B Pathophisiolology Of Asthma Biology Essay

Published: Last Edited:

This essay has been submitted by a student. This is not an example of the work written by our professional essay writers.

Asthma is a chronic condition in your lungs that has two main components. When you have asthma, two things happen inside the lungs, the tightening of the muscles surrounding the airways, and inflammation, swelling and irritation of the airways. Constriction and inflammation cause narrowing of the airways, which may result in symptoms such as wheezing, coughing, chest tightness, or shortness of breath. Furthermore, there is increasing evidence that, if left untreated, asthma can cause long-term loss of lung function. (www.healthcare south.com)

When you have asthma and are exposed to a trigger, the airways leading to the lungs become more inflamed or swollen than usual, making it harder for you to breath. The airways also get smaller due to a tightening of the muscles surrounding the airways, and they get "stuffed up" due to a build-up of mucous. (www.healthcare south.com)


Figure1 Adopted from yazmeen.files.wordpress.com

B-Pathophisiolology of asthma:

Asthma is a disease that involves in the inflammation of the pulmonary airways and bronchial hyperresponsiveness which results in the clinical expression of lower airway obstruction. Physiologically, bronchial hyperresponsiveness is known as decreased bronchial airflow after bronchoprovocation with methachline or histamine.Other factors that provoke airway obstruction such as cold air, exercise, viral upper respiratory infection, cigarette smoke and respiratory allergens.Bronchial provocation with allergen induces a prompt early phase immunoglobulin (IgE) mediated decrease in bronchial airflow followed in many patients by late-phase IgE mediated reaction with a decrease in bronchial airflow for 4-8 hours.(Linzer,2005)

Asthma is characterised by increase number of eosinophils, neutrophils, lymphocytes and plasma cells in the bronchial tissues. Initially, there is recruitment of leukocytes from blood stream to the airway by activated CD4 T-lymphocytes.The activated T-lymphocytes also triggers the release of inflammatory mediators from eosinophils, mast cells and lymphocytes.In addition,the subclass 2- helper T-lymphocytes subset of activated T-lymphocytes produce interlukin (IL)-4 , (IL)-5 ,(IL)-13 (IL)-4 in conjunction with (IL)-13 signals that change from Ig-M to Ig-E antibodies.The cross-linkage of two Ig-E molecules by allergen cause mast cells to degranulate releasing histamine, leukotrienese and other mediators sustains the airway inflammation.IL-5 activates the recruitment and activation of eosinophils. The activated mast cells and eosinophils also generate their cytokines that help to prolong the inflammation.Despite of the triggers of asthma the repeated cycles of inflammation in the lungs with injury to the pulmonary tissues followed by repair may produce long-term structural changes of the airways. (Barrios,2005 )

Epidemiology and history of asthma:

5.4 million people in the UK are currently receiving treatment for asthma.

1.1million children in the UK are currently receiving treatment for asthma.

There is a person with asthma in one in five households in the UK.(Warrell et al.,2005)

Over the last 20 years the prevalence of asthma in the Unites States has increased dramatically.In 1970 national survey by the public health service estimated that 3% of the United States population had asthma approximately 60% of these asmathtic had consulted a physician for asthma during the previous year and approximately 50% were using a medication or treatment for asthma. (Bierman et al.,1996)

In 1996 there were 14.6 million people with asthma 4.4 million of whom were less than 18 years old (Adams,Hendershot and Maranao 1999).Asthma is the third most prevalent chronic disease after respiratory allergies and recurrent ear infections and is responsible for approximately 10.1 million days lost from school, during 1996 asthma was the first list diagnosis in 474,000 hospitilisations(Graves and Kuzak 1998).

Worldwide asthma prevalences

Figure2 The highest 12-month prevalence of asthma symptoms were found in regions in the UK, New Zealand, Australia and the Republic of Ireland (between 28 and 36%). The lowest prevalence of asthma symptoms (less than 5 0/4) were reported in several Eastern European countries, Indonesia, Greece, China and India. Source: ISAAC study.

