Asthma is an inflammatory disorder of the small airways characterized by periodic attacks of wheezing, shortness of breath, chest tightness, coughing and improvement with bronchodilators. It is triggered by environmental stimuli like allergens and respiratory infections. Diagnosis involves lung function tests showing reversible airway obstruction and improvement after bronchodilator use. Treatment includes inhaled corticosteroids, long-acting bronchodilators, immunotherapy, and oral corticosteroids for severe cases. Refractory asthma affects 5-8% of asthmatics and is diagnosed based on medication requirements and symptom control.

1. Asthma and Reactive Airway Disease

2. Asthma and Reactive Airway Disease Definition of asthma : Inflammatory disorder of small airways characterized by periodic attacks of wheezing, shortness of breath, chest tightness, coughing and improvement with bronchodilator Reactive airway disease : A nonspecific term in clinical contexts ranging from asthma to wheezy bronchitis (especially in children < 3 yrs) to viral bronchiolitis or even to pneumonia and COPD

3. Pathophysiology of Asthma Environmental stimuli Allergen-Antibody reaction Release of mediators from mast cell, etc Airway inflammation Smooth muscle Edema Increase mucous production contraction

4. Pathophysiology of asthma

9. Differentiating features between Asthma and COPD Features suggesting asthma Features suggesting COPD *Young age of onset *Long history of smoking *Presence of atopy and/or allergie *Usually non-atopic rhinitis *Diurnal day to day, seasonal *Insidious onset of symptoms variation in symptoms and persistent dyspnea *Normal PE, near normal *Slow progression of symptoms spirometry while in a stable state *Marked improvement after *Hyper inflation and abnormal bronchodilators and/or spirometry corticosteroid *Progressive deterioration of lung function over time *12% and 200ml improvement in *Poor response to FEV1, or 15% improvement in bronchodilator and/or PEFR corticosteroid

10. Laboratory Investigation and Diagnostic test Peripheral blood Radiology -CBC: Eosinophil -CXR, sinus -Total Ig E and specific Ig E to allergens -CT scan -ESR Lung function -Spirometry: pre and post bronchodilator -Arterial blood gas -Histamine challenge test Additional test -Antinutrophil cytoplasmic antibodies -Ig G against asprgillus fumigatus -ECG -Nasal endoscope -24 h esophageal PH monitoring -Polysomnography -Bronchoscope -Ventilation/perfusion scan of the thorax

11. Spirometer Spirogram

12. Pulmonary Function test Equipment : Spirometer  Spirograph and spirogram Variable : Age, gender, height and size, race Terminology : FVC= Forced vital capacity (liters) FEV1= Forced expiratory volume in one second (liters) FEV1/FVC (FEV1%)= The ratio of FEV1 to FVC (%) PEFR= Peak expiratory flow rate (L/secII or L/min) FEF 25% to 75%= Forced expiratory flow during middle half of FVC (L/sec or L/min)

13. Interpretation Normal Restrictive dis. Obstructive dis. Reversible obstruction (% predicted) (% predicted) (% predicted) after bronchodilator FVC >75 <75 <75 10-15%improvement FEV1 75 <75 <75 increase 200 ml FEV1/FVC 75-80 >85 <75 or 15% of beseline FEF25-75% >75-80 >85 <75 increase ≥ 20% Normal PFT: >75% of predicted value Mild disease: >65 but <75% of predicted value Moderate disease: >50% but <65% of predicted value Severe disease: <50% of predicted value

14. Example Case 1 Predicted value (L) Measured (L)value %Predicted FVC 6.00 4.00 67% FEV1 5.00 2.00 40% FEV1/FVC 83% 50% 60% Case 2 FVC 5.68 4.43 78% FEV1 4.90 3.52 72% FEV1/FVC 84% 79% 94% Case 3 FVC 3.20 2.48 77% FEV1 2.51 2.19 87% FEV1/FVC 78% 88% 115% Case 4 FVC 3.20 3.01 94% FEV1 2.51 1.19 47% FEV1/FVC 78 39 50%

15. Flow volume loops : the shape of the loop reflects the status of the lung volume and airways throughout the respiratory cycle. Characteristic changes occur in restrictive and in obstructive disorders. Normal Restrictive disease Asthma, COPD Upper airway obstruction

17. Assessment of asthma severity Intermittent Chronic persistent mild mild moderate severe Daytime symptoms (cough,tight chest, ≤ 2/week 2-4/week >4/week continuous wheeze) Night-time symptoms ≤ 1/month 2-4/month >4/month frequent PEF ≥ 80% ≥ 80% 60-80% < 60% Treatment B2-against PRN Inhaled cortio- Inhaled cortio- Inhaled cortio- steroid steroid steroid> 200-500 ug/d 500-1000 ug/d 1000 ug/d +/- B2-agonist PRN long acting B2 oral cortio- agonist or steroid +/- SR theophyllin long acting B2-against PRN B2agaist +/- SR theopphyllin B2-against PRN to 4-6 times/day