Asthma: Clinical Findings
Asthma
Episodic airway constriction and airflow obstruction, due to hyper- responsiveness to certain triggers (see slide on asthma pathogenesis)
Author: Yan Yu Reviewers: Jason Baserman Jennifer Au Yonoglin Mai (麦泳琳) Naushad Hirani* * MD at time of publication
Variable, sporadic airway obstruction in response to triggers
Associated allergic eosinophil response
Eosinophils infiltrate: Skin
If severe:
↓ ventilation of alveoli
↓ oxygenation of blood (hypoxemia)
During expiration, positive pleural pressure squeezes on airwaysà↑↑ airway obstruction
Heart rate ­ to improve
perfusion of tissue
Tachycardia
Respiratory centers ­ rate of breathing to
compensate
Tachypnea
Gas is trapped within alveolià hyperinflates lungs
Ventilating larger lungs needs more effort
Patients need to voluntarily contract
their expiratory muscles faster and more forcefully to effectively expire
Narrower airways àturbulent
airflow, heard on auscultation
Expiratory Wheeze (high-pitched expiratory sound)
Nose
Rhinitis/ sinusitis
Runny nose, sneezing, etc
Atopic dermatitis
Skin rash, hives
Eyes
Conjunctivitis
Red itchy eyes, visual blurring
Episodic
dyspnea
(shortness of breath)
Chest tightness
During severe attacks:
Note: Asthma attacks often have two phases:
• An immediate attack (within 0-2 hours of the trigger, due to acute release of histamine from mast cells)
• A delayed attack (due to eosinophil infiltration of airways, presents within 3-4 hours after exposure to the trigger, peaks within 6-8 hours, and resolves within 24 hours).
Keep the possibility of a delayed attack in mind when treating patients in Emergency!
Note: Symptoms often worse at night or early in the morning.
Note: Asthma should be suspected in children experiencing dyspnea with multiple episodes of Upper Respiratory Tract Infections or Croup.
Patient compensates by activating accessory respiratory muscles to ↑ thoracic volume
Visible contraction of
neck muscles (Scalene, sternocleidomastoids)
↑↑↑ airway obstruction on
expiration, lungs take more time to empty
Prolonged expiratory phase of breathing
Legend:
Pathophysiology
Mechanism
Sign/Symptom/Lab Finding
Complications
Published Dec 17, 2012 and updated Dec 4, 2021 on www.thecalgaryguide.com