U.S. patent application number 10/588979 was filed with the patent office on 2011-05-05 for respiratory device and method for controlling a respiratory device.
Invention is credited to Christof Gobel, Bjorn Tiemann, Wolfgang WEDLER.
Application Number | 20110100365 10/588979 |
Document ID | / |
Family ID | 34832574 |
Filed Date | 2011-05-05 |
United States Patent
Application |
20110100365 |
Kind Code |
A1 |
WEDLER; Wolfgang ; et
al. |
May 5, 2011 |
Respiratory device and method for controlling a respiratory
device
Abstract
The invention relates to a respiratory device comprising a
respiratory gas source (20). a control unit (13) and a connecting
device for connecting to a respiratory mask. The control unit is
connected to at least one sensor (15) for detecting a measurement
parameter. The inventive method controls the respiratory device.
The control unit has a step generator (19) for specifying a stepped
modification of the pressure that.is generated by the respiratory
gas source. The sensor is configured to measure a signal that
corresponds to the pressure distribution and is coupled to an
analyser (18). The analyser evaluates the temporal distribution of
an analysis signal that is dependent on the measuring signal and
the step generator increases the pressure by a pressure step in a
respiratory cycle that follows the measuring evaluation, if the
analyser determines a deviation of the analysis signal from a limit
value after a predeterminable time limit has elapsed following the
pressure increase. The deviation must exceed a predeterminable
minimum differential in order to trigger a pressure increase.
Inventors: |
WEDLER; Wolfgang; (Hamburg,
DE) ; Tiemann; Bjorn; (Ahrensburg, DE) ;
Gobel; Christof; (Hamburg, DE) |
Family ID: |
34832574 |
Appl. No.: |
10/588979 |
Filed: |
December 7, 2004 |
PCT Filed: |
December 7, 2004 |
PCT NO: |
PCT/DE2004/002678 |
371 Date: |
May 21, 2010 |
Current U.S.
Class: |
128/204.23 ;
128/204.21 |
Current CPC
Class: |
A61M 16/0069 20140204;
A61M 16/0051 20130101; A61B 5/087 20130101; A61B 5/4836 20130101;
A61M 16/0057 20130101; A61M 16/06 20130101; A61M 2016/0036
20130101; A61M 16/0858 20140204; A61M 16/024 20170801 |
Class at
Publication: |
128/204.23 ;
128/204.21 |
International
Class: |
A61M 16/00 20060101
A61M016/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 10, 2004 |
DE |
10 2004 006 396.6 |
Claims
1. Ventilation device with a breathing gas source, a control unit,
and a connecting device for connecting the device to a ventilation
mask, where the control unit is connected to at least one sensor
for detecting a test parameter, wherein the control unit (1) has a
step generator (19) for determining an at least temporary,
essentially stepped change in the inspiratory pressure produced by
the breathing gas source (20); in that the sensor (15) is designed
to measure a signal corresponding to the change in pressure and is
connected to an analyzer (18), which evaluates the change over time
in an analysis signal dependent on the measuring signal; and in
that the step generator (19) increases the pressure by a pressure
step during a ventilation cycle following that in which measured
value was evaluated if, after a predetermined time limit has
elapsed following the pressure increase, the analyzer (18)
determines that the analysis signal deviates from a limit value by
more than a predetermined minimum difference.
2. Device according to claim 1, wherein the analyzer is designed to
evaluate the changes in the ventilation volume as an analysis
signal.
3. Device according to claim 1, wherein the analyzer (18) is
designed to analyze a flow curve as an analysis signal.
4. Device according to claim 1, wherein the analyzer (18) is
designed to detect a decrease in the maximum ventilation volume
from breath to breath at constant inspiratory pressure.
5. Device according to claim 1, wherein the analyzer (18) is
designed to detect a decrease in the flow occurring at a
predetermined time after a sudden pressure increase.
6. Device according to claim 1, wherein the sensor (15) is designed
as a flow sensor.
7. Device according to claim 1, wherein an integrator (17) is
connected downstream from the sensor (15).
8. Device according to claim 1, wherein the control unit (13)
lowers the pressure by a pressure step via the step generator (19)
the first time a reduction of the ventilation volume following a
pressure increase is not detected.
9. Device according to claim 1, wherein the control unit (13) is
connected to a setpoint memory for ventilation volume
setpoints.
10. Device according to claim 1, wherein the control unit (13) is
connected to a square-wave generator for defining the pressure
curves during the inspiration and expiration phases.
