Section B1: Diagnosing Asthma

BREATHE EASY

Diagnosing Asthma: "Hypersensitive Airways"

WHAT IS ASTHMA?

Asthma is a condition of hypersensitive airways. Normally the airways of our lungs stay open continuously so that air can enter without difficulty. The airways of asthmatics have a tendency to narrow or close down when excited by many types of stimuli. For this reason they are said to be hypersensitive or hyper-reactive. The asthmatic's airways are primed to narrow when the right stimulus comes along.

The basic reason why some people have this hyper-reactivity, and hence asthma, is unknown. Regardless of the stimulant, the end result is the same for the patient; the bronchi (another name for airways) tend to narrow or constrict (called broncho-constriction) and there is trouble breathing.

When the airways constrict the patient usually wheezes. A wheeze is a high-pitched sound produced as air is forced through the narrowed air passages. Also characteristic of asthma is its reversible nature — the airways can (almost always) be unconstricted. Often the narrowing is relieved after the stimulus is removed. Frequently, however, medication has to be given to open up the airways.

The lungs consist of multiple branching airways that become narrower and narrower as the number of branches increases (Section A). During normal breathing these airways stay open. During as asthma attack the walls of the airways are thickened. In addition, the smaller airways may become partially or completely filled with thick mucus. Thickened walls and increased mucus result in narrowing of the airways and obstruction to the flow of air (Figure 1). To the extent these airway problems can be relieved, asthma victims will also be relieved of their symptoms.

Figure 1. Thickened walls of air passages during an asthma attack.

WHAT IS AN ASTHMA ATTACK?

An asthma attack is a sudden change in the airways that makes the patient uncomfortable. It usually causes some combination of shortness of breath, wheezing, chest congestion, chest tightness, and cough. Different patients may experience varying combinations of symptoms, but cough and chest tightness and chest congestion seem to be the most common. The symptoms are often attributable to a "bad cold" or "the flu"; although these two conditions are not the same as asthma, they may lead to an asthma flare up.

WHAT CAN TRIGGER AN ASTHMA ATTACK?

We only know some of the stimuli that make asthmatics wheeze. Fortunately, however, treatment is usually effective regardless of the cause. All asthmatics react in a common way no matter what the stimulus, and they also respond to medications similarly. Table 1 lists common stimuli that may precipitate or cause wheezing and shortness of breath in an asthmatic, a condition described as an "asthma attack."

TABLE 1. Common stimuli that may bring on an asthma attack in a patient with hyper-reactive airways

Irritants - Various air pollutants, tobacco smoke, perfumes, petroleum solvents, etc.

Allergens - Pollens, ragweed, certain foods, molds, etc.

Infections - Virus and bacteria-like organisms

Temperature and Climate - Particularly cold air

Exercise - May exacerbate asthma but especially in cold, dry air

Emotional Factors - May worsen some asthmatic conditions

Aspirin & Other Analgesics - May affect some asthmatics

Drugs - Through a non-allergic mechanism

Our current understanding of asthma can be diagrammed in simple fashion, as is shown in Figure 2. Asthma is a condition of unknown cause that can flare up (asthma attack) on exposure to certain stimuli. An asthma attack can usually be traced to one or more of the stimuli listed in Table 1. Note that the number, frequency, and severity of asthma attacks can vary tremendously from patient to patient. In a way not yet understood, these stimuli can make the airways of an asthmatic narrow and fill with mucus. Exposure to the same stimuli in a non-asthmatic does not lead to airway narrowing.Treatment, which can completely reverse an asthma attack, does not cure the underlying asthma tendency, and the asthmatic remains at some risk for another attack.

Figure 2. Triggers of an asthma attack.

WHAT IS THE SPECTRUM OF ASTHMA SEVERITY?

It is estimated that asthma afflicts about 5-8% of the population, or between 12 and 20 million people in the United States, including those who have mainly hay fever but wheeze on occasion.The vast majority of asthmatics have a mild or moderate condition easily controlled by either avoiding known stimuli or by taking some medication when asthma symptoms occur. A small percentage of the asthma population suffers from severe, recurring attacks, requiring daily medication. An even smaller percentage end up in the hospital because of their asthma (Figure 3).

Figure 3. Asthma Pyramid. Most Asthmatics Have a Mild or Moderate Condition

CAN PEOPLE DIE FROM ASTHMA?

