Nebulisers in General Practice

A nebuliser is a device that converts liquid into aerosol droplets suitable for inhalation.¹ Nebulisers use oxygen, compressed air or ultrasonic power to break up medication solutions² and deliver a therapeutic dose of aerosol particles directly to the lungs.³ The use of nebulisers in the community is declining⁴ however they are useful when large doses of drugs are required and inspiratory airflow is limited such as during an acute asthma attack. Although metered dose inhalers combined with spacers generally produce equivalent effects, patients often have great confidence in nebulised therapy.⁴

Nebulisers can be driven by compressed gas (jet nebuliser) or by an ultrasonically vibrating crystal (ultrasonic nebuliser).⁴ In order to produce small enough particles from solution in 5-10 minutes, gas flow rates of at least 6 l/min are usually necessary. Ultrasonic nebulisers use a rapidly vibrating piezoelectric crystal to produce aerosol particles. Ultrasonic nebuliser machines are often smaller and quieter.⁵ Air jet nebulisers are most frequently used but ultrasonic nebulisers are becoming more common.¹

Nebulisers are highly inefficient and many deliver only 10% of the prescribed drug dose to the lungs. Much of the drug is caught on the internal apparatus or wasted during exhalation. The efficiency of drug delivery depends on the type and volume of nebuliser chamber and the flow rate at which it is driven. Some chambers have reservoir and valve systems to increase efficiency of particle delivery during inspiration and reduce environmental losses during expiration.³

Facemasks and mouthpieces are equally effective for administration of aerosol particles but breathless patients may prefer facemasks. Facemasks should be avoided or sealed very tightly when anticholinergic drugs are administered to patients with glaucoma. Facemasks should ideally also be avoided for delivery of nebulised corticosteroids, to prevent contact with the surrounding facial skin and eyes.¹

Nebulisers are used for emergency and domiciliary treatment of many respiratory diseases. Indications for nebuliser use include the emergency and prophylactic treatment of asthma, exacerbations and long-term treatment of chronic obstructive pulmonary disease (COPD), management of cystic fibrosis, bronchiectasis, HIV/AIDS and symptomatic relief in palliative care.³

Asthma

Nebulised delivery of inhaled bronchodilator is recommended in acute severe asthma with life-threatening features. Continuous nebulised high dose beta2 agonists are as effective as intravenous beta2 agonists and improve outcomes in acute severe asthma.⁶ Short acting beta2 agonists may also be combined with nebulised ipratropium bromide. Patients with severe asthma are hypoxic, which must be corrected with high concentrations of inspired oxygen. There are theoretical risks of oxygen desaturation whilst using air-driven compressors for nebulisation. Therefore nebulisers should be oxygen-driven with a "high flow regulator" fitted to the cylinder in order to provide the necessary flow rate of 6 l/min. However, the restricted availability of oxygen in general practice should not prevent administration of nebulised therapy where appropriate.⁷ It is recommended that general practitioners carry nebulisers or metered-dose inhalers with large volume spacers and high dose bronchodilators on all home visits to provide the optimal immediate treatment of acute asthma.⁸

Although nebulisers are recommended in the treatment of acute asthma, they are less useful for domiciliary management of stable asthma. The use of a metered-dose inhaler and large chamber spacer is cheap and usually as efficient as a nebuliser. Small children require close fitting facemasks and often tolerate a spacer better than a noisy jet nebuliser.⁶ Some patients with brittle asthma may benefit from a home nebuliser. Such patients require a verbal and written plan for self-treatment and it is essential that repeated use of the nebuliser does not lead to failure to seek medical help and the prompt use of steroids.⁹ All patients must be assessed by a respiratory specialist prior to long term home use of a nebuliser. ¹⁰

Chronic obstructive pulmonary disease

Although patients with COPD are considered to have irreversible bronchoconstriction, most show some reversibility with high dose bronchodilators. The nebulised aqueous vapour is also believed to alter mucus viscosity and assist expectoration. Therefore air driven nebulisers are used frequently in the treatment of acute exacerbations and maintenance of COPD.¹¹ However there is no actual evidence of superiority of nebulisers over metered-dose inhalers for delivery of bronchodilator therapy in COPD.²

