24 Asthma Flashcards
1
Q
Asthma
- Disorder of…
- Accompanied by…
- The different clinical expressions of asthma involve…
- Heterogeneity of asthma also relates to…
- Asthma is considered a good example of…
A
- Disorder of the conducting airways, which contract too much and too easily spontaneously and in response to a wide range of exogenous and endogenous stimuli
- This airway hyperresponsiveness is accompanied by enhanced sensory irritability of the airways and increased mucus secretion
- The different clinical expressions of asthma involve…
- Varying environmental factors that interact with the airways to cause acute and chronic inflammation
- The varying contributions of smooth muscle contraction, edema and remodeling of the formed elements of the airways
- Heterogeneity of asthma also relates to the different response to therapies
- Asthma is considered a good example of gene–environment interactions, although no single gene or environmental factor accounts for the disease
2
Q
Epidemiology of asthma
- Asthma and related allergic diseases have increased markedly in…
- This has been attributed to…
- The urban-rural gradient in prevalence has been demonstrated most strongly in…
- This protective effect against the onset of asthma in children is even more apparent if…
A
- Asthma and related allergic diseases have increased markedly in…
- Western countries over the past 50 years
- This has been attributed to urbanization and associated changes to diet and lifestyle
- The urban-rural gradient in prevalence has been demonstrated most strongly in children…
- Who grow up in environments with a wide range of microbial exposures
- Such as traditional livestock farms or in families who have adopted a more ‘naturalistic’ diet and lifestyle
- Who are protected from childhood asthma and atopy (the predisposition to develop IgE against common environmental allergens) in proportion to their level of exposure to bacterial and fungal microbes
- Who grow up in environments with a wide range of microbial exposures
- This protective effect against the onset of asthma in children is even more apparent if…
- The microbial exposure (for example, working with animals or drinking unpasteurized milk) occurred throughout the mother’s pregnancy
3
Q
Pathophysiology of asthma
- Most asthma begins…
- In most cases, this occurs through…
- TH2-type cytokines
- A similar inflammatory response is triggered in response to…
A
- Most asthma begins in childhood in association with sensitization of the airways to common aeroallergens
- Especially those derived from house dust mites, cockroaches, animal dander, fungi and pollens
- In most cases, this occurs through the selective expansion of T lymphocytes (particularly of the TH2 type) that secrete a cluster of cytokines, including…
- Interleukins IL-3, IL-4, IL-5, IL-9, IL-13
- Granulocyte macrophage colony–stimulating factor (GM-CSF)
- TH2-type cytokines orchestrate the allergic inflammatory cascade that occurs in asthma, including…
- TH2 cell survival (regulated by IL- 4)
- B cell isotype switching to IgE synthesis (IL-4 and IL-13)
- Mast-cell differentiation and maturation (IL-3, IL-9 and IL-13)
- Eosinophil maturation and survival (IL-3, IL-5 and GM-CSF)
- Basophil recruitment (IL-3 and GM-CSF)
- A similar inflammatory response is triggered in response to…
- Parasitic infection, suggesting that, in some way, allergy is a manifestation of ‘frustrated’ parasite elimination
4
Q
Pathophysiology of asthma
- The asthmatic epithelium is intrinsically defective in its…
- Related to this defect, a proportion of the asthma-related allergens have intrinsic biological properties that…
- Components of house dust mite, cockroach, animal and fungal allergens…
- Beyond proteolytic allergens, additional environmental stimuli…
A
- The asthmatic epithelium is intrinsically defective in its…
- Physical barrier function within complete formation of tight junctions, thereby facilitating penetration of inhaled allergens into the airway tissue
- Related to this defect, a proportion of the asthma-related allergens have intrinsic biological properties that…
- Increase their capacity to penetrate the epithelial barrier and trigger a danger signal to DCs
- Components of house dust mite, cockroach, animal and fungal allergens…
- Are proteolytic
- Can disrupt epithelial tight junctions and activate protease-activated receptors
- Beyond proteolytic allergens, additional environmental stimuli…
- Such as respiratory viruses and air pollutants (for example, ozone, particulates and environmental tobacco smoke)
- Also disrupt tight junctions to impair barrier function
5
Q
Pathophysiology of asthma
- Main cause of asthma exacerbation
- The greatest risk factor for developing asthma at 6 years of age n those genetically at risk of asthma
- What enables rhinovirus and other viruses to replicate
- Such events provide…
A
- Main cause of asthma exacerbation
- Infection with rhinoviruses
- The greatest risk factor for developing asthma at 6 years of age n those genetically at risk of asthma
