what is asthma? epidemiology signs symptoms prevention and treatment of asthma.

ASTHMA:

 The word "asthma" is  from the Greek ásthma, which means "panting".

DEFINITION :

A common lung disorder in which inflammation causes the bronchi to swell and narrow the airways, creating breathing difficulties that may range from mild to life-threatening.

           “ OR “

Asthma is a chronic disease characterized by recurrent attacks of breathlessness and wheezing, which vary in severity and frequency from person to person.(WHO).

Normal airway, Asthmatic airways, Asthmatic airway during attack

             ·        Asthma was recognized as early in ancient egypt.

^·         It  is a common long term inflamatory disease of the airways of the lungs.

·        It is characterized by variable and recurring symptoms, reversible air flow obstruction and easily triggered bronchospasm. 

EPIDEMOLOGY:

·        The rates of asthma have increased significantly since the 1960s.

^·         In 2015, 358 million people globally had asthma, up from 183 million in 1990.

·        It caused about 397,100 deaths in 2015 most of which occurred

·        Currently, 8.4% of persons in the United States have asthma as compared with 4.3% of the population worldwide, and both numbers are on the rise.

·        The average annual asthma prevalence is higher in children (9.5%) than adults (7.7%).

^·         The prevalence of asthma is higher in black persons than white persons, and the ethnicity most affected is the Puerto Rican population .

·        According to WHO estimates, 235 million people suffer from asthma.

^·         Over 80% of asthma deaths occurs in low and lower-middle income countries.

CLASSIFICATION :

^·         Asthma is clinically classified according to the frequency of symptoms, forced expiratory volume in one second (FEV) and Peak expiratory flow rate.

·        Asthma may also be classified as atopic (extrinsic) or non-atopic (intrinsic), based on whether symptoms are precipitated by allergens (atopic) or not (non-atopic) .

1 . ASTHMA EXACERBATION / ASTHMA ATTACK :

An acute asthma exacerbation is commonly referred to as an asthma attack.

SYMPTOMS :

·         shortness of breathing. 

·       wheezing.

·        chest tightness.

·        Some people present primarily with coughing.

·        In severe cases no wheezing is heard.

·         chest pain.

SIGNS :

·        Use of accessory muscle of respiration (sternocleidomastiod and scalene muscles of the neck).

·        There may be a paradoxical pulse (a pulse that is weaker during inhalation and stronger during  exhalation),

^·         Over-inflation of the chest.

^·         A blue  color of the skin and nails may occur from lack of oxygen.

     TYPES :

^·         In a mild exacerbation the peak expiratory force rate (PEFR) is ≥200 L/min, or ≥50% of the predicted best.

·        Moderate is defined as between 80 and 200 L/min, or 25% and 50% of the predicted best 

·        Severe is defined as ≤ 80 L/min, or ≤25% of the predicted best.

 Acute severe asthma:

·        Previously known as status asthmaticus,

^·         It  is an acute exacerbation of asthma that does not respond to standard treatments of bronchodilators and corticosteroids.^[

·        Half of cases are due to infections  .

·        Others caused by :

·        Allergen

·        Air pollution

·        Insufficient or inappropriate medication use.

Brittle asthma:

            ^·         It is a kind of asthma distinguishable by recurrent, severe attacks.

·        Type 1 brittle asthma is a disease with wide peak flow variability, despite intense medication.

·        Type 2 brittle asthma is background well-controlled asthma with sudden severe exacerbations.

2 . EXERCISE-INDUCED ASTHMA :

·        Main article: Exercise induce bronchoconstriction.

^·         Exercise can trigger bronchoconstriction   both in people with or without asthma.

^·         It occurs in most people with asthma and up to 20% of people without asthma.

·        Exercise-induced bronchoconstriction is common in professional athletes.

^·         The highest rates are among cyclists (up to 45%), swimmers, and cross-country skiers.

^·         While it may occur with any weather conditions, it is more common when it is dry and cold.