Nebulised bronchodilators are indicated for the acute exacerbations of COPD only if treatment with hand held inhalers is insufficient. Beta2 agonist therapy is used in combination with ipratropium bromide.³

Adequate domiciliary bronchodilator treatment can usually be delivered using hand held inhalers.³ Nebulisers should be considered only for patients with distressing or disabling breathlessness despite maximal inhaler therapy. Treatment should only be continued if there is demonstrable reduction in symptoms, improvement in activities of daily living, increased exercise capacity or lung function.¹ A recent study of domiciliary nebuliser treatment found that compliance was good and patients generally perceive it to provide good symptom control and allow them to be less dependent on carers or health professionals. The study concludes that nebulisers are helpful in managing chronic lung disease in the community with benefit to patient well-being and potential health cost savings.¹² However it has also been shown that patients poorly understand the principles of nebuliser treatment and are unaware when compressors frequently malfunction. Patients benefit greatly from improved nebuliser education and technical support, which can be provided by nurse-led domiciliary services.¹³

Cystic fibrosis, bronchiectasis, AIDS-associated infections and terminal disease

Nebulisers are used to deliver bronchodilators, corticosteroids and recombinant DNase (rhDNase) to the lungs of patients with cystic fibrosis. Bronchodilator therapy not only improves airway obstruction but also increases mucociliary clearance of viscous secretions. High dose corticosteroids are used to minimise airway inflammation in the treatment of bronchial hyperactivity and to reduce the rate of decline of respiratory function. RhDNase 1 reduces the viscosity of sputum in cystic fibrosis by digesting DNA of extracellular neutrophils, which is present in huge quantities due to chronic epithelial inflammation. Patients should use specified nebuliser systems to ensure optimal delivery of rhDNase.¹⁴ Regular nebulised anti-pseudomonal treatment also improves lung function and reduces the frequency of exacerbations of infection in people with cystic fibrosis.¹⁵

Long-term nebulised antibiotics are also useful in bronchiectasis, when other methods of delivery have been unsuccessful. Nebulised antibiotic therapy should be combined with regular postural drainage and courses of oral or intravenous antibiotics for acute exacerbations.¹⁶

Nebulised pentamidine is occasionally used in the specialist prevention or treatment of pneumocystis pneumonia (PCP). Regular treatment is effective against mild PCP and intermittent inhalation of nebulised pentamidine is effective prophylaxis against infection.¹⁷

Many nebulised drugs are employed in palliative care but few indications are based on published evidence. However, regular nebulised normal saline helps to loosen tenacious secretions, may reduce breathlessness and is unlikely to do harm. There is also anecdotal evidence to support the use of nebulised opioids in patients with dyspnoea related to cancer and but this has not been supported in clinical trials.¹⁸

A patient's ability to correctly use equipment must be assessed before recommending nebulised therapy. The actual nebulisers and compressors are not prescribable on the NHS⁴ although they can be bought VAT-free. It is important to select a nebuliser chamber and compressor that are compatible.⁵ Access to equipment, servicing, advice and support must also be organised.¹

Cleaning

• Nebulisers should be cleaned daily in regular usage and after each use in intermittent use.
• The mask, mouthpiece and chamber should be disconnected, disassembled and washed in a warm detergent and water solution. The components should be left to dry overnight.
• Before reuse, the nebuliser should be run for a few seconds before adding medications.

Maintenance

• Disposable components such as the mouthpiece, mask, tubing and nebuliser chamber should be changed every 3 to 4 months.
• Compressors require annual servicing by manufacturer or local service provider.

Breakdown

• Patients must have a written plan describing whom to contact in the case of emergency such as a respiratory or practice nurse.
• If nebuliser times are slow, the equipment should be cleaned and treatment tried again. If it remains slow, a spare nebuliser should be used.
• Patients must be advised to self-treat such as with multiple doses of a handheld device and to ask for medical help.⁵