Kim Pollard and Anita Watson Jan, 2001. Nebulisers and compressors [online]. Seacroft University Hospitals, Leeds, UK. Available from http://www.cysticfibrosismedicine.com
Nebulisers, driven by air compressors, deliver a fine mist of water, saline or drugs in a form that can be inhaled by the patient. If a mask is used, as advised for very young children, the mouth should be open or all the medication is deposited in the nose and none reaches the lower respiratory tract. Older patients should always use a mouthpiece and breathe through the mouth rather than the nose. An exception may be patients after lung transplant who may use a mask to target Pseudomonas in the upper airways. Nebuliser therapy often plays a major role in treatment and it is of vital importance that all factors regarding nebuliser therapy are considered each time a patient is reviewed in clinic or on the ward. The fine details concerning the use of nebulisers are of great practical importance (Smye et al, 1990; Littlewood et al, 1993).
The points to be considered are:
1) which compressor should be used?
2) which nebuliser should be used?
3) which drug is to be nebulised?
The correct combination of drug, nebuliser and compressor will ensure optimal droplet size, thus increasing drug deposition in areas where it is required and so improve patients’ treatment. The recent development of more efficient nebulisers means that the more powerful compressors (Medix Maxi III, Medix Turboneb, Medic-Aid CR60) are not necessarily required to drive the nebuliser units. The compressors now in common use (Medix AC2000 Hi Flo and Medic-Aid CR50) have a flow rate of approximately 6 - 8 litres/minute which is adequate to drive modern Venturi type nebulisers. Each compressor and nebuliser has its own characteristics, so simply combining any nebuliser with any compressor may not provide the optimum performance characteristics and hence the greatest benefit to the patient. Nebuliser systems have been developed which exploit the Venturi effect to enhance drug delivery. These systems include those currently used in the CF units in Leeds - the Ventstream and Sidestream from Medic-Aid, and the Pari LC Plus from Pari. The Sidestream which is used for bronchodilators, steroids, Pulmozyme, and hypertonic saline uses the compressor airflow to entrain additional air (Venturi effect) through the nebuliser and thereby increases the output from the nebuliser, and drug deposition, and reduces nebulising time
The Ventstream and Pari LC Plus, which are used for antibiotics, direct the patient’s inspiratory flow through the nebuliser chamber, thereby increasing the effective inhaled nebuliser output. For this to occur the patient’s respiratory flow must exceed the compressor flow rate through the nebuliser for a significant proportion of the inspiratory period. This does not always occur in very young children and patients with poor lung function.
Novel nebuliser systems, including the HaloLite (Medic-Aid), are currently under evaluation and it is hoped they lead to more reliable delivery of antibiotics. Conventional nebulisers deliver antibiotic continuously throughout the treatment period and even with the venturi effect some antibiotic is lost during the expiration part of the breathing cycle. This leads to wastage of antibiotic and, more importantly, antibiotic dose variations from patient to patient and from day to day, make it impossible to assess how much antibiotic has been delivered. The HaloLite nebuliser synchronises the delivery of the antibiotic to the patient’s breathing pattern and only delivers antibiotic when the patient is breathing in most deeply. The system is programmed to deliver a set amount of antibiotic and this should be independent of uncontrollable factors such as the patient’s breathing pattern. This system may overcome problems of antibiotic delivery in the very young child.
Many paediatric patients referred to the Leeds CF unit for Comprehensive CF Assessment are taking inhaled antibiotics using a mask - often with the mouth closed - and are using a compressor which is too weak to nebulise the antibiotics with the chosen nebuliser. Consequently very little antibiotic reaches the lower airways and the patients are wasting one hour each day! It is important that the disposable nebulisers are changed regularly - their useful life varies according to the type. Also the compressor should be serviced regularly by the hospital physics department or whichever department of the hospital was responsible for supplying it. The cleaning of nebulisers and compressors is an essential part of the treatment regime.
Nebulisers should be washed after every use in hot soapy water, rinsed well, dried with a paper towel and left disassembled to air dry. Some nebulisers may be cleaned in the dishwasher and, of course, all may be cold water sterilised. Tubing should be changed on a regular basis as this becomes damp during use, and is difficult to dry. It is suggested that the compressor be left switched on for a short time following disconnection of the nebuliser in order to blow-out any water droplets. Inlet and outlet filters on the compressor should be changed every 3 - 6 months (see manufacturers recommendations) and serviced yearly.
It is important that the immediate effect of any new inhaled drug is monitored, by performing respiratory function tests before and after nebulisation. Occasionally there may be a deterioration in lung function due to irritation of the airways causing secondary bronchospasm. This is more likely to occur with antibiotics, e.g. Colomycin. If the patient feels that the nebulised treatment makes him/her worse it should be stopped immediately. It is important to observe any deterioration which occasionally occurs in infants following the administration of nebulised drugs.
References
Littlewood JM, Smye S W, Cunliffe H. Aerosol antibiotics in cystic fibrosis. Arch Dis Child 1993; 68: 788-792
Smye SW, Shaw A, Norwood AH, Littlewood JM. Some factors influencing the efficiency of a jet nebuliser system. Clin Phys Physiol Meas 1990; 2: 167-175
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