Use of Aerosolized Antibiotics in Patients With Cystic Fibrosis: Ultrasonic Nebulizers
Ultrasonic Nebulizers: Ultrasonic nebulizers work by shearing forces created by a piezoelectric crystal and particle size is a function of driving frequency and nebulizer baffles. Advantages of ultrasonic nebulizers include a gas or air pressure source is not required and aerosol output is relatively high. Disadvantages include the following: the aerosol solution becomes heated unless a water bath device is used; the output is decreased as the solution’s osmolality increases; and the cycle life is relatively short. The average cycle life of an ultrasonic nebulizer is 600 to 1,000 uses, which is easily reached within one year by a CF patient receiving multiple medications.
Jet Nebulizers: Jet nebulizers work by shearing the liquid solution by gas pressure. Larger particles are baffled out and recycled into the nebulizer solution. There are two major classes of jet nebulizers in clinical use at this time: standard and breath-enhanced.
The advantages of the standard jet nebulizer are low cost as the disposable plastic device has a unit cost of < $1 and relative efficiency as standard jet nebulizers deliver approximately 5 to 10% of drug to the lung, but the balance is left in the device or exhaled. Disadvantages include quality control problems as particle size and output vary, and that although disposable, jet nebulizers have been used repeatedly by patients without proper cleaning techniques. Bacteria have been cultured from used jet nebulizers, but the actual risk to patients is unknown. asthma inhalers
The advantages of breath-enhanced jet nebulizer are improved antibiotic delivery as 10 to 20% of the patient’s inspiration must go through the nebuliza-tion chamber where the aerosol cloud is generated and compared with the standard jet nebulizer, the breath-enhanced system generally has fewer quality control problems. The disadvantages are the relatively high unit cost of approximately $20 and the required cleaning between uses. However, the unit device can last for months. The nebulizer (PARI LC PLUS) used in the 300-mg preservative-free tobramycin studies was a breath-enhanced jet nebulizer.
Patient Factors Affecting Nebulizer Efficiency: Patient factors also increase the variability of aerosol delivery. These factors include minute ventilation, breathing pattern, presence of airway obstruction, cooperation, and position of the patient. The variability between patients may be as high as 10fold; therefore, a wide safety margin for an aerosol drug is desirable.