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Q.What is the most common complaint for which patients seek medical attention?
A. Cough

Introduction
In the United States the most common complaint for which patients seek medical attention is cough and it is the second most common reason for a general medical examination. (from "Managing Cough As A Defense Mechanism and As A Symptom. ACCP Consensus Statement". Chest 114 (2; suppl 2), 1998). If you factor in the amount of money people in the US spend on nonprescription medications to treat cough or other associated symptoms and add that to the direct costs of medical visits, exams, tests and hospital stays, then the annual cost of treating cough in the United States is greater than 1 billion dollars

People seek treatment for cough because of the following complications:
• subjective perceptions of exhaustion and self-consciousness,
• symptoms of insomnia,
• hoarseness,
• musculoskeletal pain,
• sweating and
• urinary incontinence.

Cough can be either productive (i.e. accompanied with sputum) or non-productive (i.e. no sputum accompaniment). In addition, cough can be considered either acute or chronic. By definition, acute cough lasts less then 3 weeks. The most common cause of acute cough is the common cold. Chronic cough, on the other hand, is defined as a cough that lasts for 3- 8 weeks or longer. There are many causes of chronic cough. In a person who is a smoker, the most likely cause of chronic cough is chronic bronchitis. In non smokers, the most common cause of chronic cough is post nasal drip syndrome (PNDS), followed by asthma (specifically referred to as cough variant asthma) and gastroesophageal reflux disease (GERD). Other causes of cough include bronchiectasis, postinfectious cough, bronchogenic carcinoma, cough due to treatment with Angiotensin Converting Enzyme Inhibitors (ACEI) and what is termed "habit cough" or psychogenic cough.

Physiology of Cough

Cough is an important defense mechanism of the body. It serves to clear the airway of excessive secretions and foreign matter. It can be either voluntary or involuntary. As a reflex, it is activated when
• there is either inhaled particulate matter or irritant gases in the airway (certain gases such as ammonia, nitric acid and sulfuric acid and nitrogen dioxide can irritate the airway)
• there is a large amount of mucus in the airway (either because of excessive secretion or impaired clearance)
• there is a large amount of edema or pus in the airway
• thermal stimuli (very hot or very cold air can sometimes trigger the cough reflex but, usually, this only occurs in people who already have some pathology in the lungs)

The cough reflex includes transmission of impulses via afferent (sensory) neurons from specialized receptors located in respiratory tissue to a central cough center, then transmission of nerve impulse from the central cough center via efferent (motor) neurons back out to respiratory muscles. Cough receptors are located within the epithelial layer of respiratory tissue. There are both mechanical receptors and chemical receptors. The mechanical receptors are sensitive to touch and displacement and are located primarily in the larynx, trachea, and carina. Chemical receptors are sensitive mostly to noxious gases and fumes. These receptors are located more in the larynx and bronchi. Receptors are found in respiratory bronchioles. but extend no further down the respiratory tree then this. Cough receptors tend to become less sensitive when continuously stimulated.

Cough receptors send their impulses to a central cough center via the vagus nerve, the glossophayrngeal, trigeminal and phrenic nerves. The vagus may also send messages to the cough center from higher centers of the brain. These additional vagal afferents may be able to suppress the cough center. So, in one respect, vagal afferents (directly from the receptors in respiratory tissue) stimulate the cough center; in another respect, other vagal afferents (originating from a higher center in the brain) can suppress the cough center.

There is much debate about where the central cough center in the brain is located. Most likely it is not one single center, but rather is distributed throughout the brain in a few locations spread out through the medulla oblongata of the brainstem . The efferent nerves that carry impulses from the cough center to the muscles that will result in a cough include the phrenic nerve and the efferent branches of the vagal nerve.

An effective cough depends on an interaction between the volume of gas that is inhaled and the properties of the mucus lining the airways. To begin with there is an initial inspiration of air (ranging from 50% of tidal volume to 50% of vital capacity). This volume of air stretches the expiratory muscles (like a rubber band getting ready to snap back). When the muscles start to snap back (beginning of expiratory phase), the glottis closes very briefly (this increases pressure in the lungs even more so, so that when the glottis opens the air is expelled with a greater force), then the glottis opens and the air is expelled (cough). The purpose of the cough is to remove mucus, so the properties of the mucus also contribute to the effectiveness of the cough. Mucus is most effectively dispersed in the expelled volume of air if it contains a large amount of water, i.e. it is less viscous. Hence the wisdom of drinking plenty of fluids to treat the common cold