 Inhaled beta2-agonists do not appear to improve athletic performance among those without asthma, however, oral doses may improve endurance and strength.

3 . OCCUPATIONAL ASTHMA :

·        Asthma as a result of (or worsened by) workplace exposures is a commonly reported occupational  diseases.

·        Many cases, however, are not reported or recognized as such.

·        It is estimated that 5–25% of asthma cases in adults are work-related.

·        A few hundred different agents have been implicated, with the most common being: isocyanates, grain and wood dust, colophony soldering flux, latex animals, and aldehyde. 

·        The employment associated with the highest risk of problems includes :

Those who spray paint , bakers and those who process food, nurses, chemical workers, those who work with animals, welders hairdressers and timber workers.

4 . ASPIRIN-INDUCED ASTHMA  :

·     Aspirin exacerbated respiratory diseases (AERD), also known as ASPIRIN-induced asthma, affects up to 9% of asthmatics.

^·         AERD consists of asthma, nasal polyps, sinus disease, and respiratory reactions to aspirin and other NSAID Medication (such as ibuprofen and naproxen).

·        People often also develop loss of smell and most experience respiratory reactions to alcohol.

5 . ALCOHOL-INDUCED ASTHMA :

^·         Alcohol may worsen asthmatic symptoms in up to a third of people.

·        This may be even more common in some ethnic groups such as the japenes and those with aspirin-induced asthma.

·        Other studies have found improvement in asthmatic symptoms from alcohol.

6 . NONALLERGIC ASTHMA :

·        Nonallergic asthma, also known as intrinsic or nonatopic asthma, makes up between 10 and 33% of cases.

·        There is negative skin test to common inhalant allergens and normal serum concentrations of IgE.

·        Often it starts later in life, and women are more commonly affected than men. Usual treatments may not work as well

7..  ALLERGY-INDUCED ASTHMA :

Triggered by airborne substances, such as pollen, mold spores, cockroach waste or particles of skin and dried saliva shed by pets (pet dander)

SYMPTOMS :

Asthma symptoms vary from person to person. You may have infrequent asthma attacks, have symptoms only at certain times — such as when exercising — or have symptoms all the time.

Asthma signs and symptoms include:

·         Shortness of breath

·         Chest tightness or pain

·         Trouble sleeping caused by shortness of breath, coughing or wheezing

·         A whistling or wheezing sound when exhaling (wheezing is a common sign of asthma in children)

·         Coughing or wheezing attacks that are worsened by a respiratory virus, such as a cold or the flu

Signs that your asthma is probably worsening include:

·         Asthma signs and symptoms that are more frequent and bothersome

·         Increasing difficulty breathing (measurable with a peak flow meter, a device used to check how well your lungs are working)

·         The need to use a quick-relief inhaler more often

ASTHMA TRIGGERS :

Exposure to various irritants and substances that trigger allergies (allergens) can trigger signs and symptoms of asthma. Asthma triggers are different from person to person and can include:

·         Airborne substances, such as pollen, dust mites, mold spores, pet dander or particles of cockroach waste

·         Respiratory infections, such as the common cold

·         Physical activity (exercise-induced asthma)

·         Cold air

·         Air pollutants and irritants, such as smoke

·         Certain medications, including beta blockers, aspirin, ibuprofen (Advil, Motrin IB, others) and naproxen (Aleve)

·         Strong emotions and stress

·         Sulfites and preservatives added to some types of foods and beverages, including shrimp, dried fruit, processed potatoes, beer and wine

·         Gastroesophageal reflux disease (GERD), a condition in which stomach acids back up into your throat

RISK FACTORS :

A number of factors are thought to increase your chances of developing asthma. These include:

·         Having a blood relative (such as a parent or sibling) with asthma

·         Having another allergic condition, such as atopic dermatitis or allergic rhinitis (hay fever)

·         Being overweight

·         Being a smoker

·         Exposure to secondhand smoke

·         Exposure to exhaust fumes or other types of pollution

·         Exposure to occupational triggers, such as chemicals used in farming, hairdressing and manufacturing

COMPLICATIONS :

Asthma complications include:

·         Signs and symptoms that interfere with sleep, work or recreational activities

·         Sick days from work or school during asthma flare-ups

·         Permanent narrowing of the bronchial tubes (airway remodeling) that affects how well you can breathe

·         Emergency room visits and hospitalizations for severe asthma attacks

·         Side effects from long-term use of some medications used to stabilize severe asthma

Proper treatment makes a big difference in preventing both short-term and long-term complications caused by asthma.

