Respirator and method for determining a fresh gas flow
A respirator ( 1 ) includes a fresh gas port ( 23, 25, 27 ) for connecting a fresh gas supply, a gas outlet ( 3 ) for connecting a supply line for a patient, an absolute pressure sensor ( 21 ) and a data processor ( 37 ). The gas outlet and the fresh gas port are fluidically connected via an inhalation branch ( 17 ) that is connected to the absolute pressure sensor. The fresh gas port has an adjusting valve ( 31 ), to set gas flow from the fresh gas supply to the inhalation branch, and a differential pressure sensor ( 33 ). The differential pressure sensor determines a differential pressure in the fresh gas port between the inhalation branch and the adjusting valve. The data processor receives and records the absolute pressure measured and the differential pressure to determine a fresh gas flow through the fresh gas port. A method for determining a fresh gas flow is also shown and described.
1. A respirator comprising:
a fresh gas port for connecting a fresh gas supply, the fresh gas port comprising an adjusting valve and a differential pressure sensor;
an inhalation branch, a gas flow from the fresh gas supply to the inhalation branch being set via the adjusting valve, the differential pressure sensor being arranged and configured to measure a differential pressure in the fresh gas port between the inhalation branch and the adjusting valve;
a gas outlet for connecting a supply line for a patient, the gas outlet being connected fluidically with the fresh gas port via the inhalation branch;
an absolute pressure sensor arranged to measure an absolute pressure in the inhalation branch;
a data processor connected with the absolute pressure sensor and connected with the differential pressure sensor to receive and record the absolute pressure measured by the absolute pressure sensor at a plurality of times and to receive and record the differential pressure measured by the differential pressure sensor at a plurality of times, wherein the data processor is configured to determine a fresh gas flow through the fresh gas port at a defined time from the differential pressure measured at the defined time, from the absolute pressure measured at the defined time and from one or more absolute pressures measured at times chronologically preceding the defined time.
2. A respirator in accordance with claim 1 , further comprising at least one additional fresh gas port connected with the gas outlet via the inhalation branch and configured for connecting a fresh gas supply, the at least one additional fresh gas port comprising an adjusting valve and a differential pressure sensor, wherein:
a gas flow from a fresh gas supply connected to the at least one additional fresh gas port to the inhalation branch is set by the at least one additional fresh gas port adjusting valve;
the at least one additional fresh gas port differential pressure sensor is arranged and set up to measure a differential pressure in the at least one additional fresh gas port between the at least one additional fresh gas port adjusting valve and the inhalation branch;
the data processor is connected with the at least one additional fresh gas port differential pressure sensor to receive and record the differential pressure measured by the at least one additional fresh gas port differential pressure sensor at a plurality of times; and
the data processor is configured to determine a fresh gas flow through the at least one additional fresh gas port from the differential pressure measured at the defined time by the at least one additional fresh gas port differential pressure sensor, from the absolute pressure determined at the defined time and from one or more absolute pressures measured at times chronologically preceding the defined time.
3. A respirator in accordance with claim 1 , wherein:
the data processor is configured to determine a mean value of the absolute pressure for each time at which an absolute pressure is measured from absolute pressures measured at a plurality of times chronologically preceding the defined time; and
the data processor is configured to determine the fresh gas flow or fresh gas flows from the mean values of the absolute pressure, which mean values are determined for such times, at which an absolute pressure was measured, which is included in the determination of the fresh gas flow or fresh gas flows.
4. A respirator in accordance with claim 3 , wherein the data processor is configured to determine the fresh gas flow or fresh gas flows from differences of the absolute pressures and of the mean values of the absolute pressure measured and determined for the same times.
5. A respirator in accordance with claim 1 , wherein the data processor is configured to determine a corrected fresh gas flow from a corrected differential pressure, wherein the corrected differential pressure is determined by a transfer function from the measured differential pressure and the absolute pressures influencing the determination of the fresh gas flow.