Ineffective Coughs

Remember cough is a natural defense mechanism on the part of the body, it’s way of ridding itself of foreign matter and excess mucus. Therefore, an ineffective cough can be cause for concern. Those factors that can make a cough ineffective are as follows:
• Weakness of the inspiratory muscles. If the muscles of inspiration are weak, then less air can be drawn into the lungs initially. This will result in a decreased cough since there will be a decreased stretching of the expiratory muscles (less snap since they are not stretched as much).
• Weakness of the expiratory muscles. If the expiratory muscles themselves are weak, then the cough will also be ineffective since, even if there is an adequate volume of air, there is an inherent weakness of the muscles (even if stretched, they do not have adequate elastic recoil).
• Properties of the mucus. As described above, if the mucus is too viscous it will be harder to expel,
• The integrity of the cilia lining the airway. If there is an inhibition of ciliary motion, then this too can contribute to ineffective cough. The cilia, which line the airway, beat. In this beating they move the mucus along into larger airways and prevent it from accumulating. An over accumulation of mucus makes it harder to disperse into the gas and expel.

In chronic bronchitis there is both an over secretion of mucus and an inhibition or destruction of ciliary movement. The result is a chronic cough, an effort to constantly remove the mucus. .

Protussive and Antitussive Therapy for Cough

A cough is a natural mechanism on the part of the body to rid itself of irritants and secretions. As long as the cough is performing a useful function, i.e. to rid the airway of infectious material, then it is therapeutic to take measures that will enhance cough, i.e. make it more effective.. Cough enhancing therapy is referred to as protussive therapy. Only if a cough is no longer serving any useful purpose (such as clearing the airways of infectious materials) is therapy warranted that will control, prevent or eliminate the cough. This type of therapy is called antitussive therapy.

Non pharmacological protussive therapy includes: expiratory muscle training, chest physiotherapy and the use of mechanical aids. One method of mechanically aiding the effectiveness of cough is to manually compress the lower thorax and abdomen. This maneuver consists of applying pressure with both hands to the upper abdomen following an inspiratory effort and glottic closure. Other maneuvers include inhaling larger volumes of air and "huffing" on expiration. Pharmacological protussive therapy includes the use of hypertonic saline, or amiloride or terbutaline.

Antitussive therapy should first be directed at eliminating the cause of the cough, usually a chronic cough. Attempting to eliminate the cause is referred to as specific antitussive therapy. In smokers with chronic bronchitis, for example, the best antitussive therapy is to stop smoking. Other therapies would include removing environmental pollutants and reducing sputum production. On the other hand, nonspecific antitussive therapy is aimed at trying to control the cough, i.e. suppress the symptom. Non specific antitussive therapy has a limited place. It is best used when only when specific therapy will not work or when the etiology of the cough is unknown. Sometimes antitussive therapy is warranted if a cough is persistent enough to interfere with sleep. There are a variety of cough suppressants available, they include narcotic based antitussives (containing codeine usually) and non narcotic antitussives which usually contain dextromethorphan hydrobromide

Conditions in Which Cough Is a Symptom.
Acute cough is transient. It occurs most frequently in association with the common cold. On occasion is it may represent a potentially life threatening condition such as pulmonary embolism, congestive heart failure and pneumonia. Sometimes an acute cough can persist and become a chronic cough. Chronic cough can sometimes be due to more than one condition.

Postnasal Drip Syndrome (PNDS)
      Patients with PNDS present with cough, a sensation of something dripping into the throat, a need to clear the throat, a tickle in the throat, nasal congestion and or nasal discharge. Sometimes they complain of hoarseness. Often there is a history of an upper respiratory illness (a cold). There may also be the presence of a wheeze. On physical examination they are found to have drainage in the posterior pharynx, a cobblestone appearance of the orophayngeal mucosa and mucus in the oropharynx.
       The treatment is dependent on the cause of the PNDS. Although it is usually secondary to a cold (therefore, a postviral upper respiratory infection), it may be due to allergic rhinitis, or sinusitis. If a postviral upper respiratory infection is the cause, then treatment with an older generation of antihistamine/decongestant combination has been shown to be effective. Newer generation, nonsedating antihistamines, have not been shown to be as effective. If PNDS is due to allergic rhinitis, then nasal steroids and or cromolyn sodium is usually the initial drug of choice. Antihistamines can also be used. Nonsedating antihistamines are likely to be more effective in treatment of PNDS due to allergic rhinitis then due to postviral upper respiratory infection. If the PNDS is due to sinusitis, then antibiotics, intranasal corticosteroids and decongestants are warranted.

