How medicine treats asthma

DIAGNOSIS

The medical profession diagnoses asthma in a variety of ways, but the process is usually based on repeated careful measurements of how efficiently the patient can force air out of the lungs, and on a thorough medical history and laboratory tests to find out what triggers the patient’s acute attacks.

Spirometry

This is an instrument that measures the air taken into and out of the lungs (it measures air flow and air volume—how much and how quickly air can be expelled after a deep breath). The patient breathes into a device called a spirometer, which traces the rate at which the air leaves the lung. If there’s something wrong with your airflow or your lungs, it will show up as a trace on the spirometer.

The amount of air you breathe out is measured as the ‘forced vital capacity’ (FVC), and the amount breathed out in one second is called the ‘forced expiratory volume’ in one second (FEV1). The ratio of FEV1 to FVC is used to find out how bad your airflow is. A lower-than-normal FEV1 is a sign that you may have a lung disease. A falling FEV1 suggests that the lung disease is getting worse.

The ‘normal’ values for FVC and FEV1 depend on a patient’s age, gender, height and race. They are higher for younger than for older people, for tall than for short people, for men than for women and for whites than blacks or Asians. Therefore, the numbers are presented as percentages of the average expected in someone of the same age, height, gender and race. This is called the ‘per cent of predicted’. Any number smaller than 85 per cent of predicted is considered abnormal.

Peak flow monitoring

This measures how the lungs are performing. The peak flow meter is a handheld device that measures how fast you breathe air out of your lungs. This is called your ‘peak expiratory flow rate’ (PEFR). If you can breathe out quickly and easily (a higher PEFR), your lungs are working well, and your asthma may not be bothering you. If you breathe out slowly and with difficulty (a lower PEFR), it can mean that your lungs are not working well. Your PEFRs are compared with charts that list normal values according to gender, race and height.

Chest X-rays

The doctor may also refer you to have a chest X-ray to rule out the possibility of your breathing problems being caused by something other than asthma.

However, a study has revealed that doctors are relying merely on chest radiographs to determine the severity of asthma, even though they have access to sophisticated equipment and techniques such as peak flow and spirometry measurements.

How severe your asthma is depends on the severity, frequency and duration of symptoms (such as coughing or breathlessness), the level of airflow obstruction and the extent to which the condition interferes with your daily life. Patients with more than two episodes of asthma symptoms per week, or with evidence of airflow obstruction between symptoms, have persistent asthma.

In very young children—less than two years old—asthma can be very difficult to diagnose with certainty. Wheezing at this stage often follows a viral infection and may later disappear without ever leading to asthma.

TREATMENT

The medical profession treats asthma in two main ways:

Environmental control

Asthma symptoms can be activated by many agents. Generally, the severity of your asthma depends on how many agents activate your symptoms, and how sensitive your lungs are to them. People with asthma react to external irritants in a way that non-asthmatics don’t. Many, but not all, asthmatics have allergies that cause their bodies to produce an abnormal array of chemicals in response to environmental allergens.

Medication

This is the mainstay of asthma treatment. Because patterns of asthma are different for different people, the specific type of drug treatment varies a lot, depending on the frequency, severity and particular triggers for each patient’s episodes.

For people with mild asthma, medication may be needed only before exposure to triggers or when they detect the onset of an attack. Those with more frequent symptoms may take daily medicine as well as using it for specific symptoms. In the case of severe and persistent asthma, patients may be prescribed two or more doses of medicine each day.

Most asthmatics use two types of medication: a preventative inhaler, which includes steroids, and a bronchodilator, which provides temporary relief from asthma symptoms, but does not tackle the underlying inflammation.

An acute, or sudden, asthma attack is usually caused by an exposure to allergens or an upper respiratory tract infection. How severe the attack depends on how well your underlying asthma is being controlled (which reflects how well the airways inflammation is being controlled). An acute attack is potentially life-threatening because it may continue, despite your having used a quick-relief medication, such as an inhaled bronchodilator.

