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Clinical Patterns of Asthma
Now, all of you take care of asthma, and I'm sure as pediatricians, everyone of you sees a lot of asthmatics, as it's the most common chronic disease of childhood. You therefore probably appreciate there are different clinical patterns of asthma. Now, let's talk about these, because these are very important. We have patients who have purely intermittent pattern of asthma. They are totally well between recurrent acute episodes. And in fact, as I'll show you, this is probably the most common pattern of asthma. We have patients, however, who have chronic symptoms. They have persistent symptoms, virtually day in, day out, in the absence of appropriate treatment. A smaller group of patients have purely seasonal allergic asthma, they get asthma only during certain times of the year, when the inhalant allergens to which they are sensitive are predominant, and this varies depending upon what the aerobiology is of the various regions of the country. And we have mixtures of these patients who have chronic persistent symptoms, but have seasonal allergic exacerbations from those same factors. These patterns of asthma have nothing to do with severity. The severity can range from trivial to life-threatening for all of these patterns. So, intermittent does not mean mild. One of the major problems of the NIH guidelines for asthma with regard to particularly young children is these children with just intermittent viral-induced asthma can be very severe, can end up in the hospital over and over again, and it doesn't make any sense to call all intermittents mild - they certainly are not.
Determination of Clinical Pattern
How do you determine the clinical pattern? History is the only way. Ask these questions: if you've got just a few minutes to evaluate a patient, as I'm sure many of you have with the pressure of patients for primary care, do they have sleep disturbances from cough or dyspnea? Is there exercise limitation from cough or dyspnea? What's the frequency of beta 2 agonist use for cough or dyspnea? And, what's the duration of the past year's symptom-free periods? Do they have extended symptom-free periods, or do they not have symptom-free periods? The exam, at the time when they say they're well, do they have a normal auscultatory exam, and at those times, do they have normal pulmonary function, and I mean, not just the peak flow - a peak flow meter is not an evaluative instrument, it's a monitoring instrument once evaluation has been done. So, if you're going to attempt to evaluate pulmonary physiology in the office, get an office spirometer, learn how to use it, become familiar with it, don't just use one of these little toy peak flow meters, they don't give you the same information. Specifically, they won't identify small airway disease, which is important to know whether or not that is going on on a continuous basis.
Intermittent Pattern of Asthma
The intermittent pattern of asthma, again, implies that there is complete absence of symptoms and signs between acute exacerbations, when you ask those questions about nocturnal symptoms and exercise intolerance, if you don't ask the questions specifically, parents tend to tell you what bothers them the most. If they've been living for a number of years with a child who coughs every night, but they end up in the emergency room multiple times, they just tell you about the emergency room, and they may not tell you about the coughing every night. So, you need to ask the specific questions, to determine whether or not it really is an intermittent or persistent pattern. But the intermittent pattern is, in fact, the most common pattern for infants and young children, and it is predominantly viral respiratory infection-induced from common colds. Unfortunately, this pattern of asthma frequently gets misdiagnosed as bronchitis or pneumonia, which leads to inappropriate treatment with antibiotics.
Chronic Pattern of Asthma
The chronic pattern of asthma implies that there are persistent symptoms, while early onset is quite typical, and it often begins as viral respiratory infection-induced intermittent asthma, but then progresses to more persistent symptoms as they get older. It's characterized by the absence of extended symptom-free periods, and again, you have to ask specific questions as to whether or not it's milder during symptom-free periods when they just don't complain, or whether or not it's really absent.
Seasonal Allergic Asthma
Seasonal allergic asthma tends to be typically later age of onset, less likely to be viral respiratory infection-induced, if they didn't have problems when they were young, and the seasonal inhalant allergen varies with region, our part of the country, in the farm belt in the north central U.S. it's predominantly Alternaria which is a mold that grows on decaying vegetation, and this peaks when the farmers are out there stirring those millions of acres of fields and storing up the decaying vegetation. So the spring and the fall, planting and harvest time, and particularly harvest time, is the worst part. I have also practiced in California, and grass pollen in the California and Pacific Northwest valley region predominates there as a major problem, you have to know something about the aerobiology of the region, those happen to be the two regions I know well. [Asthmatic symptoms] can be superimposed on the chronic pattern as chronic with seasonal allergic exacerbations.
When does asthma begin? I showed you that picture of the bronchiolitis, the first episode, and talked about some portion of those children going on to develop different patterns of asthma. There is a very nice study that came out of the Mayo Clinic and the American Review of Respiratory Diseases in 1992. They looked at structured histories to determine when symptoms of asthma began in patients around Rochester, Minnesota, by age and gender. And by far the predominant onset of symptoms from this questionnaire was that the predominant was under 1 year of age. So, when you have 6,000 per 100,000, you're talking about 6% of children when they ask questions about when their asthma started, it had its start in the first year of life.
So 6% of all children in this area had asthma in the first year of life. And again, this is incidence, so it doesn't mean that this is not prevalence now, so this is cumulative when you look at this. And so asthma can begin at any age, but most commonly, if you have a 10 year-old with asthma, most likely it began in the first year of life. And in fact, they found that 80% of all asthma in this area began before age 5.