GE Corometrics 250cx Series, Operator'S Manual

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Revision C 250cx Series Maternal/Fetal Monitor 8-5
2036946-001
Maternal Non-Invasive Blood Pressure Monitoring: NIBP Determination
NIBP Determination
A patient’s vital signs may vary dramatically during the use of cardiovascular agents
such as those that raise or lower blood pressure or those that increase or decrease
heart rate.
Because treatment protocol based on the patient’s blood pressure may rely on
specific values and differing measurement methods, clinicians should note a
possible variance from values obtained with this unit in planning patient care
management. The GE monitor values are based on the oscillometric method of
noninvasive blood pressure measurement and correspond to comparisons with intra-
aortic values within ANSI/ AAMI Standards for accuracy. Most automatic non-
invasive blood pressure monitoring uses the oscillometric method of measurement.
To understand how this method works, it is compared to the auscultatory method.
Auscultatory – With the auscultatory method, the clinician listens to the blood flow
and determines the systolic and diastolic pressures. The mean pressure is then
calculated with reference to these pressures (as long as the arterial pressure curve is
normal).
Oscillometric – The oscillometric method measures cuff pressure oscillations.
Oscillations are small changes in cuff pressure caused by artery motion against the
cuff. During a determination, the monitor stores oscillations along with cuff
pressures. At the end of a determination, these stored data are used to determine
systolic, mean and diastolic pressures.
Due to the difference in these methods, one cannot be used to check the accuracy of
the other.
SuperSTAT NIBP Determination
The oscillometric method of determining SuperSTAT NIBP is accomplished by a
sensitive transducer which measures cuff pressure and minute pressure oscillations
within the cuff. The first determination initially pumps up to an initial target cuff
pressure of about 135 mmHg (18.0 kPa) or to the user-selected initial target
pressure. To allow for rapid setting of cuff pressure, the monitor will momentarily
inflate to a higher pressure, then immediately deflate to the target pressure.
After inflating the cuff, the monitor begins to deflate, the oscillations versus cuff
pressure are measured, and finally, systolic, mean, and diastolic pressure are
determined, and the screen is updated. In any subsequent determination, as few as
four pressure steps may be necessary to complete the process. When employing
fewer pressure steps, the system uses the stored information from the previous blood
pressure determination to decide the best pressure steps to take. The monitor
measures the consistency of pulse size to tell if the oscillations taken at a step are
good and if more steps are needed.
If the current blood pressure reading is similar to the previous reading, the monitor
may use some information from the previous blood pressure in the current
determination. The monitor constantly evaluates data during a measurement and
tries to perform a blood pressure determination in the shortest possible time
providing greater comfort to the patient.