Unfortunately, yes. An estimated three to four thousand Americans die annually from asthma alone. This number does not include the much larger group of patients whose basic problem is chronic obstructive pulmonary disease in which their may also be an asthmatic component (see Section G).

Compared to the millions of people who have asthma in this country, three to four thousand deaths is a small percentage. But asthma is a treatable condition; ideally no deaths should occur. What is troubling is that most asthma deaths appear to be increasing each year. We don't know the exact reason or reasons for the increase in asthma deaths. However, most asthma deaths can be traced to under-treatment by the patient or under-treatment by the doctor. Only a small number of asthma deaths, perhaps 10%, occur in people who seek medical care early and receive aggressive and appropriate management.

IS ALL ASTHMA DUE TO ALLERGY?

Although all asthmatics have hypersensitive airways, not all asthma is related to allergy. In fact, in many cases no allergic mechanism can be found. We now understand that allergy is only one of the potential triggers of an asthma attack (see Table 1 and Figure 1).

Generally speaking there are two broad categories of asthma. One type is related to allergy, and is triggered by things inhaled, ingested, or touched that the patient has previously been sensitized to, e.g., pollen, cat fur or shellfish. "Sensitized to" means the patient has formed antibodies to something in these substances; when these substances enter the body an allergic reaction occurs.

A true allergic reaction seems to be a more common trigger of asthma in children than in adults. When specific allergens can be identified as provoking symptoms the asthma is sometimes called "extrinsic," since the cause is outside the body. Extrinsic asthma is synonymous with allergic asthma. In extrinsic asthma the stimulant enters the body and combines with the patient's antibodies to produce the bronchoconstriction, or narrowing of the airways. In such patients allergy skin tests to the stimulating substance may show a reaction, and an allergy antibody measured in the blood will usually be increased.

WHAT IS NON-ALLERGIC ASTHMA?

Non-allergic asthma is the predominant type of asthma in adults. In most adults the trigger of asthma is not allergy and no specific allergic substances can be identified. This is true even though many adult asthmatics have a history of atopy (allergy) in the years preceding onset of asthma. There may be a history of childhood hay fever, various food allergies, or even mild asthma that remitted during adolescence, only to flare up as an adult. For an adult asthmatic, an atopic or allergic childhood history does not prove an allergic mechanism for the asthma.

The term intrinsic asthma is used to describe most cases of adult asthma, implying the cause is from within the body. Intrinsic asthma is synonymous with non-allergic asthma. However, "intrinsic" is a misnomer. Originally intended to mean from within the body, we now know that many non-allergic triggers of asthma are from the environment. An example is the inhalation of cold air that triggers an asthma attack, particularly during exercise. Probably the most common stimulus for "intrinsic" asthma attacks is a viral respiratory infection, a cause that certainly comes from outside the patient.

DOES IT MATTER IF ASTHMA IS INTRINSIC OR EXTRINSIC?

Yes, in two important ways. First, if the asthma is truly extrinsic (allergic), it may be possible to avoid the stimulus. For example, cat fur or shellfish can be avoided if they cause wheezing. The second reason is that, for the small percentage of patients who have allergic asthma, desensitization "allergy" shots may be effective. The shots work by building up an immunity to the stimulus of the asthma attack, and they are occasionally helpful. However, most adult patients do not have classic allergic asthma and so desensitization shots are rarely helpful. Experience also teaches us that most adults will know if they are allergic to a specific agent since their symptoms (shortness of breath, cough or wheezing) get worse on exposure and better when the stimulus is avoided. For adults, diagnosis of allergic asthma is best made with a careful medical history. This point is illustrated by the following case.

Eric S. – A Case of Allergic Asthma

Eric S. is a 25-year-old patient who develops a runny nose and watery eyes every spring. He has never wheezed or experienced shortness of breath. He brought a new cat home and three days later began experiencing chest tightness and wheezing. He thought he might be allergic to the cat and left it with a friend, after which his wheezing improved. A week later, when he picked up the cat, his wheezing recurred. He gave up the cat and has felt well ever since.

Such a patient likely has extrinsic or allergic asthma to cat fur. In obvious situations such as this the causative agent should be simply avoided. Skin tests are not needed.