C-Asthma in children:

Asthma can affect child's airway and breathing, approximately 1 in 8 children are currently treated for asthma in the U.K, and children are likely to grow out of it before adulthood especially if they have mild asthma. It can be so mild that it hardly noticeable or it can be sudden and severe causing them to panic. The exact cause of asthma in children is not fully understood but it is suggested that asthma can be caused due to allergic condition and also it could be hereditary condition. Children with asthma can have mild symptoms such as:



Tight feeling in the chest

Feeling out of breath/gasping for breath


These symptoms may occur for few years and stop, while others may have attacks for longer period of time. The mild asthma can be controlled by reliever inhaler. However in severe attacks of asthma symptoms can develop to :

Difficulty in talking

Skin around the neck and chest looking "pulled in" and "stomach breathing" this because the child uses extra muscles to help them to breath

Grey or blue finger nails

Very wide nostrils

Faster heart beat than normal


Children are at higher risk of airway obstruction and often respond poorly to bronchodialators the size of the airways in children under age of 5 years is smaller than in adults; because of their smaller calibre edema mucous and cellular debris can cause significant increase in obstruction in the airways of children than in those of adults. The chest wall of young infants is less rigid than that of an adult and relative lack of elastic recoil predisposes the young infant to early airway closing even during tidal breathing. (Korenblat et al.,1992)

D-Contributing factors to Asthma:

Asthma is a complex condition and its causes are not fully understood, the risk factors to asthma can be classified in to three main factors:

1-Host factors that predispose an individual to asthma, which are:

Genetic predisposition

Although environmental factors are clearly important determinants of asthma few studies have showed that asthma has strong genetic component but does not follow monogenic patterns of inheritance. Interleukin(IL)-4 genetic variants in the promoter region of the )IL-4 gene have been related to elevated immunoglobulin(Ig)E levels. The polymorphism involves a C-T substitution in the promoter region on chromosome 5q31 resulting in increased responsiveness to IL-4 this locus has been associated with asthma diagnosis in some studies.IL-13 polymorphisms within the IL-13 gene are associated with high IgE levels and with the presence of asthma.IL4-Rα on chromosome 16 is a shared component of the receptor for both IL-4 and IL-13 and polymorphisms in this gene are also associated with asthma and atopy.It is of interest that different asthma associated traits are associated with individual polymorphisms that affect splicing of IL4-Rα.Gene-gene interactions rarely have been studied but recently an interaction between polymorphisms in IL4-Rα and IL-13 was reported to increase the risk of asthma fivefold.(Bracken,2002)

Gender as a factor

Asthma in early life tends to be predominantly male disease whereas asthma in later life tends to be more common in females; this was confirmed by epidemiological data. The male to female ratio of asthma is 2 to 1 until age of 10 at age of 14 the ratio becomes mostly equal. Following puberty asthma ratio in females is higher. The exact reason for the gender difference in asthma are unknown but are likely to relate to hormonal, mechanical and differing host response to environmental exposures.(Beirman,1996)

2-Casual factors which are environmental factors that influence susceptibility to the development of asthma in predisposed individuals and the factors are:

Pets and animals:

Exposure to pets e.g (cats , dogs, pigs, rabbits, mice, guinea and rats) can trigger asthma in some people, cats and dogs are major source of allergens in the environment these allergens come from

Proteins secreted by oil glands and shed as dander

Proteins in saliva which stick to fur when animals lick themselves

Aerosolized urine from rodents and guinea

As allergens are stuck to hair and skin of pets they become airborne when the pets shed their hair and the allergen remains airborne for some time. Cat allergen is difficult to remove from houses it can remain in the house for months after cat is removed cat allergen can be found in places where cats never lived e.g it can be carried around on clothing to school and offices. The most effective method for allergen avoidance is to get rid of the pets and animals and the less effective way include:

Keeping pets out of bedrooms and living rooms

Washing pets weekly

Vacuuming carpets weekly using a high efficiency vacuum cleaner



In temperate parts of the country the warm months of the year make up three partly overlapping pollen "seasons" which are mid April to June, June to late August and August to October or the coming of the first frost, these three seasons are the sequence of high levels of tree pollens ,grass pollens and weed pollens. The peak time of each pollen type vary depending on the geographical distribution. This explains why some people get asthma symptoms during different times of the warm season. Some people are allergic to pollens of different types such as to trees and weeda, to avoid getting asthma symptoms during pollen season it is advisable to:

Stay in-door during peak time which is suggested to be 5-10 AM

Keep home and cars windows closed to lower exposure to pollen


Several mold that grow both indoors and outdoors produce allergic substances. These allergens can be found in mold spores and other fungal structures e.g Hyphae , there is no exact seasonal pattern to molds that grow indoors. However, outdoor molds are seasonal first appearing in early spring and thriving until the first frost, indoor molds are found in dark, warm, humid and musty environments such as damp basements, Cellars, attics, bathrooms and laundry they are also found where fresh food is stored. Outdoor molds grow in moist shady areas which are common in soil, decaying vegetation, composed piles. (www.niehs.gov.com)


House dust mites are tiny creatures cannot be seen with the naked eye, they feed mainly on the scales of the skin that we shed. They are common in warm, damp, dark areas include pillows, carpets, soft furnishing, soft toys and even clothings.The mites can cause allergic symptoms in some people, and these symptoms are caused by breathing in substances which are known as "allergens" they are contained within the mite's droppings. The droppings are tiny, dry pellets which form a large part of the dust in areas where mites are found, the pellets are so small that they can become airborne and may then be breathed in. If someone has allergic asthma than it is most likely they will be allergic to house dust mites to reduce the presence of house dust mites it is recommended to:

