The most important factor in the effective use of inhalation aerosols is patient skill and correct instruction in the use of inhalers.
Nebulized aerosol is introduced to the patient by compressed air, either from a constant source or from a device known as intermittent positive-pressure ventilator. Nebulized aerosols rely less on the patient's own breathing pattern. Under some circumstances the dose administered to the patient by nebulizer is inconsistent or unpredictable. In a hospital setting, the aerosol administration can be supervised by qualified individuals. Home administration is not always supervised, and there is, therefore, a potential for misuse.
The method of administration of aerosols from MDIs is more important. The MDI should be inverted several times to ensure that the aerosol particles are suspended. The patient should exhale gently and then, tilting the head slightly, place the mouthpiece either, according to the conventional approach, in the mouth, closing the lips around it, or, according to a second approach, place the mouthpiece 6 -12 in. directly in front of the open mouth. The latter suggestion is thought to aid evaporation and removal of large particles according to the principle of spacer devices. The patient should then begin to slowly inhale from resting lung volume. Just after beginning the inhalation, the inhaler must be depressed firmly. This releases the medicament, and continuing the inspiration carries the aerosol to the lung. At the end of the breath, the patient should hold for 10 sec or as long as is comfortable before breathing out slowly.
The administration of dry powder generators does not require the same degree of patient coordination as the MDI. Nevertheless, it is worthwhile considering the procedure that should be used. The device must be prepared to deliver the dose. This may mean, for example, in the case of a Spinhaler, piercing the capsule or, for the Turbuhaler, loading the base by twisting the grip at its base. The patient should exhale gently and then tilt the head and place the mouthpiece in the mouth, closing the lips around it. He should then inhale deeply and evenly. Because this device operates upon inhalation, slow breathing may not be adequate to generate the aerosol effectively. The aerosol will be transported to the lung on the breath of the patient.
Even if a patient conforms with the recommended techniques for administration of aerosols, as little as 10% of the dose reportedly reaches the site of action in the lung .
To summarize, aerosols have become a common sight in contemporary life. The efficiency of inhalation aerosols in the treatment of asthma relies, to a large extent, on characteristics of the particles or droplets generated. A number of devices are available for the administration of active compounds to the lung. These fall in the general categories of nebulizers, MDIs, and dry powder generators. The presence of baffles or other collection surfaces or the use of spacer devices may improve the size characteristics of aerosols generated to enhance the therapeutic effect and reduce the incidence of side effects. Finally, understanding the principles behind the methods of administration of drugs to the lung, combined with an awareness of anatomy and physiology and a knowledge of the advantages of certain breathing patterns, enables the patient to be instructed in the appropriate use of inhalation aerosols.
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If you suffer with asthma, you will no doubt be familiar with the uncomfortable sensations as your bronchial tubes begin to narrow and your muscles around them start to tighten. A sticky mucus known as phlegm begins to produce and increase within your bronchial tubes and you begin to wheeze, cough and struggle to breathe.