In asthma bronchial spasm occurs in response to an allergen so theoretically a patient shud find it as hard to inspire as to expire but that is not the case seen practically.The patient faces a problem mainly while breathing out. Can someone tell me the cause behind this.
Answer:
We all have a normal "reflex" in our bronchi, that decreases the lumen of them everytime we exhalate air.when there is inflamation and secretion of mucus, such as it happens in asthma, this reflex is exaggerated, bringing more of a "spasm" of the muscles of the bronchi.
So its dealt with, according to the cause (chronic infections, smoking, exposure to toxic substances like asbestos, allergies), and symptomatically, decreasing the inflamation, and dilating the bronchi, with special medications (terbutaline, ephedrine derivetives, amynophylline), and sntihistaminics and antagonist of the allergic response (if the cause is allergy) such as pralukast sodium astemizole etc...
So, as You see,normal inspiration by itself, normally DILATES the respiratory entrance (the portion surrounded by smooth involuntary muscle), and during expiration it NARROWS the outlet, because the exaggeration of the normal reflex we have cited in the beginning
Hope this wil clarify things a little bit, though..
Cheers
The problem with COPD is that it is hard to exhale. They have to work to get air out, not get air in. The lungs tend to expand and get bigger because of this.
The simpliest way to answer your question is by thinking about what generates the force to inhale or exhale a breathe of air. When you inhale, many muscles including your diaphram, intercostal muscles, and a few of you neck muscle contract to expand your lungs. Alot of force is generated here. When you exhale,(this is a different story) it is more passive. The expanded lungs has a certain elasticity and essentially the lung substance recoils and pushes the air out. So in asthma where there is narrowing of the bronchials,
during inhalation the force that your muscles can generate can overcome the narrowing of the bronchials. During exhalation, the lung recoils and air flows out but the last bit of volume of air is difficult to push out.Lets take another example of COPD like emphysema. After prolonged smoking, the smoke destroys the lung tissue. When this happens there is less tissue to generate that "recoil force" to push the air out. So people with emphysema have overinflated lungs ie barrel chested. You can get the air in but you can't get all of it out.
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