Effect of facial material softness and applied force on face mask dead volume, face mask seal, and inhaled corticosteroid delivery through an idealized infant replica.
BACKGROUND
During the aerosol delivery device design and optimization process, in vitro lung dose (LD) measurements are often performed using soft face models, which may provide a more clinically relevant representation of face mask dead volume (MDV) and face mask seal (FMS) than hard face models. However, a comparison of MDV, FMS, and LD for hard and soft face models is lacking.


METHODS
Metal, silicone, and polyurethane represented hard, soft, and very soft facial materials, respectively. MDV was measured using a water displacement technique. FMS was measured using a valved holding chamber (VHC) flow rate technique. The LD of beclomethasone dipropionate (BDP) delivered via a 100-μg Qvar® pressurized metered dose inhaler with AeroChamber Plus® Flow-Vu® VHC and Small Mask, defined as that which passes through the nasal airways of the idealized infant geometry, was measured using a bias tidal flow system with a filter. MDV, FMS, and LD were measured at 1.5 lb and 3.5 lb of applied force. A mathematical model was used to predict LD based on experimental measurements of MDV and FMS.


RESULTS
Experimental BDP LD measurements for ABS, silicone, and polyurethane at 1.5 lb were 0.9 (0.6) μg, 2.4 (1.9) μg, and 19.3 (0.9) μg, respectively. At 3.5 lb, the respective LD was 10.0 (1.5) μg, 13.8 (1.4) μg, and 14.2 (0.9) μg. Parametric analysis with the mathematical model showed that differences in FMS between face models had a greater impact on LD than differences in MDV.


CONCLUSIONS
The use of soft face models resulted in higher LD than hard face models, with a greater difference at 1.5 lb than at 3.5 lb. A lack of a FMS led to decreased dose consistency; therefore, a sealant should be used when measuring LD with a hard ABS or soft silicone face model at 1.5 lb of applied force or less.
1 Aerosol Research Laboratory of Alberta, Department of Mechanical Engineering, University of Alberta , Edmonton, Alberta, Canada , T6G 2G8.
Nicholas B
NB
Carrigy
Connor
C
O'Reilly
James
J
Schmitt
Michelle
M
Noga
Warren H
WH
Finlay
D000280:Administration, Inhalation; D000305:Adrenal Cortex Hormones / Q000008:administration & dosage* / Q000737:chemistry; D000336:Aerosols; D000367:Age Factors; D001507:Beclomethasone / Q000008:administration & dosage* / Q000737:chemistry; D002626:Chemistry, Pharmaceutical; D017076:Computer-Aided Design; D016503:Drug Delivery Systems / Q000295:instrumentation*; D004867:Equipment Design; D005145:Face / Q000033:anatomy & histology*; D006244:Hardness; D006801:Humans; D007223:Infant; D001239:Inhalation; D008168:Lung / Q000033:anatomy & histology / Q000502:physiology; D008397:Masks; D008670:Metals; D036501:Metered Dose Inhalers; D008953:Models, Anatomic; D011140:Polyurethanes; D011312:Pressure; D012212:Rheology; D012828:Silicones; D013997:Time Factors
D000305:Adrenal Cortex Hormones; D000336:Aerosols; D008670:Metals; D011140:Polyurethanes; D012828:Silicones; D001507:Beclomethasone
aerosol deposition; experiment; face mask fit; in vitro measurements; mathematical lung dose model; pediatric benchtop model; soft face model