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S2 Case 3 - asthma & COPD > Pressurised Metered Dose Inhalers + Nebulisers > Flashcards

Pressurised Metered Dose Inhalers + Nebulisers Flashcards

1
Q

What must the drug be in pMDI?

A

Dissolved/suspended in non-polar volatile propellant

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2
Q

Describe the delivery of the drug in pMDI

A

Drug in solution or suspension in pressurised canister
Actuation of metering valve - pre-determined dose released
Vol expansion of formulation
Enters airways as fine spray of droplets

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3
Q

What does deposition depend on?

A

Inspiratory flow + separation

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4
Q

What are the containers?

A

Aluminium canisters
10-30ml
Inert

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5
Q

What is the vol of medicine in the metering valve component?

A

25-100 microL

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6
Q

Describe the metering valve component

A

Inverted position
Valve stem fits into actuator

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7
Q

Describe what happens with metering valve component

A

Depression of valve stem = contents discharged
After actuation = refills with liquid

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8
Q

What must happen to pMDI?

A

Needs to be primed
= pressed multiple times

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9
Q

Describe the actuator component

A

Polyethylene or polypropylene

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10
Q

What do the dimensions of the orifice in the actuator determine?

A

Shape, speed + emitted aerosol

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11
Q

Describe the propellants component

A

Liquefied gases
Liquid under high pressure in cannister

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12
Q

What are the propellants that are used?

A

Hydrofluroalkanes

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13
Q

What are the problems with propellants?

A

Poor solvents

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14
Q

What can pMDIs be?

A

Solution or suspension

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15
Q

What should the particle size be?

A

Solution or suspension

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16
Q

Why does it say to “breathe in slowly + deeply”?

A

Minimise inertial impaction

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17
Q

Why does it say to “hold your breath for as long as possible”?

A

Allow for drug particle to follow air into lungs

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18
Q

Why does it say, “do not breathe into the inhaler”?

A

Block the valve

19
Q

Why does it say to “shake”?

A

If the formulation is a suspension

20
Q

What do spacers reduce?

A

Aerosol velocity, allowing for more time to inhale the drug

21
Q

What must you make sure when dispensing a spacer?

A

Compatible with pMDI mouthpiece

22
Q

What may be attached to a spacer for young patients?

A

Mask

23
Q

What is the drug in nebuliser?

A

Dissolved/suspended in polar solvent (usually H2O) + aerosolised

24
Q

How does nebuliser deliver it to the lungs?

A

Drug in solution/suspension added to nebuliser drug reservoir
Nebuliser connected to power source
Drug solution aerosolised
Enters airways as fine spray of droplets

25
Q

What is dissolution dependent on?

A

Droplet density, charge + size

26
Q

What is absorption dependent on?

A

Patient inhalation pattern + airways

27
Q

What are the different types of nebulisers?

A

Jet nebulisers
Ultrasonic nebulisers
Vibrating mesh nebulisers

28
Q

What do nebulisers consist of?

A

Compressor supplying compressed air
Nebulising chamber containing nebulised drug
Mouthpiece or face mask

29
Q

What are jet nebulisers driven by?

A

Driven by compressed air

30
Q

What does the rate of air flow determine in jet nebulisers?

A

Droplet size + rate of drug delivery

31
Q

Describe the Bernoulli principle + Venturi effect

A

Compressed gas passes through capillary tube
= increases air velocity = low pressure zone around nozzle (V)
= formulation to rise in liquid reservoir (B)

32
Q

What are the issues with jet nebulisers?

A

Quite noisy = affect patient acceptability
Continuous operation = significant amount of drug lost

33
Q

Describe how ultrasonic nebulisers work

A

Sound wave created from vibration of piezoelectric crystals at high frequency
= creates crests that break liquid particles into small droplets

34
Q

What do ultrasonic nebulisers require?

A

Power source

35
Q

How do vibrating mesh nebulisers work?

A

Passing liquid drug through vibrating mesh

36
Q

What droplet size do vibrating mesh nebulisers produce + what is it ideal for?

A

1-5 micrometres
Ideal for deep lung deposition

37
Q

What are the advantages of vibrating mesh nebulisers?

A

Quieter + more portable

38
Q

Describe formulating nebuliser fluids

A

Formulated in H2O
Surfactants added = suspension
Iso-osmotic fluid = pH3-10

39
Q

What isn’t often added to nebuliser fluids + why?

A

Antioxidants + preservatives = cause bronchospasm

40
Q

Why must it be pH 3-10?

A

Avoid bronchoconstriction

41
Q

What is poorly delivered from ultrasonic nebulisers?

A

Suspensions

42
Q

Why may the fluid in jet nebuliser drop in temperature?

A

Due to evaporation of solvent during nebulisation

43
Q

What may happen if the fluid drops in temperature?

A

Drug solubility may be reduced
Affect asthmatic patients who suffer from bronchoconstriction

S2 Case 3 - asthma & COPD (25 decks)

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