Respiratory Medicine/pulmonolgy Made Simple : Asthma

Asthma:

Recurrent episodes of Dyspnoea cough and wheeze cuased by reversible airways obstruction.

PATHOPHYSIOLOGY:

Three factors contribute to airway narrowing :

Mucosal swelling/

Inflammation caused by mast cell and basophil degranulation resulting in release of inflammatory mediators.

Bronchial muscle contraction triggered by a variety of stimuli

Increased mucus production

Symptoms:

Intermittent Dyspnoea

Wheeze

Cough ( mostly at night)

Increased Sputum  production.

PRECIPITATING FACTORS:

These include:

Exercise

Cold Air

Emotional Stresses

Allergens ( house dust mite,pollens,fur)

Infection

Smoking and Passive smoking

Pollution

NSAIDS,Beta blockers

Quantification:

Exercise Tolerance

This needs to be quantified and evaluated.

Disturbed Sleep:

Quantified as nights/week : a sign of severe Asthma

ASSOCIATIONS:

ACID REFLUX:

40 – 60 % of patients with Asthma have reflux.

Treating it improves spirometry but not necessarily symptoms.

OTHER ATOPIC DISEASES:

Frequently Asthma  co-exists with other atopic diseases such as Eczema,Hay fever allergies and Family History of atopic diseases.

CHURG STRAUSS SYNDROME

POLYARTERITIS NODOSA

ABPA : ALLERGIC BRONCHOPULMONARY ASPERGILLOSIS

OCCUPATIONAL ASTHMA/JOBS:

More common in occupations such as Paint sprayers,food processors,animal handlers and welders.

Symptoms are resolved during holidays when away from work.

Patients are advised to measure their peak flow at work and at home.

Signs:

Tachypnoea

Audible wheeze

Hyperinflated chest

Hyperresonant percussion notes.

Diminished Air Entry

Poly phonic wheeze

SEVERE ATTACK:

Inability to complete sentences

Pulse > 110 bpm

Resp Rate >25/min

PEFR 33 – 50 % of predicted

LIFE THREATENING ATTACK:

Silent Chest

Cyanosis

Bradycardia

Exhaustion

PEFR < 33% of predicted

Confusion

Feeble Respiratory Effort

Investigations:

ACUTE ATTACK:

Sputum culture & Sensitivity

PEFR

FBC

U & Es

CRP

ABGs : Normal or slightly reduced PaO2 and low PaCO2 due to hyperventilation.

If PaCO2 is raised,transfer to HDU or ITU for ventilation as this signifies failing Respiratory Effort.

Blood Cultures

CXR : To exclude pneumothorax and infection.

CHRONIC ASTHMA:

PEFR MONITORING:

This shows a diurnal variation of > 20 % on more than or equal to 3 days a week for 2 weeks,

SPIROMETRY:

This shows an obstructive defect : Reduced FEV1/FVC ratio and increased Residual volume.

Usually > 15 % improvement in FEV1following B2 agonists or steroid trial.

CXR : This shows hyperinflation.

Skin prick tests help identify allergens.

Histamine or methacholine chalenge.

MANAGEMENT:

BEHAVIOUR AND LIFE STYLE MODIFICATIONS:

Quit smoking

Avoid precipitants

Check Inhaler technique

Monitor PEFR twice a day by Peak Flow meter.

Train about a relaxed breathing technique to avoid dysfunctional breathing

Specific Management/ BTS Guideline

Start from the step most appropriate to severity.

Move up if necessary or down if control is good for > 3 months.

Rescue courses of prednisolone may be used at any time.

STEP 1 :

Occasional short acting B2 agonist as required for symptom relief.If being used more than once daily or night time symptoms,go to step 2.

STEP 2 :

Add standard dose inhaled steroid eg Beclometasone 100 -400 mcg/12 hrs or start at the dose appropriate for disease severity and titrate as appropriate.

STEP 3:

Add long acting B2 agonist eg salmeterol 50 mcg/12 hrs.If of benefit but still inadequate control,continue and increase dose of beclometasone to 400 micrograms/12 hrs.If no effect of Long Acting B2 agonist,it should be stopped.Diagnosis should be reviewed and Leukotriene receptor antagonists or oral theophylline may be tried.

STEP 4:

Consider trials of beclometasone of upto 1000 micrograms/12 hours,modified release oral theophylline,modified release oral Beta 2 agonist.

STEP 5 :

Add regular oral prednisolone 1 dose daily at lowest possible dose.