We claim:
1. A medical probe device comprising a catheter having a control end and a probe end, the probe end including a stylet guide housing having at least one stylet port in a side thereof and stylet guide means for directing a flexible stylet outward through at least one stylet port and through intervening tissue to a target tissue, a stylet positioned in at least one of said stylet guide means, the stylet comprising an electrical conductor enclosed within a non-conductive sleeve, the electrical conductor being a radiofrequency electrode.
2. A medical probe device of claim 1 wherein the non-conductive sleeve is mounted for longitudinal movement on the electrical conductor to expose a selected portion of the electrical conductor surface in the target tissue.
3. A medical probe of claim 1 wherein the electrode is a tube having an axial lumen extending therethrough.
4. A medical probe of claim 3 wherein a solid wire is disposed in the axial lumen for longitudinal movement therein.
5. A medical probe of claim 1 wherein the stylet guide housing includes at least two of said stylet ports.
6. A medical probe of claim 1 wherein the stylet guide housing includes two of said stylet ports positioned approximately in a plane perpendicular to the central axis of the housing.
7. A medical probe of claim 1 wherein a ultrasound reflecting means or an ultrasound transponder means is positioned in the distal end of the catheter for providing a signal indicating the position of the catheter in the body.
8. A medical probe of claim 1 including a temperature sensor means mounted on the stylet guide housing for indicating the temperature in the tissue adjacent to the guide housing.
9. A medical probe of claim 1 including an ultrasound transponder means mounted on the distal end of the non-conductive sleeve for emitting a signal indicating the position of the stylet in the body.
10. A medical probe of claim 1 including a temperature sensor means mounted on the distal end of the non-conductive sleeve for indicating the temperature of tissue at the distal end of the sleeve.
11. A medical probe of claim 1 wherein the electrical conductor is a highly flexible metal.
12. A medical probe of claim 11 wherein the highly flexible metal is nickel-titanium alloy.
13. A medical probe of claim 1 wherein the stylet guide means defines a stylet path from an axial orientation in the catheter through a curved portion to a lateral orientation at the stylet port.
14. A medical probe of claim 13 wherein the curved portion has a radius which is sufficient to permit sliding deployment of the stylet in the stylet guide and deflect the stylet during deployment to the desired angle.
15. A medical probe of claim 14 wherein the curved portion has a radius of up to 0.5 cm.
16. A medical probe of claim 15 wherein the stylet guide means defines a stylet path having a first curved portion extending in a direction away from the stylet port and a second curved portion, continuing from the first curved portion and extending to the stylet port.
17. A medical probe of claim 13 wherein the stylet guide means defines at least two non-intersecting stylet paths from parallel axial orientations in the catheter through curved portions to lateral orientations at stylet ports having central axes forming an angle of up to 180.
18. A medical probe of claim 17 wherein the angle is less than 180.
19. A medical probe of claim 17 wherein the angle is less than 90.
20. A medical probe of claim 17 in combination at least one grounding plate, the grounding plate being adapted to draw electrical current passing from the electrodes through target tissue to be ablated.
21. A medical probe of claim 13 wherein the stylet guide means defines at least four non-intersecting stylet paths from parallel axial orientations in the catheter through curved portions to lateral orientations at stylet ports extending outward at approximately 90 interval directions about the axis of the catheter.
22. A medical probe of claim 1 wherein the nonconductive sleeve comprises a leading tip, a rigid proximal control section, and a flexible portion extending from the leading tip to the rigid proximal control section, enabling the sleeve to be extended through a curved path from an axial orientation to an orientation extending outward through a stylet port.
23. A medical probe of claim 22 wherein the leading tip is tapered inward to converge toward its terminal end.
24. A medical probe of claim 22 wherein the flexible portion comprises a spiral coil or wire braid.
25. A medical probe of claim 24 wherein the flexible portion is made of conductive material enclosed in an outer non-conductive material.
26. A medical probe of claim 1 wherein the electrical conductor has a sharp blade tip.
27. A medical probe of claim 26 wherein the distal portion of the sharp blade tip defines a shoulder, and the distal end of the sleeve tapers -inward to a tip having a diameter that does not significantly exceed the thickness of the shoulder.
28. A medical probe of claim 1 wherein the distal portion of the catheter is more flexible than the proximal portion thereof, facilitating its passage through curved ducts.
29. A medical prove of claim 28 wherein the more flexible portion of the catheter comprises a spiral coil, wire braid or slotted tube having a smooth outer layer.
30. A medical probe of claim 1 comprising a control handle attached to the control end of the catheter, and stylet movement means attached to a stylet and engaging the handle for longitudinal movement of the stylet in the stylet guide means.
