Asthma

Definition

Reversible chronic inflammatory airway disease causing bronchial constriction

Risk factors

1.       Family History

2.       Atopy (eczema, allergic rhinitis, conjunctivitis, itchiness, sneezing)

Precipitating factor

1.       URTI

2.       Exercise

3.       Smoking

4.       Dust/pollen

5.       Fur

6.       Drug (aspirin/beta blocker)

7.       Emotional stress

8.       Cold environment

9.       Occupational irritant

10.   Improper inhaler technique

Pathophysiology

1.       Early phase (up to 1h)

→In a genetically predispose individual who has been sensitized

→ Exposure to allergen→ cross linking of IgE

→ mast cell degranulation → Histamine & inflamm mediator

→ mucuos hypersecretion, vasodilation, oedema, broncho constriction, airway obstruction

2.       Late phase (6-12h)

→Inflammatory cells (Lymphocyte, eosinophil, basophil)

→ accumulate & continuing inflammation

→ bronchial hyperresponsiveness

Clinical features

1.       SOB on exertion

2.       Chronic dry cough

3.       Wheezing

4.       Ask about risk factors and precipitating factors

5.       Assess asthma control:

Characteristic	Controlled	Partly controlled	Uncontrolled
Daytime symtom	<2/week	>3/week	> 3 of partly controlled asthma in any week
Nocturnal symptoms	None	Any
Need for reliever	<2/week	>3/week
Limitation of activity	None	Any
Lung F(x), FEV1	Normal	<80% predicted
Exacerbation	None	> 1/year	1 in any week

Differential diagnosis

1.       COPD (chronic smoker, sputum)

2.       Cardiac asthma (Orthopnoea, PND, leg swelling)

3.       Pulmonary fibrosis (silica, coal, asbestos)

4.       Neuromuscular disease

5.       Pulmonary hypertension

Physical examination

1.       Alert, conciousness, medical equipment

2.       Atopy, tar stain

3.       Red eye, runny nose

4.       Barrel chest, pectus excavatum, Harrison sulci

5.       Wheeze

6.       PEFR

Investigation

1.       FBC

2.       RFT

3.       ESR, CRP

4.       ABG

5.       Sputum (Microscopy, C&S)

6.       CXR (infection, pneumothorax)

7.       Spirometry (Obstructive, improvement > 15% after nebulizer)

Management

Acute

1.       Assess severity – severe attack vs. Life threatening

Severe attack	Life threatening
Unable to complete sentences	Exhaustion, confused, coma
Respiratory rate >25/min	Silent chest, cyanosis, feeble respiratory effort
Pulse rate >110/min	Bradycardia or hypotension
PEFR <50% predicted or best	PEFR <33% predicted or best
	ABG PaCO2 >5kPa (36mmHg) PaO2<8kPa (60mmHg) Low pH e.g. <7.35

2. Prop Up
3. 100% O2 via non re-breathing bag ( unless COPD: Venturi mask)
4. Set IV line
5. IV hydrocortisone (200mg if severe) OR oral prednisolone (30-60mg)
6. Prepare medication
1. Ventolin, Atrovent (Ipratropium Bromide, Anticholinergic), NS (1:1:2): nebulizer
7. ECG
8. Blood Ix (FBC, RFT, ABG)
9. Monitor V/S
10. Can repeat nebuliser up to 3x (SE: tachycardia, arryhthmia, hypokalaemia, dysphonia)
11. If uncontrolled: IV MgSO₄ (2gm over 20 minutes)
12. If uncontrolled: IV Aminophylline (5 mg/kg over 20 minutes) then 0.5 mg/kg/h
13. If uncontrolled: Intubation
14. If patient stable: History to find cause of exacerbation