Health Watch

A layman’s guide to bronchial asthma

Tomorrow is World Asthma Day:

Dr.P.N.B.Wijekoon MB.BS.MRCP(U.K.)FRCP (Lond.) FCCP Consultant Respiratory Physician

Asthma,a potentially fatal disease, has afflicted mankind for centuries,and,like many other chronic,incurable diseases (asthma is one of them),the incidence,prevalence,morbidity (ill health and disabilty) and mortality (death) from asthma has been increasing over the past 40 years,particularly in children.Approximately 300 million people worldwide suffer from asthma,and its prevalence increases by 50% every decade.In the United States of America,10% of the population(about 30 million people) suffer from asthma,and the loss to the economy from work absence, absence from school in the case of children,the cost of emergency medical care and in- hospital care is astronomical (And Sri Lanka is no different).

In the United States,for example,10 million school hours were lost during the course of one year,and,besides having a significant impact on the quality of education, the consequent loss of productivity for the parents (when a child is sick one or both parents have stay off work to care for the child), and the country was U.S.$ One billion (USD 1000,000,000),in one year.The price asthma in adults extracts from the economy and the healthcare system is incalculable.

Asthma is underdiagnosed and undertreated,leading to unnecessary morbidity,poor quality of life and avoidable deaths.Approximately 180,000 deaths worldwide are attributable to asthma,and most of these deaths,especially in young people, could have been avoided if appropriate,aggressive treatment was instituted early.

Unlike some chronic, incurable diseases like hypertension, diabetes and chronic kidney disease, which are relatively symptom free until complications set in, asthma is symptomatic from the start, having a significant impact on quality of life.

The relentless coughing,wheezing,breathlessness and sleep disturbance lead to an abyssmal quality of life, resulting in depression,loss of self esteem and repeated abscences from work or school.

William Osler (1849 - 1919), Regius Professor of Medicine at Oxford University, in 1893, defined asthma as a disease of the airways in the lung characterized by

1)Inflammation of the smaller bronchial tubes

2)Hyperaemia (Increased blood supply,redness) and turgescence (swelling)of the inner lining of the bronchial tubes

3)Spasm of the smooth muscle in the walls of the bronchial tubes and

4)A peculiar exudate of mucin inside the bronchial tubes. {Explanatory note: Bronchial tubes are the thousands of small,tree like, branching tubes inside the lung which deliver air from the windpipe (trachea) to the peripheral lung tissue (alveoli)}.

Osler further goes on to say that “the attacks may be due to direct irritation of the bronchial mucosa (the inner lining of the air tubes),or may be induced reflexly,by irritation of the nasal mucosa (inner lining of the nose ),and indirectly too,by reflex influences from the stomach, intestines or genital organsÓ(end quote).

How remarkably clever a physician Osler was and how prophetic was his definition of asthma is exemplified by the currently accepted description of asthma, which is;

? Asthma - whatever the severity-is a chronic inflammatory disease of the airways (bronchial tubes) - (Osler said so too.)

? Airway inflammation is associated with airway hyperresponsiveness (excessive irritability), airflow limitation (less air passing through the airways), and respiratory symptoms (cough, wheeze, breathlessness).

? Airway inflammation produces four forms of airflow limitation;acute bronchoconstriction (spasm of the muscle in the air tubes, making them narrower), swelling of the airway wall, excessive mucus production and chronic mucus plug formation (Osler said almost exactly the same thing, 120 years ago).

(Source: Global Strategy for Asthma Management and Prevention: National Heart, Lung and Blood Institute (NHLBI)/World Health Organization (WHO) workshop report - 2004)

It is indeed remarkable that Osler,more than 120 years ago,without the help of electron microscopes and bronchoscopes,described asthma almost exactly as the NHBLI and the world Health Organization describe it now.Critically,he described chronic inflammation of the bronchi (air tubes inside the lung),which is now accepted to be the starting point of asthma and the cause for all its symptoms and long and short term complications.He went even further than the NHBLI and WHO in describing the influence of irritation of the nasal mucosa (catarrh),and Gastro-Oesophageal Reflux Disease (GORD) on exacerbations of asthma,presently accepted as exerting a significant influence on the asthmatic process.

