Question: how is asthma diagnosed

Reference:
 Asthma attack Overview During an asthma attack, also called an asthma exacerbation, your airways become swollen and inflamed. The muscles around the airways contract and the airways also produce extra mucus, causing your breathing (bronchial) tubes to narrow. During an attack, you may cough, wheeze and have trouble breathing. An asthma attack may be minor, with symptoms that get better with prompt home treatment, or it may be more serious. A severe asthma attack that doesn't improve with home treatment can become a life-threatening emergency. The key to stopping an asthma attack is recognizing and treating an asthma flare-up early. Follow the treatment plan you worked out with your doctor ahead of time. Your treatment plan should include what to do when your asthma starts getting worse, and how to deal with an asthma attack in progress. Symptoms Asthma attack signs and symptoms include: - Severe shortness of breath, chest tightness or pain, and coughing or wheezing - Low peak expiratory flow (PEF) readings, if you use a peak flow meter - Symptoms that fail to respond to use of a quick-acting (rescue) inhaler Signs and symptoms of an asthma attack vary from person to person. Work with your doctor to identify your particular signs and symptoms of worsening asthma - and what to do when they occur. If your asthma symptoms keep getting worse even after you take medication as your doctor directed, you may need emergency room care. Your doctor can help you learn to recognize an asthma emergency so that you'll know when to get help. If your asthma flares up, immediately follow the treatment steps you and your doctor worked out ahead of time in your written asthma plan. If your symptoms and peak expiratory flow (PEF) readings improve, home treatment may be all that's needed. If your symptoms don't improve with home treatment, you may need to seek emergency care. When your asthma symptoms flare up, follow your written asthma plan's instructions for using your quick-acting (rescue) inhaler. PEF readings ranging from 50 to 79 percent of your personal best are a sign you need to use the quick-acting (rescue) medications prescribed by your doctor. Asthma can change over time, so you'll need periodic adjustments to your treatment plan to keep daily symptoms under control. If your asthma isn't well-controlled, it increases your risk of future asthma attacks. Lingering lung inflammation means your asthma could flare up at any time. Go to all scheduled doctor's appointments. If you have regular asthma flare-ups, low peak flow readings or other signs your asthma isn't well-controlled, make an appointment to see your doctor. Seek medical attention right away if you have signs or symptoms of a serious asthma attack, which include: - Severe breathlessness or wheezing, especially at night or in the early morning - The inability to speak more than short phrases due to shortness of breath - Having to strain your chest muscles to breathe - Low peak flow readings when you use a peak flow meter - No improvement after using a quick-acting (rescue) inhaler Causes An overly sensitive immune system makes your airways (bronchial tubes) become inflamed and swollen when you're exposed to certain triggers. Asthma triggers vary from person to person. Common asthma attack triggers include: - Pollen, pets, mold and dust mites - Upper respiratory infections - Tobacco smoke - Inhaling cold, dry air - Gastroesophageal reflux disease (GERD) - Stress For many people, asthma symptoms get worse with a respiratory infection such as a cold. Some people have asthma flare-ups caused by something in their work environment. Sometimes, asthma attacks occur with no apparent cause. Risk factors Anyone who has asthma is at risk of an asthma attack. You may be at increased risk of a serious asthma attack if: - You've had a severe asthma attack in the past - You've previously been admitted to the hospital or had to go to the emergency room for asthma - You've previously required intubation for an asthma attack - You use more than two quick-acting (rescue) inhalers a month - Your asthma attacks tend to sneak up on you before you notice symptoms have worsened - You have other chronic health conditions, such as sinusitis or nasal polyps, or cardiovascular or chronic lung disease Complications Asthma attacks can be serious. - Asthma attacks can interrupt everyday activities such as sleep, school, work and exercise, causing a significant impact on your quality of life - and can disrupt the lives of those around you. - Serious asthma attacks mean you're likely to need trips to the emergency room, which can be stressful and costly. - A very severe asthma attack can lead to respiratory arrest and death. Diagnosis For adults and children over 5 years old, lung (pulmonary) function tests are used to check how well the lungs are working. Poor lung function is a sign that your asthma isn't well-controlled. In some cases, lung function tests are also used in asthma emergencies to help check the severity of an asthma attack or how well treatment is working. Lung function tests include: - Peak flow. Your doctor may take a peak flow reading when you come in for a scheduled visit or for emergency treatment during an asthma attack. This test measures how quickly you can breathe out. You