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By O. Grubuz. University of Minnesota-Morris.

A few years later buy 10gm fucidin with amex, a smaller buy 10 gm fucidin with mastercard, easier to use nebulizer apparatus were marketed ( 4). Particle Size A synopsis of the significance of particle size in inhalation therapy is a necessary preface to a clinically oriented discussion of aerosol devices. Particles larger than 5 m penetrate into the bronchi poorly, but are potentially systemically absorbed if swallowed. Particles under 2 m are not deposited into the airways and are either exhaled or are deposited in alveoli ( 6,7) (Table 37. The term fine particle mass is used for the percentage of the emitted dose that is in the respirable range, less than or equal to 5 m (8). With most devices used for aerosol therapy, fine particle mass typically ranges from 10% to 25%. Deposition into peripheral airways relative to central airways is maximal at 2 to 3 m (9). A mixture of several structurally similar compounds is used to obtain desired aerosol characteristics. Freon compounds are nonflammable and are unreactive under usual circumstances, characteristics favorable for their use as aerosol propellants and in their major historical application, refrigerator technology. However, it has become apparent that Freon compounds have serious negative effects on the environment. After release into the atmosphere, they rise to the stratosphere where they are eventually decomposed by ultraviolet solar radiation ( 10). As a result of the decomposition, chlorine radicals are released that react with and deplete stratospheric ozone ( 11). Increased penetration of ultraviolet radiation occurring as a consequence of ozone depletion has several harmful effects, which include increased incidence of skin cancers and cataracts ( 12). For these reasons an international protocol for reduction in production of Freon compounds was signed in Montreal in 1987 ( 13); this was later expanded into an agreement for total elimination of Freon compounds. During actuation, the metering chamber briefly communicates with the atmosphere but is sealed off from the remainder of the formulation within the cannister; at this time, the dose within the metering chamber exits the inhaler through the valve stem. Immediately after the dose is released, however, the valve blocks the connection of the metering chamber to the atmosphere but permits the chamber to communicate with the interior of the cannister, allowing refilling of the metering chamber. Shaking the canister prior to each actuation is essential to ensure that drug particles that may have creamed to the upper surface of the propellant or settled out toward the bottom of the device are resuspended (25). If the inhaler is not shaken prior to each actuation, the aliquot of propellant that enters the metering chamber from the canister may not be a homogenous suspension and therefore may not contain the expected amount of suspended drug. The likelihood that the drug-propellant suspension drawn into the metering chamber will remain homogenous decreases if the pause between shaking and actuation is too long. The canister must be held still and in the vertical position until the valve has completely returned to its rest position. If shaking is started while the valve is still compressed, or if the canister is tilted to the side while the metering chamber is refilling, some or all of the chamber may be filled with propellant vapor rather than with drug-containing suspension. The likelihood of such problems increases toward the end of the canister life, when the volume of suspension remaining in the canister is low ( 27). Shaking usually will not be adequate to resuspend drug partitioned within the chamber. When this occurs, the amount of drug delivered with the next actuation will be reduced ( 27,28). Breath holding increases drug deposition in the airways by providing more time for the particles to settle onto the airways. Greater bronchodilatation is found with a 10-second pause compared with a 4-second pause, but a 20-second period of breath holding appears to produce no further benefit ( 31). Comparisons between the two techniques have not shown consistent superiority of either technique over the other (31,34,35). Another issue relevant to optimal inhaler technique regards the lung volume at which inhalation begins. Although it has been proposed that inhalation from functional residual capacity yields improved results as compared with inhalation from residual volume ( 36), the difference is probably minor ( 37). Moreover, health-care professionals often are not familiar with the appropriate use of the devices ( 51). Despite training, around 15% of individuals are not able to use inhalers properly without assistive devices ( 40,43). Of patients with initially inadequate technique who master proper technique with training, around 50% subsequently again develop significant deficiencies in technique over time ( 43,52). In addition to the suboptimal response to treatment with inhaled medications resulting from incorrect inhaler technique, there is significant direct economic cost as a result of wasted aerosol medication ( 54). Errors in patient use of metered-dose inhalers Holding Chambers: Adjuncts to Metered-Dose Inhalers Holding chambers (also frequently referred to as spacers) are inhalation aids designed to overcome coordination difficulties and enhance aerosol deposition in the lower airways. There are three categories of holding chambers: (a) tubes without valves, (b) tubes or reservoirs incorporating one-way flap valves near the mouthpiece (with either mask or mouthpiece attached to the device), and (c) collapsible bags ( 55,56 and 57). B Tube holding chamber integrated with metered-dose inhaler actuator (Azmacort, Aventis Pharmaceuticals).

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