Asthma

COPD or not COPD?  (Hamlet is not amused...)

Definition and Epidemiology

• Asthma is a chronic inflammatory disorder of the airways that involves many cells and cellular elements.
• The chronic inflammation causes an increase in hyperresponsiveness.
  • This leads to recurrent episodes of wheezing, coughing, and breathlessness particularly at night or in the morning.
• These episodes are usually associated with widespread but variable airflow obstruction that is reversible spontaneously or with treatment.
  • To repeat, if asthma becomes irreversible it goes into the COPD category.
• Asthma is extremely common. It is thought that ~5% of the adult merican population have asthma (I am one of them).
  • The majority of cases begin before the age of 25 (I was diagnosed at the age of 5), but asthma can develop at any age.
• The prevalence of asthma worldwide has increased more than 30% since the 1970s with the greatest increases in the newly industrialized countries.
• Asthma is found disproportionately in inner cities much like our lovely Newark!
• It accounts for ~15 million outpatient visits to physicians and yearly costs of more than $6 billion dollars.

Clinical Manifestations and Asthma Diagnosis

• Symptoms of asthma (symptoms are things a patient complains of)
  • Wheezing
  • Intermittent dyspnea
  • Cough, especially at night
  • Exercise induced wheezing and dyspnea
• Signs of asthma (signs are what we, as doctors, observe during the physical exam)
  • Wheezing on auscultation
    • Wheezing is most commonly heard on expiration, but can be heard during inspiration during severe asthma attacks.
       

• Physiologic Abnormalities
  • Variable airflow obstruction
  • Responsiveness to bronchodilators (this seems somewhat backwards – you’ve got asthma because you respond well to the drugs we use to treat it, but oh well. I’m just the scribe…)
  • Increased airway responsiveness (hyperresponsiveness)
• To diagnose a patient with asthma:
  • There should be a history of periodic airflow obstruction.
    • The patient may report feeling perfectly fine now, but if they’ve had previous problems they still have asthma.
    • It’s not a constant disease so the absence of symptoms at any given time does not mean an absence of disease.
  • Airflow obstruction is at least partly reversible.
    • An FEV1 < 80 or an FEV1/FVC ration of less than 65% is indicative of obstruction.
    • After given a short-acting inhaled β2 agonist, the FEV1 should increase at least 12% and 200mL.
    • Again, kind of backwards to diagnose through treatment…
  • All other alternative diagnoses must be excluded.
    • Apparently vocal cord dysfunction can cause some impressive wheezing that has nothing to do with asthma.
    • Other problems include, vascular rings that surround airways, foreign bodies (particularly common in children), and other pulmonary diseases.
  • Below is a table of what to do when considering alternative diagnoses.

• The unique inflammatory response of asthma isn’t quite worth it’s own subsection so I’ll include it here.
  • Antigens activate mast cells and Th2 cells in the lung which are responsible for the initial response of the body through leukotrienes and histamine.
  • They also release cytokines that recruit eosinophils which release even more inflammatory mediators and are responsible for sustained inflammation during an asthma attack.

Classification of Asthma Severity and Therapy

Drug treatments are tailored to the step diagnosis of the patient

• All patients are given quick relief, short-acting β2 agonists like albuterol.
  • Want to see an albuterol inhaler? Just ask me!
• Long term control is reserved for step 2 or higher.
  • Included in this group is anti-inflammatory agents like inhaled corticosteroids and long acting β2 agonists like salmeterol.

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