Breath actuation

Dry powder inhalers are generally described as breath actuated devices, because the inspiratory airstream releases the dose from the dose system and supplies the energy for the generation of fine drug particles from the powder formulation. Because the efficiency of dose release and powder disintegration increases with increasing inspiratory flow rate for most DPIs, these devices would be better described as breath controlled devices. In Section 3.9, the effect of resistance and clinical conditions on the flow curve and relevant flow parameters for DPIs are discussed. 

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... 

MDI, breath actuated >5 years Slow (30 1/min or 3-5 s) inhalation Indicated for patients unable to... 

Zanamivir has a bioavailability of less than 5% when absorbed through the gastrointestinal tract. It is administered using a breath-actuated inhaler device (Diskhaler)... 

O Hagan AH, Corbett JR. Contact allergy to budesonide 200. in a breath-actuated inhaler. Contact Dermatitis 1999 41(1) 53. 

An alternative approach to achieving patient coordination between actuation and inhalation is a breath actuated device such as the Autohaler. This device uses a mechanical vane to detect the appropriate inhalation rate for automatic firing of the pMDI. 

These devices permit the drug to be delivered to the airways as a dry powder aerosol. All currently available DPIs are breath-actuated, thus the respirable cloud is produced in response to the patient s effort. DPIs therefore have the following advantages over pMDIs ... 

Breath-actuated metered dose inhalers - evohalers... 

Djupesland, P. G., and Watts, J. (2005), Breath-actuated bidirectional delivery sets the nasal market on a new course, ONdrugdelivery, pp. 20-23. 

Newman, S. P., Weisz, A. W., Talaee, N., and Clarke, S. W. (1991), Improvement of drug delivery with a breath actuated pressurised aerosol for patients with poor inhaler technique, Thorax, 46, 712-716. 

Leung, K., Louca, E., and Coates, A. L. (2004), Comparison of breath-enhanced to breath-actuated nebulizers for rate, consistency, and efficiency, Chest, 126, 1619— 1627. 

The inhaler should be simple to use, require little patient coordination and preferably should be breath-actuate. 

The AeroEclipse (Monaghan/Trudell International) shown in Fig. 9, is a nebulizer powered by compressed air, which can be operated in both continuous nebuli-zation and breath-actuated modes. The nebulizer was characterized, in vitro, using different breathing patterns, with either continuous nebulization or breath-actuated nebulization. A piston pump was used to... 

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. ... 

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. 

Figure 9.47 Dispersion of Ventodisk or Becodisk contents by breath actuation a cross-section of a Diskhaler is shown with a disc located on the support wheel, (a) A disc is located beneath an aperture in the body of the Diskhaler through which a piercing needle enters, (b) The needle penetrates the upper and lower surfaces of the blister, (c) The patient inhales through the device and pierced blister, entraining the blister contents into the airstream.

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]. 

Another very elegant and highly portable device that aids patient coordination is the breath-actuated inhaler, originally developed by Riker Laboratories (3M) [47] and further enhanced by Ivax-Norton (EasiBreathe). In this type of device, a mechanical release mechanism is used, firing the MDI when a certain threshold inspiratory flowrate is reached. Once the dose has been dispensed, the device is then reprimed, ready for use. This type of device has gained wide acceptance in Europe and has been introduced for several MDI products. 

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