PBL 2 Flashcards
Name and describe 4 kinds of hypoxia
- Arterial (or hypoxic) hypoxia: in which the partial pressure of oxygen in arterial blood (PaO2) is low
- Anaemic hypoxia: in which the oxygen carrying capacity of the blood is reduced
- Ischaemic hypoxia: in which the cardiac output or local blood flow is inadequate
- Histotoxic hypoxia: in which the ability of the tissues to take up and use oxygen is impaired
How does a doctor most often recognise asthma? What are the common symptoms?
He or she recognizes bronchial asthma as being recurrent episodes of airflow limitation that are usually reversible.
- The symptoms consist of
- breathlessness
- wheezing
- chest tightness
- cough
- sometimes productive of sputum.
While these symptoms may be reversible spontaneously, more often they respond quickly to bronchodilators, in particular inhaled Beta-adrenergic agonists
Which parts of the lungs does asthma affect?
Anatomically, asthma affects both the central and more distal airways
What is the measurement of lung function used for in asthmatic patients? (2)
What is notable about the lung function of asthmatics over time, and how do you tend to measure lung function?
- Lung function tests are used in asthma diagnosis. For FEV1, for example, an improvement of 15-20 per cent in response to an inhaled Beta-adrenergic agoist is considered significant enough to support a diagnosis of asthma.
- Lung function tests are used to look for airway obstruction which gives an indication of the severity of asthma. The presence or absence of airways obstruction itself is not an important factor in the diagnosis of asthma.
- Regular peak flow measurements has shown that asthmatics may have an excessive diurnal variation of airflow obstruction, usually in the early morning, as often characterized by the early morning wheeze.
What is the measurement of lung function used for in asthmatic patients? (2)
What is notable about the lung function of asthmatics over time, and how do you tend to measure lung function?
- Lung function tests are used to look for airway obstruction. The presence or absence of airways obstruction itself is not an important factor in the diagnosis of asthma, although it provides an index of the severity of asthma in a diagnosed patient.
- Regular peak flow measurements has shown that asthmatics may have an excessive diurnal variation of airflow obstruction, usually in the early morning, as often characterized by the early morning wheeze.
What does the current best definition of asthma now include? (4)
- clinical symptoms (intermittent wheeze, cough and shortness of breath);
- lung function tests showing variability of airflow obstruction (peak expiratory flow rate diurnal variability with asthma exacerbation);
- bronchial hyperresponsiveness
- airway inflammation with bronchial mucosal infiltration with inflammatory cells, such as eosinophils and T cells
What is bronchial hyperresponsiveness?
Bronchial hyperresponsiveness: abnormal response of the airways to a provoking bronchoconstrictor stimulus, such as
- -inhaled methacholine
- -histamine
- -exercise.
The asthmatic individual shows a greater degree of responsiveness than the non-asthmatic individual:
A smaller amount of bronchoconstrictor agent causes a SIMILAR degree of bronchoconstriction, or of the maximal degree of worsening of lung function.
- What disease other than asthma shows bronchial hyperresponsiveness?
- What does the presence of BHR in the absence of other symptoms show?
- What do some consider the degree of BHR to show?
- What causes BHR?
- Chronic obstructive pulmonary disease shares bronchial hyperresponsiveness (BHR), but the degree of BHR is usually mild.
- The presence of BHR in the absence of symptoms is not considered to be asthma, although this is a predisposing factor to the onset of asthma.
- Some workers consider the degree of BHR as indicative of the severity of asthma.
- The causes of BHR are not known, but may include airway wall thickening, airway inflammation and/or abnormal airway smooth muscle contractility.
- What is airway inflammation? What is it characterised by?
- What is it often seen with?
- What does airway inflammation separate asthma from?
- the airways submucosa of patients with asthma is chronically inflamed with a cellular infiltrate characterized by eosinophils and T cells, together with epithelial damage and fragility.
- Often, there is subepithelial flbrosis characterized by an increased thickness of the ‘basement membrane’.
- This characteristic inflammatory response could be used to separate asthma from other airway conditions, such as chronic obstructive pulmonary disease and emphysema, which often cause diagnostic confusion with asthma.
Can airway obstruction be reversed in asthma?
- reversibility of airflow obstruction, spontaneously or by pharmacological means, is an important component of asthma.
- However, airflow obstruction is not always totally reversible: over time there may be total loss of reversibility of airways obstruction resulting from the chronic inflammatory process.
What are the characteristic features if you were to examine an asthmatic lung? (6)
Characteristic features:
- presence in the airway of inflammatory cells,
- plasma exudation,
- oedema,
- smooth muscle hypertrophy (thickening),
- mucus plugging
- shedding of the epithelium
In which countries is asthma most common?
The prevalence is:
- highest in the affluent English-speaking countries,
- intermediate in western Europe, Latin America, Africa and South-East Asia, and
- lowest in India, China, eastern Europe and the former Soviet Union.
There is a correlation between the rates of asthma with those of rhinoconjunctivitis.
Where in Europe is asthma most common?
What do asthma numbers in European countries strongly relate to?
- the highest prevalence in the UK and in some centres in France
- the lowest prevalence in East Germany and Spain.
- The geographical variation in atopic sensitization corresponded closely to the geographical variation of asthma
How do incidence of asthma vary between different areas of the UK?
