iBSc: Question 6 - Asthma

By Alan McLeod

Getting the best marks

Read the whole question – a latter section may give you a

clue about an earlier one.

To see how many points you need look at the marks

allocated – for example a 3 point question is generally looking for 3 salient points

If giving a list answer put the best answers first – examiners will not usually mark answers too

far down a list

Always write something – it may get you part of a mark and is anonymised so

no one will think you are stupid!

If you genuinely have no clue then re-write the question to see if this sparks

some ideas.

If not then move on and come back at the end. And remember – always

write something.

Good luck!

Question 6

Mrs Rockley, a 67 year old smoker presents with an acute attack of

breathlessness.

Q6.1• List 3 differentials (3)

Q6.2• Describe IMMEDIATE

management on arrival at A+E (3)

Question 6

She has a polyphonic wheeze

and a history of asthma.

Q6.3• As part of your

treatment you give salbutamol – this is a beta agonist. How - on a molecular level - do these drugs work? (6)

Question 4

The airway narrowing in

asthma is multifactorial

Q6.4• List the three main factors

(3)

Q6.5• If the radius is halved with

other factors remaining equal what happens to the flow of air? (3)

Question 6

Most gas exchange takes place within

the alveoli

Q6.6• Draw and lable an

alveolus showing cells and fluids present and nearby important structures (7)

Question 6

Mrs Rockley smokes 30 cigarettes a day

– you try to persuade her to

stop.

Q6.7• Describe the Stages

of Change model and how it may help you with getting Mrs Rockley to stop smokeing (8)

The Answers

View these on ‘note view’ rather than on full screen – additional

notes are provided for some slides

Generating Differentials:I’D GET VINO…

I Infectious / inflammatory

D Degenerative

G Genetic / Idiopathic

E Endocrine

T Trauma

V Vascular

I Iatrogenic / ingested

N Neoplastic

O Organs

Acute Dyspnoea

I Infectious / inflammatoryAsthma, Pneumonia, COPD exacerbation (e.g. upper resp tract infection)

D Degenerative

G Genetic / ideopathic

E Endocrine

T Trauma Pneumothorax

V Vascular Myocardial infarction, PE

I Iatrogenic / ingested Foreign body (mostly children)

N Neoplastic

O Organs / other Lungs

Emergency ManagementD Danger? Check that the scene is safe

R Run Check for response

H Happily Call for HELP!

A Away andCheck and secure airway and C-spine

B Buy Check breathing, Resp rate

C Chocolate! Pulse, Heart rate

Emergency Management

D ‘Disability’Neuro exam: minimum is pupil size / response + GCS or AVPU

E ‘Exposure’1: Expose to seek injuries

2: Keep warm + take temperature

DEFG Don’t Ever Forget Glucose!!!

An AMPLE history

A Allergies

M Medications

P Past med Hx

L Last meal (time)

E Event – what happened

GPCRs

Salbutamol is a beta agonist – it binds to beta receptors – the are G-protein coupled receptors

http://uk.youtube.com/watch?v=tOcGbnBCdMM

http://uk.youtube.com/watch?v=bU4955rLv_8&feature=related

GPCR Summary

• Receptor complex + G protein

• G Protein has 3 subunits (alpha, beta & gamma)

• Receptor binds ligand

• Conformational change

• Loss of GDP from G protein alpha subunit

• Binding of GTP

• Separation of alpha subunit from beta-gamma dimer

• Alpha and beta-gamma freed to interact with effectors.

• Cascade effect.

• Cycle starts again

GPCRs in the lung

Beta receptors• GPCRs• Gs actvates

adenylate cyclase– Increased cAMP– ATP cAMP

• cAMP causes relaxation of the smooth muscle

• Decreases sensitivity of the IP3 receptor, decreasing release of calcium from intracellular stores in response to IP31

• Some proponents argue for a cAMP independent PKA mechanism as well2

GPCRs in the heart

Beta receptors

• GPCRs

• Gs activates adenylate cyclase– Increased cAMP

– ATP cAMP

• cAMP activates PKA

• PKA phosphorylates alpha-1 subunit on voltage-gated Ca++ channels

• Increased Ca++ influx

• Increased inotropy

• Increased rate

Ca++ In

Ca++ In

Beta-adrenergic antagonists

‘Beta blockers’• Combat the harmful

activation of the sympathetic nervous system

• Decrease HR• Decrease contractility

Examples• Propranalol• Sotalol

Side effects• Bronchoconstriction• Bradycardia

Asthma

Airway

COS of Three Pathologies

Constriction Oedema Secretions

Velocity and Flow

Velocity• Displacement of single

particle per unit time • Inversely proportional to

cross sectional area– Faster in thinner tubes

• Aorta is thinner than total mass of capillaries– V slow capillary flow– Time for gaseous exch

Flow• Volume of fluid passing

point A at time B• Proportional to pressure

difference• Inversely proportional to

tube length• Proportional to r4

• Inversely proportional to viscosity

The Alveolus

Vessels in the Lung

• Pulmonary Artery– Deoxygenated blood– From Right Ventricle– Oxygenated in lungs– Affected in PE

• Bronchial Artery– Oxygenated blood– From systemic supply– Supplies tissues of lung

• Pulmonary vein– Oxygenated blood– From lungs– To Left atrium

Stages of Change Model

• AKA ‘Transtheoretical’

• By Prochasta and Diclemente

• Patient focus• Explains why some

interventions don’t work

• Allows you to predict which ones might!

Contempla-tion

Mainten-ance

Pre Contemplation

Preparation Action

Two Useful Concepts

Body Mass Index (BMI)

20-25: Ideal

26-30: Overweight

31-35: Obese

Pack Years

> 20 = increased chance complications

PY=Cigs / day

x Yrs20

BMI=Wt (kg)

Ht2 (M)

The End

The slides here should allow you to mark your own work – remember 1 mark per

answer up to the maximum for the question. Multiply by 3 to get percentage points. I assume a 60% pass mark. Sorry but I am unable to give further advice on

answers due to time constraints.