Posted by Dong won shin, MD at Physicians Herbal Formula on February 13, 2014
THEORIES ON PATHOGENESIS OF COUGH
Why does Jenny cough so oftener than Tom in dry weather? Jenny is a good singer at a casino who uses her voices a lot, and whenever she gets a cold with a sore throat and fever,she has persistent cough, with dry throat, and ticklish cough with a scant amount of yellow phlegm which is difficult to expectorate for many weeks, and the symptoms get worse after a concert in Las Vegas in summer. Her medical doctor prescribes her dextromorphan, and even phernegan with codeine syrup which makes her drowsy and constipated. Even worse, her dry cough becomes worse.
Why does John cough up so much phlegms after catching a cold when he does not even smoke? John is a middle aged man who has always liked wine, cheese, and alcoholic parties with women as a successful business man, has chronic catarrhea with nasal congestion and discharge, and after a minor cold, gets frequent bronchitis with expectoration of sticky, yellow phlegms rattling in the throat and the chest with fever, barking coughs, and chest oppression. John is prescribed levaquin ( an antibiotic ) and prednisone by his internist, but he often gets edema of face, elevated blood sugar and hypertension from the steroids as well as upset stomach and bitter taste from levaquin, but he is told that these are the minor side effects that are necessary to cure his bronchitis and asthma. Both Jenny and John are crying out, " Aren't there any herbal remedies that are more effective? without the side effects of modern drugs? Jenny is vaguely aware that her singing occupation is making her treacheas and bronchus drier and predisposes her to frequent dry coughs, but John does not know that all that alcoholic drinks and pizzas and cheeses are making him the hyperproducer of phlegms , and making him a target for productive bronchitis/asthma by exterior wind pathogens and viruses. Both Jenny and John visit the medical office of Physicians Herbal Formula in L.A., are explained both biomedical and eastern herbal theories on pathogenesis of persistent cough: Jenny takes Dryish Cough, and within a few days, all her dry coughs are healed. John takes Cough,Yellow Phlegm, and seeing the great responses, throws away the antibiotics and prednisones, and after becoming free of yellow phlegms within a few days, he also vows to cut down alcohol and excess cheese parties.
Tales of Hypersecretors of phlegms and hyposecretors of mucus
We explain 1) the biomedical model of pathogenesis of cough, 2) discuss some unanswered issues in that model, 3) propose a new expanded model, 4) describe how this model fits not only pathological model of modern medicine but also fit with the languages of Chinese herbal medicine, and 5) finally describe briefly the workings of the herbal remedies.
Pathogenesis of cough according to biomedical model
Cough is a reflex defense mechanism for clearing the trachea and bronchial tree of secretions and foreign materials to protect the lungs. Irritation of bronchial mucosa by any materials causes activation of sensory receptors of the afferent limb within the nasopharynx and the bronchial trees. The efferent limb consists of the recurrent laryngeal nerve and the spinal nerves causing the forced expiration of cough. Other possible stimulants of the afferent sensory nerves include 1 ) sudden changes in humidity and temperatures in some susceptible persons and 2) constriction of small airways in some asthmatic persons. So there are numerous stimulants, endogenous and exogenous, which can trigger cough.
Finding the cause of cough is identifying what are the stimulators of the sensory receptors of the afferent limb of reflex, according to biomedicine. But in chinese herbal medicine, the individual pecularities and sensitivities of not only the bronchial trees but also other organ systems are considered in finding the cause of cough. The kinds of material stimulants of the afferent limb of cough vary among individuals; For instance, why does cold air or dry air cause cough only in some individuals? Biomedicine rarely discusses the factors depending on the individual differences in constitution, except in the case of cough among the asthmatics. Chinese herbal medicine explains that cough with exposure to cold air is due to wei ( defensive ) qi deficiency or weak lung and kidney yang in those individuals. Translated into biomedical language, cold air caused cough is due to weak or altered immunity with Ig E mediated hypersensitivity or T cell defects.
In sum, Cough is thus initiated by multiple stimuli, but is also dependent on individual sensitivities.
1. airway irritants by inhalation ( smoke, dust, fumes), or aspiration ( postnasal drip, gastroesophageal reflux , aspiration of stomach contents ), or by phlegms ( mixture of mucosal cells and inflammatory debris from airways ). Some persons have overproduction of phlegms independent of smoking or exposure to irritants, and are prone to flares of bronchitis with cold. Only some phlegms are from smoking induced inflammation and bacterial infection of the airways. Chinese herbal medicine is emphatic that the hypersecretors of phlegms, due to altered fluid metabolism in the whole body, have weak spleen Qi, or Lung Qi, or stagnation of liver Qi often, and are most prone to productive cough from minor colds.
2. Any diseases with inflammation or constriction of airways ( viral and bacterial bronchitis, bronchiectasis meaning dilation of bronchi by scarring, whooping cough, asthma, tumors, parenchymal lung diseases, and congestive heart failure ),
3. Exposure to very dry or damp air, or sudden changes of temperature in susceptible persons ( a small category, with “ heightened cough reflex “; otherwise, everyone in Alaska or in Sahara deserts would have significant cough ),
4. Sudden Constriction of small airways ( asthma or Cough variant asthma meaning asthma with cough as the only symptom )
5. Hyperirritability of respiratory epithelium, sometimes with unidentified irritants or minor stimuli; a subgroup is called heightened cough reflex, ( Postviral bronchial hyperreactivity, ACE inhibitor induced cough )
Acute cough is defined as cough lasting less than 3 weeks, while chronic cough is cough lasting more than 3 weeks. Acute cough is most often caused by viral infections including the common cold.
