9 WHILE MONITORING THE PATIENT
Monitoring starts when a belt, properly applied on a patient, is linked through a belt connector to a LuMon
Monitor in the on-state (8).
NOTE
The LuMon System is not intended for diagnosis, it is intended only as an adjunct in patient assessment. It
must be used in conjunction with other clinical signs and symptoms.
As an introduction to this section, sub-sections 9.1, 9.2, and 9.3 address several particular features of the
LuMon System or more generally Sentec EIT. Sub-section 9.1 provides information about the patient-specific,
CT-derived thorax and lung models used by the LuMon System. Why the LuMon System determines and
how it visualizes the patient position (
rotation
and
inclination
) is covered in 9.2. Sub-section 9.3 describes how
the LuMon System continuously evaluates and visualizes the quality of the measured
EIT raw data
and of the
thereof derived
EIT data
.
Sub-section 9.4 introduces the
Global Dynamic Image
and the
Plethysmogram
.
Global Dynamic Images
provide a movie-like display that visualizes regional impedance variations within the
Thorax ROI.
Considering
Lung Pixels
only, the
Plethysmogram
displays relative variations of
Lung Impedance
(i.e. the sum of impedance
of all
Lung Pixels
) over time. Breath detection (9.5) is based on dynamics of the
Plethysmogram
, the
determination of
Respiratory Rate
(9.6) and, with the exception of
Aeration
, of all other
EIT images
and
indices
provided by the LuMon System is based on detected breaths. The determination of the aforementioned data
based on detected breath is herein referred to as
breath-based
(BB) analysis and the hereby determined
EIT
images
and
indices
as
breathing-related EIT images and indices
. To determine
breathing-related EIT images
and indices
the operator can also select a
time-based
(TB)
analysis
, e.g. when breaths are not easily detected.
The different, selectable
Analysis Modes
are described in 9.7. Sub-sections 9.8, 9.9 and 9.10 describe the
breathing-related EIT images and indices
.
The possibility to mark operator events, to store screenshots on a USB stick and to record or export data on a
USB stick are covered in sub-sections 9.10 and 9.11.
9.1 Selection of patient-specific, CT-derived thorax and lung models
The LuMon System makes use of thorax and lung models that have been derived from computed
tomography (CT) to optimize the measured and displayed images as described below. On the one hand,
anatomically enhanced
EIT image
reconstruction has been shown to be superior to non-individualized
reconstruction [5]. On the other hand, using
Thorax
and
Lung ROIs
corresponding to the thorax and lung
model best adapted to the individual patient , permits the LuMon System to determine those
image pixels that most likely represent areas in most importantly, areas within the
lung. Herein, pixels located within the
Thorax ROI
and the
Lung ROI
are respectively referred to as
Thorax Pixels
and
Lung Pixels
(14.2). It is herewith emphasized that, with the exception of the
Global Dynamic Image
(9.4), the
LuMon System solely evaluates the impedance of
Lung Pixels
in order to determine the displayed data.
Lung
Impedance
, for example, is the total impedance within the
Lung ROI
for a given image frame, i.e. the sum of the
impedance values of all
Lung Pixels
(14.2).
In Adults/Children configuration, various CT-derived thorax and lung models covering a wide body mass index
(BMI) range are available for both women and men.
Figure 9-1 illustrates for a few models the associated
Thorax
and
Lung Contours
, i.e. the borders of the
Thorax
and
Lung ROIs
. As can be seen from the examples, the
Thorax
and
Lung Contours
for females and males are
different and their sizes and shapes mainly depend on BMI for both genders. As the width of the
Thorax
Contour
is always scaled identically in the
EIT images
, the size of the displayed
Lung ROI
decreases with
increasing BMI, though in this case mainly the size of the thorax increases in reality. For the same reason the size
and shape of the
Thorax
and
Lung Contours
are similar in patients with similar BMI but different heights.
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