8. Asthma Flashcards Preview

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Flashcards in 8. Asthma Deck (15)
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1
Q

what type of resp. deficit is asthma

A

obstructive

2
Q

draw the time-volume curve, and flow volume loop of a P with asthma

A

time-volume curve:

  • FVC nearly normal
  • FEV1 sig. reduced
  • FEV1/FVC ratio <70%

flow-volume loop:

  • PEFR reduced
  • ‘scalloped’ curve
3
Q

how can asthma be differentiated from COPD

A

Both show airway obstruction but:

  • obstruction in asthma often REVERSIBLE - >15% improvement spontaneously or with bronchodilators/steroids
  • obstruction in COPD NOT FULLY REVERSIBLE - <15% improvement with treatment
4
Q

define the term ‘asthma’

A
  1. Chronic inflammatory disorder of the airways in susceptible Ps…
  2. associated with airway hyper-responsiveness to various stimuli…
  3. and widespread but variable airflow obstruction…
  4. that is often reversible, spontaneously or with treatment
5
Q

describe the 2 phases of cellular response in asthma

A

Chronic inflammation is driven by Th2 cells:

  1. macrophages process and present Ag to T cells… Th2 cells preferentially activated…
  2. release cytokines which attract and activate inflammatory cells, inc. mast cells and eosinophils, and activate B cells which produce IgE…

Immediate response (20mins) - T1 hypersensitivity

  1. promotes mast cell and eosinophil degranulation… release of mediators (histamine, prostaglandin D2, leukotriene)…
  2. bronchial smooth muscle contraction… bronchoconstriction

Late phase response (3-12hrs later) - T4 hypersensitivity
5. eosinophils, mast cells, lymphocytes and neutrophils release mediators and cytokines… airway inflammation and epithelial cell shedding

6
Q

name 5 reasons for airway narrowing during an asthma attack

A
  1. bronchial smooth muscle contraction
  2. mucous over-production, and abnormal mucus (thick, tenacious and slow-moving) more likely to form mucus plugs
  3. oedema (mucosal swelling) due to vascular leak
  4. thickening of bronchial walls due to infiltration by inflammatory cells
  5. epithelium is shed and incorporated into thick mucus
7
Q

why can non-allergic stimuli like cold and exercise trigger asthma attacks

A

airway hyper-responsiveness: inflammatory damage can lead to exposure of sensory nerves… smooth muscle spasms

8
Q

why is long term treatment with anti-inflammatory drugs important in asthma

A

Poor control can lead to airway remodelling, some of which may not be fully reversible, inc.

  1. smooth muscle hypertrophy and hyperplasia
  2. goblet cell hypertrophy
  3. basement membrane thickening
9
Q

describe the clinical symptoms/signs of asthma

A
  1. recurrent, acute attacks dyspnoea
  2. chronic, nocturnal cough
  3. wheeze
  4. obstructive pattern on spirometry (low FEV1, FEV1/FVC, PEFR)
  5. use of accessory muscles of inspiration, e.g. SCM, scalene muscles
10
Q

what type of resp. failure is involved in asthma and why does this occur

A

Mild-moderate asthma:
i) airway narrowing with reduced ventilation of affected alveoli… V/Q mismatch in affected area…
ii) hyperventilation of better ventilated areas of lung cannot compensate for hypoxia but can compensate for CO2 retention by increased CO2 exhalation
= T1RF

Severe asthma:
i) extensive airway involvement (fewer unaffected areas where hyperventilation washes out CO2) and exhaustion (limits resp. effort)… rise in CO2
= T2RF (sign of life-threatening asthma - often require assisted ventilation)

11
Q

name possible asthma triggers

A
  1. allergens, eg pollen, animals
  2. cold air
  3. exercise
  4. air pollution, eg fumes, cigarette smoke
  5. drugs - NSAIDS and beta-blockers
  6. emotional distress
12
Q

state 3 types of drug that can be used in the treatment of an acute asthma attack

A

nebulised bronchodilators - relievers:

  1. (short acting) beta-adrenoR agonists, e.g. salbutamol
  2. antimuscharinics, e.g. ipratropium
  3. oral/IV steroids - reduce inflammation

+ O2 therapy

13
Q

which drugs should be used in long-term management of asthma

A
  1. inhaled corticosteroids (reduce inflammation, preventers)
  2. long acting beta-adrenoR agonists (bronchodilation), e.g. salmeterol - if symptom persistence, only in conjunction with steroids
14
Q

why are asthma symptoms often worse at night

A

physiological bronchoconstriction due to PNS activation

15
Q

why are beta-adrenoRs often more effective in relieving asthma than antimuscharinics

A

B-adrenoRs promote bronchodilation whatever the cause for bronchoconstriction, whereas antimuscharinics only effective at relieving bronchoconstriction if it is caused by PNS overstimulation