In fact,in the mid 20th century (1959),asthma was thought to be(quote) “a disease characterized by widespread narrowing of the airways (bronchi), which alters in severity either spontaneously or in response to treatment.” There is no mention at all of inflammation or the consequences of inflammation - inflammation is now known to be the foundation of the symptoms, pathophysiology, and the basis for the present day,rational management of asthma. In the latter part of the 20th century,however, Osler's original definition was found to be remarkably more accurate,and that narrowing of the airways was a CONSEQUENCE and not the cause of asthma,the cause being widespread inflammation of the airways.

Definition

Asthma may be defined,very simply,as “ a chronic inflammatory disease of the intrapulmonary airways”.For the layman,Óchronic” means lasting a long time, “inflammatory” means red,swollen and warm, “intrapulmonary” means within the lung tissue ,and “airways” are the millions of tiny,branching tubes which carry oxygen from the environment to the extremities of the lung (the alveoli,which are balloon like structures where oxygen is exchanged for carbon dioxide (a waste product) in the blood,and the carbon dioxide is expelled out into the environment via the same intrapulmonary airways.So,it is clear that the function of the airways is to supply oxygen (without which survival is not possible) to the blood,and expel carbon dioxide (a buildup of which is equally fatal) from the the blood out into the environment.

Because airways resemble cylinders or tubes,according to Pousille's law,a reduction in the diameter of the cylinder or tube by 50% increases the resistance to the flow of air by 16 times,and increases the effort needed to move air in and out of the cylinder or tube by 16 times.In other words ,a 50% or greater narrowing (as happens in asthma) of the intrapulmonary airways increases the effort of breathing by 16 times or more,which is why patients with poorly controlled asthma are so breathless and exhausted and can even die of the exhaustion.

Because inflammation is the starting point and the sole reason for the pathophysiology,symptoms,treatment and control of asthma,it is essential for the layman to have a mental picture of what inflammation is .A satisfactory analogy is a minor burn on the skin.The affected area is red (latin;rubor),swollen (tumour),painful (dolor),warm (calor),hypersensitive (hyperirritable)and loses its function (functio lasae).Exactly the same thing happens in the asthmatic airway.The affected airway is red,swollen,warm and it's function(carrying air in and out of the lung) is impaired because it is narrowed due to the swelling of its inner lining,spasm of the muscles in its wall,and due to excess mucus production within.This narrowing of the airway makes it much more difficult for the patient to breathe because of the tremendously increased effort (remember Pousille's law),and almost all patients who die of asthma die of exhaustion and hypoxia (very low levels of oxygen in the blood inadequate to sustain life),because the airway is too clogged up and too narrow to carry sufficient oxygen to the alveoli,and the patient is too exhausted to breathe adequately.This is also why the first thing a doctor should do for a patient suffering from acute severe asthma is to administer high concentration oxygen,because prolonged hypoxia can lead to confusion, coma or death.

Bronchial hyperreactivity

One more, crucially important consequence of airway inflammation is a phenomenon called bronchial hyperreactivity (syn;hyperresponsiveness, hyperirritability). The term is self explanatory - when inflamed, the airways are extremely irritable, and react to substances which would pass unnoticed by a non- asthmatic individual. This is why asthmatic patients with poorly controlled asthma react to air conditioning (the dry, cold air irritates the already irritable airway), or to cigarette smoke, or to diesel fumes or to viral respiratory tract infections. The hyperirritable airways react to environmental insults in the only way they know, which is by narrowing further, swelling further and producing even more mucus -a protective mechanism, nature's way of preventing the ingress of the insult further in to the lung.Unfortunately, however, this protective mechanism worsens the airway obstruction even more.The predominant symptom of this hyperirritability is a hacking dry cough (which almost never responds to antibiotics and cough syrups),and often wheezing.It is important to note that non- asthmatic individuals,too,can develop temporary bronchial hyperreactivity after a respiratory tract infection,which explains why many patients come to respiratory physicians in desperation,because their cough would not go away after repeated courses of antibiotics (useless in viral infections and which do absolutely nothing to reduce the inflammation), cough syrups and diethyl carbamazine,which they have been swallowing ad nauseum.Some are even treated for tuberculosis,with absolutely no rationale, and without any clinical,radiological or bacteriological evidence of tuberculosis.What these patients need is something to control the ongoing inflammation .It is that simple.

