bronchial asthma dr. shaikh mujeeb ahmed assistant professor almaarefa college ims 423 block
Post on 27-Dec-2015
221 Views
Preview:
TRANSCRIPT
Bronchial Asthma
Dr. Shaikh Mujeeb AhmedAssistant ProfessorAlMaarefa College
IMS 423 BLOCK
Intended Learning Outcomes
• Describe pathophysiology of Bronchial asthma• Enumerate the predisposing factors for
asthma• Describe the clinical features of asthma• Interpret the spirometry results lab results and
correlate with severity of the disease.
EpidemiologyAccording to epidemiological studies
asthma affects 1-18% of population of different countries.
What is Asthma?
• Asthma is a chronic inflammatory disease of
the airways characterized by variable recurring
symptoms,
• air flow obstruction, and
• bronchial hyper responsiveness.
Airway obstruction
• Episodic wheezing• Difficulty breathing, • Chest tightness, and • Cough that often is worse at night and in the
early morning.
Types of Asthma
• Extrinsic – initiated by type I hypersensitivity– Atopic
• Intrinsic – Non immune mechanisms– Respiratory tract infections– Exercise, – Ingestion of aspirin,– Emotional upset, and – Exposure to bronchial irritants such as cigarette
smoke.
Some allergens which may cause asthma
House-dust mites which live in carpets, mattresses and upholstered furniture
Spittle, excrements, hair and fur of domestic animals
Plant pollen
Pharmacological agents (enzymes, antibiotics, vaccines, serums)
Food components
(stabilizers, genetically modified products)
Dust of book depo-sitories
Etiology & Pathogenesis
Early phase response
Late phase response
Etiology & Pathogenesis
Extrinsic (Atopic) Asthma
Allergen
Mast cells release inflammatory
mediators
WBCs enter region and release more
inflammatory mediators
• Type I hypersensitivity
• Mast cells’ inflammatory mediators cause acute response within 10–20 minutes
• Airway inflammation causes late phase response in 4–8 hours
Role of T lymphocytes
T - Lymphocytes
TH 1 - Lymphocytes TH 2 - Lymphocytes
B - Lymphocytes B - Lymphocytes
Plasma Cells Plasma Cells
Ig G & Ig M Ig E
Intrinsic (Nonatopic) Asthma
• Respiratory infections – Epithelial damage, IgE production
• Exercise, hyperventilation, cold air– Loss of heat and water may cause
bronchospasm• Inhaled irritants
– Inflammation, vagal reflex• Aspirin and other NSAIDs
– Abnormal arachidonic acid metabolism
Aspirin and other NSAIDs
Airway Obstruction in Asthma
inflammatory
mediatorsairway
inflammation
bronchospasm
edema
impaired
mucociliary
function
epithelial
injury
increased
airway
responsiveness
airflow limitation
Pathologic anatomyMacroscopic changes:
• viscous mucous/ mucopurulent phlegm
• airway dyskinesia with zones of spastic contraction and paralytic expansion of bronchi
• obstruction of airway lumen
• lung emphysema, pneumosclerosis• RV and RA hypertrophy and dilation
Microscopic changes:
• Bronchial wall infiltration with mast cells, eosinophils, basophils and T-lymphocytes
• Edema of mucous and submucous tunics • Destruction of bronchial epithelium• Hypertrophy of bronchial smooth muscles,• Hyperplasy of submucous glands • Microvessels dilation
Muscles
Cartilage
Gobletcells
Bronchial glands
cells Ciliated
Bronchioles (section)
Muscle contraction
Mucosal edema
Mucus secretion increase
Asthma
Risk Factors for Developing Asthma
• Genetic characteristics• Occupational exposures • Environmental exposures
Diagnosing Asthma: Medical History
• Symptoms– Coughing– Wheezing– Shortness of breath– Chest tightness
• Symptom Patterns • Severity• Family History
Diagnosing Asthma
• Troublesome cough, particularly at night• Awakened by coughing• Coughing or wheezing after physical
activity• Breathing problems during particular
seasons• Coughing, wheezing, or chest tightness
after allergen exposure • Colds that last more than 10 days• Relief when medication is used
Diagnosing Asthma
• Wheezing sounds during normal breathing
• Hyperexpansion of the thorax
• Increased nasal secretions or nasal polyps
• Atopic dermatitis, eczema, or other allergic skin conditions
Diagnosing Asthma:Spirometry
Test lung function when diagnosing asthma
Spirometry
• Measurement of • Forced expiratory volume (FEV1 )• forced vital capacity (FVC)• FEV1/VC• Peak Expiratory Flow rate (PEFR)
Pulmonary Function Tests
Reversibility Test
Inhalational challenge test
• Administration of sequential increasing conc. of either histamine , methacholine or mannitol.
Diurnal variation in PEFR
Exercise induced Asthma
• Allergic skin testing• X-ray chest• Induced sputum
differential eosinophil count - >2%
• FENO
Management
Asthma is extremely common and causes considerable morbidity. The aims of treatment are to:
Abolish symptoms Restore normal or best possible lung function Reduce the risk of severe attacks Enable normal growth to occur in children Minimize absence from school or employment.
This involves:
• patient and family education about asthma • patient and family participation in treatment • avoidance of identified causes where possible • use of the lowest effective doses of
convenient medications to minimize short-term and long-term side-effects.
Control of extrinsic factors• Measures must be taken to avoid causative
allergens such as the house-dust mite, moulds and certain food stuffs (e.g eggs ,checolate), particularly in childhood.
• Active and passive smoking should be avoided, as should beta-blockers in either tablet or eye drop form.
• Individuals intolerant to aspirin may benefit by avoiding salicylates and should avoid NSAIDs.