There is little variation in asthma prevalence among children or adults throughout the UK
How many people in the uk have asthma?
1 out of every 7 children and 1 out of every 25 adults - have asthma symptoms requiring treatment. One worrying feature about the prevalence of asthma is the increase over recent decades.
How is the overall severity of an asthma condition measured? (6)
The severity of asthma can be defined in many ways, including:
- The frequency of daily symptoms;
- The need for medical consultations, either at the surgery or attendance in casualty departments;
- Time taken off work or school
- Poor quality of life characterized by non-participation in communal activities such as sports.
Other parameters that can define the severity of asthma include: the number of admissions to hospital for treatment of acute severe asthma episodes; the variability in peak flow measurements and lung function tests.
What are the risk factors for deaths from asthma? (7)
- age (for those over 40 years),
- cigarette smoking,
- a past history of severe or life-threatening attacks,
- previous hospital admissions and emergency room visits
- discontinuity of physician care.
A fatal outcome was also associated with inadequate assessment and inappropriate treatment of severe asthma, with overreliance on high doses of bronchodilator therapy and insufficient use of corticosteroids
How has the number of deaths from asthma been changing in the UK and why? (5 reasons)
The gradual reduction in mortality in the UK over the past decade may have been due to a combination of factors, including:
- increased use of inhaled corticosteroids,
- reduced reliance on potent Beta2 adrenergic agonist,
- better education of patients (and doctors) regarding asthma management,
- adherence to national management guidelines by health carers,
- recognition of severe asthma and of patients at risk of dying as the result of asthma.
Asthma deaths have continued to fall over the past 5 years.
- At what age is the incidence of asthma highest?
- What tends to happen in asthma up to the age of 6?
- What will you tend to find in those who have wheezing at 6 years old?
- The incidence of asthma is highest in early childhood, decreasing throughout later childhood and adolescence.
- The majority of wheezers at 3 will have remitted by 6.
- The persistent wheezers at age 6 more often have a family history of asthma (particularly maternal), elevated immunoglobulin E (IgE) levels in infancy and at age 6 years, and had decreased lung function at age 6.
What happens in the evolution from childhood asthma to adulthood? (3)
- Between 30 and 70 per cent of children with asthma become markedly improved or symptom-free by early adulthood
- Significant asthma symptoms persist in about 30 per cent.
- Some may have asymptomatic periods before developing wheeze again as adults.
- What types of sensitisation do you often find in patients admitted to hospital with asthma?
- What factor in childhood asthma is an indication of future adult asthma?
- Sensitization and exposure to house dust mite (and cockroaches, as found in some inner cities in the US) is very common amongst children and young adults attending emergency rooms for treatment of severe asthma episodes.
- Children with mild asthma are likely to have a good prognosis, but children with moderate or severe asthma will likely continue to have some degree of airway hyperresponsiveness and will be at risk from the long-term effects of asthma throughout life
What causes are there for asthma which begins in adulthood? (2)
- Sometimes this may be in response to sensitizing agents in the workplace leading to occupational asthma, or from the development of atopy later in life.
- Often, there is a history of an upper respiratory tract viral infection with the first exacerbation.
What are the 3 Medullary Centers Controlling Respiration?
1) The medullary respiratory centres
2) The apneustic centre
3) The pneumotaxic center
What do the medullary respiratory centres do?
What is reciprocal inhibition of the medullary respiratory centres?
- Sometimes called the “medullary rhythmicity” centers, as they are believed to set the baseline rhythm for respiration.
- In the normal resting state, respiration is due to the inspiratory center and when these nerves shut off, there is passive exhalation. The expiration center is only required when activity and requirements are increased.
- When your ventilation requirements are increased, as during exercise, your inspiratory center can suppress activity of the expiratory center while you inhale, and the expiratory center can suppress activity of the inspiratory center while you exhale. This is reciprocal inhibition.
What does the apneustic centre do?
Apneusis refers to an inspiratory gasp.
The apneustic center facilitates inspiration… for example, the apneustic center may prolong inspiration when your oxygen requirements become elevated, as during exercise. In this sense, the apneustic center helps to control depth of respiration.
Where are the central chemoreceptors located, and what are they sensitive to?
Central Chemoreceptors are located on both sides of the medulla where cranial nerves 9 (glossopharyngeal nerves) and 10 (vagal nerves) leave the brain. These chemoreceptors are primarily sensitive to pCO2 and the pH of blood
What substance do the pH chemoreceptors detect? How is this produced in the blood from Co2?
H+!
Describe the first, short term stage of the immune response in atopic asthma
- there are lots of T-cells in asthmatic lungs
- When T cells are presented with an antigen, they stimulate B cells to produce specific IgE
- This IgE binds to receptors on mast cells
- When an allergen binds to the IgE on the mast cells, the mast cells release granules of histamine and prostaglandin
- These products produce bronchoconstriction, vasodilation, mucus secretion and tissue destruction (asthma symptoms)
Decribe the second, long term stage of the immune response in atopic asthma
- The activated T cells recruit and activate eosinophils
- IgE also binds to the eosinophils
- When an allergen binds to the IgE on the eosinophils they release major basic protein which destroys epithelium (epithelial disquamation)