31. A medical probe of claim 30 wherein the stylet movement means comprises manual engagement means for translating manual motion into longitudinal motion of the stylet in the stylet guide means.
32. A medical probe of claim 2 comprising a control handle attached to the control end of the catheter, a non-conductive sleeve movement means attached to a non-conductive sleeve and an electrical conductor movement means attached to the electrical conductor enclosed therein, the non-conductive sleeve movement means comprising means for translating manual motion into longitudinal motion of the non-conductive sleeve in the stylet guide means, the electrical conductor movement means comprising means for translating manual motion into longitudinal motion of the electrical conductor in the non-conductive sleeve, the non-conductive sleeve movement means and the electrical conductor movement means engaging the handle for movement thereon.
33. A medical probe of claim 32 wherein the non-conductive sleeve movement means and the electrical conductor movement means include separate, adjacent manual movement means mounted on the handle for both separate and coordinated movement thereon.
34. A medical probe of claim 32 wherein the control handle has at least two parallel longitudinal slots through a wall thereof, the manual movement means each including a finger engaging surface connected to a slide extending through one of the longitudinal slots to a connector in the interior of the housing, the connector being attached to a respective non-conductive sleeve or electrical conductor.
35. A medical probe device comprising a catheter having a control end and a probe end, the probe end including a stylet guide housing having at least one stylet port in a side wall thereof and guide means for directing a flexible stylet outward through the stylet port and through intervening tissue to a target tissue.
36. A medical probe of claim 35 wherein the stylet is directed outward at an angle in a plane through the central axis of the catheter housing of from about 200 to 1600 with the central axis of the stylet guide housing.
37. A medical probe of claim 35 wherein the catheter includes a stylet guide lumen communicating with the stylet port and a stylet positioned in said stylet guide lumen for longitudinal movement from the port through intervening tissue to a target tissue.
38. A medical probe of claim 35 wherein the stylet is an electrical conductor enclosed within a non-conductive layer, the electrical conductor being a radiofrequency electrode.
39. A medical probe of claim 38 wherein the nonconductive layer is a sleeve which is longitudinally moveable on the electrical conductor to expose a selected portion of the electrical conductor surface in the target tissue.
40. A medical probe of claim 35 wherein the stylet is a microwave antenna.
41. A medical probe of claim 35 wherein the stylet is a cannula having an axial treatment fluid supply lumen extending therethrough and the catheter has a treatment fluid transport lumen communicating with the treatment fluid supply lumen.
42. A medical probe of claim 35 wherein the stylet guide housing includes an array of said stylet ports.
43. A medical probe of claim 35 wherein the catheter includes an inflation fluid delivery lumen extending therethrough, and the probe end includes at least one inflatable balloon in communication with the inflation fluid delivery lumen.
44. A medical probe of claim 43 wherein the inflatable balloon is an annular dilation stabilizer balloon means for expanding outwardly against a duct wall and is positioned adjacent a stylet port.
45. A medical probe of claim 35 wherein an ultrasound transponder is attached to a distal end of the stylet.
46. A medical probe of claim 35 wherein an ultrasound transducer is attached to a distal end of the probe.
47. A medical probe of claim 35 wherein the stylet includes a radiofrequency electrode or microwave antenna, and at least one temperature sensor is attached to at least one of the probe end, stylet guide housing and stylet.
48. A medical probe of claim 47 wherein the temperature sensor is a thermistor, thermocouple or fiber optic cable.
49. A medical probe of claim 35 wherein the stylet comprises a fiber optic cable means for laser treatment.
50. A method for medical treatment of a tissue mass comprising:
a) introducing a catheter to a zone adjacent to the target tissue to be treated;
b) moving a flexible stylet from the catheter through a catheter port in the sidewall of the catheter and through surrounding tissue into a target tissue to be treated; and
c) performing the medical treatment of the target tissue with the stylet.
51. A method of claim 50 wherein the stylet is a radiofrequency electrode at least partially enclosed within a non-conductive sleeve means for preventing significant transfer of current from the electrode to tissue surrounding the sleeve, and the medical treatment energy comprises generating heat in the target tissue by passing electric current from the electrode into the target tissue.
52. A method of claim 51 comprising moving the nonconductive sleeve means from a preselected area of the electrode in the target tissue to be treated and generating heat in the target tissue by passing electrode current from the preselected area of the electrode into the target tissue.
53. A method of claim 50 wherein the stylet is a microwave antenna.
54. A method of claim 50 wherein the electrical conductor is extended into the tissue to be treated, positioned by use of ultrasound imaging.