There are5 major categories of chronic cough according to the biomedical model.
1)Chronic Bronchitisis clinically definedas 3 or more months of cough productive of sputum for at least 2 years,and is mostly presentin smokers.
2)Postnasal Drip( 34 % of chronic cough in nonsmokers ) from rhinitis or sinusitis.
3)Cough Variant Asthma ( Cough is the only manifestation of asthma )supposedly causes 28 % of chronic cough in nonsmokers.
4)PostViral Bronchial Hyperreactivity ( 18 % ) is persistent cough after viral infection.
5)Gastroesophageal Reflux supposedly cause 18 % of chronic cough. This is likely an overrated reason for clinically significant chronic cough. Half the people suspected to have reflux caused cough do not have the classic symptoms of reflux such as heartburn, acid regurgitation, or dysphagia. Often clinicians suspect this diagnosis when the searches for chronic cough turn out negative. However, intensetreatment of reflux with antiacids and proton pump inhibitors such as nexium or prilosec is usually not effective for relieving chronic cough. Biomedicine says that one needs to treat this category of chronic cough for at least 12 weeks.
Similarly cough variant asthma is oversited as a cause of chronic cough, because such cough is rarely longstanding. If cough poorly responds to asthma medications, it is not asthma, and usually clinicians prescribe inhalers for asthma at the first hint of chronic cough. Then, why are there so many cases of chronic cough due to hidden asthma?
Finally, there is a new category called "CHRONIC IDIOPATHIC COUGH" with heightened cough reflex recognized by lung specialists. This may be a large category, which may include a large percentage of chronic coughers who are labeled with gastroesophageal reflux induced cough or cough variant asthma, but do not respond to biomedical treatments.
Importantly, there arecommon etiologies for cough which are not fully discussed in biomedical textbooks. These etiologies include 1st) the exposure to dry hot air or cold air,( many lay persons without asthma have experienced cough due to this, and yet the pulmonologists mention this factor more as a minor trigger of asthma or of cough variant asthma, but not as the normal, usual sensory trigger of cough reflex like the mechanical stimulants of foreign particles or postnasal drip ). It can cause cough in not just asthmatics but a category of individuals with heightened cough reflex,
And2nd and foremost) isDRY BRONCHIAL AIRWAYS IN SOME INDIVIDUALS WITH RELATIVE UNDERPRODUCTION OF DEFENSIVE MUCUS BY RESPIRATORY EPITHELIUM. After all, there are dry skin, dry eyes, dry nasal cavities, dry mouth, throat, and treachea with dry cough , and dry, atrophic stomach with thinned out mucosa,etc. Respiratory epithelia are a continuous layer from nasal cavities with mucosal layer into the small airways, and there is no reason to envision a perfect mucosal layer in susceptible individuals. The pathogenesiswould be 1) moderate to extensive sqamous metaplasiaof mucosa from normal ciliated respiratory epithelia needed to brush away the irritants from the bronchial trees, 2)Atrophy of mucus producing glands and goblet cellsgiving rise to thinner mucosal surface, analogously to chronic atrophic gastritis, 3) A novel concept of "Deficient Heat in lung " , according to chinese herbal medicine, causing arteriolar dilation in submucosa and causing relative desication of mucosal surface of respiratory trees, analogously to dried up red tongue with little saliva and cracks associated with chronic dry mouth. The reason why2nd etiology for cough is not discussedis that it is hard to study such phenomenon of mild to moderate hyposecretion of mucus by lab measurements on human beings ( hard to see this by microscopy of tissue biopsies in formalin or by bronchoscopy which cannot enter small airways, but hyposecretion of mucus has been demonstrated in cystic fibrosis model pigs, in vitamin A deficient mice, and in human subjects during acute repreparatory phase of acute injury in chronic obstructive lung disease ).
The underproduction of mucus is a " fertile ground" for chronic dry cough or chronic heightened cough reflexwhich is postulated to cause not only idiopathic cough but also a large proportion of chronic cough explained otherwise. In another word, in our newly proposed biomedical model, a category of individuals may have relatively" dry respiratory mucosa" predisposing them to heightened cough reflex from cold, viral infections, or any other triggers of cough reflex. In the language of chinese herbal medicine, these are most often the individuals withlung , or lung and kidney yin deficiency with lack of moistening the lungs.Our natural herbal remedies for cough, especially Dryish Cough, Persistent Cough & Cold, and Very Dry Cough moisten the lungs, enrich the immunological mucus layer, and decrease the heightened cough reflex, and treat chronic dry cough with sticky phlegms.
We also proposed a category of individuals with hypersecretion of phlegms causing heightened cough reflex with mild attacks of cold, or any airway irritants. In chinese herbal medicine these are the individuals with spleen Qi or lung Qi deficiency producing abudant phlegms with slightest triggers. Our formulas White Phlegm Cough and Yellow Phlegm Cough decrease the endogenous production of sputums, reduce the inflammations in the airways, and fight off the infections, thereby calming the productive coughs.