nebuiliser 1 and 2 Flashcards
what do nebulisers do?
nebulizers convert an aqueous solution or suspension (of microniseddrug) into an aerosol either by:
•a high velocity airstream (i.e. using a jet nebulizer), or•ultrasonic energy (i.e. using an ultrasonic nebulizer)
what is the process called where process of converting a bulk liquid into small droplets ?
atomization
what is the most common application of nebulized therapy?
to deliver bronchodilator drugs to patients with asthma or COPD
what would be the ideal characterists in a nebulised system?
high rate of nebulization - maximum amount of nebulized aerosol is potentially available to patient
•minimum waste of drug aerosol - maximum amount of aerosol released is delivered to the patient (peripheral or centrally, depending on requirements) and not emitted into the environment
•low residual volume -more of the volume will be delivered to patient as aerosol
when may a nebulised treatment be used?
- where a patient requires very high doses of inhaled bronchodilator medication (severe airflow obstruction)
- if a patient needs an inhaled drug such as recombinant human deoxyribonuclease(rhDNase) or an antibiotic which cannot be given by any other means (e.g. in cystic fibrosis)
- for patients who are unable to use other devices or in situations such as acute severe asthma
what would be the clinical uses of nebulisers?
- in hospital for asthma patients, the driving gas should be oxygen (O2) (for acutely ill patients) or air (for stable patients)
- COPD patients should ideally receive monitored oxygen therapy while using an air-driven nebulizer system (to avoid increasing CO2retention)
- shorter nebulization periods (<10min)
- theoretically a mouthpiece may be better as it avoids nasal deposition of drugs
- patients may prefer a face mask, especially when acutely breathless, - however this is a situation where patients are likely to mouth-breathe anyway•a mouthpiece may avoid the risk of ocular complication with anticholinergic agents
what is a jet nebuliser?
an electrically powered device - compressed air or oxygen forced through a nozzle into the nebulizer chamber
how does a jet nebuliser work?
results in drop in pressure that creates a vacuum effect (Venturieffect), forcing the liquid drug solution to come up from the reservoir •the solution to is entrained into the gas stream and is sheared into a liquid film.
smaller particles pass out of device and are inhaled•larger particles return to the liquid reservoir (may be more than 99% of the particles) to be renebulized
what factors would affect output from the nebuliser?
- the characteristics of the solution: density/viscosity/surface tension/vapour pressure
- the velocities of the gas and solution - increase in gas velocity decreases droplet size
- the flow rates for the gas and the solution•an increase in the ratio of liquid to gas flow
what is the dead volume?
dead volume - amount of solution that is trapped inside the nebulizer and not made available for inhalation• typically in the range of 1.0 to 1.3 ml from initial volumes of 1.5 and 3.0 ml respectively
how can the dead volume be minimised?
minimize by using:
a conical shape for nebulizer solutiondecreasing the surface area of the internal surface of the nebulizer improving the wettability of the plastic surfaces
what affects nebulisier output?
ue to evaporative water loss, the solution becomes increasingly concentrated with time• also, due to evaporation, the solution cools
the droplet size produced by the nebulizer also varies directly with temperature
how do ultrasonic nebulisers work?
ultrasonic nebulizer uses a piezoelectric transducer
produces ultrasonic waves that pass through solution and aerosolize it at the surface
cause crystals to come out of solution
what determines the size of the particles in ultrasonic nebulizer?
frequency of the ultrasonic waves determines the size of the particles, with an inverse relationship between frequency and particle size, usually. 1–6 μm MMAD
what are the 3 components of the ultrasound nebulizer?
ultrasonic nebulizer has 3 components: the power unit, the transducer, and a fan.
what is the power units job?
power unit also controls the amplitude of the ultrasonic waves. This is user adjustable (not the frequency), increase in amplitude gives increase in output
how does a solution become nebulized?
either placed directly over the transducer or placed into a nebulization chamber and a water couplant chamber is placed between the transducer and the medication chamber
what is the job of the fan?
fan is used to deliver the aerosol to the patient, or the aerosol is evacuated from the nebulization chamber by the inspiratory flow of the patient
what are drug solutions usually dissolved in?
rug solutions contain drug that is dissolved in saline (0.9 % w/v NaCl) or occasionally in other liquids (cyclosporine, for example, is dissolved in alcohol)
when is the amount of drug deposited in the lung of value?
total mass deposited in deep lung only of value when equal to or greater than therapeutic dose
what kind of solutions should you use for nebulisers?
aqueous solutions
if not soluble, try a co-solvent e.g. ethanol or propylene glycol, but these will influence surface tension and viscosity and hence output and droplet size
what needs to be condiered in formulation of nebulizers
tonicity
if hypertonic solution– movement of water out of cell – bronchospasm
what is the basic formulation of nebulizers?
• antioxidants e.g. sodium metabisulphite, ascorbic acid – to prevent drug degradation by light, oxygen and trace metals• chelating agents e.g. ethylene diaminetetraaceticacid EDTA, citric acid - form complexes with metal ions (e.g. Cu2+, Fe3+) and thus improve stability• inclusion of antioxidants and chelating agents must be weighed against potential to cause adverse affects on lung• co-solvents• preservatives
when are preservatives and antioxidants not needed?
if the solutions are presented as small unit-dose packs which are sterile and isotonic e.g. Nebules
why is unit dose prefered to multidose?
avoids use of antibacterials(preservatives)–bronchconstriction, avoids source of infection and dosing errors
what are the advantages of nebulizers?
•nebulizers – good for hospitals. Same nebulizer can be used to deliver variety of drugs. •easy to administer drugs to children or patients with severe obstruction or agitation problems•administer drugs that can’t be administered by other inhalers•inhalers suit more active lifestyles for people with chronic pulmonary disease. No electrical output needed.
what are some disadvantages of nebulizers?
inefficient delivery method –delivers more drug than is needed (without any added benefit)•more non-pulmonary side effects – e.g. tremor, anxiety•more expensive – purchasing and maintenance. patients either rent or purchase nebulizer
what is an eflow mesh nebulizer?
eFlow® Rapid - the liquid medication is in contact with a micro-perforated membrane, with the opposing side of the membrane open to the air. Pressure causes the liquid to be pushed through uniform sized holes in the membrane, creating an aerosol. High-frequency vibration of the membrane drives the aerosol outwards more efficiently than a non-vibrating, passive membrane.
what are some of the new approaches with nebulizers
non-water soluble drugs –use liposomes or nanoparticles•for proteins/peptides (low/no oral bioavailability) – formulation difficulties:•unstable in aqueous environment•shear sensitive - degredation•prone to rapid oxidation and thermolabile•adsorption on plastics•low solubility•incompatibility with other drugs