Reduce dampness by opening windows or vents in kitchens during and after cooking

Prevent the build up of dust by regularly cleaning surfaces by using a damp cloth

Wash the soft toys and beddings regularly at high temperature

Choose very short piled wool carpets

Use high efficiency filter vacuum cleaners

Treatment of furnishing and replacing them if necessary


Drug-induced asthma:

Although the triad of asthma nasal polyps and aspirin intolerance is primarily recognised in adults aspirin-induced asthma was seen in 14 of 50 children without the presence of nasal polyps in one study, it is possible that cyclooxygenase inhibitor such as acetylsalicylic acid cause increased production of lipoxygenase pathway metabolites such as leukotrienes which would cause bronchoconstriction and inflammatory reactions in the asthmatic lung.This led to general recommendation that aspirin must be avoided by asthmatic children as well as by asthmatic adults .(Korenblat,1992)


The most common cause of coughing and wheezing during the first year of life is viral respiratory tract infection. Respiratory syncytial virus and parainfluenza virus are implicated most often in infants and preschool children,and parainfluenza is implicated most often in older children.A history of bronchiolitis or croup especially during the first 6 months of life is a risk factor for development of asthma approximately half of the children with that history develop reactive airway disease.Bacterial pulmonary infection are not characterised by wheezing , and indiscriminate administration of antibiotics to children with acute asthma has not proved to be effective therapy and should therefore be avoided.(Korenblat,1992)

Smoking as factor:

Active smoking can increase airway responsiveness and increases serum IgE levels and eosinophilia.In addition tobacco smoke damages tiny hair like structures called cilia when cilia gets damaged they will be unable to sweep the dust and mucous out of the airways as a result more mucous will build up in the airways triggering the attack. Passive smoking can be also harmful to people with asthma they can get symptoms of wheezing and coughing and shortness of breath. (Haslett,2002)

Occupational asthma:

There are over 200 materials encountered at the workplace give rise to occupational asthma. The causes are recognised occupational diseases in the U.K and patients in insurable employment therefore eligible for statutory compensation provided they apply within 10 years of leaving the occupation in which the asthma developed (Kumar et al.,2005)

3-Trigger factors which are environmental factors that precipitate asthma exacerbations and/or cause symptoms to persist and the factors are:

Food reactions and asthma:

An allergic reaction occurs when the body's immune system reacts abnormally to a harmless substance such as food. Symptoms of food allergies can vary widely you may get symptoms in your mouth like swelling or tingling or in your gut like vomiting and diarrhoea or skin like rash and swelling of face these allergies may flare up your asthma.

Food that triggers asthma by way of an allergic reaction includes peanuts, nuts, sesame, fish, shellfish, dairy products and fish.

Some people become wheezy when they take food containing certain additives such as dye tetrazine(E102),preservatives such as benzoic acid(E210)

Some foods and wines contain histamine or similar chemicals called vasoactive amines

Sodium metadisulphite (E220-227) may also trigger asthma but not via an allergiceaction


The effects of fatty acids:

Studies from Australia have found a protective effect of eating oily fish

Supplementing omega-3 polyunsaturated fatty acids given in a special margarine had no beneficial effect.( www.asthmatrak.org)

Exercise-induced asthma:

Exercise is a common trigger for asthma it can effect anybody with asthma children or adults recreational sport players or elite athletes, symptoms of asthma include coughing, wheezing, chest tightness and difficulty in breathing these symptoms usually begin after exercise and worsen about 15 minutes after exercise stops. Research shows that if exercise is tried again within three hours the symptoms will be less severe it is not known exactly how exercise triggers asthma, when people exercise they breath faster which will make it more difficult for the nose and upper airway to warm and add moisture to the air breathed in resulting in the air being drier and colder than usual. This cold, dry air in the airways triggers the symptoms of asthma, to help diagnose exercise-induced asthma the physician may ask about the medical history of the patient and may take peak flow test. If the diagnosis is difficult than the physician may request special test. (www.niehs.gov.com)

Types of exercises which may trigger asthma:

A-Long distance or cross-country running is strong triggers because they are under taken outside in cold air without short breaks.

B-Team sports such as football or hockey are likely to cause asthma as they are played in brief bursts without short breaks in between.

C-Swimming: the warm humid air in the swimming pool is less likely to trigger symptoms of asthma, however swimming in cold water are heavily chlorinated pools may trigger asthma.

