Diagnosed Asthma

DR. SOPHOCLES: How is asthma diagnosed?
DR. COX: Asthma diagnosis is based on history and physical examination and some objective testing. The history is probably one of the most key features to making the diagnosis of asthma. You will be interviewing the patient and asking if they’re having episodes of difficulty breathing, or they may also perceive it as chest tightness. Cough can be another symptom of asthma, particularly cough that gets worse with exercise or may wake them up at at 2 a.m. at night. Asthma is in most cases a chronic inflammatory disease of the airways but this can make the airways more susceptible or twitchy to other stimuli like cold air, exercise, viral infections or even laughing can trigger asthma in somebody who’s very hyper-responsive. The objective measures of airflow that we use commonly in clinical practice is pulmonary function testing, but peak flow monitoring can also be used to help monitor asthma primarily and sometimes it may assist when you’re trying to gather information about day-to-day lung function in making the diagnosis of asthma.

One of the symptoms that the patient might report is wheezing, which could be high pitched in young children. The parents might see an increased work of breathing, rib contractions. Typically symptoms of asthma worsen at night. It is actually one of the symptoms that we use in the expert panel guidelines to evaluate asthma severity—how often the person is waking up with asthma symptoms at night. Typically these episodes of wheezing or shortness of breath will be brought on by an identified trigger. One might question if somebody’s saying, “I’m having difficulty breathing and wheezing when I’m sitting, watching TV and nothing else is going on.” So it’s important to also find out what seems to be the trigger of the wheezing, or the coughing, or the shortness of breath when you’re interviewing the patient. A typical trigger of asthma would be exercise, and it may trigger up to 75% of asthmatics. As I mentioned earlier, viral infections are thought to be the most common cause of asthma exacerbations. In a population survey of skin testing about 12% of patients had skin test reactivity to animals so it is not an uncommon allergen. Dust mites, depending on the geographic location, can be a very common allergen. Exposure to dust mites that might provoke symptoms may occur after vacuuming a rug where there’s a lot of disturbed dust, ruffling or changing the bed, pulling up a carpet. Molds, indoor and outdoor, can be a trigger as an allergen. Molds can also produce substances that irritate the respiratory mucous, which can cause problems for non-asthmatics and asthmatics. Tobacco smoke and strong fragrances are irritant triggers. Some patients report changes in weather as a trigger. There is a phenomenon known as thunderstorm asthma where there are changes in the osmotic pressure that lead to a greater dispersal of pollen sub-particles and actually mold fungi, so there is increased allergen in the air. As I mentioned earlier, laughing can be a trigger, and some women actually have worsening at the time of their menstrual cycles on a consistent basis. It is not known why that occurs, but it seems to be related to hormonal changes.

Regarding the objective measures of asthma, the most commonly used objective measure is simple spirometry, or pulmonary function tests that can be performed in the office with a computer device. As I mentioned, peak flow meters are useful in gathering information about lung function over time, but they’re not as sensitive for making the diagnosis of airflow obstruction in asthma. And then there are more sensitive detailed tests that are generally done in hospital facilities that will measure diffusing capacity and airway resistance.

The expert panel guidelines currently recommend pulmonary function tests at the time of initial assessment and after treatment is initiated and has been stabilized. There should be re-evaluation during periods of progressive or prolonged loss of asthma control, and every one to two years. This recommendation of the National Heart, Lung, and Blood Institute is the newest updated set of guidelines. The guidelines state that the objective assessment of pulmonary function are necessary for the diagnosis of asthma because medical history and physical examinations are not reliable means of excluding other diagnoses, or of characterizing the status of lung impairment. There are a number of asthmatics, particularly if they’ve had asthma for a long period of time, who may not be perceiving the degree of airflow obstruction.

The advantages of spirometry are that it is a relatively simple device to use and it can be readily used in an office setting. It gives you objective documentation of the severity of that patient’s obstruction. It also may help you identify poor perceivers and you will be able to document and assess their response to acute and chronic therapy. An acute response would be giving the patient a beta-agonist, such as Albuterol, waiting fifteen minutes, repeating the test, and looking for a change in the pulmonary function test. A significant improvement, according to the American Thoracic Society’s guidelines, is a 12% improvement in the FEV1, which is the Forced Expiratory Volume in one second. The other instance of documenting response to treatment might be if you give patients a course of oral corticosteroids to see if there is some reversibility to their pulmonary function test. This is recommended in the instance where the patient does not have a response to the beta-agonist and you want to determine if they are truly patients who have irreversible airway obstruction or that they’re not improving because they have airway inflammation that needs to be addressed with an anti-inflammatory drug. The recommendation is to give two weeks of oral corticosteroids and then reassess at that point in time. The majority of responders to the corticosteroids would have responded at that two week time and that point might give you an idea of what this patient’s best pulmonary function test baseline is, after you’ve given them that course of oral corticosteroids. Limitations of the spirometry; it does require good patient effort so you need a cooperative patient. A good reading set is three readings that provide you with an FEV1 of within 5% of each other with the exception of a pattern that you might see in some asthmatics, and that is with each effort, their pulmonary function test gets worse because of the effort of performing the test is beginning to make them go into bronchospasm. Sometimes we refer to that as a twitchy pattern. You would see a worsening of the lung function with each subsequent blow. The other limitation of spirometry is it provides you only with a snapshot of that point in time and you may not be picking up the patient at the times when their asthma is typically worse, which is at night or early in the morning. The following slides give you some examples of what you might see on a pulmonary function test.

