Other Inhalation Mode Factors

Timing of the aerosol entry at a particular point in the breathing cycle can have a profound effect on deposition. With the metered-dose inhaler without a spacer, poor synchronization of inspiration with the firing of the valve can result in a substantial loss of the aerosol bolus. For this reason, breath-actuated valves have been developed [91-93].

Stahlhofen's group [94,95] developed the technique of delivering boluses of monodisperse aerosols at predetermined points in the breathing cycle to achieve very selective deposition, especially in the upper and central airways. Early work by Gottschalk et al. [96] indicated that tidal breathing of an aerosol produced by an ultrasonic nebulizer caused less deposition than a deeply inspired aerosol followed by breath holding. Other breathing maneuvers, such as forced expiratory effort that enhances the central deposition of aerosols [97], can be used in principle to control to some extent the sites of deposition. However, it must be remembered that most patients are unable to follow even relatively simple inhalation instructions [28,29]. A complex breathing pattern might be impossible for a patient with compromised respiratory function to exercise, and even in able patients, the breathing patterns should be enforced as much as possible by the aerosol-producing device. A study utilizing an electronic device that managed the patient's breathing was carried out by Farr et al. The device guided the patient with a light prompt into a preprogrammed inspiratory flow rate range, and it automatically actuated the aerosol generation from the MDI at a preprogrammed inspired volume. Using gamma scintigraphy, the authors demonstrated profound differences in lung deposition between the different settings simulating both correct and incorrect use of MDIs [98]. This study also provided evidence that visual prompting using color signals and electronic actuation of aerosol generation at specified inhaled volume was a practicable way to manage the patient's inhalation delivery technique.

An effective and feasible method to enhance deposition in the small airways and alveoli is breath holding; this is important, especially for submicronic particles that would be otherwise exhaled [99].

Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

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