CR: PBL 5 (Asthma)

Question 1

What is asthma?

Answer 1

Spasm in bronchi of lungs, causing difficulty in breathing, resulting from an allergic reaction or hypersensitivity

Question 2

What is peak flow?

Answer 2

Device measures maximum air flow out of lungs during forced expiration

Question 3

What does salbutamol do?

Answer 3

Causes bronchodilation

Question 4

Describe the pathophysiology of asthma

Answer 4

Allergen exposure –> antigen moves through epithelia of bronchi –> antigen binds to IgE-mast cell complex –> degranulation of mast cell –> release of histamine, proteases and chemotactic factors –> bronchoconstriction, vasodilation and increased vascular permeability –> eosinophils and neutrophils drawn in from the blood –> inflammation and redness

Question 5

What is status asthmaticus?

Answer 5

Asthma attacks follow one another without pause

Question 6

How can asthma be diagnosed with peak flow tests?

Answer 6

When the volume of air that can be forced out of the lungs in one breath is reduced

Question 7

How can asthma be diagnosed with spirometry tests?

Answer 7

Measures FEV1 and FVC and compares them to averages measurements for people of same age, sex and height

Question 8

How is asthma treated?

Answer 8

Reliever inhalers and preventer inhalers predominantly (can use oral steroids)

Question 9

Describe how ‘reliever inhalers’ work

Answer 9

Contain short-acting beta 2 agonist

Question 10

Describe how ‘preventer inhalers’ work

Answer 10

Reduce inflammation and sensitivity of airways to prevent asthma attack by containing an inhaled corticosteroid

Question 11

Why may oral steroids be given in the treatment of asthma?

Answer 11

To regain control of asthma when it’s temporarily upset or when long-term control of asthma remains a problem despite maximal doses of inhalers

Question 12

Why are steroids not commonly used as a long-term treatment of asthma?

Answer 12

Have serious possible side effects

Question 13

What are some of the potential side effects of oral steroids taken for more than 3 months?

Answer 13

Osteoporosis, hypertension, diabetes, increased appetite, cataracts, glaucoma, skin thinning, muscle weakness

Question 14

Describe the mechanism of action of salbutamol

Answer 14

Bind to b2 adrenoreceptors on bronchial smooth muscle –> activation of adenyl cyclase –> catalyses ATP to cAMP –> cAMP lowers intracellular Ca2+ concentration –> smooth muscle relaxation and high cAMP levels inhibit bronchoconstrictor mediators e.g. histamine and leukotriene from mast cells

Question 15

Describe how corticosteroids work

Answer 15

Inhibit the recruitment of inflammatory cells (T cells, mast cells, eosinophils and dendritic cells) by suppression of chemotactic factors and adhesion molecules

Question 16

Why was the patient in status asthmaticus suffering from alkalaemia?

Answer 16

Tachypnea/hyperventilation removed more CO2 than normal so there is less CO2 to combine with water and form H2CO3 and therefore H+ ions are used to buffer this change, and therefore the pH increases

Question 17

What is involved in a long-term asthma plan

Answer 17

Proactive monitoring and managing of symptoms, reducing exposure to allergens,

Question 18

What controls respiration?

Answer 18

Respiratory centres in the brainstem

Question 19

How do higher centres of the brain contribute to respiratory control?

Answer 19

Involved in voluntary control (pain, emotion, temperature) and changes the impulses from the pontine respiratory centre to the medullary respiratory centre to affect the lungs

Question 20

How do peripheral chemoreceptors contribute to respiratory control?

Answer 20

Carotid and aortic bodies detect changes in blood composition, and if there is more CO2, less O2 and decreased pH –> stimulates increased breathing rate

Question 21

Do chemoreceptors respond more quickly to CO2 or O2 changes?

Answer 21

CO2 accumulation

Question 22

How do central chemoreceptors contribute to respiratory control?

Answer 22

Medullary chemoreceptors and respond to increase in CO2 –> increased breathing rate

Question 23

How do receptors in muscles and joints contribute to respiratory control?

Answer 23

Respond to contraction/exercise to increase the breathing rate

Question 24

How do irritant receptors in the lungs contribute to respiratory control?

Answer 24

Aim to help exhale irritant –> supress inhalation in medullary respiratory centre –> blowing off substance

Question 25

How do stretch receptors in the lungs contribute to respiratory control?

Answer 25

Prevent extreme over-inflation of the lungs (Hering-Brever reflex) –> reduces inspiration size

Question 26

What is the role of the pontine respiratory centre?

Answer 26

Interacts with the medullary respiratory centre to smooth/coordinate res

Question 27

What is the role of the medullary respiratory centre?

Answer 27

To control inspiration of diaphragm and breathing rhythm

Question 28

What are the two aspects of the medullary respiratory centre?

Answer 28

Dorsal - inspiration of diaphragm

Ventral - breathing rhythm

Question 29

What is the normal oxygen saturation for a healthy adult?

Answer 29

95-100%

Question 30

How can asthma be distinguished from COPD during lung function tests?

Answer 30

Peak flow wouldn’t improve after salbutamol use in COPD

Question 31

Describe the symptoms of a severe asthma attack

Answer 31

SaO2 25/min, Inability to complete sentences in one breath

Question 32

Define hypocapnia

Answer 32

Having an abnormally low arterial carbon dioxide level

Question 33

Why may an asthmatic have hypocapnia?

Answer 33

Hyperventilation leads to excess CO2 removal leading to less than normal –> hypocapnia

Question 34

How can beta 2 adrenoreceptor agonists be used in the treatment of asthma?

Answer 34

Mimics sympathetic bronchodilator action and acts as a bronchodilator. Activates adenylate cyclase to increase cAMP and may also reduce mediator release from inflammatory cells and airway nerves.

Question 35

What is FVC?

Answer 35

Functional vital capacity (volume of hair that can be maximally exhaled)

Question 36

What is FEV1?

Answer 36

Forced expiratory volume in one second (amount of air you can breathe out in 1 second)

Question 37

Why may reliever inhalers be insufficient in status asthmaticus?

Answer 37

There is often smooth muscle hypertrophy and basement membrane thickening, so smooth muscle relaxation still may not notably improve the flow impedence in the airways (remain largely obstructed)

Question 38

Which receptors can contribute to increasing respiratory rate?

Answer 38

Higher centres of brain, peripheral and central chemoreceptors, receptors in muscle and joints

Question 39

Which receptors can contribute to decreasing respiratory rate?

Answer 39

Higher centres of brain, irritant and stretch receptors in the lungs

Question 40

What is the Hering-Brever reflex?

Answer 40

reflex triggered to prevent over-inflation of the lung. Pulmonary stretch receptors present in the smooth muscle of the airways respond to excessive stretching of the lung during large inspiration –> reduces inspiration size