55. A method of claim 54 wherein the ultrasound imaging is obtained with an ultrasound transponder positioned on the stylet.
56. A method of claim 54 wherein the ultrasound imaging is obtained with an ultrasound transducer positioned at the end of the catheter.
57. A method of claim 50 wherein the temperature of the target tissue being treated is monitored during the treatment using a temperature sensor attached to the catheter or flexible stylet.
58. A method for ablative treatment of a target tissue without exposing tissue surrounding the target tissue to destructive temperatures comprising:
a) advancing an electrical conductor through surrounding tissue into a target tissue to be ablated, the conductor being a flexible stylet surrounded by a moveable non-conductive sleeve means for preventing significant transfer of energy from the conductor to tissue surrounding the sleeve; and
b) moving the non-conductive sleeve means to remove it from a preselected portion of the conductor positioned in the body mass to be treated, and generating heat in the body mass from an electric current from the preselected portion of the conductor.
59. A method of claim 58 including the additional steps for creating a drainage canal from the treated target tissue comprising:
c) retracting the non-conductive sleeve means from a length of the conductor which corresponds to the position and length of the desired drainage canal, and
d) generating sufficient destructive heat in the tissue adjacent the exposed conductor from an electric current from the exposed conductor to form a canal.
60. A method for treating a target tissue such as the prostate comprising:
a) introducing a catheter up the urethra to a zone adjacent to the prostate target tissue to be treated;
b) moving two flexible stylets from the catheter through catheter ports in the sidewall of the catheter and through the urethra wall and surrounding tissue into the prostate target tissue to be treated, the catheter ports having axes forming an angle of less than 180; and
c) performing the medical treatment of said target tissue with the stylet.
61. A method of claim 60 wherein the angle is less than 110.
62. A method of claim 60 wherein the stylets are flexible electrical conductors surrounded by moveable non-conductive sleeves for preventing significant transfer of energy from the conductors to tissue surrounding the sleeves, and the non-conductive sleeves are retracted to remove them from preselected portions of the conductors positioned at the prostate to be treated, and generating heat in the prostate from electric current from the preselected portions of the conductors.
63. A method of claim 60 wherein the stylets are flexible electrical conductors surrounded by a non-conducting sleeve means for preventing significant transfer of energy from the conductor to tissue surrounding the sleeve, and grounding plates are placed on the skin in positions which draw electrical current passing from the electrodes through target tissue to be ablated, and ablating heat is generated in. the target tissue from electrical current passing through the electrodes to the grounding plates.
64. A method for ablative treatment of a target tissue without exposing tissue surrounding the target tissue to destructive temperatures comprising:
a) advancing an electrical conductor through surrounding tissue into a target tissue to be ablated, the conductor being a flexible stylet surrounded by a non-conductive sleeve means for preventing significant transfer of energy from the conductor to tissue surrounding the sleeve;
b) placing a grounding plate on the skin to direct an electrical current passing from the electrode through the target tissue to be ablated; and
c) generating heat in the target tissue from an electrical current passing from the electrode to the grounding plate.
65. A method of claim 64 wherein the stylets are flexible electrical conductors surrounded by moveable non-conductive sleeves for preventing significant transfer of energy from the conductors to tissue surrounding the sleeves, and the non-conductive sleeves are retracted to remove them from preselected portions of the conductors positioned in the prostate, and generating heat in the prostate from electric current from the preselected portions of the conductors.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
What is claimed is:
1. A system for providing a flow of breathing gas to a patient comprising:
a gas flow generator adapted to provide a flow of breathing gas;
a gas flow controller associated with the gas flow generator and adapted to control the flow of breathing gas delivered to a patient responsive to a control signal;
a patient circuit coupled to the gas flow generator and adapted to communicate the flow of breathing with an airway of a patient;
a flow sensor adapted to measure the flow of breathing gas in the patient circuit and to output a first flow signal indicative thereof;
a pressure sensor adapted to measure a pressure of the flow of breathing gas in the patient circuit and to output a first pressure signal indicative thereof;
an exhaust assembly adapted to communicate gas from within the patient circuit to ambient atmosphere; and
a controller that receives the first flow signal and the first pressure signal and outputs the control signal that controls the flow of breathing gas delivered to the patient circuit by the pressure generating system and, hence, the flow of breathing gas at a patient’s airway, wherein the controller detects onset of an inspiratory phase of a patient’s breathing cycle for triggering the inspiratory flow of breathing gas based on such a patient’s inspiratory effort, which is determined based on both the first flow signal and the first pressure signal.