11. Device according to claim 1, wherein the control unit (13) is
connected to a curve generator for defining the pressure curves
during the inspiration and expiration phases.
12. Device according to claim 1, wherein the analyzer (18)
evaluates a pressure difference between the inspiration phases and
the expiration phases.
13. Device according to claim 1, wherein the step generator (19)
lowers the expiratory pressure to increase the pressure
difference.
14. Method for controlling a ventilator, in which a breathing gas
source is controlled by a control unit as a function of at least
one test parameter, wherein the control unit (13) produces an at
least temporary, essentially stepped change in the pressure
generated by the breathing gas source (20); in that the sensor (15)
detects a measuring signal corresponding to the change in pressure;
and in that the change over time in an analysis signal dependent on
the measuring signal is evaluated, and the inspiratory pressure is
increased in a subsequent ventilation cycle whenever the analysis
signal deviates from a limit value by a predetermined minimum
difference at a minimum of one predetermined time.
15. Method according to claim 14, wherein a decrease in the
ventilation volume relative to the ventilation volume observed
immediately after a pressure increase is detected, and in that the
control unit (13) increases the pressure precisely when the
decrease in the ventilation volume exceeds a predetermined minimum
difference after a predetermined time following the pressure
increase has elapsed.
16. Method according to claim 14, wherein, following an at least
approximate step-like pressure increase, the pressure curve
realized during the preceding breath is maintained if a decreasing
flow at essentially constant pressure is detected after a
predetermined time interval following the step-like pressure
increase.
17. Method according to claim 14, wherein the sensor (15) carries
out a flow measurement.
18. Method according to claim 15, wherein the volume signal is
produced by integration of the flow signal.
19. Method according to claim 14, wherein the pressure is lowered
by a pressure step the first time a decrease in the ventilation
volume following a pressure increase is not detected.
20. Method according to claim 14, wherein the control unit (13)
considers a target value for the ventilation volume.
21. Method according to claim 14, wherein the ventilation pressure
is controlled according to the course of a square-wave signal.
22. Method according to claim 14, wherein the ventilation pressure
is varied by the control unit (13) according to a predetermined
pressure curve.
23. Method according to claim 14, wherein a pressure difference
between the inspiratory and expiratory pressure is determined.
24. Method according to claim 14, wherein the pressure difference
is increased by lowering the expiratory pressure.
25. Method according to claim 14, wherein a pressure is changed
from ventilation cycle to ventilation cycle.
26. Method according to claim 14, wherein the pressure is held
constant for at least two successive inspiration phases.
27. Method according to claim 14, wherein the pressure is held
constant for at least two successive expiration phases.
28. Method according to claim 14, wherein the control unit (13)
decreases the pressure only when an actual value of the ventilation
volume exceeds the predetermined setpoint.
29. Method according to claim 14, wherein, in a first step, the
control unit (13) increases the pressure until the ventilation
volume reaches the predetermined setpoint, and in that an
additional pressure increase is then carried out.
30. Method according to claim 14, wherein an at least approximate
square-wave form pressure increase is selected for at least a
single breath.
31. Method according to claim 30, wherein the flow curve following
the stepped pressure increase is analyzed for the presence of an
increase to a maximum and a subsequent decelerating curve.
Description
[0001] The invention concerns a ventilation device with a breathing
gas source, a control unit, and a connecting device for connecting
the device to a ventilation mask, where the control unit is
connected to at least one sensor for detecting a test
parameter.
[0002] In addition, the invention concerns a method for controlling
a ventilator, in which a breathing gas source is controlled by a
control unit as a function of at least one test parameter.
[0003] A device of this type and the method for controlling the
ventilator can be used, for example, in connection with so-called
bi-level ventilation. The ventilator produces an inspiratory
pressure and an expiratory pressure. Basically, it is necessary to
distinguish among controlled ventilation, assisted ventilation, and
mixed forms of ventilation.
[0004] In controlled ventilation, the respiratory parameters during
inspiration are completely determined by the ventilator. There are
basically two forms of controlled ventilation, namely,
volume-controlled and pressure-controlled ventilation. In
volume-controlled ventilation, a well-defined tidal volume is
delivered breath by breath; the pressure can vary between the
respiratory strokes as a function of resistance. The basis for the
switch to the expiratory phase is the attainment of a predetermined
target volume or inspiration time. In pressure-controlled
ventilation, the therapeutic pressure is held constant. The
resulting volume can vary as a function of mechanical respiratory
parameters. The switch to the expiratory phase is controlled as a
function of time.