Why are the airways of asthmatic patients so predisposed to inflammation?The causes are legion-A genetic predisposition (asthma can be hereditary),gender (asthma is commoner in boys than in girls,though this difference disappears by age 10),race (asthma incidence is high in Australia and New Zealand and in black children than in white children in the United States (though these differences may be attributable more to socio-economic factors,allergen exposure and dietary factors than a racial disposition), indoor allergens (e.g;house dust mite, animal dander, cockroach allergen, rodent allergens and fungi), outdoor allergens (e.g;pollens,fungi), drugs (e.g;antibiotics, aspirin, certain pain killers of the NSAID class) , foods (e.g;peanuts, shellfish, milk) and food additives (e.g; monosodium glutamate, tartrazine). However, it has to be emphasized that an asthmatic patient may not be predisposed to any of the above factors,but still develop asthma-many patients in our clinical practice belong to this category.

Contributory factors

Contributory factors,though they do not actually cause asthma,increase the likelihood of asthma developing upon exposure to a causal factor (e.g; house dust mite) in a susceptible individual.Contributory factors may be active or passive smoking (asthma is commoner in children in a smoking household than a non-smoking household), outdoor pollutants (e.g;Sulphr dioxide, ozone,nitrogen oxide,diesel smoke,dust),indoor pollutants (cooking with natural gas,liquid propane,kerosene,coal or wood),building or furnishing with foam installations, glues, fibreboard, pressed board, particle board or carpet backings.

If inflammation is responsible for all the symptoms,long term consequences and complications of asthma,it is obvious that the most logical way of controlling asthma and its symptoms would be to control the inflammation. And this is indeed so. The present day, logical management of chronic asthma is based almost entirely on controlling the underlying inflammation.Control the inflammation,and you control asthma and its complications.

In the 1950's and 60's, management of asthma was based on relieving bronchospasm (making the narrowed airways bigger by relieving the spasm of the muscles in their walls ) with bronchodilators (drugs that relieve the spasm in the muscles) like Salbutamol.It was later discovered that long term,regular treatment with bronchodilators actually made asthma WORSE in the long term,because such treatment did nothing to control the underlying inflammation.It is akin to applying fresh paint over rust,without cleaning off the rust (inflammation) first-with time,the rust (inflammation)breaks out to an even worse extent.Regular treatment of chronic asthma with solely bronchodilators leads to the patient requiring larger and larger doses to control the symptoms,because the underlying inflammation continues unabated and becomes progressively worse.At some point in time,maximal doses of bronchodilators are unable to control symptoms,and the underlying inflammation erupts with such ferocity that the severity of the attack could well kill the patient.

Therefore, the present day management of asthma focuses almost totally on controlling the chronic airway inflammation.This is the foundation of adequate treatment and control of asthma-Control of inflammation rapidly renders the patient asymptomatic,improves quality of life,prevents sleep disturbance,improves work/school performance,prevents life threatening complications and prevents long term damage to the airways,which,if the inflammation is uncontrolled, can become distorted and permanently narrowed (airway remodelling),and unresponsive or only partially responsive to any form of treatment,a condition known as Chronic Obstructive Pulmonary Disease (COPD).

Anti-inflammatory agents

How is the inflammation inside the airways controlled? Obviously,with anti-inflammatory agents.Though there are many kinds of anti-inflammatory agents,the most efficacious in the case of asthma are a class of drugs known as corticosteroids, commonly known as steroids.Before the reader throws up his hands in horror, let him/her be reassured that inhaled forms of this class of drug ,because the doses are so tiny,are safe for long term use.The benefits of inhaled corticosteroids far outweigh their disadvantages.

They control the ongoing inflammation in the airways rapidly and effectively because all the symptoms of asthma are due to the underlying inflammation, the patient rapidly becomes asymptomatic, to such an extent that he either forgets to continue his medication or erroneously believes he is cured- a fatal error, because the airway inflammation in asthma never really goes away, and can last weeks,months,years or lifelong-inflammation can only be controlled,but not really cured.

Inhaled corticosteroids,if delivered by a correctly used inhaler device,deliver a tiny dose of the medication to where it is required -the inflamed airway.