To manage doing exercise without getting asthma always:

Consult your doctor regularly

Keep your asthma well controlled

Take the correct medicine

Warm up and down

Avoid the cold air

Stay fit

Special situations:

At school:

Full participation in sport at school should be possible for most asthmatic patients except for those with severe symptoms, the teacher should be aware and help the student with asthma to warm up and down and it is advised to bring their reliever inhaler with them.

Competitive sport:

None of the inhaled medicines commonly used for managing asthma are banned in competitive sports. However the sport governing body should be informed as this will help the patient to be provided with details of substances which are banned.


Recently it has been recognised that people with controlled asthma can take part in scuba diving. However, this sport can trigger asthma as the patient is exposed to cold air , exercise, stress and emotion. Rules on scuba- diving for asthmatic patients vary between countries for example the British sub-aqua club suggests that those with mild controlled asthma may dive provided that:

You don't have asthma that is triggered by cold

Your asthma is well controlled

You have not needed to use reliever inhaler or had symptoms of asthma in previous 48 hours

Your peak flow must be within 10% of your best value for at least 48 hours before diving

You may be asked to undertake an exercise test


The mountain environment contains several triggers for people with asthma (cold, dry-air and exercise) always consult your doctor before planning a trip.

Para-chut jumping:

Always ask your physician before planning parachute jump or sky dive. The medical advices are as follow:

your asthma is completely controlled

cold air does not trigger your asthma

exercise does not trigger your asthma

E-Hygiene hypothesis:

It is thought that the hygiene hypothesis emerged from the early studies reporting an inverse association between family size and manifestations of atopy in early life to childhood. These findings coupled with changing patterns of microbial exposure. Exposure to microbes through active infection or in the absence of infection may initiate protective responses. This exposure to microbial derivatives may play a critical role in the shaping of the immune response during the maturation of the immune response this could result in the development of immune tolerance to potential allergens. Improved hygienic conditions in western or developed countries results in less infection or microbial pressure during early childhood but critical time periods.In association with reductions or proposed that Th2 immunity dominated through critical childhood periods resulting in the higher incidence of atopy and asthma, several studies have advanced the theory that faecal contamination of the environment and unhygienic food handling may similarly protect against development of atopy.Much of the hygiene hypothesis rests on the theory that atopy/asthma is Th2 driven and that there is imbalance between Th1 and Th2 immunity. Atopic individuals do show an increase in IL-4,IL-5,IL-13 and immunoglobulins IgE antibody responses and decrease in IFN-gamma,it is unclear wether asthma is Th2 disease or whether Th1 also plays a role in the development of the disease.Lower prevalence of allergic diseases are described in rural areas of Africa and China.There are strong differences within rural areas showing incidence of atopy,asthma and hay fever in children growing up on dairy farms compared with nonfarm children .The source of protective effects is not clear revealed from studies in Germany,Canada and Australia..Initial enthusiasm focused on a major product from gram negative bacteria lipopolysaccharide (LPS) or endotoxin as levels were found to be higher within the farming families than the non farming surroundings. Levels of LPS exposure were negatively related to the prevalence of atopy, hay fever, and even atopic asthma.On the other hand endotoxin exposure may play a major role in determining the severity in asthma for example in occupational asthma endotoxin exposure induces airflow obstruction and neutrophil inflammation, asthmatic are hypersensitive to endotoxin exposure.The protective effects of a farming environment in childhood provide important evidence in favour of the hypothesis that environmental factors encountered in childhood could have a lifelong protective effect against the development of allergy.Since there are numerous reports of an increase in asthma in a number of settings for example urban African towns and inner cities in the United states it is not simply a clean with dirty environment that may dictate outcome.The farming environments may be creating an immunologic setting beyond endotoxin exposure that directs the immune response along a particular pathway. Defining these important factors and pathways that appear to protect against allergic sensitisation will have major therapeutic implications as we consider strategies for early intervention.(Gelfand,2008)

F-Asthma mortality and morbidity:

After a long period of steady increase, evidence suggests that asthma mortality and morbidity rates continue to decrease. The number of death due to asthma in 2002 was approximately 8.5% lower than the number of death seen in 1999.Hospital discharges have been declining since 1995 and 2002 the hospital discharge rate has declined 13% since it peaked at 19.5 per 10,000 in 1995.However, asthma remains a major public health concern. In 2003 approximately 20 million Americans had asthma and the condition accounted for an estimated 12.8 million lost school days in children and 24.5 million lost work days in adults. Asthma ranks within the top ten prevalent conditions causing limitation of activity and costs U.S nation $16.1billion in health care costs annually.(American Lung association,2005)


Figure adopted from www.nationalasthma.org.au


Figure adopted from www.aihw.gov.au