[0005] In volume-controlled ventilation, the administration of a
sufficient, well-defined gas volume per respiratory stroke is the
main consideration. Pressure-controlled ventilation has the
advantage that when the parameters are suitably adjusted, there are
no impermissible pressure peaks to damage lung tissue. Of course,
the administered tidal volume is strongly dependent on the
cooperation of the patient with respiration and on the mechanical
respiratory variables of resistance and lung compliance. On the
other hand, volume-controlled ventilation basically makes sense
primarily in the case of invasive ventilation, since leakage occurs
during mask ventilation, and such leakage makes it impossible to
measure the actual control parameter accurately, even when the
leakage that occurs is included in the calculations.
[0006] In pressure and volume-controlled ventilation, the
advantages of volume-controlled ventilation are combined with those
of pressure-controlled ventilation. The administered ventilation
volume depends on the mechanical properties of the lung and on the
ventilation pressure. If the volume falls below a preset value, the
inspiratory pressure is increased in small increments during the
following respiratory strokes until the target volume is
reached.
[0007] In assisted ventilation, the patient himself can determine
the times at which he inspires and expires. The ventilation strokes
of the apparatus are thus synchronized with the inspiratory and
expiratory effort of the patient. The ventilation strokes of the
apparatus are volume-controlled or pressure-controlled. In
assisted, pressure-controlled ventilation, the ventilator switches
between an inspiratory and an expiratory pressure level
synchronously with the respiratory effort of the patient.
[0008] Assisted ventilation in so-called S mode allows free
switching between inspiratory and expiratory pressure (IPAP, EPAP),
depending on the breaths initiated by the patient (triggered by
spontaneous respiration).
[0009] In assisted ventilation in so-called ST mode, the ST mode
describes a mixed form of support of spontaneous respiration (S
mode) and mandatory ventilation. A background respiratory rate is
determined, by which the minimum gap between respiratory intervals
is defined. It is possible for the patient to trigger an
inspiration within these intervals (from an expiratory phase),
i.e., to switch into IPAP by respiratory effort. If the patient
fails to trigger an inspiration before the maximum allowed gap is
reached, as defined by the background respiratory rate, the
ventilator triggers the switch to the inspiratory pressure level to
provoke a breath of the patient. This mode also allows mandatory
respiration, during which the patient can demand additional
breaths.
[0010] In another ventilation method, the patient triggers the
switch to inspiratory pressure by his respiratory effort. However,
he no longer has any freedom with respect to expiration. After a
determined inspiratory time, an automatic switch to the expiratory
pressure level occurs.
[0011] The objective of the present invention is to design a device
of the aforementioned type in such a way that during the
inspiration phases, the ventilator generates a pressure in such a
way that the ventilator performs the greatest possible portion of
the respiratory work.
[0012] In accordance with the invention, the solution of this
problem is characterized in that [0013] the control unit has a step
generator for predetermining an at least temporary, essentially
stepped change in the inspiratory pressure produced by the
breathing gas source; in that [0014] the sensor is designed to
measure a signal corresponding to the change in pressure and is
connected to an analyzer, which evaluates the change over time in
an analysis signal dependent on the measuring signal; and in that
[0015] the step generator increases the pressure by a pressure step
during a ventilation cycle following that in which the measured
value was evaluated if, after a predetermined time limit has
elapsed following the pressure increase, the analyzer determines
that the analysis signal deviates from a limit value by more than a
predetermined minimum difference.
[0016] A further objective of the present invention is to improve a
method of the aforementioned type in a way that supports optimum
apparatus control.
[0017] In accordance with the invention, the solution of this
problem is characterized in that the control unit produces an at
least temporary, essentially stepped change in the pressure
generated by the breathing gas source; in that the sensor detects a
measuring signal corresponding to the change in pressure; in that
the change over time in an analysis signal dependent on the
measuring signal is evaluated; and in that the inspiratory pressure
is increased in a subsequent ventilation cycle if the analysis
signal deviates from a limit value by a predetermined minimum
difference at a minimum of one predetermined time.
[0018] The stepped change in the inspiratory pressure and the
corresponding evaluation of the analysis signal make it possible,
during the performance of the ventilation, to control the apparatus
in such a way that precisely the desired relief of the patient from
respiratory work is achieved. This ensures, first, that the relief
from respiratory work is not too small and, second, that the
ventilator is prevented from generating unnecessarily high
pressures.
