|HOLLAND SLEEP RESEARCH
CAPABLE/KEMP RESPIRATION GAUGES
We have developed an experimental
cable for recording of chest and
abdominal respiration effort. It is a silicone
with a resistive silicone-carbon core.
The recorded signal is roughly proportional to lung
Practical evaluations in several laboratories in the years 1995-2005
demonstrated that the cables:
on that result we have made a theoretical redesign that:
- are reliable and hygenic
and do produce very good respiration signals
- also pick up external electrical fields (50Hz mains,
- 'roll' over the body despite being rather tightly strapped.
We are now working with a company to realize this design.
- is based on the same materials
- is more elastic
- is virtually insensitive to external electrical fields
- can be more
to the body
- stays better in position
The old evaluations were based on cables of
4.5mm and 3.5mm diameters.
The 4.5mm types had lengths of 80cm, 100cm, 120cm, and 150cm. The 3.5mm
prototypes were 30cm, 40cm, 50cm, 60cm, 80cm, 100cm,
150cm. The gauges had a resistance
between 300 and 1000 Ohm/cm. So, a 100cm cable was typically between
and 100kOhm. Inspiration and expiration caused the resistance value to
and decrease roughly proportional to respiratory volume by about 0.1 -
1%. The active part of
the gauges ended in
integrated silicone-insulated wires. The respiration gauges did not have
electronics. Nor any special means to attach them to the body.
The circuit below was used to
connect the gauge to an
input. The resistance bridge produces the
respiration signal, superimposed on a DC voltage. DC is rejected by an
RC network with long time-constant (R=1MOhm, C=10uF, results in
some cases the DC component should not be rejected, for instance in
diagnosing Rett syndrome or when you wish to standardize the tension by
which the gauge is applied to the patient.
In such cases, the DC component can be very large and thus drive the
amplifiers out of range. A simple solution for this problem is on http://edfplus.info/specs/DCattenuator.html .