DIAGNOSIS :

·        There is currently no precise test for the diagnosis, which is typically based on the pattern of symptoms and response to therapy over time.

^·         A diagnosis of asthma should be suspected if there is a history of recurrent wheezing, coughing or difficulty breathing and these symptoms occur or worsen due to exercise, viral infections, allergens or air pollution.

·      spirometry is then used to confirm the diagnosis.

·        In children under the age of six the diagnosis is more difficult as they are too young for spirometry.

Spirometry

·     spirometry is recommended to aid in diagnosis and management.

·        It is the single best test for asthma.

·        If the FEVI measured by this technique improves more than 12% and increases by at least 200 milliliters following administration of a bronchodilator such as salbutamol, this is supportive of the diagnosis.

·        It however may be normal in those with a history of mild asthma, not currently acting up

^·         As caffeine is a bronchodilator in people with asthma, the use of caffeine before a lung function test may interfere with the results.

·    single breath diffusing capcity can help differentiate asthma from COPD.

OTHERS :

 The Methacholine challanges  : 

·        It  involves the inhalation of increasing concentrations of a substance that causes airway narrowing in those predisposed.

·        If negative it means that a person does not have asthma.

·        if positive, however, it is not specific for the disease.

Other supportive evidence includes:

^·         a ≥20% difference in peak expiratory flow rate on at least three days in a week for at least two weeks, a ≥20% improvement of peak flow following treatment with either salbutamol, inhaled corticosteroids or prednisone, or a ≥20% decrease in peak flow following exposure to a trigger.

·        Testing peak expiratory flow is more variable than spirometry, however, and thus not recommended for routine diagnosis

TREATMENT :

·        Medications used to treat asthma are divided into two general classes:

^·         Quick-relief medications used to treat acute symptoms and long-term control medications used to prevent further exacerbation.

·     Antibiotics are generally not needed for sudden worsening of symptoms.

FAST–ACTING :

•  salbutamol metered dose inhaler commonly used to treat asthma attacks.

·         Short-acting beta2 receptor agonist (SABA), such as salbutamal (albuterol USAN) are the first line treatment for asthma symptoms.

·          Anticolinrgic medications, such as ipratropium bromide , provide additional benefit when used in combination with SABA in those with moderate or severe symptoms.

·          Anticholinergic bronchodilators can also be used if a person cannot tolerate a SABA. 

LONG–TERM CONTROL :

1.Corticosteroids are generally considered the most effective treatment available for long-term control.

2. Inhaled forms such as beclomethasone are usually used except in the case of severe persistent disease, in which oral corticosteroids may be needed.^[

3.Long acting beta adrenergic agonist (LABA) such as salmetrol and formeterol can improve asthma control, at least in adults, when given in combination with inhaled corticosteroids.

4.anti-leukotriene agents such as montelukast and zafirlukast) may be used in addition to inhaled corticosteroids, typically also in conjunction with a LABA

5.mast cell stabilizer such as cromylon sodium) are another non-preferred alternative to corticosteroids.

6.For children with asthma which is well-controlled on combination therapy of inhaled corticosteriode (ICS) and long-acting beta₂-agonists (LABA), the benefits and harms of stopping LABA and stepping down to ICS-only therapy are uncertain.

REFERENCES :

https://web.archive.org/web/20110629035454/http://www.who.int/mediacentre/factsheets/fs307/en/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2853245

https://www.ncbi.nlm.nih.gov/pubmed/26977741

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2764772/

https://www.who.int/respiratory/asthma/en/