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TUBERCULOSIS

Tuberculosis (TB) is an infectious disease caused by bacteria whose scientific mane is Mycobacterium tuberculosis. It was first isolated in 1882 by a German physician named Robert Koch who received the Nobel prize for this discovery. TB most commonly affects the lungs but also can involve almost any organ of the body. Many years ago this disease was referred to as "consumption" because without effective treatment these patients often would waste away. Today, of course, tuberculosis can usually be treated successfully with antibiotics.

There is also a group of organisms referred to as atypical tuberculosis. These involve other types of bacteria that are in the Mycobacterium family. Often these organisms do not cause disease and are referred to as "colonizers" because they simply live alongside other bacteria in out bodies without causing damage. At times, these bacteria can cause an infection that is sometimes clinically like typical tuberculosis. When these atypical mycobacteria cause infection they are often very difficult to be cured. Often drug therapy for these organisms must be administered for one and a half or two years and requires multiple medications.

How does a person get TB? A person can become infected with tuberculosis bacteria when he or she inhales minute particles of infected sputum from the air. The bacteria get into the air when someone who has a tuberculosis lung infection coughs, sneezes, shouts, or spits (which is common in some cultures). People who are nearby can then possibly breathe the bacteria into their lungs. You don't get TB just touching the clothes or shaking hands of someone who is infected. Tuberculosis is spread (transmitted) primarily from person to person by breathing infected air during close contact.

There is a form of atypical tuberculosis, however, that is transmitted by drinking unpasteurized milk. Related bacteria called Mycobacterium bovis cause this form of TB. Previously, this type of bacteria was a major cause of TB in children but it rarely causes TB now since most milk is pasteurized (undergoes a heating process that kills the bacteria).

What happens to the body when a person gets TB? When the inhaled tuberculosis bacteria enter the lungs the can multiply and cause a local lung infection (pneumonia). The local lymph nodes associated with the lungs may also become involved with the infection and usually become enlarged. The hilar lymph nodes (the lymph nodes adjusted to the heart in the central part of the chest) are often involved.

In addition, TB can spread to other parts of the body. The body's immune (defense) system, however, can fight off the infection and stop the bacteria from spreading. The immune system does so ultimately by forming scar tissue around the TB bacteria and isolating it from the rest of the body. Tuberculosis that occurs after initial exposure to the bacteria is often referred to as primary TB. If the body is able to form scar tissue (fibrosis) around the TB bacteria then the infection is contained in an inactive state. Such an individual typically has no symptoms and cannot spread TB to other people. The scar tissue and lymph nodes may eventually harden, like stone, due to the process of calcification of the scars (deposition of calcium from the bloodstream in the scar tissue). These scars often appear on X-rays and imaging studies like round marbles and are referred to as a granuloma. If these scars do not show any evidence of calcium on X-ray they can be difficult to be distinguished from cancer.

Sometimes, however, the body's immune system becomes weakened and the TB bacteria break through the scar tissue and can cause active disease referred to as reactivation tuberculosis or secondary TB. Foe example, the immune system can be weakened by old age, the development of another infection or cancer, or certain medications used to treat arthritis or inflammatory bowel disease. The breakthrough of bacteria can result in a recurrence of pneumonia and a spread of TB to other locations in the body. The kidneys, bones, and lining of the brain an spinal cord (meninges) are the most common sites affected by the spread of Tb beyond the lungs.

How common is TB and who gets it? Over 8 million new cases of TB occur each year worldwide. In the United States it is estimated that 10-15 million people are infected with the TB bacteria and 22,000 new cases of TB occur each year.

Anyone can get TB but certain people are at higher risk including those living with individuals who have an active TB infection, poor or homeless people, foreign-born people from countries that have a high prevalence of TB, nursing home residents and prison inmates, alcoholics and intravenous drug users, people with diabetes, certain cancers, and HIV infection (the AIDS virus), and health-care workers. There is no strong evidence for a genetically determined (inherited) susceptibility for TB.

