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Approach to Asthma Symptoms, Signs and Diagnosis Summary

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By Ashesh

Overview

Asthma is a reversible airway disease. 

Recurrent episodes of dyspnoea, cough, and wheeze 

Caused by reversible airway obstruction.


Asthma has 3 contributory factors:

  • bronchial smooth muscle contraction

  • mucosal swelling/inflammation

  • increased mucus production


All these factors result in airway narrowing.





Symptoms

  • Dyspnoea or shortness of breath --- Intermittent

  • wheeze, cough (often nocturnal)

  • Diurnal variation -- symptoms vary over day,

    • Marked morning dipping of peak flow can occur

  • Precipitants: Cold air, exercise, allergens -- dust, pollen, mites

  • History of family history of atopy

  • Drugs: Aspirin, B-blockers

  • Occupational Asthma

    • are symptoms better on days away from work?

    • are symptoms better when on holiday/vacation?

  • Drug-Induced Asthma

    • Aspirin

    • B-blocker

Signs

  • Tachypnea

  • Audible wheeze, Hyperresonant, Hyperinflated, widespread polyphonic wheeze

  • listen to wheeze here

  • Severe attack:

    • unable to complete sentences

    • PR>110, RR>25, PEF 33-50% predicted

  • Life-threatening Attack

    • confusion, exhaustion, cyanosis PaO2<60mmHg

    • silent chest, bradycardia

    • PEF < 33%

PaCO2 in Asthma

  • Mostly Normal

  • Life-threatening Attack

    • confusion, exhaustion, cyanosis

    • PaO2<60mmHg

    • PaCO2 is normal 35 - 45 mmHg

  • Near-Fatal

    • Increased PaCO2


Tests

  • Spirometry

  • Bronchodilator Reversibility BDR

  • FE NO -- Fractional Exhaled Nitric Oxide

  • Peak Flow Variability

  • Direct Bronchial Challenge Test with Histamine or Methacholine

Non Diagnostic Tests

  • Skin Prick Tests

  • Serum total and specific IgE

  • Eosinophil count

  • Exercise challenge (adults age 17 and over)

  • Do not use these tests to diagnose asthma

Tests Types

  • Airway Inflammation

    • FE NO -- Fractional Exhaled Nitric Oxide

  • Lung Function

    • Spirometry

    • Bronchodilator Reversibility BDR

    • Peak Flow Variability

  • Airwar Hyperreactivity

    • Direct Bronchial Challenge Test with Histamine or Methacholine

Diagnostic Tests of Asthma

  • Spirometry

    • Obstructive lung disease

    • ↓↓FEV1, ↓FVC ---> ↓FEV1/FVC

    • FEV1/FVC ratio less than 70%

  • FeNO test Fractional Exhaled Nitric Oxide

    • FeNO level of 40 parts per billion (ppb) or more is considered as a positive test, and 35 ppb or more in children and young adults

  • Bronchodilator Reversibility BDR

    • Improvement in FEV1 after B-agonist or steroid trial

    • Improvement of 12% or more in BDR

  • Peak Flow Variability

    • Monitor peak flow variability over 2-4 weeks in those with diagnostic uncertainty

    • Peak flow variability of >20% is a positive test

  • Direct Bronchial challenge Test with Histamine/Methacholine

    • the provocative concentration of methacholine causing >20% drop in FeV1 aka PC20 value of 8mg/ml or less

Asthma Tests Summary

  • Acute Asthma: Treat immediately and test only if testing does not impair treatment or after symptoms have resolved

  • Age < 5: Treat based on Clinical Judgement

  • Age 5-16: Spirometry and BDR, FeNO +/- PEF variability if uncertain

  • Age 17 or more: Spirometry +/- BDR and FeNO, and PEF if uncertain

Asthma Diagnostic Tests Criteria Summary

  • Spirometry

    • FEV1/FVC less than 70%

  • Bronchodilator Reversibility BDR

    • >=12% improvement

  • FE NO -- Fractional Exhaled Nitric Oxide

    • >=40 ppb

  • Peak Flow Variability >=20%

  • Direct Bronchial Challenge Test with Histamine or Methacholine PC20 value <=8mg/mL

Differential Diagnosis of Asthma

  • Pulmonary Oedema aka Cardiac Asthma

  • COPD

  • Large airway Obstruction by FB, Tumor

  • SVC Obstruction

  • Pneumothorax

  • PE

  • Bronchiectasis

Lower Probability of Asthma Predictors

  • Cardiac Disease, prominent dizziness, lightheadedness, tingling

  • Chronic productive cough with no wheeze, significant smoking history >20 pack year

  • Change in voice

  • Normal examination when symptomatic, Normal PEF when symptomatic

  • Symptoms with cold only

Reference: Recommendations | Asthma: diagnosis, monitoring and chronic asthma management | Guidance | NICE

ⒸPathologynuggets.

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