Methods and systems for exhalation control and trajectory optimization
This disclosure describes systems and methods for controlling pressure and/or flow during exhalation. The disclosure describes novel exhalation modes for ventilating a patient.
1. A method for controlling an exhalation phase during ventilation of a patient on a ventilator, the method comprising:
determining, by a ventilator, a pressure profile for a future exhalation phase, the pressure profile causing a decrease in an exhalation time of the future exhalation phase relative to a previous exhalation phase of the patient;
selecting the pressure profile for delivery to the patient; and
based on the selected pressure profile, controlling, by the ventilator, at least one of airway pressure and flow during the future exhalation phase.
2. The method of claim 1 , wherein determining the pressure profile is based on at least one criterion.
3. The method of claim 2 , wherein the at least one criterion is a nonlinear relationship between airway resistance and lung pressure and the airway pressure.
4. The method of claim 2 , wherein the at least one criterion is an exhalation pressure fall time parameter.
5. The method of claim 2 , wherein the at least one criterion is an actual rate of pressure decay.
6. The method of claim 5 , wherein the actual rate of pressure decay is defined by an exhalation pressure fall time parameter.
7. The method of claim 2 , wherein the at least one criterion is an amount of time that the patient takes to exhale a delivered volume of gas inspired by the patient.
8. The method of claim 2 , wherein the at least one criterion is a measured end inspiratory pressure.
9. The method of claim 2 , wherein the at least one criterion is a trajectory for the pressure profile calculated with an equation of p y =PEEP+(EIP−PEEP)e −αt ,
wherein the α is greater than zero and denotes an exhalation fall time parameter,
wherein the PEEP is a set positive end-expiratory pressure (PEEP),
wherein the EIP is a measured end expiratory pressure,
wherein the t is an exhalation time, and
wherein the P y is a pressure at a wye-fitting.
10. The method of claim 2 , wherein the at least one criterion is a predetermined pressure profile that comprises:
allowing pressure to fall below a set PEEP by a predetermined amount;
increasing the pressure after the pressure falls below the set PEEP to another pressure above the set PEEP by a set amount; and
subsequently allowing the another pressure above the set PEEP to fall to the set PEEP at a predetermined rate.
11. The method of claim 1 , wherein the pressure profile for the exhalation is associated with complete lung emptying.
12. The method of claim 11 , wherein determining the pressure profile is further based on a received PEEP.
13. The method of claim 12 , further comprising:
delivering a volume of gas to the patient for inspiration during ventilation on the ventilator,
wherein the exhalation by the patient includes exhaling at least 90% of the volume of gas delivered to the patient that was inspired by the patient.
14. A medical ventilator comprising:
a display;
a processor; and
memory storing instructions that, when executed by the processor, cause the ventilator to perform a set of operations comprising:
delivering at least one of airway pressure and flow based on a pressure profile during a current exhalation to a patient during ventilation on the ventilator;
modifying the pressure profile for a future exhalation based on a non-linear relationship between an airway resistance, a lung pressure, and an airway pressure to form a modified pressure profile, wherein the modified pressure profile maintains a received PEEP; and
based on the modified pressure profile, delivering at least one of a modified airway pressure and a modified flow to the patient during the future exhalation, wherein the modified pressure profile provides a decrease in an amount of time the patient takes to passively expire an inspired volume of gas for the future exhalation than a previous amount of time required by the patient to passively expire the inspired volume of gas during the current exhalation.
15. The medical ventilator of claim 14 , the set of operations further comprising:
monitoring at least one parameter during the current exhalation by the patient, wherein the at least one parameter is at least one of:
a time to exhale a predetermined percentage of the inspired volume;
a percent of the inspired volume or the elapsed time; and
a force expiratory volume in 1 second (FEV 1 ).
16. The medical ventilator of claim 15 , wherein the modified pressure profile is further based on the at least one parameter.
17. The medical ventilator of claim 14 , wherein the non-linear relationship is modeled based on a lung resistance equaling a nonlinear function between a first amount of a first pressure in an upper airways compartment of a lung and a second amount of a second pressure in a lower airways compartment of the lung.
18. The medical ventilator of claim 14 , wherein a trajectory of the modified pressure profile is an exponential decay from EIP to PEEP.
19. The medical ventilator of claim 14 , wherein the modified pressure profile further provides a decrease in an amount of time the patient takes to passively expire 90% of an inspired volume of gas than a previous amount of time required by the patient to passively expire 90% of the inspired volume of gas.
20. A medical ventilator comprising:
a display;
a processor; and
memory storing instructions that, when executed by the processor, cause the ventilator to perform a set of operations comprising:
determining, with a ventilator, a pressure profile for a future exhalation phase, the pressure profile causing a decrease in an exhalation time of the future exhalation phase relative to a previous exhalation phase of a patient;
selecting the pressure profile for delivery to the patient; and
based on the selected pressure profile, controlling, with the ventilator, at least one of airway pressure and flow during the future exhalation phase.