What are the symptoms of TB? As previously mentioned, TB infection usually occurs initially in the upper part (lobe) of the lungs. The body's immune system, however, can stop the bacteria from continuing to reproduce. Thus, the immune system can make the lung infection inactive (dormant). On the other hand, if the body's immune system cannot contain the TB bacteria the bacteria will reproduce (become active or reactivate) in the lungs and spread elsewhere in the body.

It may take many months from the time the infection initially gets into the lungs until symptoms develop. The usual symptoms that occur with an active TB infection are a generalized tiredness or weakness, weight loss, fever, and night sweats. If the infection in the lung worsens then further symptoms can include coughing, chest pain, coughing with sputum (material from the lungs) and blood, and shortness of breath. If the infection spreads beyond the lungs the symptoms will depend upon the organs involved.

How does a doctor diagnose TB? Tuberculosis can be diagnosed in several different ways including chest X-rays, analysis of sputum, and skin tests. Sometimes, the chest X-rays can reveal the evidence of active tuberculosis pneumonia. Other times, the X-rays may show scarring (fibrosis) or hardening (calcification) in the lungs suggesting that TB is contained and inactive. Examination of the sputum on a slide (smear) under the microscope can show the presence of the tuberculosis-like bacteria. Bacteria of the mycobacterium family including atypical mycobacteria stain positive with special dyes and are referred to as acid-fast bacteria (AFB). A sample of the sputum is also usually taken and grown (cultured) in special incubators so that the tuberculosis bacteria can subsequently be identified as tuberculosis or atypical TB.

Several types of skin tests are used to screen for TB infection. These so-called tuberculin skin tests include the Tine test and the Mantoux test also known as the PPD (purified protein derivative) test. In each of these tests a small amount of purified extract from dead tuberculosis bacteria is injected under the skin. If a person is not infected with TB no reaction will occur at the site of the injection (a negative skin test). If a person is infected with tuberculosis, however, a raised and reddened area will occur around the site of the test injection. This reaction (a positive skin test) occurs about 48 to 72 hours after the injection.

ASTHMA

What is it?Asthma is a chronic lung condition with symptoms of difficulty breathing and wheezing caused by inflammation and narrowing of the air passages. The condition ranges from mild to severe. Some people have only occasional, mild symptoms while others have nearly constant symptoms with severe, life-threatening flare-ups.

During an asthma attack the airways become inflamed and narrower as the muscles surrounding them constrict. The flow of air is blocked partially or completely as mucus produced by the inflammation fills a narrower passageway. Asthma affects both the lungs larger airways called the bronchi and the lungs smaller airways called the bronchioles. Treatment focuses on preventing or stopping the inflammation and relaxing the muscles that line the airways.

What causes asthma-related inflammation is not clear but several environmental "triggers" have been identified. Many asthma triggers are allergens, substances that cause the immune system to overreact in some people. Common allergens include animal dander and saliva, pollens, molds, dust mites, cockroaches, some medications and certain foods. Also high on the list of asthma triggers are viral infections such as colds and influenza, exercise, breathing cold, dry air, environmental pollutants such as cigarette smoke, wood smoke, paint fumes and chemicals, strong odors, and emotional stress. For some people with severe asthma no specific triggers can be identified

Although asthma can develop early often before age 5, its symptoms can begin at any age. The condition has a genetic (inherited) component and often affects people with a family history of allergies. The American Lung Association estimates that 25 million people in the United States will be diagnosed with asthma in their lifetime. One-third of Americans with Asthma symptoms are children.

Symptoms.Symptoms of asthma include: wheezing (a whistling sound as air is forcibly expelled), difficulty breathing, chest tightness, a persistent cough.

For some people with asthma a chronic cough is the main symptom. For some people symptoms flare up only during or after exercise. Between asthma attacks or flare-ups people with mild or moderate asthma may have no symptoms at all. Asthma can lead to more severe cold or flu symptoms, or make a person more prone to bronchitis.

Symptoms of a severe asthma attack include: a rapid pulse, sweating, extreme shortness of breath, flared nostrils, using the chest and neck muscles during breathing, a bluish discoloration of the lips and fingernails (cyanosis).