ARE ALLERGY SHOTS OF VALUE?

Allergy shots means injections of material to "de-sensitize" the allergen that triggers the asthma. Their value depends on the individual patient and the type of asthma. Most adults don't have true allergic asthma, but in some children allergy shots may be beneficial. Also, allergies can manifest in ways other than asthma, such as hay fever with a runny nose and watery eyes. If hay fever symptoms are a seasonal problem, allergy shots may help. However, for most adults who suffer from asthma, allergy shots are simply not helpful. They certainly should not take the place of medications when there is wheezing or shortness of breath. At best, allergy shots work over the long range (months or years); they are never helpful immediately.

DOES CIGARETTE SMOKING CAUSE ASTHMA?

No, not directly. Smoking can, however, cause bronchitis that can then lead to wheezing and shortness of breath and for all practical purposes behave just like asthma. We use the term "asthmatic bronchitis" to describe such a condition.

Asthmatic bronchitis, when due to cigarettes, differs from asthma in that there is underlying lung damage from prolonged smoke exposure. In such patients lung function is often permanently impaired. By contrast, lungs of true asthmatics (non-smokers) usually show normal function between attacks. Also, patients with asthmatic bronchitis (when due to cigarette smoking) can go on to develop emphysema; as far as is known emphysema does not occur in true asthmatics unless they also smoke (emphysema is actual destruction of lung tissue — see Section G).

WHAT IS OCCUPATIONAL ASTHMA?

Occupational asthma is asthma that results directly from inhaling dusts or fumes at the work place. Occupational asthma is a condition caused by the job. A worker with pre-existing asthma who simply gets worse on the job does not, strictly speaking, have occupational asthma. Occupational asthma is a very common, yet commonly misunderstood, problem, one so important that a separate section is devoted to it (see Section D).

IS WHEEZING ALWAYS PRESENT IN AN ASTHMA ATTACK?

Wheezing is both a sign and a symptom. Patients frequently know when they are wheezing and that makes it a symptom. They can hear a high pitched sound coming from their lungs. Usually, however, wheezing is something the doctor is more aware of than the patient, since it is easily heard with the stethoscope and that also makes it a medical sign. Either way, the absence of wheezing does not rule out asthma. In fact, patients can suffer from severe asthma without ever wheezing.

Some patients have asthma whose only symptom is cough or shortness of breath on exertion. Asthma may remain undiagnosed because no wheezing is heard, but it is asthma nonetheless. Since non-wheezing asthmatics respond to medication as well as those who wheeze, the correct diagnosis is very important. To be sure of the diagnosis, lung function testing is carried out. The patient is asked to blow through a tube in order to measure air flow. If lung function testing cannot be done, asthma medication may be tried anyway. Because there are other causes for cough and shortness of breath besides asthma, treatment should only be under medical supervision.

DOES THE PRESENCE OF WHEEZING ALWAYS MEAN ASTHMA?

Just as asthma may be present without wheezing, the presence of wheezing does not always indicate asthma. Wheezing does indicate airway narrowing or obstruction, of which there are several causes. Chronic obstructive pulmonary disease (Section G) is commonly accompanied by wheezing, and may even have a true asthma component (i.e., some reversibility of airway obstruction with treatment).

So-called "cardiac asthma" is a heart condition that may be accompanied by wheezing. Another cause of wheezing that may masquerade as asthma is upper airway obstruction-narrowing of the large airway in the neck region. Wheezing may also occur on one side of the chest only, as from lung cancer or pneumonia. (Wheezing from asthma is always on both sides of the chest, i.e., it comes from both lungs.)

Most patients with diffuse wheezing have asthma or an asthma component to their illness. However, common medical wisdom states: "not all that wheezes is asthma."

WHAT ROLE DO EMOTIONS PLAY IN ASTHMA?

A common misconception is that asthma is of psychological origin or is a psychosomatic disease. There is simply no basis in fact that asthma is caused by psychological factors. Most physicians accept that asthma attacks can be triggered by emotional factors, but emotions are simply one of several stimuli to which the hypersensitive airways of asthmatics may react (see Table 1 and Figure 2). Not being able to breath comfortably is emotionally distressing, so it is difficult to know if emotional upset is a stimulus or a result of the asthma attack.