The following four slides are examples of what you would see on a pulmonary function test report. The first slide is aime/Volume Tracing and what you look at is the amount of air that is expired in the first second. You also look at it in comparison to the total amount, and that’s referred to as the Forced Vital Capacity, or FVC, and you also look at the ratio of the FEV1 over the FVC. In a non-obstructed airway, that ratio is roughly 80% or better. If the individual is putting out less than 80% of their Forced Vital Capacity in the first second, that would suggest that there is obstruction. The other parameter that is given here is the Forced Expiratory Flow Rate from the 25-75% vital capacity and that’s referred to as the FEF25-75 percent. And this is felt to reflect the airflow in the small airways which is where air exchange takes place.

The next slide is a Pre- and Post-Bronchodilator Flow Volume Loop. Now in this slide, we have both the inspiratory and the expiratory cycle mapped. The expiratory cycle is looking at airflow obstruction where the inspiratory may give you some other clues and there are certain patterns that may suggest that you’re dealing with another illness, such as vocal cord dysfunction and I’ll give you some examples of flow volume loops that give you different abnormalities.

In the next slide, you can see a difference in the before and after bronchodilator flow volume loop so this patient did have improved lung function after being given a bronchodilator. Regarding volume loops that are found in different conditions, you can see an obstructive pattern where there’s marked sloping and diminution of the expiratory loop. You can see a restrictor pattern where you actually have increased flow rates because it’s a stiff, restricted lung pushing air out more quickly. D is a Variable Extrathoracic obstruction and what you see that’s so notable is a very flat inspiratory loop. You would see that with vocal cord dysfunction which is a condition that sometimes mimics asthma, but it is due to obstruction coming outside of the thoracic cavity from the vocal cords coming together paradoxically during inspiration. The other two flow loops show you a Variable Intrathoracic and a Fixed Obstructive pattern.

And lastly, again looking at the Time/Volume, which is usually what you look at when you look at simple spirometry results, you’re going to be looking at the change in FEV1 after bronchodilator administration, and in this case, the patient improved by 13% which is considered significant.

DR. SOPHOCLES: How do you measure lung function?
DR. COX: Peak flow monitoring. A Peak flow meter is a relatively inexpensive device and it can be used for a number of reasons in asthma.

Basically it can help teach the patient to be a better perceiver of airflow obstruction. It can be used initially to assess how well they are responding to treatment. It can be used during times of exacerbations to determine how long, how slowly you should taper medications. It may be helpful to detect early exacerbations that may allow you to intervene early and prevent the exacerbation from being as severe. The expert panel does suggest peak flow monitoring should be considered, but it is not a strong recommendation for all patients.

They recommend you consider peak flow monitoring for patients who’ve had history of severe exacerbations, patients who have moderate to severe persistent asthma, and patients who have difficulty perceiving signs of worsening of asthma. This is primarily because there really haven’t been any studies that clearly say peak flow monitoring is superior to monitoring asthma based on patient symptoms alone.

According to the current National Health, Lung and Blood Institute expert panel guidelines, asthma is now defined in a couple ways. It’s defined by its severity and severity is the intrinsic intensity of the disease—basically what the person is born with in terms of asthma. You can really assess severity best before the patient is receiving a long-term controller therapy. Then there is control and that’s the degree to which asthma manifestations can be minimized and the goals of therapy met. So you can actually have a severe asthmatic but they can be well-controlled, and you can have a mild asthmatic who is not well-controlled for a number of reasons.

Responsiveness is the ease to which asthma control is achieved with therapy. The severity of asthma is closely related to its responsiveness to treatment and that implies that asthma severity can be inferred, and the initial assessment of severity allows an estimate of type and intensity of treatment that will be needed.

Now in terms of judging severity, there are two domains. You have impairment, and impairment is the clinical presentation—how often they have need for medications, how often they’re waking up at night. You also have lung function measurement. So impairment, you look at symptoms and lung function capability. And then there is risk. Risk is the risk of exacerbations, the risk of medication side effects. So severity has two domains: Impairment and Risk. Control reflects the extent to which the current discomfort and future risks are normalized and treatment goals are to reduce discomfort of the disease, the medications, and also reduce risk.
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