A nebuliser is a form of drug delivery in which a drug in solution is converted into an aerosol mist by passing a pressurised gas through it. The drug is then inhaled directly into the lungs. The drug is deposited in the tracheobronchial region or the alveoli depending on the size of the particles in the aerosol mist.
Nebulising a drug is a highly effective method of delivering drugs directly into the lungs, providing the correct equipment and gas flow is used with the appropriate drug. However, in certain instances hand held inhalers with a large volume spacer device may be equally effective e.g. administering bronchodilators.
Nebulised drugs are used in the following situations:
· Patients requiring emergency or high doses of bronchodilators
· Patients unable to use inhalers
· Patients with severe chronic airways disease
· A drug which is to be given by the inhaled route but is not available in inhaler form e.g. Lignocaine or Pentamadine
Drugs which are commonly nebulised
E.g. Salbutamol (Ventolin), Terbutaline (Bricanyl), Ipratropium Bromide (Atrovent). Nebulising these drugs allow them to be given in acute situations such as asthma exacerbations, or for patients with chronic respiratory conditions who do not respond to conventional doses via inhalers.
E.g. Budesonide (Pulmicort), Flixotide (Fluticasone). Inhaled corticosteriods are considered to have fewer systemic side effects than oral corticosteroids. They can also be given in higher doses than if given via an inhaler.
Administered via nebuliser for topical treatment, which reduces systemic side effects. If certain antibiotics e.g. pentamidine, colomycin, tobramycin, and gentamycin, are to be administered, a breath activated open-vent nebuliser should be used, with an expiratory filter-check with pharmacy. The drug should be given in a separate room away from staff or other patients. This is to ensure maximum inhalation of the drug and prevents others inhaling drug which may result in sub therapeutic dose and resistance.
E.g. Lignocaine and opioids. Occasionally used in palliative care for treatment of intractable cough and severe breathlessness.
E.g. Sodium chloride 0.9% hypertonic saline, Dornase alpha (Pulmozyme). These drugs are prescribed to facilitate expectoration by helping to thin the sputum. They may be used in the acute setting such as exacerbations of COPD, or in chronic conditions such as cystic fibrosis.
It is possible to mix some of these drugs for administration — check manufacturers' instructions for details. NB maximum volume for nebulisation is 4-5 mls.
Volume of drug to be nebulised
To be effective a nebuliser should contain between 2 and 4.5 mls of fluid. This is the volume of most nebulised drug doses therefore they do not normally require dilution, though the manufacturer's instructions should be followed-
If dilution is required, a sterile ampoule of sodium chloride 0.9% should be used for each patient. A sterile technique should be used to prepare each dose. Water should not be nebulised as it may cause bronchoconstriction.
In the most common types of nebulisers, approximately 0.5 mls of the drug remains in the chamber at the end of the nebulisation (called the residual volume).
Types of nebulisers
There is a wide range of compressors and nebuliser chambers commercially available. There are two main modes of operations:
A driving gas of compressed air or oxygen is forced through a narrow orifice to create a negative pressure causing suction of the liquid drug through a supply tube. The liquid mixed with the gas is blown out as a cloud of particles. As this hits a baffle (the green cap which fits over the gas delivery spout) the large particles adhere to the baffle and then fall back into the reservoir of the liquid drug. The small particles are suspended in the stream of gas and are inhaled by the patient.
The efficiency of a jet nebuliser and the size of the particles depend on the construction of the nebulising chamber and the power of the driving gas.
An aerosol is created by high frequency sound waves. These nebulisers can produce a higher output than a jet nebuliser but the particles are larger and are not deposited as far down the respiratory tract as small particles.
Jet nebulisers are most commonly used but ultrasonic nebulisers have a role in delivering high humidity to patients with excess viscous secretions e.g. bronchiectasis.
Ideally, a mouthpiece should be used during the administration of nebulised drugs because it provides a direct route of access to the lungs so the drug is not wasted and does not come into contact with the skin or eyes.
A facemask should be used only if the patient is very drowsy, disorientated or unable to breathe solely through the mouth. The face should be washed, and teeth cleaned or mouth rinsed following administration of the drug to prevent damage to the skin and oral mucosa. This is particularly important with steroids, antibiotics or Ipratropium Bromide as these drugs are known to irritate skin and in the case of ipratropium Bromide, cause disturbances in vision.
Patients with tracheostomies should receive nebulisers via a tracheostomy mask with a wide white connector. To prevent skin reactions the skin surrounding the tracheostomy should be washed and dried when the drug has been delivered.
Selection of the gas driving the nebuliser
Nebulisers may be given via air or oxygen. The driving gas flow rate is very important and should be 6-8 L/min. [t is important to take care when selecting which gas to use. Remember all oxygen should be prescribed.
· Patients on 24% or 28% supplementary oxygen are usually patients who rely on their hypoxic drive for respiration and it is recommended that patients who rely on hypoxic drive are not given high flow O2. However, if they are acutely unwell and hypoxic it may be appropriate to give high flow O2 under the advice of a respiratory expert. Replace the oxygen mask with nasal cannula with supplementary oxygen flowing at the same rate% as was provided by the mask/nasal cannula, then use air to supply the nebuliser.
