Biomedical Engineering Reference
In-Depth Information
allows operation from 6 to 24 months using the same batteries (wake
up time
B
15 ms, 250 kpps data rate, 64,000 nodes, 30 m range), as
pointed out by Hao and Foster (2008). Wired connections limits a
broader deployment of sensors (mainly in remote locations and large
physical areas), while wireless sensors are usually limited by lifespan
and size (or weight) of batteries.
Electronic prostheses have batteries that need to be charged often
because power consumption is quite high, in the order of 1 W. Batteries
for powered prostheses have higher capacity as power consumption is
higher. Batteries for IMDs account for 25
60% of the volume of
implanted devices; this produces relatively large devices in order to last
for several years (Schmidt and Skarstad, 2001). Batteries for pacemakers
have an average duration of 5
12 years with power consumption that
tops at 100
W (Katz and Akiyama, 2007; Mallela et al., 2004; Schmidt
and Skarstad, 2001). Implantable neurostimulators and infusion pumps
have a lifespan of 3
µ
5 years because of the higher power requirements
(Paulo and Gaspar, 2010; Schmidt and Skarstad, 2001). Power consump-
tion of hearing aids varies significantly depending on the model and
capabilities of the device, power requirements vary from 50
2,000
µ
W.
The small button cell used needs to be replaced periodically, as short as a
few days in some cases (Flipsen et al., 2004). The main advantage of
implantable devices with longer battery lifespan is the reduction in the
surgeries for replacing batteries (and the device itself), which reduces
health-care costs and enhances patient quality of life.
Nowadays there is a number of IMD in use to treat several condi-
tions, from heart conditions (bradycardia, tachyarrhythmia, fibrillation),
muscle stimulators (incontinence), neurological stimulators (deep brain,
spinal cord), and cochlear implants to drug pumps (Soykan, 2002).
Table 4.2
summarizes common IMD. Powering these devices has been
Table 4.2 Implantable Medical Devices
Cardiac pacemakers
Cardiac defibrillators
Muscle stimulators
Neurological stimulator
Cochlear implants
Monitoring devices
Drug pumps
