The three main symptoms of asthma include wheezing, coughing and difficulty in breathing. Some people may not have wheezing, others have only coughing which may be more common at night or after exercising. The symptoms of asthma are not continuous. Typically they occur in bouts. The length of an attack varies and depends upon the factors that trigger the attack. The symptoms may either appear suddenly or increase gradually.
Coughing: Coughing is a spontaneous reaction of the body to expel excessive mucus in the respiratory passages. You cough when the pressure built up in these passages explodes with a rush of air. Normally, thin hair -like projections on the inner lining of the respiratory passages remove excessive mucus or irritants that you breathe in. If the secretions are very thick, these hair-like projections cannot expel them and therefore the body responds by coughing. Formation of very thick mucus plugs or complete blockage of the smaller airways (bronchioles) results in the inability to expel mucus, and therefore in dry cough.
Wheezing: Most people think wheezing is the main symptom of asthma. Wheezing develops when the air is pushed through narrowed respiratory passages very forcefully while breathing out. The normal process of breathing out involves narrowing of the respiratory passages. If these passages are already narrow, further narrowing requires increased effort to squeeze the air out. Normally, the duration of breathing in and out is the same, but during an attack of asthma, the duration of breathing out is longer, Wheezing is accompanied by a whistling sound caused by the expelling of air through the narrow bronchioles.
It is important to remember that if there is very severe narrowing of the airways, the air that flows through is too thin to produce a wheeze. That is why absence of wheezing during a very severe asthmatic attack is a dangerous sign.
Contraction of the muscles: The muscles of the bronchi contract and the airways inside the bronchi therefore become narrow. Contraction of the bronchi is called bronchospasm. The severity of bronchospasm varies from person to person and depends on the severity of the attack. If the attack is severe, bronchospasm is also severe. It causes difficulty in breathing and results in wheezing and coughing. Increased mucus secretion: During an attack of asthma, the glands of the inner lining of the respiratory passages secrete large amounts of mucus which is thicker than normal mucus. Secretion of mucus is a protective step the body takes against the irritant that has caused the asthmatic attack. In asthma, the mucus clumps together in the respiratory passages and blocks them partially.
Excessive mucus can also form plugs that completely block very small airways in the lungs. These mucus plugs can be expelled by coughing. In case there are several mucus plugs, you can have continuous arid irritating cough. If appropriate treatment is not taken, the mucus plugs can prolong the duration of an asthmatic attack and increase the risk of infections in the respiratory tract.
