Metered-dose inhaler breath actuated

Aerosolized medications are available as pressurized or breath-actuated metered-dose inhalers (MDIs), dry powder inhalers (DPIs), and nebulized or wet aerosols. Most inhaled medications currently used are available as metered-dose inhalers (Table 3). For the patient who has difficulty to coordinate activation of a MDI, a spacer improves delivery. Spacers reduce deposition of the drug in the... 

Breath-actuated metered dose inhalers - evohalers... 

Larsen, J.S. Hahn, M. Kochevar, J.W. Morris, R.J. Kasier, H.B. Weisberg, S.C. Halverson, P.C. Quessey, S.N. Administration errors with a conventional metered dose inhaler versus a novel breath actuated device. Ann. All. 1993, 71, 103-106. 

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]. 

Metered-dose inhaler (MDI) Canister held inverted Formulation (CFC, HFA, solution, suspension) Actuator cleanliness Addition of a spacer device Inspiratory flow (slow, deep) Breath-holding Coordinating actuation with inhalation Priming and shaking the device... 

Riker Laboratories, now 3M Healthcare, invented the pressurised metered dose inhaler (MDI) in 1955 when they combined the atomising power of CFCs and a metering valve design. The great majority of valves still use this basic retention valve principle, and hence pressurised MDIs (pMDIs) are all similar in appearance and operation when used with a standard actuator in the normal press and breathe manner. 

Many drugs have been formnlated for use with pressurized metered-dose inhalers (pMDIs) (Table 1). The main market for these devices is in the treatment of asthma, allergic diseases, and chronic obstructive pulmonary disease (COPD), for which approximately 500 million pMDIs are produced each year. Their major selling points are that they are cheap and portable. Despite their huge sales, there is increasing concern that the dose of drug patients with asthma receive will vary considerably due to their inhalational technique and to a lesser extent to the variabihty of dose delivery from the pMDI. It is likely, however, that the popularity of pMDIs will continue due to various modifications and additions that are aimed to help with inhalational technique and improve drug delivery. Examples of these include breath-actuated devices, discussed in this chapter, and spacer devices discussed in a subsequent chapter. 

Key pMDI, pressurized metered-dose inhaler VC, vital capacity BHT, breath holding tune BA, breath-actuated measured by scintigraphy. 

Hanania NA, Wittman R, Kesten S, Chapman KR. Medical personnel s knowledge of and ability to use inhaling devices metered dose inhalers, spacer chambers, and breath actuated dry powder inhalers. Chest 1994 105 111-116. 

Chapman KR, Love L, Brubaker H. A comparison of breath-actuated and conventional metered-dose inhalation techniques in elderly subjects. Chest 1993 104 1332-1337. 

The AERx, developed by Aradigm (Hayward, CA), is a metered dose liquid inhaler designed to deliver various pharmaceutical compounds to the peripheral lungs. The system, as shown in Fig. 10, consists of a unit dose disposable container equipped with a nozzle array, a piston assembly, and electronics associated with breath actuation and compliance monitoring functions. ... 

Figure 10 Photograph of a breath-actuated metered-dose pressurized-pack inhaler (Autohaler).

The Easi-Breathe is a breath-actuated metered-dose aerosol inhaler developed by Norton Healthcare. The device is primed when the mouthpiece is opened. When the patient breathes in, the mechanism is triggered and a dose is automatically released into the airstream. The inhaler works on a pneumatic principle. An internal vacuum restrains an operating spring. A valve that is operated in response to the patient s inhalation that allows the spring to fire the canister releases the vacuum. It can be actuated at a very low flow of approximately 20 L/min (72). Not surprisingly the device scored better than a pMDI on a number of features, including ease of use and having an attached mouthpiece cover. Practice nurses found it easier to teach and patients easier to learn to use than a conventional pMDI (73). 

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