Cough is one of the most common symptoms found in medical practice. Besides being a sign of a possible respiratory disease, cough is also a vital defense mechanism of our airways. In this paper we explain how the cough arises and what its causes.
Coughing is a reflex of the airways which aims to free the passage of air into the airways. Coughing can happen voluntarily or involuntarily. This reflex can be stimulated by secretions, irritants, fumes, foreign objects, inflammations, infections etc.
The cough reflex mechanism is very complex, so we will try to explain it in a simple way.
The entire respiratory (lung, pleura, trachea, larynx and diaphragm) epithelium (tissue) is called cough receptors responsible for detecting any mechanical or chemical insult, like an object aspirated into the secretions, strong smokes or smells for example. These receptors are attached to the laryngeal nerves and, when stimulated, bring this information directly to the brain. Every time the brain receives a message of cough receptors, it interprets this as a potential danger of airway obstruction. The brain then sends back an order to the airways, closing the glottis and contracting the muscles of breathing rapidly, causing the intrathoracic pressure to rise rapidly. Immediately after this sudden rise in pressure, the glottis relaxes letting out this trapped air, which can reach speeds above 200 km/h, expelling any potential obstruction to airflow.
Cough is therefore a defense mechanism against airway obstruction, however, there are many other stimuli other than a potential obstruction, which can activate it. In addition to the airways, cough receptors also exist in the esophagus, heart and stomach, causing various conditions such as gastroesophageal reflux disease, pericarditis and heart failure, which may also be causes of cough.
Medications, especially captopril, enalapril and similar
Stress (psychogenic cough)
Foreign body aspiration
Irritation of the airways by inhaled substances
In cases of acute coughs, or less than of 3 weeks' duration, symptoms that often come bundled normally help in defining a diagnosis. Sneezing, sore throat and fever are usually present in the flu; fever, weight loss and purulent sputum are common in tuberculosis; hoarseness and dry cough are typical of laryngitis, shortness of breath and wheezing usually indicate asthma, just to get in examples.
There are a few different types of cough, with features that help us in investigating its cause. The cough may be dry or sputum, purulent or even bloody and may be acute when it lasts less than 3 weeks, subacute, when it lasts between 3 and 8 weeks, or chronic which lasts longer than 8 weeks. Cough may be accompanied by fever, weight loss, shortness of breath, hoarseness, constipation, nasal, chest pain etc.
Let's talk a little bit of some common types of cough and its causes.
Persistent cough
When the cough lasts long, the diagnosis is not always simple. However, most of the complaints of persistent cough frames occur after viral infection of the respiratory tract. Often respiratory symptoms and fever disappeared several days ago, but the patient keeps coughing. This occurs because the airways remain irritable, sometimes even cough by the effort of previous days, making the cough receptors remain stimulated. Any picture of respiratory tract infection may be followed by several weeks of dry cough without having any clinical relevance.
A cause of chronic cough that often goes unnoticed by the patient is that caused by drugs of the class of Angiotensin Converting Enzyme (ACE) inhibitors, used to treat hypertension, kidney disease and heart failure. The most common drugs of this class are captopril, enalapril, ramipril and lisinopril. In these cases, cough may appear only after 6 months of use of the drugs, so that patients do not relate one to the other. The suspension of the drug is enough for cough to fade.
In patients who smoke for many years, a chronic cough with expectoration, especially early in the day, is a very common symptom and can display a picture of chronic bronchitis in the initial phase.
Every patient with chronic cough, especially smokers, fears that the cause is lung cancer. In fact, less than 2% of cases of prolonged cough are caused by cancer. However, this diagnosis should always be thought of if the patient is a smoker and present, besides cough, bloody expectoration and weight loss.
In many patients anxious or depressed, a picture of chronic cough can be caused by periods of emotional stress, called psychogenic cough.
Other common causes of prolonged cough is chronic sinusitis and gastroesophageal reflux. In sinusitis cough is usually caused by post-nasal drip that is the small stream that falls secretions of the nasal and sinus toward the throat.
Cough with Expectoration
A very common feature is the presence of cough sputum, popularly called coughing with phlegm. In medicine we call it a productive cough. The phlegm, or sputum, is actually produced by mucus secretions and airway. This mucus is usually clear, but if it is being produced by an infection, it becomes purulent, whose appearance most commonly makes a greenish-yellow sputum.
The main causes of cough are respiratory infections, including influenza, pneumonia, sinusitis and even tuberculosis. Chronic bronchitis usually caused by smoking also causes a cough. Every patient with cough fever should be seen by a doctor as this picture is highly suggestive of respiratory infection.
Dry cough
Dry cough is one that has no expectoration. It can be caused by allergic processes, residual irritation of the airways after pictures of respiratory infection, asthma, medication (captopril, lisinopril, ramipril and enalapril), irritation of the diaphragm, exposure to smoke and chemicals or foreign body aspiration.
Blood cough
A cough with bloody sputum was examined in a text which itself can be read here: cough and bloody sputum.
Perhaps no other symptom has so many homemade recipes and syrups like cough. It is, however, need to be understood that first and foremost, coughing is a defense mechanism of the airways. Cough is a symptom and not a disease. Taking drugs indiscriminately to stop it can be harmful. Most cases of coughs are caused by respiratory viruses which heal spontaneously after a few days, and therefore it is unnecessary to take medicines for these frames.
If the airways are filled with secretions, cough is the most important mechanism to clear them; inhibit cough in these cases will only cause accumulation of secretions in the lungs, which obviously is not a good idea. Therefore, no productive cough should be interrupted by drugs, syrups or home recipes. In fact, no drug that acts by inhibiting the cough must be used without medical supervision. "Calming" the cough is not always the appropriate procedure.
Oddly enough, the best treatment for cough is water, which serves to keep the airways hydrated, reduces tissue irritation and leaves the mucus more liquid, facilitating its expectoration. Avoiding contact with cigarettes is also essential.
In most cases the treatment of cough passes through the treatment of the disease that is causing it this includes asthma, pneumonia, tuberculosis, allergies, heart failure, reflux etc.
The use of syrups or other drugs or expectorants called mucolytics can be used. Nowadays it has become very common prescription of effervescent tablets of N-acetylcysteine to facilitate expectoration, but there are no definitive studies on its effectiveness.
The most important is to remember that coughing is a symptom, so treatment should be done against the condition that is causing it and not the symptom itself.
