Methods for controlling mechanical lung ventilation
A ventilator includes electronic control circuitry configured to control a supply of breathing gas for a plurality of respiratory cycles, measure a volume received by the patient in each of the plurality of respiratory cycles, and determine, for each cycle of the plurality of respiratory cycles, a cycle score corresponding to a deviation between the volume of the cycle and a predetermined target volume. The determined cycle score can be selected from a predetermined number of cycle scores that span positive and negative numbers based on the deviation. A pressure step value can be determined based on a plurality of cycle scores corresponding to the plurality of respiratory cycles, and a current pressure of the breathing gas is adjusted by an amount corresponding to the determined pressure step value. The pressure step value may be generated by dividing a sum of the plurality of cycle scores by a sample size.
1. A system for controlling lung ventilation, the system comprising:
one or more processors; and
a memory including instructions that, when executed by the one or more processors, cause the one or more processors to perform operations comprising:
receiving at least one of a flow signal and a pressure signal from one or more transducers associated with a supply of a breathing gas to a patient airway connector;
measuring, based on the received at least one signal, a volume received by the patient airway connector during a plurality of respiratory cycles;
determining, for each cycle of the plurality of respiratory cycles, a deviation between the volume of the cycle and a predetermined target volume;
determining a plurality of cycle scores comprising, for each cycle of the plurality of respiratory cycles, a cycle score that represents a range of values that includes the deviation between the volume of the cycle and the predetermined target volume;
selecting a predetermined step value based on a function of the plurality of cycle scores being within a predetermined range of values that correspond to the predetermined step value; and
adjusting the breathing gas supplied to the patient airway connector based on the selected step value.
2. The system of claim 1 , wherein each determined cycle score is selected from a predetermined number of cycle scores that span positive and negative numbers based on the deviation.
3. The system of claim 1 , wherein a number of the plurality of respiratory cycles for which cycle scores are determined is automatically calculated based on a measurement of variability of breathing.
4. The system of claim 1 , wherein the plurality of respiratory cycles is a sample size of a larger plurality of respiratory cycles in which the breathing gas is supplied to the patient airway connector, and wherein
the step value is based on summing the plurality of cycle scores and dividing a result of the summing by the sample size.
5. The system of claim 4 , wherein, for each cycle of the plurality of respiratory cycles, the cycle score is determined based on which range of a first predetermined number of ranges that the volume of the cycle lies within, each range of the first predetermined number of ranges being based on the predetermined target volume.
6. The system of claim 5 , wherein the step value is selected based on which range of a predetermined number of second value ranges that an outcome of the dividing lies within, the predetermined number of second value ranges spanning positive and negative numbers.
7. The system of claim 4 , further comprising:
determining a Coefficient of Variation; and
determining the sample size based at least partially on the Coefficient of Variation, the Coefficient of Variation determined as follows:
CV
=
Std
M
,
where
:
a
CV
=
Coefficient
of
Variation
;
and
Std
=
∑
(
Vt
-
M
)
2
(
Nt
-
1
)
,
2
where
:
Vt
=
Tidal
volume
of
each
cycle
;
M
=
Mean
of
all
measured
tidal
volumes
;
and
Nt
=
Test
sample
size
(
number
of
cycles
)
.
8. The system of claim 7 , further comprising attributing the sample size based at least partially on the Coefficient of Variation and on a patient category.
9. The system of claim 4 , wherein the sample size is a user adjustable value set based on a patient's inspiratory effort and associated variability, or set based on a patient condition.
10. The system of claim 1 , wherein the plurality of respiratory cycles are controlled by pressure, selecting the predetermined step value comprises selecting a pressure step value, and adjusting the breathing gas comprises adjusting a pressure of the breathing gas supplied to the patient airway connector by an amount corresponding to the selected pressure step value.
11. A ventilator, comprising:
electronic control circuitry configured to:
receive at least one of a flow signal and a pressure signal from one or more transducers associated with a supply of a breathing gas to a patient airway connector;
measure, based on the received at least one signal, a volume received from a patient airway connector during a plurality of respiratory cycles;
determine, for each cycle of the plurality of respiratory cycles, a deviation between the volume of the cycle and a predetermined target volume;
determine a plurality of cycle scores comprising, for each cycle of the plurality of respiratory cycles, a cycle score that represents a range of values that includes the deviation between the volume of the cycle and the predetermined target volume;
select a predetermined step value based on a function of the plurality of cycle scores being within a predetermined range of values that correspond to the predetermined step value; and
adjust the breathing gas supplied to the patient airway connector based on the selected step value.
12. The ventilator of claim 11 , wherein each determined cycle score is selected from a predetermined number of cycle scores that span positive and negative numbers based on the deviation.
13. The ventilator of claim 11 , wherein a number of the plurality of respiratory cycles for which cycle scores are determined is automatically calculated based on a measurement of variability of breathing.
14. The ventilator of claim 11 , wherein the plurality of respiratory cycles is a sample size of a larger plurality of respiratory cycles in which the breathing gas is supplied to the patient airway connector, and wherein
the step value is based on summing the plurality of cycle scores and dividing a result of the summing by the sample size.
15. The ventilator of claim 14 , wherein, for each cycle of the plurality of respiratory cycles, the cycle score is determined based on which range of a first predetermined number of ranges that the volume of the cycle lies within, each range of the first predetermined number of ranges being based on the predetermined target volume.
16. The ventilator of claim 15 , wherein the step value is selected based on which range of a predetermined number of second value ranges that an outcome of the dividing lies within, the predetermined number of second value ranges spanning positive and negative numbers.
17. The ventilator of claim 14 , further comprising:
determining a Coefficient of Variation; and
determining the sample size based at least partially on the Coefficient of Variation, the Coefficient of Variation determined as follows:
CV
=
Std
M
,
where
:
a
CV
=
Coefficient
of
Variation
;
and
Std
=
∑
(
Vt
-
M
)
2
(
Nt
-
1
)
,
2
where
:
Vt
=
Tidal
volume
of
each
cycle
;
M
=
Mean
of
all
measured
tidal
volumes
;
and
Nt
=
Test
sample
size
(
number
of
cycles
)
.
18. The ventilator of claim 17 , further comprising attributing the sample size based at least partially on the Coefficient of Variation and on a patient category.
19. The ventilator of claim 14 , wherein the sample size is a user adjustable value set based on a patient's inspiratory effort and associated variability, or set based on a patient condition.
20. The ventilator of claim 11 , wherein the plurality of respiratory cycles are controlled by pressure, selecting the predetermined step value comprises selecting a pressure step value, and adjusting the breathing gas comprises adjusting a pressure of the breathing gas supplied to the patient airway connector by an amount corresponding to the selected pressure step value.