Diagnosis.A thorough medical history is an important part of diagnosing and treating asthma. Your doctor will ask about any symptoms you have, how severe they are, when and where they occur, how frequently they occur, and what triggers and relieves them. These details will help your doctor find ways to prevent your asthma attacks. Your doctor will also want to know about your personal history of allergies and respiratory illnesses as well as your family history of asthma, allergies and respiratory illnesses.

Your doctor will listen to your back with a stethoscope to detect wheezing. During an attack your doctor can assess the severity of your flare-up by listening for the amount of airflow and by looking at how you are using your chest muscles to breathe. Blue lips or skin are a sign that you are not getting enough oxygen. Other tests that can be done in the office include a measurement of the speed of the air you can exhale forcibly done with a peak-flow meter. Another test measures oxygen levels in your blood and is done with a pulse oximeter, a small device that is placed on the tip of your finger.

During an asthma flare-up blood tests may be done to check for signs of an elevated white blood cell count which can indicate that you have an infection. A special test, called an arterial blood gas (ABG) can be done on blood drawn from your wrist to measure oxygen levels more accurately. Your doctor also may want you to have a chest X-ray.

Two tests show how well your lungs are functioning and can help to diagnose asthma and measure its severity: spirometry and peak-flow meter.

During spirometry you exhale into a device that analyzes the amount and volume of airflow. One part of the test may be repeated after you are given a medication called a bronchodilator that relaxes the muscles surrounding the airways to improve airflow. If airflow improves after use of a bronchodilator this helps to diagnose asthma. Sometimes a challenge test is performed, especially when spirometry appears normal. In this procedure you inhale a medication to see if it provokes a measurable contraction of the airway muscles (bronchospasm). People with asthma are more sensitive to this medication.

Peak-flow meter is a small portable tube measuring the speed of air expelled when you blow forcibly through it. These devices are often given to asthma patients for use at home to monitor their asthma and help to detect the earliest signs of an asthma flare-up.

There is no one test to diagnose asthma. Your doctor will rely on a combination of information from your history, physical exam and tests. If your symptoms are mild your doctor may prescribe an inhaler. If this relieves your symptoms your doctor can be sure you have asthma.

If your doctor suspects that your asthma is being triggered by allergens and the symptoms are not treated or controlled easily with medications a blood test or allergy skin testing may be performed. The blood test called the radioallergosorbent test (RAST) looks for antibodies to potential specific allergens. In allergy skin testing the skin is exposed to weak dilutions of different potential allergens either by pricking the skin with the allergen or using a patch taped to the skin for several days. If there is redness or swelling at the injection site an allergy to that substance is confirmed.

Expected duration.Asthma in adults is often a lifelong condition. But with treatment symptoms can be controlled and can be infrequent or very mild. In about half of children with asthma it can go away on its own or decrease in severity over time. However, it often reappears later in life.

Asthma episodes can go away on their own or with the help of asthma medications. Attacks vary in frequency and severity often dependent on which triggers cause the attack.

Prevention.In some cases asthma episodes can be prevented by avoiding or minimizing exposure to triggers. These include environmental triggers such as cigarette smoke, environmental pollutants (especially when pollution and ozone levels are high) and strong chemicals.

If exercise triggers your asthma you can prevent an attack by breathing warm, humidified air before and during exercise or by using inhalers. Preventive medicine also can be used before an anticipated exposure to animals.

Eliminating allergens at home often can go a long way to control asthma symptoms. Some people may need to avoid animals entirely or to take special measures with their pets such as keeping them out of bedrooms or bathing them regularly. If dust mites are a trigger some household anti-mite measures include encasing mattresses in airtight enclosures, frequent household cleaning, washing bedding frequently in very hot water, and removing carpets and heavy draperies from sleeping areas.

Those who are affected by pollens might stay indoors whenever possible, use air conditioning and keep windows closed during high pollen season.