Because it is inhaled and not swallowed,and because the doses are so tiny (measured in micrograms and not milligrams),very little or hardly any of the drug gets in to the blood stream,and,consequently ,adverse effects of the drug on the other organs of the body are minimal or nil,to such an extent that inhaled corticosteroids are recommended first line treatment for chronic asthma in children and in pregnancy complicated by asthma.Typically, one puff from a corticosteroid inhaler contains only 100 - 250 micrograms of the drug,whereas a single tablet of Prednisolone (an orally administered corticosteroid tablet)contains 5000 micrograms,though the inhaled dose is far superior to the orally administered dose.

There are other drugs which complement inhaled corticosteroids and reduce the requirement for steroids.At the forefront are Long Acting Bronchodilators (LABD's),which make the narrowed airways bigger and also possess some anti- inflammatory effect. Long acting bronchodilators are excellent companions to inhaled corticosteroids,so much so that they are now almost invariably combined with an inhaled coricostertoid in the same inhaler device,giving far smoother control of asthma,reducing exacerbations,improving quality of life and sleep and reducing the amount of inhaled steroid required.

Unlike in the mid 20th century,short acting bronchodilators like salbutamol (Relievers) are used only on an as required basis,and not regularly.In fact,if the patient's asthma is perfectly controlled,he/she should not require any reliever at all.

Other drugs which complement the above classes of drugs do exist,useful in difficult to control asthmatics on maximal doses of inhaled corticosteroids and long and short acting bronchodilators,and in very mild asthma where inhaled corticosteroids are not required.Leukotriene receptor modifiers,which block pro-inflammatory substances called leukotrienes,and drugs belonging to the theophylline group of drugs are two classes of such drugs.Space does not permit me to elaborate.

Drugs are NOT the only component in the perfect management of asthma.Adequate management of asthma has six interrelated parts:

1. Educate patients to develop a partnership in asthma management

2. Assess and monitor asthma severity with both symptom reports and,as much as possible,measurements of lung function

3. Avoid or control asthma triggers

4. Establish individual medication plans for long term management

5. Establish individual plans for managing exacerbations

6. Provide regular follow up care

Unfortunately,elaborating on the above will likely run in to several more pages.Suffice it to say that asthma,for so long a cause of untold misery to millions of patients,can,with appropriate medication,be controlled (though not cured),to such an extent as to give the patient a symptom free,near normal quality of life.

This discourse is meant to,as far as possible,provide a clearer insight into their affliction for the tens of thousands of asthma sufferers in this country,so that they may be rid of their phobias about the disease and its treatment,and achieve a quality of life comparable to that of a normal individual.

Keratoconus and cross-linking

S Anandarajan - Senior Ophthalmologist

Recently the premier eye hospital in Colombo has introduced this cross-linking system for keratoconus.

Many patients and others will be anxious to know what this procedure is.

The cross-linking is actually a medical procedure that consists of the use of ultra-violet and riboflavin (vitamin B2).

The aim of this treatment is cross-linking which reduces and stops keratoconus in the early stages of the condition.

If this condition is thus not prevented it may lead to corneal transplantation, a major surgical procedure.

Riboflavin is instilled on the cornea and then it is exposed to ultra-violet light.

This light makes the riboflavin to fluoresce.

This action leads to the formation of bonds between collagen molecules which are called collagen cross-linking.

This procedure was born in 1998 in Germany.

Now I will describe how the cross-linking is performed.

Anaesthetic eye drops are instilled and the surface cells of the cornea are gently removed making the riboflavin eye drops penetrate into the cornea. The drops are allowed to enter into the cornea.

The cornea is then exposed to ultra-violet light.

Today the ultra-violet sources are so advanced making the procedure time less than an hour. After the procedure a bandage contact lens is put in and the eye is patched for the night.

New methods are being developed that may allow the outer cells to remain in place during cross-linking.

Minor complications may occur like pain, sensitivity to light for many days and blurring of vision will occur for a few weeks. The purpose of cross-linking is to make the cornea regular allowing soft contact lenses to be worn without the need for rigid gas permeable lenses. RGP are good for vision in keratoconus.

Corneal collagen cross-linking with riboflavin is a developing treatment for keratoconus.

This works by increasing the cross-links of the collagen which are real anchors within the cornea.

These anchors prevent the cornea from bulging out and becoming steep and irregular.

This method is not a cure for keratoconus.

This treatment is to arrest progression of keratoconus reducing the need for keratoplasty. Contact lenses may be needed for following cross-linking treatment.

This procedure is simple, painless and safe.