Asthma (which originally meant “shortness of breath”) is among the most common of ailments—up to 5 percent of Americans, 10 million people, suffer from it. Recent studies indicate that one in nine Californians has the disease. In childhood, it is one-third more common and more severe in males but, after puberty, the sex distribution is about even. It is more often found in urban, industrialized settings, in colder climates, and among the urban disadvantaged, especially African-Americans.
Asthma is a collection of respiratory symptoms, the most prominent of which are shortness of breath, wheezing, coughing, and increased production of mucus. The shortness of breath (which can be sudden in onset) and wheezing is produced by “twitchiness” of the respiratory airways. As air is inhaled through either the nose or the mouth, it flows through a series of airways. These airways—tubes, really—begin in the throat and descend all the way down to the base of the lungs. At the level of the throat and upper chest they are fairly large. The uppermost and largest is called the trachea. About one-third of the way down into the chest, the trachea branches into two somewhat smaller airways known as main stem bronchi. Each of these main stem bronchi supplies air to one of the lungs. As the bronchi extend deeper and deeper into the chest, the air tubes proliferate and become smaller and smaller. The result is a complex maze of small tubes—airways—which resemble the root structure of a tree. Surrounding these airways is a layer of smooth muscle. This muscle maintains the size and shape of the airways. In asthmatics the muscle is “spastic” or “twitchy”—likely to go into a spasm when stimulated by any of a number of factors. When the smooth muscle sheath does go into spasm, it chokes or constricts the airways thus making less room for the air to move in and out of the lung. It is this restriction of airflow that produces the high-pitched wheezing and the struggle to breathe that are characteristic of asthma.
In addition to the layer of spastic muscle tissue around the airways, mucus producing cells called goblet cells are important contributors to asthma. Everybody, whether normal or asthmatic, has these mucus-producing cells. Mucus is important because it carries the enzymes and chemicals that help the lungs to fight infection. In asthmatics, however, there is an increase in the number of mucus cells with the number increasing with the severity of asthma. These cells produce an excess of mucus which clogs airways and obstructs the flow of air. This is especially true in the small airways at the bottom of the lungs.
There are several medications available that keep asthma symptoms from appearing or relieve them when they are present. These medications are beta-agonists, theophyllines, cromolyn, leukotriene inhibitors and corticosteroids (cortisone). Most patients rely on inhalers to deliver their drugs because the most frequently prescribed drugs for asthma are beta agonists and inhaled corticosteroids. Accordingly, knowing how to use your inhalers and knowing what order to take them is very important for effective care of asthma symptoms.
Beta agonists are the major class of medications for asthma. These drugs can be taken orally, but are most commonly and effectively administered by operating a metered, hand-held, aerosol canister. They provide rapid relief of asthmatic wheezing and shortness of breath. Activating the canister releases a puff of drug-saturated aerosol which is carried directly to the twitchy smooth muscle in the airways. This direct action quells the symptoms much more rapidly than the theophyllines do.
Since they work almost instantaneously they are extremely satisfying to use. Serevent is a long-acting beta agonist. In many people it has been shown to be extremely effective in preventing bronchospasms as opposed to treating bronchospasms. It is not to be used, however as a rescue medication once an asthma attack has started. Serevent is usually prescribed for adults and children 12 and over at 2 puffs twice a day in the morning and evening.
Beta agonists are the first line of treatment for mild asthma because they have fewer side effects, they are more convenient, and they act more rapidly.
The effectiveness of aerosols depends very much on knowing how to use them effectively.
DO NOT OVERUSE THEM. (2 inhalations every 4 hours and not more than l2 total inhalations per day.)
To use a metered aerosol effectively, do the following:
- Shake inhaler.
- Begin inhalation and, at the same time, place aerosol just in front of the mouth at a distance of l-2 inches and release a properly aimed puff of aerosol (aerosol should go straight to the large airways; it should not impact at the back of the throat).
- Inhale at a moderate rate with open mouth.
- Hold breath for five seconds.
To direct the spray efficiently, “spacers” are often useful. A cheap, effective spacing device is the cardboard cylinder found within a roll of toilet paper. With seals between the mouth and the metered aerosol, it works quite well. A small plastic container made into a simple cylinder has also been shown to be an effective delivery system. Many commercial spacers are available. These spacers simply hold the aerosol in suspension for several seconds. The person who is unable to inhale the aerosol successfully thus has more than one inspiration to get the medication to the lungs.
Their form, because of their toxicity, are rarely the first line of treatment in the management of asthma.
Cromolyn sodium and Tilade, also given by inhalation, are second-line drugs used for asthma and are anti-inflammatory. Thus they are given as preventative and have no role in the treatment of acute asthma. The metered dose of cromolyn (Intal) and Tilade are administered in the same way as the beta agonists.
Steroids, very potent drugs for asthma, are now available as inhalers. When taken by inhalation, these inhaled preparations of steroids have few toxicities and are often considered first line drugs. When properly taken, they act only on the lungs and do not carry the negative side effects associated with the other forms. These aerosol steroids can be quite effective in improving breathing. While they do not deliver the amount of cortisone required for severe (but unhospitalized) asthmatics, they are extremely helpful in sub-acute cases. These agents include Beclovent, Vanceril, Aerobid, Azmacort and Flovent. Flovent is the only such drug available in 3 different concentrations. It easily appears to be the best of these topical steroids and some patients do well when using Flovent as their only drug. Another topical steroid, Aero-Bid, is unpleasant to take because it has a bad taste and often induces nausea.
On occasion, Atrovent is also given to patients with asthma. Most often it is used in patients with bronchitis or emphysema. However, when Atrovent is administered at the same time as a beta agonist, then there is an additive function and one gets a better response with more dilation of airways. In the past this had to be done with two different inhalers but recently an inhaler containing both Atrovent and Albuterol (a beta agonist) was approved. This drug is called Combivent and is gaining increased usage.
A common question asked by patients is which inhalers should be taken first and in what order. This is actually a very important issue because if the airways are constricted, then the inhaled medication will not go down to the small airways. Accordingly, it is recommended that the first inhaler be the beta agonist. The second inhaler should be the topical steroid. Any other inhalers can be used thereafter as long as it is always remembered to dilate the airways first with a beta agonist. It is also recommended that patients keep track of the color of the cannisters and what the drugs are used for. For example, during acute bronchospasm, it is important that the patient reach for the beta agonist to gain an immediate action, rather than a topical steroid which has a delayed onset of action. Used correctly, inhalers have made the life of asthmatics much easier.