also may use a peak flow meter at home to monitor your lung function. The results of this test are known as peak expiratory flow (PEF). A peak flow test is done by blowing into a mouthpiece as hard and as fast as you can with a single breath (expiration). - Spirometry. During spirometry, you take deep breaths and forcefully exhale into a hose connected to a machine called a spirometer. A common spirometry measurement is forced expiratory volume, which measures how much air you can breathe out in one second. The results of this test are known as forced expiratory volume (FEV). Spirometry can also measure how much air your lungs can hold and the rate at which you can inhale and exhale. - Nitric oxide measurement. A newer diagnostic test, this exam measures the amount of nitric oxide gas you have in your breath when you exhale. High nitric oxide readings indicate inflammation of the bronchial tubes. Exhaled nitric oxide can be measured by having a patient exhale directly into an analyzer. Exhaled air may be captured in a nitric-oxide-impervious container for measurement later. - Pulse oximetry. This test is used during a severe asthma attack. It measures the amount of oxygen in your blood. It's measured through your fingernail and only takes seconds. Treatment If you and your doctor have worked out an asthma plan, follow its directions at the first sign of an asthma attack. This generally means taking two to six puffs of a quick-acting (rescue) inhaler to get airway-expanding medication, such as albuterol (ProAir HFA, Proventil HFA, Ventolin HFA, others), deep into your lungs. Small children and those who have trouble with inhalers can use a nebulizer. After 20 minutes, you can repeat the treatment one time if necessary. For an asthma attack with severe symptoms, such as difficulty speaking because you're so short of breath, start with the same initial step of using quick-acting medication - but instead of waiting for the drug to work, get to a doctor's office or urgent care immediately. Same-day medical care is also warranted if you continue to wheeze and feel at all breathless after initial treatment. Your doctor may recommend that you continue to use quick-acting medication every three to four hours for a day or two after the attack. You might also need to take oral corticosteroid medication for a short time. Emergency treatment If you go to the emergency room for an asthma attack in progress, you'll need medications to get your asthma under immediate control. These can include: - Short-acting beta agonists, such as albuterol (ProAir HFA, Proventil HFA, Ventolin HFA, others). These are the same medications as those in your quick-acting (rescue) inhaler. You may need to use a machine called a nebulizer, which turns the medication into a mist that can be inhaled deep into your lungs. - Oral corticosteroids. Taken in pill form, these medications help reduce lung inflammation and get your asthma symptoms under control. Corticosteroids can also be given intravenously, typically to patients who are vomiting or under respiratory failure. - Ipratropium (Atrovent). Ipratropium is sometimes used as a bronchodilator to treat a severe asthma attack, especially if albuterol is not fully effective. - Intubation, mechanical ventilation and oxygen. If your asthma attack is life-threatening, your doctor may put a breathing tube down your throat into your upper airway. Using a machine that pumps oxygen into your lungs will help you breathe while your doctor gives you medications to bring your asthma under control. After your asthma symptoms improve, your doctor may want you to stay in the emergency room for a few hours or longer to make sure you don't have another asthma attack. When your doctor feels your asthma is sufficiently under control, you'll be able to go home. Your doctor will give you instructions on what to do if you have another asthma attack. If your asthma symptoms don't improve after emergency treatment, your doctor may admit you to the hospital and give you medications every hour or every few hours. If you're having severe asthma symptoms, you may need to breathe oxygen through a mask. In some cases, a severe, persistent asthma attack requires a stay in the intensive care unit (ICU). Lifestyle and home remedies All asthma attacks require treatment with a quick-acting (rescue) inhaler such as albuterol. One of the key steps in preventing an asthma attack is to avoid your triggers. - If your asthma attacks seem to be set off by outside triggers, your doctor can help you learn how to minimize your exposure to them. Allergy tests can help identify any allergic triggers. - Washing your hands frequently can help reduce your risk of catching a cold virus. - If your asthma flares up when you exercise in the cold, it may help to cover your face with a mask or scarf until you get warmed up. 

Answer: Poor lung function is a sign that your astha isn't well controlled. Lung function tests can be used to determine how well the lungs are working. Lung function tests include peak flow readings to measure how quickly you can breathe out, spirometry to measure how much air you breathe out, or nitric oxide measurement, which can indicate inflammation of the bronchial tubes. Pulse oximetry is used during a severe asthma attack to measure the amount of oxygen in your blood.