Pressurized metered dose inhalers (pMDIs) can deposit up to seventy percent of medication in the oropharyngeal tract, reducing therapeutic efficacy and increasing systemic exposure. This thesis presents the conceptualization, optimization, and validation of a next generation valved holding chamber (VHC) integrating (i) an aerodynamically tuned spacer body and (ii) a fully adjustable impaction valve incorporating a passive, spring loaded peak flow indicator. Four prototypes—geometrically mimicked Vortex®—were manufactured with interchangeable nozzles and impaction plates to characterise the governing fluid particle interactions. A particle coupled CFD framework (SST κ–ω) captured airflow and Rosin–Rammler particle fields representative of Ventolin® spray. Aerosol generation was modeled using a validated steady-state CFD approach with a secondary droplet breakup model. A mesh independency analysis (Richardson Convergence Study) established a 1 mm grid as the fidelity–efficiency optimum. Design spaces were explored implementing multi objective genetic algorithm in 3-parameter cylindrical bodies, refining with gradient approach for 5-parameter valve design, or surrogate based, Efficient Global Optimization (EGO) in 31-parameter Bézier body; studies were benchmarked with Anderson Cascade Impactor (ACI) at the standard flow rate. The optimal cylindrical spacer delivered 78% of the medication and reduced mean particle diameter by 46%. Bézier curve optimisation further decreased particle diameter by 62% while sustaining a 75% delivery—doubling the fine particle fraction compared to Volumatic® (36%) and Optichamber® Diamond (43%). A hybrid optimisation on valve resulted a 90.6% filtration index. Plate displacement first governed by a soft spring to maintain high efficacy; substituting a stiffer spring yields a 30 mm stroke capable of registering expiratory peak flows, thereby embedding real time pulmonary monitoring into the delivery path. ACI experiments agreed with CFD predictions within ±4 % for wall deposition, fine mass yield, and coarse particle interception, validating the steady state simulation that shortened computation run time by 87 times. The resulting VHC doubles therapeutic drug while eliminating coarse particle escape. The diagnostic enabled and self adjustability advance inhalation therapy toward personalised care. Then, the primary contributions of this work are the design of a novel, dual-function impaction valve, and the aerodynamic optimization of the spacer body. The valve uniquely provides both selective particle filtration and passive peak-flow monitoring. The final combined design represents a patient-adaptive, personalized inhalation therapy device.