[0019] The invention can basically be realized by two different
variants of the method. In accordance with a first variant of the
method, the ventilation volume is incrementally increased between
one breath and the next, starting from an initial state. This also
includes the idea of initially generating the same inspiratory
pressure over the course of several successive breaths and then,
depending on an evaluation of the analysis signal, i.e., if the
triggering condition for a pressure increase is detected, of
providing a higher pressure for one or again several successive
ventilation cycles.
[0020] In the first variant of the method, the use of a measuring
instrument to detect a possible decrease in a maximum value of the
ventilation volume after a previous pressure increase makes it
possible to determine whether the patient's spontaneous activity is
contributing to the respiratory volume. After the pressure has been
increased, the patient at first typically continues his own
respiratory work at the same level, so that the respiratory volume
produced by the apparatus and the respiratory volume produced by
the patient are additive. After a certain reaction time, the
patient then automatically reduces his spontaneous activity, so
that a decrease in the ventilation volume can be detected by
measurement. The decrease can occur, for example, incrementally or
successively.
[0021] After a pressure increase, the ventilation pressure is
typically maintained at a constant level for several ventilation
cycles, and the time interval after which a possible volume
reduction is evaluated automatically extends over several
ventilation cycles of inspiratory and expiratory phases. If the
patient has completely stopped his own breathing activity, no
decrease in the ventilation volume relative to the response volume
that develops will be detected after a pressure increase, since
there is no activity of the patient's own which can be reduced, and
ventilation will be completely determined by the ventilator. The
maximum value of the ventilation volume during the first
ventilation cycle following the pressure increase can be used here
as the limit value with which the maximum value of the ventilation
volume is compared during the ventilation cycles following the
pressure increase.
[0022] In accordance with a second variant of the method of the
invention, ventilation is carried out during the vast majority of
breaths with a standard ventilation pressure curve, in which the
slope of the pressure as a function of time decreases over the
course of breaths during the inspiration phase, after which, at the
end of the inspiration phase, there is a relatively steep drop to
the expiration pressure, which is essentially constant during the
expiration phase. Pressure curves by which the pressure is
increased in stepwise fashion for one or more breaths and have a
more or less square-wave form are then incorporated into this
sequence of standard ventilation pressure curves.
[0023] If a detected flow curve approximately follows the
square-wave pressure curve over at least most of the inspiration
phase, then active patient breathing is occurring. If, after an
increase of the flow curve following the stepped increase in
pressure, there is a decline in the flow volume while the applied
pressure continues at a constant level, this is a sign of a passive
lung of the patient. When a flow curve of this type is detected for
the first time after a stepwise pressure increase, the sought-for
pressure level for relieving the patient from respiratory work has
just been found.
[0024] The use of sensors of simple design is facilitated by
designing the sensor as a flow sensor.
[0025] To determine a signal for the ventilation volume without
direct volume measurement, it is proposed that an integrator be
connected downstream from the sensor.
[0026] The automatic control can be optimized by designing the
control unit to lower the pressure by a pressure step via the step
generator the first time a decrease in the ventilation volume
following a pressure increase is not detected. Expanded
functionality is achieved by connecting the control unit to a
setpoint memory for the setpoints of the ventilation volume.
[0027] In a typical control sequence, the control unit is connected
to a square-wave generator for defining the pressure curves during
the inspiration and expiration phases.
[0028] To generate individually adapted pressure curves, it is also
proposed that the control unit be connected to a curve generator
for defining the pressure curves during the inspiration and
expiration phases.
[0029] Standardized signal processing is facilitated if the
analyzer evaluates the pressure difference between the inspiration
phases and the expiration phases.
[0030] According to another variant of automatic pressure control,
the step generator lowers the expiratory pressure to increase the
pressure difference.
[0031] It is easier to carry out ventilation with a well-defined
volume curve if the control unit uses setpoints to adjust the
ventilation volume.
[0032] In an advantageous variant of the automatic control, the
control unit calls for a pressure decrease only when an actual
value of the ventilation volume exceeds the given setpoint.
[0033] It is also proposed that, in a first step, the control unit
increase the pressure until the ventilation volume reaches the
predetermined setpoint, and that the pressure then be increased
again.
[0034] Another automatic control variant is defined by the fact
that an at least approximately square-wave form pressure increase
is selected for at least a single breath.
[0035] In particular, it is possible for the flow curve following
the stepped pressure increase to be analyzed for the presence of an
increase to a maximum and a subsequent deceleration.
[0036] The drawings show schematic illustrations of specific
embodiments of the invention.
[0037] FIG. 1 shows a perspective view of a ventilator with a
connecting hose running to a ventilation mask.