2. The system according to claim 1, wherein the gas flow generating system includes:
a blower that receives a supply of breathing gas from a breathing gas source and provides the flow of breathing gas;
a flow controller associated with the blower to control a rate of the flow of breathing gas responsive to the flow control signal.
3. The system according to claim 2, wherein the flow controller is a flow restricting valve disposed in the patient circuit downstream of the blower that controls the rate of the flow of breathing gas by restricting a flow of gas in the patient circuit responsive to the flow control signal.
4. The system according to claim 1, wherein the flow sensor is disposed in the patient circuit at a location proximal to the gas flow generating system.
5. The system according to claim 1, wherein the patient circuit is a two-limb circuit with a first limb having a first end operatively connected to the gas flow generating system and a second end, and a second limb having a first end operatively connected to the exhaust assembly and a second end, wherein the second ends of the first and the second limbs are located proximal to an airway of a patient responsive to such a patient being ventilated by the ventilator.
6. The system according to claim 5, wherein the exhaust assembly includes an exhaust flow controller to control a rate of the exhaust flow of gas from the patient circuit responsive to an exhaust flow control signal provided by the controller.
7. The system according to claim 1, further comprising a secondary gas flow system that delivers a secondary flow of gas to the patient circuit, wherein the secondary gas flow system includes:
a conduit configured and arranged so as to communicate the secondary flow of gas from a source of the secondary flow of gas to the patient circuit; and
a second flow sensor adapted to measure the secondary flow of gas in the conduit and to output a second first signal indicative thereof.
8. The system according to claim 1, wherein the controller establishes a trigger lockout interval, which is a period of time during each expiratory phase of a breathing cycle in which triggering the inspiratory flow of breathing gas is prevented, based on at least one of the first flow signal and the first pressure signal.
9. The system according to claim 1, wherein the controller:
determines a patient flow difference (QpatientQref), where Qpatient is the current patient flow from the first flow signal and Qref is a reference patient flow determined from the first flow signal at a start of a trigger window;
determines a patient pressure difference (PrefPpatient), where Ppatient is the current patient pressure from the first pressure signal and Pref is a reference patient pressure determined from the first pressure signal at the start of a trigger window;
determines the patient’s inspiratory effort as a product of the patient flow difference and the patient pressure difference; and
triggers the inspiratory flow responsive to the patient’s inspiratory effort exceeding a threshold.
10. The system according to claim 1, wherein the controller
determines a patient flow difference (QpatientQref), where Qpatient is the current patient flow from the first flow signal and Qref is a reference patient flow determined from the first flow signal at a start of a trigger window;
determines a patient pressure difference (PrefPpatient), where Ppatient is the current patient pressure from the first pressure signal and Pref is a reference patient pressure determined from the first pressure signal at the start of the trigger window;
determines the patient’s inspiratory effort as a product of the patient flow difference and the patient pressure difference;
sums the patient’s inspiratory efforts accumulated over a time interval; and
triggers the inspiratory flow responsive to the sum of the patient’s inspiratory efforts over the time interval exceeding a threshold.
11. The system according to claim 10, wherein the time interval has fixed duration.
12. The system according to claim 1, wherein the controller:
determines a patient pressure difference (PrefPpatient), where Ppatient is the current patient pressure from the first pressure signal and Pref is a reference patient pressure determined from the first pressure signal at a start of a trigger window;
delays the patient pressure difference in time to determine a delayed patient pressure difference;
determines a product of a current patient flow from the first flow signal and the delayed patient pressure difference as the patient’s inspiratory effort;
sums the patient’s inspiratory efforts accumulated over a time interval; and
triggers the inspiratory flow responsive to the sum of the patient’s inspiratory effort exceeding a threshold.
13. The system according to claim 1, wherein the controller detects onset of an expiratory phase of a patient’s breathing cycle for cycling from providing the inspiratory flow to allowing an expiratory flow of breathing gas from the exhaust assembly based on such a patient’s expiratory effort, which is determined based on both the first flow signal and the first pressure signal.
14. The system according to claim 13, wherein the controller:
determines a patient flow difference (QrefQpatient), where Qpatient is the current patient flow from the first flow signal and Qref is a reference patient flow determined from the first flow signal at a start of a cycling window;
determines a patient pressure difference (PpatientPref), where Ppatient is the current patient pressure from the first pressure signal and Pref is a reference patient pressure determined from the first pressure signal at the start of the cycling window;
determines the patient’s expiratory effort as a product of the patient flow difference and the patient pressure difference; and
cycles from providing the inspiratory flow to allowing an expiratory flow of breathing gas from the exhaust assembly responsive to the patient’s expiratory effort exceeding a threshold.
