is the loss of lung compliance. So this would make it harder for the lung to expand causing inspiration difficult.

My questioon is why can't this make exhaling difficult. Losing the elasticity of the lung would make both recoil and expansion difficult right. This might sound funny but let's say the lung was in expanded position and then suddenly lost its elasticity, wouldn't this make exhaling difficult.

Is barrel chest restricive or obstructive air way disease.

Thanks a lot for your help in advance

 

[Andy Resnick]

Interesting question... I think.

I'm not an expert, but my understanding is that inhalation involves relaxation of the diaphragm and can be considered a 'passive' process, while exhalation involves contraction of the diaphragm and is thus 'forced'. You can increase the resistance to breathing by pursing your lips- it's a good trick to increase the uptake of O2 during aerobic exercise- and in my experience, inhalation is made significantly more difficult than exhalation.

 

[Moonbear]

It's the other way around. Contraction of the diaphragm flattens it, which expands the space in the pleural cavity for inspiration to occur. Relaxation of the diaphragm returns it to it's dome-shaped position during exhalation. The intercostal muscles (between the ribs) also contribute to inspiration and expiration, and there are some other weak accessory muscles.

Someone who is "barrel chested" usually has COPD, and may use other muscles that are not typically considered muscles of respiration to compensate for the additional work needed for each inhalation.

In a condition with less elasticity of the lung, you can still essentially "squash" the air out of it when the space in the pleural cavity decreases, even without the lung functioning properly. You can't make it re-expand into the space created during an inhalation.

 

[Danger]

Speaking as one with terminal COPD, I can definitely say that exhalation is the main problem. The 'pursed lips' breathing mentioned by Andy is not merely a choice; it's the only way to exhale during exertion. I've tried not doing so, and it isn't possible. After a few 'normal' exhalations, unconsciousness was imminent and pursing resumed involuntarily.
I should mention, as well, to any fellow COPD sufferers who might not be aware of it, that emphysema forces a false positive on a breathalyzer. If you get charged with impaired driving, insist upon a blood test. I lost my license and a couple of thousand bucks in fines because the law student who represented me refused to enter that fact into evidence and pled me guilty. (Legal Aid won't touch traffic-related issues, and I couldn't afford a real lawyer. In retrospect, a real lawyer would have been cheaper, since I would have been found innocent.) The alveoli, having lost their elasticity, don't give up their gasses without a fight. If you breathe 'normally', therefore, over a few days, and then force a full exhalation, the alcohol consumed during the full intervening period will be released and registered.

 

[AyazM]

To answer your question requires using graphs and some calculations but rather than doing that, I'd prefer to be succinct. Restrictive lung diseases cause the lung to "collapse" somewhat. Imagine this: rather than lungs going WAY out during inspiration because an elastic can be stretched to maximal lengths and it RETURNS when the force is removed, in restrictive disease this elastic is replaced by something that has LESS elastic properties.

Now imagine: the lung is at a LOWER resting volume because it just can't expand much and it stays that way. Because the elastic material is gone, the TOTAL expansion and TOTAL relaxation is also reduced which means there is less ground covered during a tidal volume (a tidal volume is air you inhale and exhale when you are at rest).

I'm really finding it difficult to explain without a graph but let's stick to it. You have to understand that merely "inspiration" and "expiration" being difficult doesn't hold much merit because it's the final VENTILATION from your alveoli towards blood that is the real question.

When your lungs are already "collapsed" and you can't just expand the not-so-elastic material that much, and when you try it, it causes a great collapsing force and readily tends to come back to the same initial point. So no, this can't make expiration "difficult" in a sense that this wouldn't cause much of a trouble in a clinical scenario.

This might sound funny but let's say the lung was in expanded position and then suddenly lost its elasticity, wouldn't this make exhaling difficult.

It's not about exhaling; the lungs in that manner would immediately collapse if for example, the elastic is replaced by something not-so-elastic. In another scenario when nothing replaces the elastic, the lungs would REMAIN where they are. This WOULD make exhaling difficult because remember one FACT: During exhalation, the pressure causes the airways to COLLAPSE. The more you try to EXERT on your lungs, the more your airways collapse easier and the more difficult it is to exhale in that case.

Barrel chest is an obstructive disease. It happens in emphysema because the lung in that case is just full of empty spaces containing air which can't be exhaled readily causing the chest wall to SPRING OUT making it barrel shaped.