Biomedical Engineering Reference
In-Depth Information
Table 10.2 Cumulative mass-weighted data for Flovent ® -110 measured by modified C-FSA a
( n = 5 replicates) without coating on collection plates ( From [ 19 ]— used with permission )
Number of actuations per determination
1 2 5 10
Cumulative mass % < stated upper size
limit (mean ± SD)
Location in
C-FSA
Size range
(
Upper size
limit (
Size
fraction
μ
m)
μ
m)
Induction port
Undefined
Undefined
CPF >4.7μm
59.3 ± 2.3
61.7 ± 2.6
60.5 ± 1.7
61.1 ± 3.4
Upper stage 2A
>4.7
Lower stage
1.0-4.7
4.7
FPF <4.7μm
40.7 ± 2.3
38.3 ± 2.6
39.5 ± 1.7
37.8 ± 4.0
Back-up filter
<1.0
1.0
EPF <1.0μm
9.4 ± 0.7
7.5 ± 0.6
6.4 ± 0.4
5.3 ± 0.4
a First stage cut size was 4.7
m rather than 5.0
μ
m aerodynamic diameter
μ
Table 10.3 Key size fraction metrics determined for 5-actuations of Flovent ® -110 into the T-FSA
( n = 5 replicates/CI system): comparison with equivalent data from a modiied a C-FSA and ACI
( From [ 19 ]— used with permission )
Cumulative mass % < stated
upper size limit (mean ± SD)
T-FSA
Upper size
limit (
Size
fraction
Location
Size range (
μ
m)
μ
m)
C-FSA
ACI
Induction port
Undefined
Undefined
CPF >4.7μm
57.6 ± 3.5
60.1 ± 1.2
57.7 ± 2.2
Upper stage a :
2A—C- FSA;
2—T-FSA
>4.7
Lower stage
1.0-4.7: C-FSA;
1.1-4.7:
T-FSA, ACI
4.7
FPF <4.7μm
42.4 ± 3.5
39.9 ± 1.2
42.3 ± 2.2
Back-up filter
<1.0: C-FSA;
<1.1: T-FSA,
ACI
1.0: C-FSA;
1.1: T-FSA,
ACI
EPF <1.0μm
3.8 ± 0.5
3.5 ± 0.4
1.2 ± 0.2
a First stage cut size of modified C-FSA was 4.7
μ
m rather than 5.0
μ
m aerodynamic diameter
CI for the same number of actuations of the inhaler, resulting in the potential for
earlier overloading of stages. Interestingly, the small but measurable wall losses
associated with those stages in the full ACI that were removed to create the abbre-
viated designs were believed to have been transferred to the lower stage in the
abbreviated systems. Fortunately this resulted in an increase in extra-fine particle
mass of only ca. 2%.
It is perhaps to be expected that collection surface coating will be especially
critical in abbreviated systems since any tendency toward non-ideal behavior is
magnified as a consequence of the increased inertia of particles that would otherwise
be collected by previous stages in the full-resolution configuration.
In the follow-on investigation [ 20 ], measurements were made with a formulation
containing 8% w/v ethanol as cosolvent (Qvar™; 80
g/actuation beclomethasone
dipropionate (BDP) ex-actuator mouthpiece), using surfactant-coated collection
surfaces with both the C-FSA and T-FSA. Tests with liquid ethanol-sensitive paper
confirmed that the ethanol evaporated inside the impactor during measurement,
penetrating only to the first stage (Fig. 10.6a, b ).
μ
 
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