- Rhinovirus-induced wheezing in the first three years of life
- What enables rhinovirus and other viruses to replicate
- Reduced primary IFN-gamma production by lower-airway epithelial cells
- Leads to cytotoxic cell death (rather than apoptosis), release of inflammatory products, and enhanced viral shedding
- Such events provide…
- A strong stimulus for recruitment of immature DCs and their priming for allergen sensitization
6
Q
Pathophysiology of asthma
- Once established, airway inflammation in asthma is a multicellular process involving mainly…
- The inflammatory process is largely restricted to…
- As the disease becomes more severe and chronic, the inflammatory infiltrate…
- The inflammatory response in the small airways appears to be predominantly…
- This Th2 type of inflammation
A
- Once established, airway inflammation in asthma is a multicellular process involving mainly…
- Eosinophils
- Neutrophils
- CD4+ T-lymphocytes
- Mast cells
- Eosinophilic infiltration (the most striking feature)
- The inflammatory process is largely restricted to…
- The conducting airways
- As the disease becomes more severe and chronic, the inflammatory infiltrate…
- Spreads both proximately and distally to include the small airways and in some cases adjacent alveoli
- The inflammatory response in the small airways appears to be predominantly…
- Outside the airway smooth muscle whereas in the large airways inflammation of the submucosa dominates
- This Th2 type of inflammation
- Common to chronic allergic inflammatory responses at multiple tissue sites
- Seen at these sites in patients with asthma who frequently express comorbidities such as chronic rhinitis, sinusitis, atopic dermatitis, and food allergy
7
Q
Pathophysiology of asthma:
Role of mast cells
- The allergic response in asthma is characterized by…
- Allergens…
- Mast cells
- Mast cell activation
A
- The allergic response in asthma is characterized by…
- An immediate or early allergic response (EAR) and a late allergic response (LAR)
- EAR develops within 10 minutes of allergen exposure, reaching a maximum at 30 minutes, and resolving within 1-3 hours
- Allergens…
- Initiate EAR through IgE-dependent mechanisms and the cell that initiates EAR is mast cell
- Mast cells
- Present as resident cells in all tissues capable of mounting allergic responses
- Bind IgE with high affinity to FcERI on their cell surface membranes
- Mast cell activation
- Occurs when allergen cross-links IgE-FcepsilonRI complexes on mast cells
- Leads to degranulation of the mast cell and the release of preformed mediators including histamine, proteases and proteoglycans
- Stimulates the mast cell to synthesize and generate newly generated mediators including…
- Leukotrienes (LTC4, LTD4, and LTE4)
- Prostanoids (PGD2, PGF2alpha, and TXA2)
8
Q
Pathophysiology of asthma:
Role of mast cells
- What has the ability to contract human bronchial smooth muscle
- Mast cell also releases…
- This latter stage of inflammation
- The influx of eosinophils and T lymphocytes results in…
A
- What has the ability to contract human bronchial smooth muscle
- Histamine, PGD2 and leukotrienes
- Mast cell also releases…
- Cytokines, growth factors and other mediators that attract T cells and inflammatory cells, especially eosinophils, into the airway tissue
- This latter stage of inflammation
- Represents LAR
- Occurs several hours after EAR
- The influx of eosinophils and T lymphocytes results in…
- The further release of mediators
- Subsequent epithelial damage
- The development of airway narrowing
- Associated bronchial hyperresponsiveness
9
Q
Pathophysiology of asthma
- Combinations of cytokines and contact signals cause…
- These different leukocyte subsets generate…
A
- Combinations of cytokines and contact signals cause…
- DCs and the thymic epithelium to conspire to drive the differentiation of an array of different leukocyte subsets that augment or protect the airways from inflammatory responses linked to asthma
- These different leukocyte subsets generate…
- Cytokines that influence different cell types
- The attendant inflammatory response, driving allergic airway inflammation and airway hyperreactivity
10
Q
Symptoms of asthma
- The most common cause of asthmatic inflammation
- The relationship of allergens to the symptoms of asthma
- Intrinsic asthma
- Asthma can also be linked to the workplace
- Viral infections
A
- The most common cause of asthmatic inflammation
- Inhalation of allergens
- The relationship of allergens to the symptoms of asthma
- May be obvious to the patient (immediate symptoms upon exposure to the cat)
- Many patients who are allergic to dust mites are not aware of the association between exposure and their symptoms
- Intrinsic asthma
- Patients who do not have allergies that suffer from asthma
- Asthma can also be linked to the workplace
- Occupational exposure to sensitizing chemicals (e.g. isocyanates) is an important cause of asthma as the timely removal from exposure can cure the disease or at least prevent progression
