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Airflow Limitation: David L. Simel, MD, MHS, discusses the clinical examination for airflow limitation.
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Airflow Limitation: David L. Simel, MD, MHS, discusses the clinical examination for airflow limitation.
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Language: EN.
Segment:0 .
>> I'm Joan Stephenson, editor of JAMA's Medical News and Perspectives section. Today I have the pleasure once again of talking with Dr. David Simel about identifying airflow limitation, a topic discussed in Chapter 13 of the Rational Clinical Examination. This chapter was co-authored by Dr. Simel. Welcome back to the podcast, Dr. Simel, and please introduce yourself to our listeners. >> Hi. I'm David Simel. I'm a professor of medicine at the Durham Veterans Affairs Administration Medical Center and Duke University, and I'm the editor of the Rational Clinical Examination series.
>> Dr. Simel, what is airflow limitation and why is recognizing it by clinical examination important? >> Well, I'm going to give you an explanation from a general internist perspective that I think simplifies things, and that is that airflow limitation can occur during inhalation, exhalation, or both. And the limitation is caused by a narrowing of the airway diameter in relation to the amount of air that is being inhaled or exhaled. Now, the narrowing can be dynamic and reversible, which is a phenomenon that we see in asthma.
Or it can be static and fixed, which is what is seen in emphysema. Now, the phenomenon of the inability to fully exhale creates air trapping in the lungs and is responsible over a long period time for some of the clinical findings in patients with advanced airflow limitation. Airflow limitation is important to recognize because its presence may require specific treatment that for all patients is going to include smoking cessation, avoidance of environmental precipitants, and preventive treatment with vaccination for influenza and pneumococcus.
For the actual symptoms of airflow limitation, the treatment might include bronchodilators or immunosuppressive therapy such as steroids, or during times of bacterial infection, with antibiotics. >> Should clinicians routinely screen patients for airflow limitation? >> Well, the short answer is no, we should not be screening asymptomatic patients. But we should be counseling all smokers to stop smoking so that they will have decreased risk for the disease. We should be screening the patient with chronic or recurrent unexplained cough or shortness of breath.
>> During the clinical examination for airflow limitation, what risk factors or symptoms should clinicians review? >> So the most important risk factor is one that I've already alluded to, which is the presence of a smoking history. Compared to patients who've never smoked, patients with a smoking history will have about double the likelihood of airflow limitation. But the importance of the smoking history increases rapidly with greater exposure. And at a threshold of greater than 40-pack years of smoking, these high exposure patients have about 12 times the likelihood of airflow limitation.
Now, to help determine the years of smoking exposure, we suggest asking at what age the patient started smoking and in what year he or she quit, if the patient is a former smoker. Now, when considering the symptom of cough, its presence can have multiple causes. Because of that, as a single symptom, coughing is only going to double the likelihood of airflow limitation. So, a likelihood ratio positive of two. But when we're assessing chronic bronchitis, what we want to know is if there is sputum production.
So chronic bronchitis is defined as sputum production for at least three consecutive months in at least two consecutive years. We also want to know if the patient with chronic bronchitis is experiencing wheezing. Now, the presence of sputum production of greater than or equal to a fourth a cup a day of sputum or the symptom of wheezing each quadruple the likelihood of airflow limitation. >> Which signs are best associated with an increased likelihood of airflow limitation?
>> So the signs are what we pick up on our physical exam. In the presence of wheezing on lung auscultation is going to have a likelihood ratio of four, which is pretty high. The other findings such as the presence of, say, a barrel chest or hyper-resonance to percussion, or decreased cardiac dullness, or a laryngeal height less than 4 cm, are seen in patients with more advanced emphysema, and they're not going to be present in patients at early phases of chronic airflow limitation. The laryngeal height is the distance between the top of the thyroid cartilage and the suprasternal notch.
Now, a direct measure of airflow limitation can be quite useful. In patients with a prolonged forced expiratory time of greater than nine seconds are going to have about a sevenfold increase in the likelihood of airflow limitation. This test is done by having the patients take a deep breath and then forcefully exhale until no more air can be expelled. The physician listens over the larynx or lower trachea during this maneuver while they time the audible airflow. >> How accurate is the overall clinical impression for predicting airflow limitation?
>> Well, we only found three studies that looked at this, and not surprisingly, the results vary. So, physicians are pretty good at detecting moderate to severe limitation to airflow with a likelihood ratio of five to six. But, unfortunately, we can't have too much confidence in whether or not physicians can detect mild disease. Now, rather than relying on the overall impression for ruling out disease, the explicit findings of the absence of wheezing symptoms, no auscultated wheezing, and a smoking history of less than 30-pack years makes airflow limitation much less likely, with the probability of obstructive airways disease being only 2% in such patients.
>> Is there anything else you would like to tell our listeners about the clinical examination for airflow limitation? >> Well, yes. Many listeners may be familiar with the Choosing Wisely campaign of the American Board of Internal Medicine and the Less is More series published in JAMA Internal Medicine. The American Academy of Allergy, Asthma, and Immunology recommends that physicians not rely solely on symptoms when diagnosing and managing asthma, which is one of the forms of airflow limitation. Instead, before embarking on chronic treatment, they recommend spirometry to confirm the presence of disease, to stratify the disease severity, and to use the information to guide treatment selection.
So this is an interesting recommendation for choosing wisely, as it could lead to more spirometry tests rather than less. Now, as opposed to its use for diagnosing asthma, spirometry may not be necessary in patients who have a variety of findings that suggest chronic airflow limitation, such as smoking, wheezing symptoms, and wheezing on auscultation; however, it can still be necessary even in these patients to stage them and guide treatment. >> Thank you, Dr. Simel, for this helpful look at recognizing airflow limitation.
Additional information about this topic is available in Chapter 13 of the Rational Clinical Examination. This has been Joan Stephenson of JAMA talking with Dr. David Simel about identifying airflow limitation for JAMAevidence.