6. A respirator in accordance with claim 5 , wherein the transfer function has the form of
d
P
corr
(
z
)
=
d
P
(
z
)
-
b
1
P
~
(
z
)
+
b
2
P
~
(
z
-
1
)
+
b
3
P
~
(
z
-
2
)
a
1
P
~
(
z
)
+
a
2
P
~
(
z
-
1
)
+
a
3
P
~
(
z
-
2
)
,
wherein z is the defined time, dP(z) is the differential pressure at the time z, dP corr (z) is the corrected differential pressure at the time z, {tilde over (P)}(z) is the difference from the absolute pressure measured for the time z and the mean value of the absolute pressure determined for the time z, z−1 and z−2 being times preceding the defined time z, and a 1 , a 2 , a 3 , b 1 , b 2 and b 3 are coefficients.
7. A respirator in accordance with claim 2 , wherein the data processor is configured to determine a corrected fresh gas flow or corrected fresh gas flows from a corrected differential pressure or corrected differential pressures, wherein the corrected differential pressure or corrected differential pressures is/are determined by a transfer function from the measured differential pressure or measured differential pressures and the absolute pressures influencing the determination of the respective fresh gas flow.
8. A respirator in accordance with claim 1 , wherein:
the adjusting valve is a mechanical adjusting valve, adjusted manually by a user of the respirator; and
the data processor comprises a display device, on which the previously determined fresh gas flow or previously determined fresh gas flows can be displayed for the user of the respirator.
9. A respirator in accordance with claim 2 , wherein:
the adjusting valves are each mechanical adjusting valves, adjusted manually by a user of the respirator; and
the data processor comprises a display device, on which the previously determined fresh gas flow or previously determined fresh gas flows can be displayed for the user of the respirator.
10. A method for determining a fresh gas flow at a defined time through a fresh gas port of a respirator from a differential pressure and a plurality of absolute pressures, which are measured at different times, the method comprising:
providing the fresh gas port of the respirator with an adjusting valve with which a fresh gas flow through the fresh gas port is set;
connecting the fresh gas port, at least in some sections, with a respirator gas outlet via an inhalation branch for connecting a supply line for a patient;
measuring a differential pressure between the adjusting valve of the fresh gas port and an inhalation branch of the respirator,
measuring an absolute pressure in the inhalation branch; and
determining a fresh gas flow for the defined time from the differential pressure measured at the defined time, from the absolute pressure measured for the defined time and from at least one absolute pressure measured for a time chronologically preceding the defined time.
11. A method in accordance with claim 10 , wherein:
a mean value of the absolute pressure is determined from the absolute pressures that were measured at a plurality of times preceding the defined time for each time at which an absolute pressure taken into account in the determination of the fresh gas flow was measured; and
the fresh gas flow is additionally determined from the mean values of the absolute pressure, which mean values were determined for such times at which an absolute pressure, which is included in the determination of the fresh gas flow or fresh gas flows, was measured.
12. A method in accordance with claim 11 , wherein the fresh gas flow is determined from the differences of the absolute pressures and the mean values of the absolute pressure, which were measured or determined for the same times.
13. A method in accordance with claim 10 , wherein a corrected fresh gas flow is determined from a corrected differential pressure, wherein the corrected differential pressure is determined by means of a transfer function from the measured differential pressure and the absolute pressures that are included in the determination of the fresh gas flow.
14. A method in accordance with claim 13 , wherein the transfer function has the form of
d
P
corr
(
z
)
=
d
P
(
z
)
-
b
1
P
~
(
z
)
+
b
2
P
~
(
z
-
1
)
+
b
3
P
~
(
z
-
2
)
a
1
P
~
(
z
)
+
a
2
P
~
(
z
-
1
)
+
a
3
P
~
(
z
-
2
)
,
wherein z is the defined time, dP(z) is the differential pressure at the time z, dP corr (z) is the corrected differential pressure at the time z, {tilde over (P)}(z) is the difference from the absolute pressure measured for the time z and the mean value of the absolute pressure determined for the time z, z−1 and z−2 being times preceding the defined time z, and a 1 , a 2 , a 3 , b 1 , b 2 and b 3 are coefficients.