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    Asthma Exacerbation in Adults – Diagnosis

    Cardinal Presentations / Presenting Problems, Inflammatory, Respiratory

    Last Updated Jun 09, 2020
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    • 8% of Canadians over the age of 18 have asthma.
    • Onset is less common with increasing age.
    • Typically presents with dyspnea, cough, wheezing and chest tightness.
      • Wheezes are generally widespread, expiratory, high-pitched and musical.
    • Common exacerbating factors include:
      • Viral respiratory infections,
      • Allergen/irritant exposures,
      • Poor adherence with controller medications.
    • Severe cases can be fatal.

    Diagnostic Process

    1. While initiating therapy, measure SpO2 and Peak Expiratory Flow (PEF).
    2. Assess severity to guide management.
    3. Consider alternate or comorbid conditions.
    • Pulmonary Function Testing
      • Peak expiratory flow (PEF) is mainstay of objective testing.
      • If possible, perform before treatment.
      • Inability to perform this test in a cooperative patient = severe obstruction.
      • Normal PEF values depend on gender, height and age. However, in general PEF > 300 L/min = mild/moderate exacerbation.

    • Alternative or comorbid diagnoses:
      • COPD Exacerbation.
      • Heart failure.
      • Pulmonary embolism.
      • Pneumothorax.
      • Pneumonia.
      • Anaphylaxis.
      • Foreign body:
        • Poor airway protection, unilateral/localized wheeze.
    • Investigations:
      • Arterial Blood Gasses:
        •  Consider for severe exacerbations or in patients not improving.
        • PaCO2>45mmHg or PaO2<60mmHg suggest respiratory failure.
      • Chest Radiograph:
        • For severe exacerbations or those requiring hospitalization.
        • If there is suspicion of a comorbid process, or if diagnosis uncertain.

    Quality Of Evidence?


    Evidence comes from sources published within the last few years, including the 2019 GINA guidelines, which are in relative agreement about methods of recognizing and investigating asthma exacerbations.


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