Monitoring your symptoms and peak-flow readings helps to identify a coming attack hours or even days before symptoms develop which allows you to start treatment early. In many cases early treatment can stop an attack from occurring.

Early signs or symptoms of an asthma flare-up include: coughing more often, increased mucus or phlegm, becoming short of breath quickly with exertion or exercise, developing a sinus headache or fever, having symptoms that resemble a cold such as a runny or congested nose, sneezing or watery eyes.

Treatment. If you have chronic asthma you should work with your doctor to develop a written asthma-management plan. The plan specifies how to avoid asthma triggers, when and how regular medications should be taken, how to handle acute attacks, and how a peak-flow meter should be used. It is important that preventive asthma medications be taken as prescribed even when you are not having symptoms.

Several types of medication are available to treat asthma. Some treat acute attacks while others prevent attacks from happening.

1. Bronchodilators relax the muscles around the airways to improve airflow and they are commonly inhaled. One class of bronchodilators called beta agonists including albuterol typically can be prescribed alone for mild occasional symptoms. Albuterol also is used as a "rescue " medication to stop an attack. It can be inhaled in an inhaler or taken with a nebulizer, a device that mixes medications with a mist for inhalation. Other bronchodilators including salmeterol and theophylline (sold under numerous brand names) are used to prevent and control asthma. They are not useful for an asthma attack because they take too long to begin working.

2. Anti-inflammatory medications usually are taken regularly to prevent asthma attacks from occurring. These drugs work by reducing inflammation and reducing constriction of airway muscles. Steroid medications inhaled or taken orally reduce inflammation and are used to treat moderate or severe disease. People with moderate disease often can control their asthma quite well by using a steroid inhaler. Oral or intravenous steroids are given in higher doses to serve as a rescue-type medication and then tapered off over several days to weeks. Cromolyn sodium and nedocromil are anti-inflammatories that can help prevent attacks in mild to moderate asthma if used daily. They also can be used before contact with a known asthma trigger, for example, before exercise or exposure to animals. Leukotriene modifiers are the new type of anti-inflammatory medication. Taken orally these drugs block leukotrienes, one of the many chemicals that cause inflammation and airway narrowing in many people with asthma.

Some people with asthma also benefit from immunotherapy in which the person is injected with increasing amounts of allergens to desensitize the person's immune system. Immunotherapy for asthma appears to be most effective for mild to moderate symptoms that are caused by sensitivity to indoor allergens such as dust mites, mold spores and animals.

Severe asthma attacks must be treated in a hospital where oxygen can be administered and drugs may be given either intravenously or with a nebulizer. In life-threatening cases the patient may require intubation (placing a breathing tube in the large airway) and artificial ventilation in an intensive care unit.

When to call a professional. Call your doctor whenever you or your child has persistent wheezing, chest tightness, difficulty with breathing or cough. Some children with asthma may not complain specially of shortness of breath. However, they may flare their nostrils or use their chest and neck muscles when breathing - signs that they are having trouble.

If you already have been diagnosed with asthma call your doctor if your symptoms are worsening or are not being controlled by your regular medications. For example, you should call your doctor if you must use your rescue inhaled bronchodilator more than four times a day to control symptoms or your peak-flow-meter readings are in the yellow or red zones.

If you have an asthma attack and your symptoms persist despite your medications, seek emergency help immediately.

Prognosis. Although asthma cannot be cured it almost always can be controlled successfully. Most people who have asthma can expect to lead relatively normal lives.

Facts about asthma.if you have asthma you're already familiar with its chest-clutching, short-of-breath feeling. If you don't have asthma but want to know what it feels like, try this: take two of those little straws that people use to stir coffee or tea. Clamp your lips tightly around them and hold your nose. Now breathe. Feel how hard your lungs work to get air in and out? Or how quickly you get short of breath? That's full-blown asthma.

Of course, there are milder examples of symptoms such as a whistle or wheeze when you breathe a tightness in your chest or a nagging cough. But all asthma symptoms stem from the same problem - you are breathing through smaller straws in your lungs.

