Although some synchrony of activation of the pMDI with inhalation is still desirable when using a spacer/VHC, the patient has a lot more time to accomplish this effectively. The correct use of a spacer/VHC negotiates with the common and potentially critical problem of poor coordination of activation of the pMDI with commencement of inhalation. It certainly significantly filters out and thereby reduces oropharyngeal deposition of the larger particles emitted from a pMDI, even with “perfect” technique. Use of a spacer/VHC slows down the aerosolised particles emitted from the pMDI, which may further increase lung deposition of the respirable fine particles, although the clinical significance of this effect is not well established. The concept of activating the pMDI into a spacer (an additional reservoir placed between the mouthpiece of the pMDI and the mouth of the patient) or a valved holding chamber (VHC) (a reservoir with a one-way valve permitting airflow into, but not out of, the patient's mouth) prior to inhalation was developed in the 1950s to address some, but not all, of the problems and potentially critical errors when using a pMDI. With suboptimal or incorrect technique, this fraction is further reduced, potentially to zero. Even with optimal technique and modern hydrofluoroalkane propellants, however, pMDIs deliver, at best, only ∼20% of the emitted dose to the lower airways, leaving ∼80% in the oropharynx. min −1), deep inhalation commencing immediately after pMDI activation followed by a breath-hold pause of ≥4 s and optimally up to 10 s.Maximising airway deposition of a pMDI-delivered drug requires a slow (30 L Incorrect pMDI usage may have knock-on effects on efficacy, safety and patient compliance. An important weakness of pMDI devices, however, is their propensity to be used suboptimally or incorrectly, a problem that has been recognised since their inception and that is unfortunately still prevalent today. Development of the pressurised metered-dose inhaler (pMDI) in the mid-1950s paved the way for widespread, personalised delivery of topical inhaled therapy for the pharmacological management of obstructive airways diseases (asthma and chronic obstructive pulmonary disease (COPD)), which has since proved its worth in terms of benefit/risk ratio and tolerability.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |