Everybody experiences cough at some point in their lives. Coughing is an involuntary reflex action intended to expel some foreign object or irritant from the throat or the respiratory tract. This can occur as a one off episode or it may be recurrent and sometimes even persistent. When coughing becomes uncontrollable it needs to be investigated in order to identify the underlying cause and for the appropriate treatment to be implemented.
Why do we cough?
Although most people think of coughing as a single act, the cough reflex is a sequence of two main events:
- Building up pressure in the lungs: The cough reflex begins with a sudden intake of lots of air into the lungs, followed by the closure of the epiglottis and vocal cords to prevent the inhaled air from escaping. The pressure in the lungs is then built up by contraction of the abdominal muscles that pushes the diaphragm upwards into the chest cavity.
- Forceful expulsion of air from the lungs: The built-up pressure in the lungs is then released as the air is expelled forcefully by the opening of the epiglottis and the vocal cords. This forceful expulsion of the air is heard as a cough.
Coughing can also be performed voluntarily, but never with the force that accompanies the involuntary coughing reflex.
Reasons for Uncontrollable Coughing
In certain conditions, an individual might start coughing continuously. These uncontrollable bouts or fits of coughing can occur due to two reasons:
- Pulmonary receptor activation: The pulmonary receptors in the airways or lungs become activated due to various causes and send signals to the region of the brain (medulla) that initiates the cough reflex.
- Brain dysfunction: The medulla in the brain starts acting on its own without any sensory inputs from the pulmonary receptors, causing uncontrollable coughing without any respiratory cause. However, this is a rare condition.
Other Signs and Symptoms
Following are some of the symptoms of an uncontrollable cough:
- Continuous involuntary coughing even when the person feels out of breath
- Sore throat due to continuous coughing
- Expulsion of sputum in cases of productive cough
- Vomiting might also happen in an effort to expel an offending trigger
- Blood may also come out during a cough (a condition called hemoptysis)
- Breathing sounds may become abnormal
- Cyanosis or a bluish coloration of the skin affecting various regions of the body such as the lips, hands, feet, white part of the eye and sometimes the entire face.
- Sleep deprivation, if continuous coughing happens during night
- A loss of appetite accompanying prolonged fits of coughing during the day
Coughing is classified as acute, sub-acute or chronic depending on the duration of the coughing fits. Acute coughing lasts for less than three weeks, whereas sub-acute coughing lasts for more than three weeks. If persistent uncontrollable coughing lasts for more than 8 weeks, it is termed as chronic.
Causes of Uncontrollable Coughing
Coughing is not a disease. Uncontrollable cough is usually a symptom of another underlying condition or disease that needs to be identified and treated. The following are some of the main causes of uncontrollable cough:
Whooping cough (Pertussis)
Whooping cough is caused by a bacterial infection of the respiratory tract in children. It is caused by the bacteria Bordetella pertussis. This disease is infectious in nature and the persistent coughing lasts throughout the disease progression and remission periods, even when other symptoms subside. Widespread vaccination at a young age has helped in reducing the incidence of this disease in children.
Bronchiectasis is a common cause of chronic uncontrollable coughing in adults. This disease is caused by an abnormality in the lower respiratory tract in the lungs, which results in an irreversible widening of the airways and an outgrowth of pouches from their walls. The weakening of the lower respiratory airways reduces mucus clearance. This mucus then accumulates in the pouches in the airway walls and becomes a breeding ground for bacteria. Tuberculosis and pneumonia are the most common infectious causes of bronchiectasis, although the condition can also be caused by hereditary and autoimmune diseases.
Chronic obstructive pulmonary disease (COPD)
Chronic obstructive pulmonary disease, also abbreviated as COPD, is a progressive lung disease caused by smoking and inhalation of air pollutants. These air pollutants damage the airways of the lungs over time and make it difficult for the affected person to breathe. COPD is further classified into two main types: chronic bronchitis and emphysema. Uncontrollable persistent coughing is a characteristic feature of chronic bronchitis.
Excessive mucus production by the mucus membranes in the nose can lead to passing of the excess mucus into the back of the throat. This is known as postnasal drip and can lead to persistent coughing in an attempt to clear the excessive mucus from the throat. Postnasal drip is caused by various allergies (e.g., rhinitis), gastroesophageal reflux disease (GERD), and cigarette smoking. A disorder in the swallowing process (e.g., in esophageal motility disorder) could also lead to postnatal drip and uncontrollable coughing.
Asthma is a common, chronic disease that causes reversible constriction of the airways in the lungs and uncontrollable coughing. The most common cause of asthma is allergy to environmental factors such as smoke, dust, pollen, cold weather and air pollutants. It can also be caused by viral infections, GERD and certain medications. Psychological stress can also precipitate asthma attacks.
Tuberculosis is a bacterial infection caused by Mycobacterium tuberculosis. It is a chronic condition that most commonly affects the lungs and causes persistent coughing. Blood may also be present in the sputum of the affected individuals. Coughing in tuberculosis is a mode of infection. However, it can be controlled by drugs but the focus is usually on eradicating the pathogen.
Gastroesophageal reflux disease
Gastroesophageal reflux disease, also known as GERD, refers to a backflow of acid from the stomach to the esophagus. The esophagus gets damaged by this acid reflux because its walls are not built to withstand the low pH of the stomach acid. This acid-induced irritation and injury to the esophagus causes uncontrollable coughing along with symptoms of heartburn.
Croup is an acute condition caused by viral infections of the upper respiratory tract. The airways get swollen and breathing becomes difficult. The cough produced in croup has a characteristic barking sound.
Some cancers of the respiratory system could also lead to persistent coughing by irritating the airways as the malignancy destroys healthy tissue.
While several different drugs can cause coughing as a side effect, this is most prominent with certain drugs such as ACE inhibitors.