Coughing is a reflex action triggered by some irritant in the respiratory passage. It is intended to expel this irritant as rapidly and forcefully as possible. When the cough reflex is triggered usually by stimulation of the pulmonary irritant receptors lining the lower respiratory tract, the following sequence of events occurs – (i) deep and sudden intake of air (inhalation), (ii) epiglottis closes and the vocal cords contract, (iii) abdominal muscles contract forcefully thereby pushing against the diaphragm, (iv) muscles of expiration contract suddenly and forcefully, (v) pressure increases within the lower respiratory tract, (vi) epiglottis and vocal cords suddenly open and (vii) air is forced out at a high speed.
A cough can also be voluntarily initiated but tends to lack the same force compared to when the cough reflex is triggered. Fits of coughing (paroxysmal coughing) may occur in various diseases. It is usually uncontrollable bouts that continue even though a person feels out of breath, there is soreness in the airways and chest and can even lead to vomiting. Any condition that leads to uncontrollable coughing fits is either stimulating the pulmonary receptors which are then sending signals via the vagus nerve to the medulla of the brain, or this area of the medulla is dysfunctional and eliciting the cough reflex repeatedly even without appropriate stimulation (rare).
Signs and Symptoms
Coughing is a symptom and not a disease on its own. A cough is classified as acute when it lasts for less than 3 weeks, subacute when it persists for more than 3 weeks and chronic if it is ongoing for 8 weeks or more. Most acute and subacute causes are related to infections of the respiratory tract or acute episodes of a chronic allergic respiratory condition. Chronic causes are mainly related to allergies. chronic pulmonary conditions or cardiac disease. A very few infectious causes such as tuberculosis can lead to chronic coughing that may persist for several months. It is important to note that some of the causes of a chronic cough can be fatal if left untreated – it is not the cough that is life-threatening but the underlying disease that causes the cough among other symptoms.
Other symptoms may depend on the underlying cause, extent of the coughing fit and whether a meal was consumed shortly before the onset of the cough. These symptoms may include :
- Sore throat
- Chest pain
- Sputum (productive cough)
- Coughing up of blood (hemoptysis)
- Abnormal breathing sounds
- Cyanosis – bluish discoloration of the skin particularly on the lips, hands, feet, sclera (“whites” of the eye) and less frequently on the entire face.
- Lack of sleep when coughing fits occur at night, while asleep or when lying flat.
- Loss of appetite if coughing fits occur with or immediately after eating or with continuous bouts of coughing fits throughout the day.
Causes of Uncontrollable Coughing Fits
The majority of causes of uncontrollable coughing fits are common to both adults in children. The more common cause of coughing fits in children is whooping cough while in adults it is bronchiectasis. Croup in children may cause sudden bursts of coughing. Various other conditions which may be more prevalent can cause episodes of coughing that are similar to uncontrollable coughing fits.
Whooping cough, or pertussis, is a respiratory tract infection caused by the Bordetella pertussis bacterium. In the second phase of infection, which sets in after the contagious phase, there are fits of uncontrollable coughing often with no other symptoms. These coughing fits may persist even into the convalescent phase (phase three) of the disease but is usually not as severe as in the paroxysmal phase (phase two). Routine vaccination for pertussis in children has made it less prevalent in children over 12 years and adults.
Bronchiectasis is an abnormal and irreversible widening of the lower airways. The weakening of the airway walls leads to outpouchings and when combined with the reduced mucus clearances, bacteria can set in and lead to repeated infections. Bronchiectasis may be caused by hereditary and autoimmune conditions but the most common causes are severe respiratory tract infections like tuberculosis and pneumonia.
Chronic obstructive pulmonary disease (COPD) is a progressive airway disease that is often irreversible. Most cases are associated with cigarette smoking and other inhaled toxins or air pollutants. The two main types of COPD are chronic bronchitis and emphysema. Of these two conditions, it is chronic bronchitis that is known for the most prominent coughing, often referred to as a smoker’s cough.
Post nasal drip is among the more common causes of a persistent cough. Although it does not tend to present as uncontrollable coughing fits, it can cause short bouts of coughing in an attempt to clear the throat. Post nasal drip is a result of excessive mucus production in the nasal cavity which empties into the back of the throat. It may be due to allergic or infectious causes primarily, but can also be associated with repeated irritation of the nasal mucosa from cigarette smoking and even severe GERD.
Asthma is a chronic disorder characterized by episodes of airway constriction (narrowing) which is reversible. There are several different causes associated with the various types of asthma – allergies (atopic), after a viral infection (non-atopic), medication (drug-induced) and industrial vapours, gases or dusts (occupational). The most common type seen from childhood is atopic asthma which is associated with an immune-mediated hypersensitivity of the airways that may be inherited. Exposure to dust, smoke, certain medication, air pollution, col weather, psychological stress and various other trigger factors may bring on or exacerbate an attack. Gastroesophageal reflux disease (GERD) is now known to be a major causative and trigger factor.
Tuberculosis is a chronic infection that affects mainly the lungs. It is caused by Mycobacterium tuberculosis which may be spread from one person to another when airborne droplets from an infected person is inhaled. Coughing is one of the main ways that these droplets containing M.tuberculosis is spread. However, most people who are infected do not develop an active disease as the healthy immune system suppresses it. The active disease is therefore more commonly seen in immunocompromised people, like those with HIV/AIDS. The most common symptom, coughing, develops weeks after the active disease begins. It is a productive cough which may be blood. It quickly subsides once treatment is commenced.
Gastroesophageal reflux disease (GERD) is an upper gastrointestinaltract disorder where there is backward flow of stomach acid into the esophagus. It is commonly referred to as acid reflux and the most prominent symptom is heartburn. In severe cases, particularly at night when sleeping, the acid may reach up to the throat, enter into the airways or even reach the nasopharynx. This irritation of the throat and airways can elicit a coughing fit in an attempt to expel the offending agent. However, the acid can irritate the lining of the throat and airways even with momentary contact and coughing can therefore not remove the irritation.
Other causes that can cause persistent coughing includes :
- Cancer of the lungs and airways may also present with bouts of coughing and even bloody coughing. It is usually not uncontrollable fits.
- Medication like ACE inhibitors can cause a nagging dry cough but here as well, fits of coughing are not common.