Psychoanalytic thought has in the past emphasized a faulty mother-child relationship involving asthmatic children. This is a myth not substantiated by scientific evidence; in fact many asthmatic children have a normal, healthy mother-child relationship. Certainly the relationship between a mother and her asthmatic child can be unhealthy from a psychological point of view and make the affliction worse. However, this is also true with many chronic diseases, and does not in any way imply a cause and effect relationship.

WHAT ROLE DO EMOTIONS PLAY IN ASTHMA?

HOW CAN A PATIENT HELP MANAGE HIS OR HER OWN ASTHMA?

A positive trend in recent years has been for patients to assume management of their asthma. An analogy is the patient with diabetes. Diabetics who need insulin routinely inject themselves, and monitor their own blood sugar levels at home. Asthmatics now have a tool to monitor the progress of their airflow obstruction at home or on the job. It's called a portable peak-flow meter, shown in Figure 4.

A peak-flow meter is a hand-held device which contains an opening for the patient to blow through. When the patient exhales with force, after a deep inhalation, the device registers a specific number; that number represents how hard the person blew through the tube, and thus the amount of air flow. Since it only records the maximum amount of air flow, the test is called "peak flow." For adults, normal peak flow is 400-700 liters per minute (L/min). Patients with a history of asthma attacks establish their own normal baseline (say, 500 L/min). When they have symptoms, that number will fall. It may drop to 400, 300 or 200 L/min. The lower the number the more severe the air flow problem.

After consultation with a physician, the patient may learn that when his peak flow falls, say to 250 L/min, he should start taking prednisone or should increase inhaler use and/or call the doctor. Through trials and close follow-up, the patient becomes knowledgeable about his asthma and has an objective number to follow, similar to the diabetic's blood sugar measurement.

Figure 4. A Portable Peak Flow Meter

Many patients with asthma that flares during the year will keep prednisone tablets on hand and know when to start them, based on how they feel and the peak flow measurement. They may also have a regimen of inhalers that they can use and know when to start them. Thus, by knowing the medications they need and having them available, and by following their own peak-flow measurements, many asthmatics can maintain good control of their asthma. In conjunction with talking to a physician, usually on the telephone, they can keep out of trouble.

Figure 5. Peak Flow Measurements

WHERE CAN I GO FOR HELP IF I HAVE ASTHMA?

Any patient with asthma that is debilitating, limiting or causing disruption in daily living should seek medical attention. Asthma is a treatable disease and one should not suffer needlessly. The best source for help is your personal or family physician. Most cases of asthma are treatable by most primary care physicians; all that is required is an interested and knowledgeable physician and a compliant patient. The number of available medications is large and varied, and patients should not rely on over-the-counter drugs unless the symptoms are very mild and easily reversible (see Section E). By all means, if you do not feel adequately treated or your physician is unable to devote sufficient time to your problem, you should seek referral. There are many physicians who deal with difficult asthmatic problems.

This is not to say that all asthmatics need treatment by a specialist; most do not. Severe asthma, refractory to regular therapy, is relatively uncommon. More typical reasons for lack of improvement are physician failure to treat adequately and patient non-compliance. Frequently, patients who do not respond with one physician will be referred on the initiative of that physician. However, if your personal physician is unable (for whatever reason) to adequately manage your case, you should do one of two things: Ask for referral to an allergist or pulmonary physician who specializes in the management of asthma; or, if this is not possible, contact your local medical society for a referral in your area.

For no other lung disease is proper treatment so critical; asthma is a reversible and eminently treatable condition. It may require above average effort to achieve a proper balance of medical care and patient compliance, but for patients who cannot breathe the effort is warranted. Until both the patient and physician are assured everything feasible has been tried, there is no reason for anyone to suffer from asthma.

WHY DO SOME ASTHMATICS NOT IMPROVE WITH THERAPY?

Sometimes asthmatics don't seem to respond to proper therapy. There are three broad reasons why an asthmatic may not improve.

1. Under-treatment. Usually this occurs from not using oral steroids, or using too low a dose. Steroids are the most potent anti-inflammatory drug available for asthma, and are necessary for virtually all exacerbations that don't improve with bronchodilating medication. They must be used orally as tablets (or in severe cases, intravenously) to be effective. Inhaled steroids don't work in most asthma exacerbations, since the dose available by inhalation is too low.