• 50% of individuals sensitized to occupational agents may be cured if they are kept permanently away from exposure. The remaining 50% continue to have symptoms that may be as severe as when exposed to materials at work, especially if they were symptomatic for a long time before the diagnosis was made.
This emphasises: • the importance of the rapid identification of
extrinsic causes of asthma and their removal wherever possible (e.g. occupational agents, family pets)
• once extrinsic asthma is initiated, it may become self-perpetuating possibly by non-immune mechanisms.
Drug treatment • The mainstay of asthma therapy is the use of
therapeutic agents delivered as aerosols or powders directly into the lungs The advantages of this method of administration are that drugs are delivered direct to the lung and the first-pass metabolism in the liver is avoided; thus lower doses are necessary and systemic unwanted effects are minimized.
• Both national and international guidelines have been published on the stepwise treatment of asthma based on three principles:
1. Asthma self-management with regular asthma monitoring using peak flow meters and individual treatment plans discussed with each patient and written down.
2. The appreciation that asthma is an inflammatory disease and that anti-inflammatory (controller) therapy should be started even in mild cases.
3. Use of short-acting inhaled bronchodilators (e.g. salbutamol and terbutaline) only to relieve breakthrough symptoms. Increased use of bronchodilator treatment to relieve increasing symptoms is an indication of deteriorating disease.
Drugs used in asthma• Quick relief medication
– short acting β2 agonist (salbutamol, terbutaline) – oral steroids– Anticholinergic agents
• Long-acting relief/disease controllers - Long-acting β2 agonists - salmeterol,
formoterol - Sodium cromoglicate (mast cell stabilizer)- Leukotriene modifiers• Other agents with bronchodilator activity
– Theophylline preparations
• Steroid-sparing agents - Methotrexate - Ciclosporin - Gold - Intravenous immunoglobulin - Anti-IgE monoclonal antibody - Omalizumab
Asthma severity classification
Clinical course, severity
Daytime asthma symptoms
Nighttime awakenings
FEV1, PEF
Intermittent< 1 /week 2 and < /month >80%
predicted. Daily variability < 20%
Mild
persistent
1 /week but not daily > 2 /month
>80% predicted. Daily variability – 20-30%
Moderate persistent
Daily > 1 /week> 60 but < 80% predicted. Variability>30%.
Severe persistent
Persistent, which limit normal activity
Daily<60% predicted. Variability > 30%.
Level of Asthma control
Managing Asthma: Peak Expiratory Flow (PEF) Meters
• Allows patient to assess status of his/her asthma
• Persons who use peak flow meters should do so frequently
• Many physicians require for all severe patients
Managing Asthma: Peak Flow Chart
People with moderate or severe asthma should take readings:– Every morning– Every evening– After an
exacerbation– Before inhaling
certain medications
Source: “What You and Your Family Can Do About Asthma” by the Global Initiative For Asthma Created and funded by NIH/NHLBI
A stepwise approach to the management of asthma
• Step 1: Occasional use of inhaled short-acting β2-adrenoreceptor agonist bronchodilators
• Step 2: Introduction of regular ‘preventer’ therapy• Step 3: Add-on therapy• Step 4: Poor control on moderate dose of inhaled
steroid and add-on therapy: addition of a fourth drug
• Step 5: Continuous or frequent use of oral steroids
Acute severe asthma
Patients with acute severe asthma typically have:
• inability to complete a sentence in one breath • respiratory rate ≥ 25 breaths per minute • tachycardia ≥ 110 beats/min (pulsus
paradoxus, is not useful as it is only present in 45% of cases)
• PEF < 50% of predicted normal or best.
Features of life-threatening attacks are: • a silent chest, cyanosis or feeble respiratory
effort • exhaustion, confusion or coma • bradycardia or hypotension • PEF < 30% of predicted normal or best
(approximately 150 L/min in adults).
Treatment of severe asthmaAt home • The patient is assessed. Tachycardia, a high respiratory rate
and inability to speak in sentences indicate a severe attack. • If the PEFR is less than 150 L/min (in adults), an ambulance
should be called. (All doctors should carry peak flow meters.) • Nebulized salbutamol 5 mg or terbutaline 10 mg is
administered. • Hydrocortisone sodium succinate 200 mg i.v. is given. • Oxygen 40-60% is given if available. • Prednisolone 60 mg is given orally.
At hospital The patient is reassessed. Oxygen 40-60% is given. The PEFR is measured using a low-reading peak flow meter,
as an ordinary meter measures only from 60 L/min upwards.Measure O2 saturation with a pulse oximeter.
Nebulized salbutamol 5 mg or terbutaline 10 mg is repeated and administered 4-hourly.
Add nebulized ipratropium bromide 0.5 mg to nebulized salbutamol/terbutaline.
Hydrocortisone 200 mg i.v. is given 4-hourly for 24 hours.
• Prednisolone is continued at 60 mg orally daily for 2 weeks. • Arterial blood gases are measured; if the Paco2 is greater than
7 kPa, ventilation should be considered. • A chest X-ray is performed to exclude pneumothorax. • One of the following intravenous infusions is given if no
improvement is seen:
– salbutamol 3-20 μg/min, or – terbutaline 1.5-5.0 μg/min, or – magnesium sulphate 1.2-2 g over 20 min.
• Arterial blood gases should always be measured in asthmatic patients requiring admission to hospital. Pulse oximetry is useful in monitoring oxygen saturation during the admission and reduces the need for repeated arterial puncture. Features suggesting very severe life-threatening attacks are:
• a high Paco2 > 45 • severe hypoxaemia Pao2 < 60 despite treatment with
oxygen • a low and falling arterial pH.
A Public Health Response to Asthma: Interventions
• Medical management• Education• Environment • Schools
top related