M.A.Zohal pulmonologist asthma

Definition • Chronic inflammatory disease of airways, characterized by increased responsiveness of the tracheobronchial tree to stimuli • Manifested physiologically by a widespread narrowing of the air passages and clinically by paroxysms of dyspnea, cough, and wheezing • Episodic disease, with acute exacerbations interspersed with symptom-free periods • Most attacks are short-lived, lasting minutes to hours.

Epidemiology • Prevalence Increasing in many parts of the world Approximately 10–12% of adults and 15% of children affected by the disease Asthma is among the most common reasons to seek medical treatment. currently affects approximately 300 million people worldwide • Age Asthma can present at any age, with a peak age of 3 years. ~50% of cases develop before 10 years of age. Another one-third of cases occur before 40 years of age. • Sex 2:1 male-to-female ratio in childhood Sex ratio equalizes by 30 years of age.

Epithelial damage may contribute to AHR in a number of ways, including loss of its barrier function to allow penetration of allergens; loss of enzymes (such as neutral endopeptidase) that normally degrade inflammatory mediators; loss of a relaxant factor exposure of sensory nerves, which may lead to reflex neural effects on the airway

Airway Remodeling The characteristic structural changes are increased airway smooth muscle, fibrosis, angiogenesis, and mucus secreting cell hyperplasia

allergens Dust mites (often found in pillows, mattresses, carpets and drapes) Cockroaches Animal dander, especially cats Seasonal pollens

Physiology a reduction in FEV1, FEV1/forced vital capacity (FVC) ratio, and peak expiratory flow (PEF), as well as an increase in airway resistance Lung hyperinflation (air trapping) and increased residual volume mismatching of ventilation and perfusion arterial PCO2 tends to be low due to increased ventilation

Classification • Allergic (extrinsic) asthma Associated with a personal and/or family history of allergic diseases, such as rhinitis, urticaria, and eczema Immunoglobulin E mediated Increase Eosinophil in peripheral blood smear

Exposure to antigen typically produces an immediate response. Airway obstruction develops in minutes and then resolves. 30–50% of patients have a second wave of bronchoconstriction, a "late reaction," 6-10 hours later. In a minority, only a late reaction occurs.

Classification Idiosyncratic (intrinsic) asthma No defined immunologic mechanism Adult onset asthma No family history Most related to occupation

Symptoms & Signs • Classic symptom triad • Typical acute attack Wheezing Dyspnea Cough • Typical acute attack Often occurs at night Patients experience a sense of constriction in the chest, often with a nonproductive cough. Respiration becomes audibly harsh. Wheezing first during expiration and then in both phases of respiration Expiration becomes prolonged.

Symptoms & signs Respiratory rate Heart rate Relative bradycardia with impending respiratory failure Use of accessory respiratory muscle Paradoxical thoracoabdominal movement with impending respiratory failure Pulsus paradoxus (normally < 10 mmHg) 10-25 mmHg in moderate episode >25 mmHg in severe episode Ear, nose, and throat examination Nasal polyps in patients with allergic asthma, cystic fibrosis, aspirin sensitivity

Occupational asthma If occupational exposure is suspected : Ask about workplace and work history in detail. Specific contaminants? Availability and use of protective devices? Ventilation (dose of environmental agent influenced by intensity and physiology—ventilation rate and depth) Do coworkers have similar complaints? Ask about every job; short-term exposures may be significant.

DIAGNOSIS Lung Function Tests : reduced FEV1, FEV1/FVC ratio, and PEF Reversibility is demonstrated by a >12% and 200-mL increase in FEV1 15 min after an inhaled short-acting β2-agonist Measurements of PEF twice daily may confirm the diurnal variations in airflow obstruction Increased total lung capacity and residual volume. Diffusing capacity of the lung for carbon dioxide (DLCO) is usually normal or slightly increased.

DiaGn0sis Airway Responsiveness The increased AHR is normally measured by methacholine or histamine challenge with calculation of the provocative concentration that reduces FEV1 by 20% (PC20). exercise testing

Laboratory Tests • Complete blood count may show eosinophilia. • Serum immunoglobulin E level o Elevated in allergic asthma o Normal in idiosyncratic asthma o Marked elevations may suggest allergic bronchopulmonary aspergillosis. • Sputum examination o Eosinophilia o Curschmann’s spirals (casts of small airways) o Charcot–Leyden crystals o Presence of large numbers of neutrophils suggests bronchial infection.

Laboratory Tests Arterial blood gas Shows hypoxemia during attacks Usually, hypocarbia and respiratory alkalosis are present. Normal or elevated arterial partial pressure of carbon dioxide suggests severe respiratory muscle fatigue or airways obstruction and impending respiratory failure.

differential Diagnosis Upper airway obstruction by a tumor or laryngeal edema endobronchial obstruction with a foreign body. left ventricular failure Vocal chord dysfunction Eosinophilic pneumonias and systemic vasculitis, including ChurgStrauss syndrome and polyarteritis nodosa COPD

Control asthma

Prognosis Mortality Only 0.09–0.25% of admissions to hospital are at risk of an untoward event. Particularly good prognosis for those whose disease is mild and develops in childhood The proportion of children who still have asthma 7–10 years after the initial diagnosis varies from 26–78% (average, 46%). Only 6–19% continue to have severe disease. Even when untreated, persons with asthma do not continuously move from mild to severe disease with time. Clinical course is characterized by exacerbations and remissions. Some studies suggest: Spontaneous remissions occur in approximately 20% of those who develop the disease as adults. ~40% can be expected to experience improvement, with less frequent and severe attacks, as they grow older.