2. A complicating condition. Sinusitis is a common problem in patients with asthma. If specific measures are not taken to correct it, the asthma may not improve. Specific measures may include antibiotics and decongestants, drugs not ordinarily used to treat asthma. Typical symptoms include headache or pain behind the cheek bones, nasal stuffiness and a constant drip in the back of the throat. Often a CT scan of the sinuses is necessary to make the diagnosis, as typical symptoms may be absent. Sinus CT scan is now a routine test in asthmatics who don't respond to therapy. Another complicating condition that may lead to chronic asthma is "gastric reflux," the condition of stomach acid coming up the esophagus and spilling into the throat. The problem is called "GERD," for gastro-esophageal reflux disease. GERD requires specific treatment before the asthma will improve (see next section).

3. Some other condition altogether, i.e., not asthma. For example, the patient could have congestive heart failure which, in some cases, can mimic asthma, but does not respond to asthma treatment. It shows up on the chest x-ray as fluid in the lungs. (The chest x-ray of asthma is clear; no fluid is seen.) Another condition that can mimic asthma is upper airway obstruction, usually diagnosed with pulmonary function tests and a CT scan of the neck area; this may occur from a large thyroid gland or an upper airway tumor, for example. A third condition that can mimic asthma (and baffle physicians) is called "vocal cord dysfunction syndrome" which is seen almost exclusively in young women. Here the patient "causes" the asthma-like symptoms by keeping her vocal cords tight together. The result is a narrowed upper airway, which causes wheezing and shortness of breath and looks like classic asthma. However, vocal cord dysfunction is a psychological problem, even though the patient does not know she is doing it. The lungs are normal and there is no asthma. Drugs for asthma don't work. Treatment involves speech therapy to learn vocal cord control and, sometimes, psychological counseling.

WHAT IS GERD AND HOW DOES IT CAUSE ASTHMA?

GERD stands for gastro-esophageal reflux disease. Normally, food travels from the mouth to the esophagus and then to the stomach, where it is digested by stomach acid. In GERD, stomach acid refluxes or backs up from the stomach into the esophagus. The reflux acid can then travel back up the esophagus and spill over into the throat and then drip into the lungs. Stomach acid is an irritant, and in the lungs it can cause several problems. Asthma is just one of them. The patient may also have a chronic cough. When patients are evaluated for chronic cough, GERD is one condition that physicians think of, along with asthma and sinusitis. One interesting aspect of GERD is that patients who have it don't always complain of heartburn or "acid indigestion". That is, they may have no stomach problems and have only the pulmonary symptoms.

GERD is a motility problem in the esophagus which allows stomach acid to reflux. Drugs used to treat the motility problem include Propulcid and so called "H-2 blockers," such as Zantac and Tagamet. Other modalities to treat GERD include: raising the bed about 30° so that acid tends to stay in the stomach and not reflux back up to the esophagus; weight reduction for patients who are obese; and cessation of alcohol for patients who drink. Also, one of the drugs sometimes used to treat asthma, theophylline, can make reflux worse; this drug should be stopped if the patient with reflux is taking it.

Most patients with asthma, of course, do not have GERD. However, if there is persistent asthma or chronic cough, GERD ought to be considered.

WHAT IS SINUSITIS AND WHY IS IT COMMONLY ASSOCIATED WITH ASTHMA?

One of the least understood aspects of respiratory disease is the effects of sinus problems on the lungs. The sinuses, air pockets in the head, are in communication with the rest of the respiratory passages. Because of gravity, any inflammation, mucus or infection of the sinuses has a tendency to fall into the throat, then into the upper airway and down to the lungs.

Patients with asthma may be treated with bronchodilator and anti-inflammatory drugs, but if a focus of inflammation or infection in the sinuses doesn't clear up, mucus can continue to drip into the lungs and cause cough and wheezing. For this reason doctors often order a sinus CT scan in patients who seem refractory to ordinary asthma therapy. In most cases sinusitis can be cleared up with antibiotics, decongestants and, sometimes, steroids. Sometimes a sinus full of mucous has to be mechanically drained by an ENT (ear, nose, throat) specialist. On rare occasion, sinuses have to be opened up surgically so they can drain. It is important that sinusitis always be considered in the patient who has continued chronic cough (or asthma symptoms) that don't clear up with conventional therapy.