Configurable respiratory muscle pressure generator
Systems and methods are provided for etiologic-based breath simulation and/or ventilator test platforms that provide operator-configurable breathing patterns, patient respiratory muscular effort waveform characteristics and patient parameter values. According to one embodiment, multiple respiratory muscle effort waveform specifications, each of which have associated therewith one or more waveform parameters, are provided for use by a breathing effort generator. The waveform specifications include (i) a specification based upon an empirical model that approximates clinically-observed, patient-generated muscle pressures, (ii) a specification based on configurable etiology-driven templates and/or (iii) a specification based on a configurable piecewise trajectory template. A waveform engine of the breathing effort generator is configured in accordance with a selected waveform specification and corresponding waveform parameter values. Finally, the desired breathing pattern is simulated by a lung simulation system based on one or more model parameter values and a respiratory muscle effort waveform generated by the waveform engine.
1. A non-transitory machine-readable medium comprising instructions that, when executed by a processing unit of an electronic computing system, cause the processing unit to perform a method comprising:
providing a plurality of respiratory muscle effort waveform specifications for use by a breathing effort generator of a test platform, each of the plurality of respiratory muscle effort waveform specifications having associated therewith one or more waveform parameters, the plurality of respiratory muscle effort waveform specifications including each of (i) a first waveform specification based upon an empirical model that approximates clinically-observed, patient-generated muscle pressures, (ii) a second waveform specification based on configurable etiology-driven templates and (iii) a third waveform specification based on configurable piecewise trajectory templates;
wherein each configurable etiology-driven template comprises a generalized, case-specific template representing quantifiable patterns of breathing behavior associated with a respiratory disease; and wherein each configurable piecewise trajectory template comprises piecewise effort coordinates for configurable time differentials;
configuring a waveform engine of the breathing effort generator in accordance with (i) a selected waveform specification of the plurality of respiratory muscle effort waveform specifications and (ii) values for each of the one or more waveform parameters of the selected waveform specification; and
causing a desired breathing pattern to be simulated by a lung simulation system of the test platform based on ( 1 ) one or more model parameter values and (ii) a respiratory muscle effort waveform generated by the waveform engine.
2. The method of claim 1 , further comprising prompting an operator of the test platform to provide desired values for each of the one or more waveform parameters utilizing case-specific template menus.
3. The method of claim 1 , further comprising receiving information regarding one or more of patient size, ventilatory rate, rhythm, volume, flow, pressure, pattern, shape, compliance, airway resistance and other variables to generate a customized patient profile.
4. The method of claim 1 , further comprising providing a plurality of pre-programmed pathophysiologic profiles reflecting specific reproducible ventilatory patterns associated with common acute disease states.
5. The method of claim 1 , further comprising providing a plurality of pre-programmed patient profiles reflecting specific reproducible ventilatory patterns associated with patients in one or more categories including (i) normal spontaneous tidal ventilation, (ii) ventilatory drive abnormalities, (iii) increased airway resistance, (iv) compliance/elastance problems and (v) neuromuscular abnormalities.
6. The method of claim 1 , wherein the empirical model includes one or more periodic or semi-periodic functions.
7. The method of claim 6 , wherein the one or more periodic or semi-periodic functions include a periodic function for an inspiratory phase of respiration that approximates clinically-observed, inspiratory muscle pressures.
8. The method of claim 7 , wherein the periodic function for the inspiratory phase of respiration is generally expressed as:
P
mus
i
(
t
)
=
-
P
max
(
1
-
t
t
v
)
sin
(
π
t
t
v
)
where,
P max represents a maximum inspiratory pressure, which may be a constant or a time-varying parameter;
t v represents duration of inspiration; and
t represents an elapsed breath time varying between 0 and a total sum of inspiration and expiration periods.
9. The method of claim 8 , further comprising receiving information from an operator of the test platform indicative of the maximum inspiratory pressure, an amplitude multiplier for the inspiratory phase and the duration of inspiration.