- Viral infections
- One of the most common causes of asthma exacerbations
11
Q
Symptoms of asthma
- Symptoms of asthma occur due to…
- Bronchocostriction results from a combination of…
- Additionally, many patients with asthma develop symptoms to nonspecific stimuli such as…
- Bronchial hyperresponsiveness
- The cardinal symptoms of asthma
A
- Symptoms of asthma occur due to…
- The narrowing of the airways or bronchconstriction
- Bronchocostriction results from a combination of…
- Bronchial smooth muscle contraction
- Increased vascular permeability leading to edema
- Increased airway mucus production
- Additionally, many patients with asthma develop symptoms to nonspecific stimuli such as…
- Exercise, cold air, or passive smoking
- Bronchial hyperresponsiveness
- The fact that the lungs of the patients with asthma can react to these kinds of stimuli
- The cardinal symptoms of asthma
- Wheezing, coughing, chest tightness, and shortness of breath
12
Q
Symptoms of asthma
- In all patients, the symptoms…
- In the majority of patients, the symptoms…
- Thus, most patients have…
- Attacks may occur…
- Careful questioning about factors that influence symptoms should distinguish between…
- Questions about seasonal variations in symptoms are important; however, some patients…
A
- In all patients, the symptoms…
- Fluctuate in intensity
- In the majority of patients, the symptoms…
- Are intermittent
- Thus, most patients have…
- Normal or near-normal lung function and no symptoms between episodes
- Attacks may occur…
- Spontaneously (often at night or first thing in the morning)
- After exercise
- Shortly after exposure to a known trigger factor
- Careful questioning about factors that influence symptoms should distinguish between…
- Nonspecific triggers
- Specific reactions that suggest that the patient is allergic
- Questions about seasonal variations in symptoms are important; however, some patients…
- Who are allergic to common indoor allergens do not describe seasonal variation
- Whose attacks are triggered by viral infection report seasonal exacerbations in the autumn
13
Q
Symptoms of asthma
- The presence or absence of seasonality…
- The attacks of asthma vary
- Evidence of severity is based on…
- The occurrence and the frequency of…
- Treatment requirements, especially the use of…
- Other
A
- The presence or absence of seasonality…
- Is not a basis for distinguishing between allergic and nonallergic causes
- The attacks of asthma vary
- Transient wheezing that recovers rapidly either spontaneously or after treatment with a bronchodilator
- Episodes that develop over minutes, hours, or days into severe symptoms that are not responsive to any inhaled medicines
- Evidence of severity is based on…
- The occurrence and the frequency of…
- Acute episodes
- Emergency room visits
- Hospitalizations
- Treatment requirements, especially the use of…
- Bronchodilators
- Inhaled or oral steroids
- Obstruction of lung function measured by spirometry
- The occurrence and the frequency of…
14
Q
Diagnosis of asthma
- Diagnosis of asthma is based on…
- Further evaluation of patients with asthma involves establishing whether they are allergic with…
- Evaluation of persistent or severe cases that are not responsive to treatment may also require…
A
- Diagnosis of asthma is based on…
- History
- Spirometry before and after treatment with bronchodilators
- Provocation tests to establish bronchial hyperresponsiveness
- Further evaluation of patients with asthma involves establishing whether they are allergic with…
- Routine blood count focusing on eosinophilia
- Measurements of total serum IgE or specific IgE antibodies
- Skin tests for immediate hypersensitivity
- Evaluation of persistent or severe cases that are not responsive to treatment may also require…
- Chest X ray
- Sinus CT
- Evaluation of the upper airway
15
Q
Diagnosis of asthma
- Clinical examination of the chest may identify…but…
- Peak flow meter
- General
- Measures…
- May establish…
- The results…
- Spirometry
- Provides…
- Most commonly expressed as…
A
- Clinical examination of the chest may identify…but…
- WheezingProlonged expiration
- Poor air entry
- But it is an unreliable method of estimating the extent of airway obstruction
- Peak flow meter
- The simplest technique for monitoring obstruction
- Measures the maximum rate of expiratory flow in liters per minute
- A chart showing repeated measurements over 2 weeks may establish…
- Diurnal variation
- Major changes from day to day
- Consistently normal values
- However, the results…
- Are dependent on effort
- Require consistent recording by the patient
- Do not provide information about the pattern of flow
- Spirometry
- Provides a record of the forced expiratory volume (FEV) over time
- Most commonly expressed as…
- FVC- the forced vital capacity which is the forced volume over 6 seconds
- FEV1- forced volume for the first second
- FEV 25-75- the midflow forced expiratory flow