available. This is usually the case in mechanically ventilated patients or spontaneously breathing patients with
regular breathing patterns characterized by regular
Respiratory Rate
s and tidal volumes. The less regular and/or
the weaker breathing-related
Lung Impedance
changes are, the fewer breaths the LuMon System detects
and the less appropriate the selection of
BB mode
is.
TB-I mode is adequate to analyze episodes during which the minima and maxima of the
Plethysmogram
(9.4)
and, hence, the maximal
Lung Impedance
changes detected within
Analysis Intervals
are frequently related to
breathing. In addition to episodes during which use of
BB mode
is appropriate, this also includes episodes
during which the
Plethysmogram
reflects breathing patterns that present (significant) variations in amplitude
and/or frequency. This can, for example, be the case in spontaneously breathing patients with irregular
breathing rate and/or varying tidal volumes or in patients breathing rather shallowly. In such conditions, breath
detection (9.5) may be hindered and RRi computation (9.6) may often not be possible.
TB-II mode is always adequate, even to analyze episodes during which the minima and maxima of the
Plethysmogram
(9.4) and, hence, the maximal
Lung Impedance
changes detected within
Analysis Intervals
are
not related to breathing. In addition to episodes during which use of
TB-I mode
is appropriate, this also includes
episodes during which the
Plethysmogram
exhibits very weak or no clear breathing pattern and instead is
dominated by non-breathing-related
Lung Impedance
changes such as cardiac-related
Lung Impedance
changes. This can, for example, be the case in very shallowly breathing patients, in patients being ventilated at
frequencies above a few Hz or on extracorporeal lung support or during apnea or breath holds. In such
conditions, breath detection (9.5) and RRi computation (9.6) are typically not possible.
In
BB mode
breathing-related EIT images and indices
are only calculated when a breath is detected, whereas in
TB-I mode
these data are calculated every 15 seconds, i.e. even if maximal
Lung Impedance
changes detected
within
Analysis Intervals
are not breathing-related. Be aware that if this is the case,
breathing-related EIT images
and indices
generated in
TB-I mode
may not always be physiologically meaningful. Also be aware, that
breathing-related EIT images and indices
obtained with
BB mode
may differ from those obtained with
TB-I
mode
. Moreover,
breathing-related EIT images and indices
are not available in
TB-II mode
,
Aeration
is shown
instead.
CAUTION
In
TB-I mode
the minima and maxima and, hence, the maximal
Lung Impedance
changes detected within
Analysis Intervals
are, irrespective of the magnitude or rate of the
Lung Impedance
changes, assumed to be
related to breathing, more specifically to end-expiratory and end-inspiratory time points. In order to avoid
misinterpretation of data, be aware that
breathing-related EIT images and indices
generated in
TB-I mode
may
consequently not always be physiologically meaningful.
In order to assess the adequacy of an
Analysis Mode
as outlined above and summarized in Table 8-1 use
VentVie Figure 6-14). Irrespective of the currently selected
Analysis Mode
this view displays:
• the
Plethysmogram
(9.4)
o with, in
BB mode
(Figure 9-9),
▪ two solid black vertical lines identifying the start and end of the last detected breath, also
identifying the two most recent expiratory time points and the corresponding minima of the
Plethysmogram
▪ a broken black vertical line identifying the end-inspiratory time point and the corresponding
maximum of the
Plethysmogram
within the last detected breath
o with, in
time-based modes
(Figure 9-10, Figure 9-11),
▪ two solid black vertical lines identifying the start and end of the most recent completed
Analysis Interval
of 15 seconds duration
▪ two broken black vertical lines identifying the minimum and maximum of the
Plethysmogram
within the
Analysis Interval
• RRi (either the -- an be calculated (9.6))
• the RRi trend where gaps if any - represent episodes during which no RRi value could be calculated.
A. If, as in the case of examples (a) and (b) in Table 8-1,
• the minima and maxima identified by the above mentioned broken black vertical lines and, hence, the
maximal
Lung Impedance
changes are mainly breathing-related,
• the
Plethysmogram
reflects a regular breathing pattern,
• breaths are frequently detected (respective markers only visible in
BB mode
)
• RRi is frequently available, and
• breathing pattern is unlikely to become less regular and/or weaker, then all three modes
are adequate with BB mode being recommended.
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