Resp - Asthma

Question 1

Give 5 reasons why airways are narrowed during an asthma attack.

Answer 1

Activated B cells produce IgE which activate mast cells… mast cell degranulation: histamine, prostaglandin D2 and leukotrienes. Also released by eosinophils.

Cause:

1. Smooth muscle bronchospasm
2. Over-production of abnormally thick mucus - forms mucus plugs
3. Shedding of airway epithelium - incorporated into mucus
4. bronchial wall thickening (infiltration by inflammatory cells)
5. oedema due to vascular leak

Question 2

what type of respiratory failure is produced in mild and severe asthma?

Answer 2

Mild-moderate asthma = T1RF
Airway narrowing causes reduced ventilation of affected alveoli, with V/Q mismatch in these areas. Hyperventilation of better ventilated areas of lungs cannot compensate for hypoxia but can compensate for CO2 retention by increased CO2 exhalation.

Severe asthma = T2RF
Extensive airway involvement (fewer unaffected areas) and exhaustion (limits respiratory effort) result in hypercapnia.

Question 3

describe the symptoms of chronic asthma

Answer 3

1. Recurrent acute attacks of SOB with wheeze and chest tightness.
2. Chronic, nocturnal cough.

Symptoms are:

• worse at night and in early morning (as PEF decreased at night) - diurnal pattern
• present in response to exercise, allergen exposure and cold air
• present after taking aspirin or B-blockers

Question 4

name 3 signs of an acute asthma attack

Answer 4

1. widespread wheeze
2. increased RR
3. use of accessory muscles of respiration

Question 5

describe the typical spirometry results in asthmatic pts

Answer 5

OBSTRUCTIVE deficit with:

• FEV1 significantly reduced
• FEV1/FVC ratio <70%
• FVC nearly normal

Question 6

which measure should be frequently recorded in pts with asthma and what does this typically show?

Answer 6

Peak expiratory flow rate (PEFR)

• marked diurnal variation (>20%)
• day-to-day variations
• decreased after certain aggravating activities

Question 7

describe the step-wise pharma management for chronic asthma

Answer 7

1. SABA (eg. salbutamol, terbutaline) as required for symptom relief or prevention
   2a. Add low dose ICS (e.g. beclomethasone) if using SABA or symptoms 3+/wk, or waking once/wk or asthma attack in last 2 yrs.
   2b. If still not controlled, add on LTRA e.g. montelukast.
2. Offer low dose ICS + LABA (e.g. salmeterol or formoterol) and review use of LTRA.
   4a. Change LABA + ICS to MART regimen with low dose ICS.
   4b. If still not controlled, increase ICS to moderate dose.
3. Consider:
   - increase ICS to high maintenance dose
   - trial of additional drug e.g. LAMA, theophylline or daily oral steroid

Question 8

describe the features of an acute severe asthma attack

Answer 8

Any one of:

i) PEF 33-50% of best or predicted
ii) RR 25+/min
iii) HR 110+/min
iv) inability to complete sentences in 1 breath

Question 9

describe the features of a life-threatening asthma attack

Answer 9

Any one of the following in a pt with severe asthma:

1. Clinical signs
   - altered conscious level
   - exhaustion
   - arrythmia
   - hypotension
   - cyanosis
   - silent chest
   - poor resp. effort
2. Measurements
   - PEF <33% best or predicted
   - SpO2 <92%
   - PaO2 <8 kPa
   - ‘normal’ PaCO2 (4.6-6 kPa)

Question 10

how would you manage an acute severe asthma attack?

Answer 10

1. High flow O2
2. 5mg salbutamol nebulisers (continuous if necessary, until response achieved)
3. 40-50mg prednisolone stat PO (continue for at least 5 days) or 100mg hydrocortisone IV
4. 500ug nebulised ipratropium bromide
5. consider IV aminophylline if no improvement with life-threatening features (beware if taking PO theophylline)