· NB: It is important to remember that the rate of oxygen delivery is dependant on the apparatus used for delivery e.g. l/min is stated on the venturi mask barrel;
· All other patients receiving supplementary oxygen. These patients should receive their nebulisers using oxygen at a minimum flow of 6 l/min and a maximum of 8 l/min
· Patients requiring nebulisers but not receiving supplementary oxygen. Use air to supply the nebuliser
· Patients receiving non-invasive ventilation (NIV) should receive nebulisers on air
Electrically powered compressors are the preferred source of compressed air, and should be used when possible, in hospital or in the community. Utilising cylinder or piped air may have the effect of 'drying out' the solution and thus affecting the amount of drug deposited in the lungs.
If the compressors are unavailable, compressed air from cylinders or piped sources should be used at 6-8 litres per minute.
Compressed oxygen from wall or cylinder supply.
Trouble shooting nebulisers
No mist appears when the gas flow is turned on.
· Check if there is solution in the nebuliser
· Check if there is sufficient gas flow
· Change the nebufiser as the air inlet hole inside the chainber is probably blocked
· Check the "baffle" is insitu.
The compressor is switched on but nothing happens.
· Check if the compressor is plugged into the mains
· Check if the mains lead is firmly plugged into the compressor
· If still not working contact Medical Electronics
The tubing becomes disconnectedfrom the gas source.
· Turn off the gas source
· Firmly reconnect the tubing
· Restart the nebulisation
The administration is taking longer than usual.
· If using piped gas, is the flow sufficiently high?
· If using a compressor, is the air intake filters blocked?
· An excessive volume of drug solution has been used
The patient starts to cough violently.
Occasionally nebulised drugs may cause paradoxical bronchospasm. Stop the administration and reassure the patient. Inform the doctor.
The drug solution should always be at room temperature as cool aerosol may cause bronchospasm
Care and Maintenance of Compressors
All compressors require regular servicing each year. This is to check electrical connections, change air filters and ensure the correct flow rate is generated. Within the hospital, this service is co-ordinated by the Medical Electronics Department but must be initiated and organised by the ward/department staff.
It is imperative that the compressor is cleaned using 70% alcohol spray after each patient's use, as bacterial contamination is a significant risk.
· Appropriate gas source
· Gas supply tubing
· Mouth piece or face mask
· Prescribed drug
· Sterile normal saline 0.9% for dilution
· Sterile syringe and needle to prepare drug
1. Assemble equipment using the correct compressor for drug to be given
Gas source must be sufficiently powerful to aerosolise the drug e.g. antibiotics.
2. Check the prescription. The drug in solution should be at room temperature.
Prevents risk of bronchospasm
3. If using compressor, place on hard surface, but not on the floor
Dust particles may be drawn in.
4. Place the drug in nebuliser chamber, diluting if necessary according to the prescription.
A minimum of 2 mls and maximum of 4.5 mls should be used
5. Ensure patient is in an upright position and the nebuliser is upright.
To maximise lung expansion and drug delivery.
6. Switch on gas supply. If piped oxygen or air is used, flow rate to be 6-8 1/min.
To ensure adequate aerosolising of drug.
7. Encourage patient to breathe normally, with occasionally deep breathing, and to avoid talking.
With most nebulisers, 60-70% of the drug is wasted during the expiratory phase, unless breath assisted nebulisers are used.
8. The end-point of nebulisation is when the nebuliser spits intermittently, or when no further aerosol is delivered. This should be no more than 10 minutes for bronchodilators.
80% of the drug is delivered in the first 5 minutes. Timing is affected by the type of drug, the volume, and the equipment used.
9. At the end of nebulisation disconnect the nebuliser from the tubing. Turn on the compressor for a short period to clear any moisture in the tubing.
There are significant potential risks of bacterial contamination if moisture remains in the tubing.
10. After each use, unscrew the nebuliser top; separate the nebuliser into three parts, wash in warm soapy water, and rinse with clean water. Excess water should be removed with a paper towel. Leave to dry in a clean area.
When reassembling the nebuliser, ensure the plate component is fully pushed down onto the spigot in the base component before screwing on the top.
Users must ensure no droplets of water remain in the nebuliser before re-use.
Never reuse nebulisers designated as single use.Potential risk of transmission of Legionella bacteria due to poor drying after cleaning.
Particular attention should be paid to the find bore nozzle. If this becomes blocked, the drug may not aerosolise sufficiently. Replace as appropriate.
11. If steroids or antibiotics have been nebulised, advise patient to rinse mouth afterwards, or to wash their face if a mask was used.
A build up of drug deposits may cause irritation of the mouth or skin.
12. Change the nebuliser apparatus:
· Every 3 days or
· If it becomes contaminated with sputum
· If it is not working
To ensure clean, functioning equipment is available.
13. In all aspects of nebulisation, patient education is vital
Knowledge can improve compliance. Advise the patient that the benefits may not be felt immediately e.g. with steroids.
14. Document actions in the patients records.
Maintain ongoing evaluation