[0038] FIG. 2 is a schematic diagram of the essential functional
components.
[0039] FIG. 3 shows a graph of pressure as a function of time and a
graph of volume as a function of time with envelopes for the actual
curves.
[0040] FIG. 4 shows a graph of volume as a function of time after a
pressure increase with actual volume values measured from breath to
breath in the presence of spontaneous patient breathing
activity.
[0041] FIG. 5 shows graphs in greater detail than FIG. 3 with a
series of several successive ventilation cycles at the same
inspiratory pressure.
[0042] FIG. 6 shows curves of pressure and flow as a function of
time with preselection of a rectangular pressure increase for an
individual breath.
[0043] FIG. 1 shows the basic design of a ventilation device. In
the area of the unit housing (1), which has a control panel (2) and
a display (3), a breathing gas pump is installed in an internal
space in the unit. A connecting hose (5) is attached to a socket
(4). An additional pressure-measuring hose (6), which can be
connected to the unit housing (1) by a pressure input connection
(7), can run along the connecting hose (5). To allow data
transmission, the unit housing (1) has an interface (8).
[0044] An expiratory device (9) is installed in an expanded area of
the connecting hose (5) at the end facing away from the unit
housing (1). An expiratory valve can also be used.
[0045] FIG. 1 also shows a ventilation mask (10), which is designed
as a nasal mask. In another embodiment, it is also possible to use
a full-face mask. The mask can be held in place on the patient's
head by a head fastening device (11). A hose connector (12) is
provided in the expanded region of the ventilation mask (10) on the
side facing the connecting hose (5).
[0046] FIG. 2 shows the basic design of the automatic control
components of the ventilation device. A control unit (13) is
provided with an input module (14) for data input. The desired
ventilation values can be entered by a physician, for example, via
the input module (14). The control unit (13) is connected to a
sensor (15), which detects at least one ventilation parameter of a
patient.
[0047] In the illustrated embodiment, the sensor (15) is designed
as a flow sensor, which sends its measuring signal to an integrator
(17) to determine a volume value. The integrator (17) is connected
to an analyzer (18) for evaluating the volume curve. The analyzer
(18) is also supplied with a volume reference value stored in the
setpoint memory (16). In addition, the analyzer (18) is connected
to a step generator (19), which defines a given nominal pressure
for the breathing gas source.
[0048] The automatic control sequence is further explained by the
graphs in FIG. 3. The illustrated curves are each envelopes for the
actual pressure and volume curves obtained as a function of the
given ventilation rate. To begin with, it is apparent that, when
the first pressure increases are effected, there are also sudden
increases in the ventilation volume. After each increase, the
ventilation volume decreases again. This system behavior is
characteristic of a patient with some remaining spontaneous
activity. After the fourth pressure increase shown in the drawing,
however, the ventilation volume remains at the high level that was
reached. This is the result of the cessation of the spontaneous
activity of the patient that has already occurred at this point. To
help optimize the operation of the apparatus, the ventilation
pressure produced can thus be dropped back a step.
[0049] FIG. 4 shows the measured ventilation volume from breath to
breath for a patient who is still showing spontaneous activity. The
graph shows that after an initial sudden increase in the
ventilation volume following a pressure increase, the ventilation
volume returns approximately to its initial value. The values
actually measured are scattered within a tolerance range around a
decreasing curve similar to an exponential function.
[0050] FIG. 5 shows the pressure curves represented as envelopes in
FIG. 3 in greater detail. The graphs show that the same inspiratory
pressures are specified several times in a row. When spontaneous
patient activity is still present, the peak values of the analysis
signal decrease from breath to breath in the corresponding volume
curves. When the pressure reaches a level high enough that all of
the patient's work is being done for him, the analysis signal
remains at approximately the same maximum value from breath to
breath.
[0051] Alternatively or additionally to the measurement of a test
parameter corresponding to the volume curve, it is also possible,
when ventilation is being carried out with a pressure curve that
deviates from the square-wave form, to specify an at least
approximately square pressure increase for an individual breath and
to measure the flow that develops. This possibility is shown in
FIG. 6. In the absence of spontaneous respiratory activity of the
patient, the flow will increase rapidly to a maximum and then
decelerate as the result of a passive lung. If this flow behavior
is not present, the analyzer (18) will conclude that the patient is
actively breathing.
[0052] In particular, when there is definite deviation from this
flow behavior, it can be concluded that there is a high degree of
spontaneous activity of the patient.
* * * * *