This chronic disease has several types. What makes them different are the triggers, the things that set asthma off. For sвовремяome people the trigger is an allergy to cats or to mold. Exercise can be a trigger as can chemicals in the air, cigarette smoke or a cold or the flu. Some triggers are so stealthy that some people are never able to identify them.

No matter what the trigger is, the end result is always the same - the airways tighten up and narrow, making it hard to move air in and out of the lungs. The whistle or wheeze you can sometimes hear when someone with asthma breathes is the sound of air rushing through these constricted airways and blocked air sacs in the lungs.

Misconceptions about asthma. Asthma is shrouded in mystery and misconception. The mystery reflects the ingoing efforts of scientists to understand this disease better. The misconception represents outdated or overly dramatic images of asthma. If you've ever read Lord of the Flies or seen the movie you might remember Piggy, the pudgy, bespectacled boy who can't keep up with the pack because of his asthma. Perhaps you've seen a TV program that shows someone with asthma suddenly start to wheeze and then use an inhaler for immediate resolution. Or maybe you've heard that asthma is mostly a childhood disease that may outgrow.

Recent advances have put a new face on asthma. Scientists have shown that this condition is caused by inflammation, the same process that makes a sprained ankle swell. Preventing inflammation by avoiding the things that trigger it and/ or by blocking it with drugs can help people with asthma to have relatively mild symptoms and few, if any, full-blown asthma attacks. New drugs that target inflammation - some delivered by inhalers, some in pill form - can ease asthma symptoms and help to limit the side effects in older drugs such as heart palpitations and nausea.

Overall, the goal of managing and treating asthma is to make it easier for you to lead a normal, healthy life. Managing your asthma even when you don't have symptoms will help keep you out of the emergency room and minimize long-term damage to your lungs.

Causes and triggers of asthma: understanding inflammation. Unfortunately, medical researchers don't know exactly what causes asthma. It's entirely possible that no single cause will ever be found. What health-care professionals do know is that people with asthma have trouble breathing because the tubes that carry air to from the lungs (that is the airways) become inflamed. Inflammation causes mucus to build up in these tubes cutting down on the space available to move air. Inflammation also stimulates the muscles around these tubes to contract narrowing the tubes and further cutting down the air flow. Although inflammation is the root of all asthma, the trigger for this inflammation is different for different people.

Understanding how inflammation causes asthma will bring you one step closer to controlling this disease. That's because stopping or preventing inflammation by avoiding the things that trigger it is key to keeping the airways open which promotes good airflow and comfortable breathing. Understanding the role that inflammation plays also will help you to understand why you may need to take at least two different drugs - one to control or prevent inflammation and another to open constricted airways.

Unraveling asthma link to inflammation has led to huge advances in treating this disease. This work has laid the groundwork for new classes of drugs aimed at controlling or preventing airway inflammation. These new drugs work hand in hand with the old and still important standbys - drugs that relax and open the airway,

The how and why of inflammation. Inflammation is an important part of your body's response to injury or infection. Basically, inflammation is the immune system call to action . Signals sent by the immune system recruit an army of cells to fight off invaders such as bacteria or viruses. They also start the healing process when there are signs of tissue damage. For example, when you scrape a knee on a dirty sidewalk bacteria cling to the wounded tissue. "Scout" cells sense these foreigners and send chemical signals that attract other cells to this spot. These new arrivals release substances that attract still more cells that help clean the wound and draw more body fluid to it. This is why the area becomes swollen.

In people with asthma the lungs and airways overreact to foreign substances in the air such as cat hair, mold, or pollution. Sometimes even clean, cold air can constrict the airways especially in people with exercise-induced asthma. In many ways asthma is a type of allergic reaction that is why many people with asthma also see an allergy specialist to help manage their condition.

 



PNEUMONIA | BLOOD PRESSURE

Text A. THE BRAIN | SENSE ORGANS | Text A. FIVE SENSES | VII. Read text B and | REVISION | SENSE ORGANS | COMMON COLD | RUBELLA | SMALLPOX | ALLERGY |

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