A pulse oximeter is a photoelectric device that measures the oxygen
saturation of the blood. This device uses a probe with a "red" light
sensor system. The probe can be placed on a finger, toe, ear lobe or heal.
With each heart beat the unit measures the oxygen saturation of the blood
flowing through the body where the probe is placed.
A capnometer is a device used to measure the level of carbon dioxide that
is present. This can be done via nasal cannula or directly from the trach.
When Kristen is in the sleep lab they measure her end tidal CO2 using a
capnometer. When she is in the pulmonary function lab they use a
transducer called a pneumotachometer to measure expired air flow.
Sometimes, when Kristen is in the PICU, they measure both her oxygen and
carbon dioxide levels transcutaneously using a heated probe. This system
requires high maintainance for frequent probe position changes so the
patient doesn't get burned and callibration. The values can also change
significantly depending on the location/position of the probe so falsely
high or low values are frequently observed.
Several companies now distribute monitoring units that are capable of doing
both pulse oximetry and capnometry. Several of the families with CCHS
children have theses units at home. Most of the parents perfer the
individual units though. It allows them greater flexibility and the
maintainance seems to be required less often.
Nellcor/Puritan Bennett/EdenTec seems to offer the largest select of units
for "sleep/respiratory" based home monitoring.
Joanne Kocourek
The University of Chicago
jskocour(AT)midway.uchicago.edu