Prolonged asthma attacks that don’t respond to bronchodilator treatment are classed as severe and you need to get to the doctor or a hospital. Severe asthma symptoms are persistent coughing, and being unable to speak in full sentences or walk without shortness of breath. Your chest may feel closed and your lips may have a bluish tint.

Drug treatment for asthma is given largely on a suck-it-and-see (or, more properly, an inhale-it-and-see) basis, ending up with the patient taking a medicine chest of potentially lethal drugs. The British Thoracic Society (BTS) has published new guidelines for following a ‘step’ approach, only graduating on to the next step in terms of potency of drugs if the step before hasn’t helped. It also advises that, when control is established with one step, consider moving down to the step below.

‘Step One’ begins with short-acting inhaled beta2-agonists for patients who experience symptoms infrequently or with only mild exercise-induced asthma. These adrenoceptor stimulants cause the nervous system to act on adrenaline (epinephrine) receptors throughout the body. But unless the drugs are highly selective, aiming to stimulate only beta2-receptors (which relax bronchial muscles and reduce the chemicals causing inflammation), they can cause the heart to race and force it to produce larger quantities of blood, thus raising blood pressure. The selective beta2-agonist drugs are sold in the UK as salbutamol, or albuterol in the US, fenoterol and terbutaline.

If the doctor feels that inhaled beta2-agonists aren’t doing the job, or you find you’re using them more than three times a week, the doctor moves up to ‘Step Two’, which includes anti-inflammatories. Children are usually started on a six-to-eight week trial of sodium cromoglycate (Intal), three or four times a day. This drug, called a ‘mast-cell stabiliser’, works by preventing the mast cells lining the bronchial tubes from releasing chemicals, causing the bronchial muscles to contract. It is effective in preventing an attack from starting, but cannot treat an attack once it has begun.

Nevertheless, the medical profession, which is mostly at a loss as to how best to treat the condition, prescribes a wide range of aggressive drugs, including anti-inflammatories such as sodium cromoglycate or short-acting beta2-agonists such as salbutamol. Newer approaches for those who work out regularly include pretreatment with longer-acting beta2-agonists, such as salmeterol, or the regular use of inhaled corticosteroids. However, these have a range of adverse effects if used for the longer term and don’t appear to be appropriate for EIA.

A similar, but more potent, drug is nedocromil sodium. Most adults (and children who haven’t been helped by sodium cromoglycate) are placed on inhaled steroids, which are supposed to reduce the daily dose and, hence, the general risks of corticosteroids. These drugs include beclomethasone and budesonide.

‘Step Three’ employs the same steroids, but a more powerful inhaler. Dry-powder inhalers have cartridges that blast the powder when you breathe in, and utilise more drug than the usual pressurised aerosol cartridges. Another possibility is the use of a spacer, which offers a ‘space’ between the inhaler and the mouth to allow more time for the propellant chemical to evaporate before the drug reaches you. There are also nebulisers, which produce a spray, slowly releasing the drug into the bronchial tubes.

If this still doesn’t control your asthma, or you have persistent symptoms at night despite all the other inhaled therapies, the BTS suggests that you move on to ‘Step Four’, increasing the daily dose of inhaled steroids and using an additional bronchodilator, such as theophylline or aminophylline, on top of the other medication. Theophylline belongs to a drug category called the xanthines, which includes caffeine. Theophylline works by relaxing the bronchial muscles and also breaking down a chemical that controls the muscles in the bronchial tubes.

Another possibility is to take oral beta2-agonists, which release more drug into the body, or a non-selective adrenoceptor stimulant like ipratropium bromide, which affects your heart as well as your bronchial muscles.

If all else fails, you are put on a course of oral steroids in addition to the other drugs in ‘Step Four’. You might even be given a trial of cyclosporin, originally developed to prevent the body’s rejection of organ transplants and now medicine’s drug of the month, investigated for everything from psoriasis to arthritis.