10. The method of claim 6 , wherein the one or more periodic or semi-periodic functions include a periodic function for an expiratory phase of respiration that approximates clinically-observed, expiratory muscle pressures.
11. The method of claim 10 , wherein the periodic function for the expiratory phase of respiration is generally expressed as:
P
mus
e
(
t
)
=
P
max
(
t
t
v
)
sin
(
π
(
t
-
t
v
)
t
tot
-
t
v
)
where,
P max represents a maximum expiratory pressure, which may be a constant or a time-varying parameter;
t v represents duration of expiration;
t tot represents a total sum of inspiration and expiration periods; and
t represents an elapsed breath time varying between 0 and t tot .
12. The method of claim 11 , further comprising receiving information from an operator of the test platform indicative of the maximum expiratory pressure, an amplitude multiplier for the expiratory phase and the duration of expiration.
13. The method of claim 1 , wherein when the selected waveform specification comprises the third waveform specification, the method further comprises receiving information from an operator of the test platform indicative of desired inspiratory and expiratory effort trajectories.
14. The method of claim 13 , wherein the method further comprises smoothing out slope transitions between consecutive intervals defined by the piecewise effort coordinates.
15. A breathing effort generator comprising:
a storage device having stored therein one or more routines for causing a desired breathing pattern to be simulated by a lung simulation system; and
one or more processors operable to execute the one or more routines to generate a respiratory muscle effort waveform in accordance with a selected waveform specification of a plurality of respiratory muscle effort waveform specifications, the plurality of respiratory muscle effort waveform specifications include each of (i) a first waveform specification based upon an empirical model that approximates clinically-observed, patient-generated muscle pressures, (ii) a second waveform specification based on configurable etiology-driven templates and (iii) a third waveform specification based on configurable piecewise trajectory templates;
wherein each configurable etiology-driven template comprises a generalized, case-specific template representing quantifiable patterns of breathing behavior associated with a respiratory disease; and wherein each configurable piecewise trajectory template comprises piecewise effort coordinates for configurable time differentials.
16. The breathing effort generator of claim 15 , further comprising prompting an operator of the test platform to provide desired values for one or more waveform parameters utilizing case-specific template menus.
17. The breathing effort generator of claim 15 , wherein the selected waveform specification comprises the first waveform specification and the empirical model comprises a sinusoidal function for an inspiratory phase of respiration that approximates clinically-observed, inspiratory muscle pressures generally expressed as:
P
mus
i
(
t
)
=
-
P
max
(
1
-
t
t
v
)
sin
(
π
t
t
v
)
where,
P max represents a maximum inspiratory pressure, which may be a constant or a time-varying parameter;
t v represents duration of inspiration; and
t represents an elapsed breath time varying between 0 and a total sum of inspiration and expiration periods.
18. The breathing effort generator of claim 17 , wherein the empirical model further comprises a sinusoidal function for an expiratory phase of respiration that approximates clinically-observed, expiratory muscle pressures generally expressed as:
P
mus
e
(
t
)
=
P
max
(
t
t
v
)
sin
(
π
(
t
-
t
v
)
t
tot
-
t
v
)
where,
P max represents a maximum expiratory pressure, which may be a constant or a time-varying parameter;
T v represents duration of expiration;
t tot represents a total sum of inspiration and expiration periods; and
t represents an elapsed breath time varying between 0 and t tot .
19. The breathing effort generator of claim 15 , wherein when the selected waveform specification comprises the third waveform specification, information is received from an operator of the breathing effort generator indicative of desired inspiratory and expiratory effort trajectories.
20. The method of claim 1 , wherein the non-transitory machine-readable medium comprises at least one of: floppy diskettes, optical disks, compact disc read-only memories, magneto-optical disks, read-only memories, random access memories, erasable programmable read-only memories, electrically erasable programmable read-only memories, magnetic cards, optical cards, flash memory, MultiMedia Cards, and secure digital cards.