Biomedical Engineering Reference
In-Depth Information
Table 12.5
Inhalation profi les used by Olson et al. [
55
] in studies to investigate DPI performance
with mixing inlet arrangement shown in Fig.
12.15
; the fl ow resistance of their DPI was 66 Pa
0.5
/
sL (
From
[
55
]
—used with permission
)
Profi le
Peak inspiratory fl ow rate, PIFR (L/min)
Flow increase rate, FIR
10-30 l/min
(L/s
2
)
Weak
65
4.0
Medium
77
5.9
Strong
92
13.5
Servomotor
Servomotor
computer
computer
Throat
Throat
DPI
Cylinder+piston
DPI
Cylinder+piston
0 L/min
60 L/min
80 L/min
80 L/min
Pressurized air
Pressurized air
Mixing
Inlet
Mixing
Inlet
80 L/min
20 L/min
80 L/min
80 L/min
NGI Impactor
NGI Impactor
Vacuum
Vacuum
Stand-by: no piston movement
with balanced flows
Test: piston movement in breathing
simulator causes flow through DPI
Fig. 12.16
Breathing profi le simulator developed by Olson et al
.
, using the “Miller” mixing inlet
with a full-resolution NGI as CI system; an AIM-based CI could also have been used (
From
[
55
]
—
used with permission
)
fl ow rate (
Q
const
) to the sidearm. This way, the fl ow through the impactor is kept
constant also at
Q
CI-const
, ensuring good aerodynamic performance is maintained
even when the fl ow rate through the device (
Q
br-sim
(
t
)) itself is low. In addition, (
Q
br-
sim
(
t
)) is always maintained smaller than
Q
CI-const
in this confi guration.
This inlet has been applied to the assessment of DPIs by Olson et al. [
55
], evalu-
ating their performance with realistic upper airway models under three different
adult breathing conditions, representing weak, medium, and strong inhalations
(Table
12.5
). The experimental arrangement they used in conjunction with a full-
resolution NGI sampling at 80 L/min is illustrated in Fig.
12.16
.
Olson et al. reported excellent agreement between the target adult patient inhala-
tion profi le for which the breathing simulator was programmed (dotted line) and
generated profi le (solid line) for the medium fl ow profi le for one of the DPIs evalu-
ated (Fig.
12.17
). They reported that the inlet fl ow rate in “standby” mode when the
vacuum-generated fl ow from the NGI was counterbalanced by the infl ow of com-
pressed air was within ±0.05 L/min and the repeatability for a given downloaded
inspiratory profi le to the breathing simulator with PIF of 70 L/min and FIR
10-30 L/min
of 8 L/s
2
was about 1 % in terms of the coeffi cient of variation. These fi ndings indi-
cate that the arrangement is suffi ciently stable and repeatable for routine use. In the
context of this chapter, the NGI could potentially be replaced by an AIM-based
system, most conveniently the rNGI described in Chap.
10
.
The “Miller” mixing inlet could also be useful for the evaluation of add-ons, such
as VHCs, since these devices should ideally be evaluated while mimicking tidal
Search WWH ::
Custom Search