Asthma
      Asthma has been shown in many studies to be one of the most common causes of chronic cough in all age groups.. If cough is the only symptom of the asthma, then this is referred to as cough variant asthma. Cough variant asthma occurs anywhere from 6.5% to 57% of the time. (N.B. it is important, therefore, not to exclude a diagnosis of asthma just because there are no other symptoms of asthma present).
     The treatment of cough variant asthma should be the same as for asthma presenting with other symptoms. In other words, cough variant asthma is best treated with beta agonists and steroids (inhaled or oral)

Gastroesophageal Reflux Disease (GERD)
        In GERD acids and other substances from the stomach move into the esophagus producing symptoms. The symptoms include heartburn, epigastric or retrosternal discomfort, chest pain and often cough. The cough may be present in the absence of the other symptoms. As a matter of fact, when GERD is the cause of chronic cough, GI symptoms are absent 75% of the time. Most likely, the cough is due to stimulation by acid reflux of vagally mediated receptors present in the esophagus. The objective of therapy is to decrease the amount and frequency of reflux. Non pharmacological measures include weight reduction, high protein low fat diet, elevation of the head of the bed, avoiding coffee and smoking. Pharmacological measures include prokinetic agents and H2 antagonists.

Chronic Bronchitis (CB)
    In diagnosing CB as the cause of chronic cough, the health history is very important. It is unlikely to occur in nonsmokers unless there is significant long-term exposure to dusts or fumes. On physical examination the patient is usually a blue bloater (i.e. exhibits peripheral edema, obesity and central cyanosis). The cough is caused by chronic airway inflammation due to contact with an irritant (usually smoke). The inflammaiton results in an overproduction of mucus and prevents the cilia from being able to do their job of clearing mucus from the airway. Hence, the mucus builds up and there is a need to cough in order to clear the airways. The best treatment is to remove the irritant. Smoking cessation works, it has been shown to cause cough to either disappear or markedly decrease in 94% to 100% of the patients who stop smoking. Ipratropium can decrease sputum production and therefore can also decrease the cough of CB.

Bronchiectasis
     Bronchiectasis is a dilatation of the sub segmental bronchi. It comes about as the result of exposure to severe childhood infection, inhalation injury, or aspiration. An inflammatory response subsequently sets up a cycle of progressive airway damage. A productive cough is a cardinal symptom of bronchiectasis. Wheezing may also be present Treatment includes chest physiotherapy, with or without antibiotics. Surgery may be needed in some cases.

Postinfectious Cough
        This can occur after a respiratory tract infection. Most of the infection is gone since clients have a normal chest radiograph but, apparently, enough inflammation persists to cause a chronic cough. Eventually, the cough will resolve on its own. Back to back infections, especially in winter months, can lead to this. In the adult respiratory viruses such as M. pneumoniae, C. pneumonia and B. pertussis have been implicated. In infants and children respiratory viruses such as C. trachoamtis are often the cause.

Bronchogenic Carcinoma
      This cancer is a primary neoplasm of the lungs Tobacco smoking is the cause in approximately 85% of the cases. The risk increases with the duration of smoking and the quantity of tobacco smoked per day. The treatment of choice is surgery.

Angiotensin Converting Enzyme Inhibitor Induced Cough
      ACE inhibitors are used to treat hypertension and congestive heart failure. As many as 0.2% to 33% of those being treated with these drugs will develop a dry non-productive cough. The cough occurs with any of the ACE inhibitors and is not dose dependent. Although the pathogenesis is not known, it is thougt that the cough is due to the accumulation of inflammatory or pro inflammatory mediators such as bradykinin, substance P and or the prostaglandins. These substances can increase the sensitivity of the cough reflex The definitive therapy is discontinuation of the drug.

Psychogenic or Habit Cough
    This presents as a throat clearing noise made by a patient who is often withdrawn and self-conscious. It is sometimes hard to distinguish it from PNDS. It occurs mostly in children. Typically patients do not cough at night. Suggestion therapy is the principal treatment for psychogenic cough. Antitussives can be used as a short-term therapy to help control the cough.

©Kenneth Zwolski, RN, EdD, CS