description:
An observation form that determines parameters or attributes of an Act. Examples are
the settings of a ventilator machine as parameters of a ventilator treatment act;
the controls on dillution factors of a chemical analyzer as a parameter of a laboratory
observation act; the settings of a physiologic measurement assembly (e.g., time skew)
or the position of the body while measuring blood pressure.
Control variables are forms of observations because just as with clinical observations,
the Observation.code determines the parameter and the Observation.value assigns the
value. While control variables sometimes can be observed (by noting the control settings
or an actually measured feedback loop) they are not primary observations, in the sense
that a control variable without a primary act is of no use (e.g., it makes no sense
to record a blood pressure position without recording a blood pressure, whereas it
does make sense to record a systolic blood pressure without a
diastolic blood pressure).
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