15. The system according to claim 13, wherein the controller:
determines a patient pressure difference (PpatientPref), where Ppatient is the current patient pressure from the first pressure signal and Pref is a reference patient pressure determined from the first pressure signal at a start of a cycling window;
delays a patient flow from the first flow signal to determine a delayed patient flow;
determines a product of the current patient pressure difference and the delayed patient flow as the patient’s expiratory effort;
sums the patient’s expiratory efforts accumulated over a time interval; and
cycles from providing the inspiratory flow to allowing an expiratory flow of breathing gas from the exhaust assembly responsive to the sum of the patient’s expiratory effort exceeding a threshold.
16. The system according to claim 13, wherein the controller:
determines a patient flow difference (QrefQpatient), where Qpatient is the current patient flow from the first flow signal and Qref is a reference patient flow determined from the first flow signal at a start of a cycling window;
determines a patient pressure difference (PpatientPref), where Ppatient is the current patient pressure from the first pressure signal and Pref is a reference patient pressure determined from the first pressure signal at the start of the cycling window;
determines the patient’s expiratory effort as a product of the patient flow difference and the patient pressure difference;
sums the patient’s expiratory efforts accumulated over a time interval; and
cycles from providing the inspiratory flow to allowing an expiratory flow of breathing gas from the exhaust assembly responsive to the sum of the patient’s expiratory efforts over the time interval exceeding a threshold.
17. The system according to claim 16, wherein the time interval has fixed duration.
18. The system according to claim 1, wherein the controller cycles from providing the inspiratory flow to allowing an expiratory flow of breathing gas from the exhaust assembly by comparing patient flow determined from the first flow signal against a cycle threshold flow and cycles responsive to the patient flow falling below the cycle threshold flow.
19. The system according to claim 18, wherein the controller:
monitors patient pressure, via the first pressure signal, at an end portion of the inspiratory phase and monitors patient flow, via the first flow signal, at a beginning portion of the expiratory phase to determine whether the system cycled too early or too late; and
adjusts the cycle threshold flow for a next breathing cycle responsive to a determination that the system cycled too early or too late.
20. A system for providing a flow of breathing gas to a patient comprising:
a gas flow generator adapted to provide a flow of breathing gas;
a gas flow controller associated with the gas flow generator and adapted to control the flow of breathing gas delivered to a patient responsive to a control signal;
a patient circuit coupled to the gas flow generator and adapted to communicate the flow of breathing with an airway of a patient;
a flow sensor adapted to measure the flow of breathing gas in the patient circuit and to output a first flow signal indicative thereof;
a pressure sensor adapted to measure a pressure of the flow of breathing gas in the patient circuit and to output a first pressure signal indicative thereof;
an exhaust assembly adapted to communicate gas from within the patient circuit to ambient atmosphere; and
a controller that receives the first flow signal and the first pressure signal and outputs the control signal that controls the flow of breathing gas delivered to the patient circuit by the pressure generating system and, hence, the flow of breathing gas at a patient’s airway, wherein the controller arms a plurality of triggering mechanisms over an expiratory phase of a breathing cycle to increase the ventilator system sensitivity to a patient initiated trigger as the expiratory phase of the breathing cycle progresses.
21. A method of providing a flow of breathing gas to a patient comprising:
generating a flow of breathing gas;
providing the flow of breathing gas to a patient via a patient circuit;
controlling the flow of breathing gas delivered to a patient responsive to a control signal;
measuring the flow of breathing in the patient circuit and outputting a first flow signal indicative thereof;
measuring a pressure of the flow of breathing gas in the patient circuit and outputting a first pressure signal indicative thereof;
communicating gas from within the patient circuit to ambient atmosphere; and
detecting onset of the inspiratory phase of a patient’s breathing cycle for triggering an inspiratory flow of breathing gas based on such a patient’s inspiratory effort, which is determined based on both the first flow signal and the first pressure signal.
22. The method according to claim 21, wherein detecting the onset of the inspiratory phase includes:
determining a patient flow difference (QpatientQref), where Qpatient is the current patient flow from the first flow signal and Qref is a reference patient flow determined from the first flow signal at a start of a trigger window;
determining a patient pressure difference (PrefPpatient), where Ppatient is the current patient pressure from the first pressure signal and Pref is a reference patient pressure determined from the first pressure signal at the start of the trigger window; and
determining the patient’s inspiratory effort as a product of the patient flow difference and the pressure difference.
23. The method according to claim 22, further comprising triggering the inspiratory flow responsive to the patient’s inspiratory effort exceeding a threshold.
24. The method according to claim 21, wherein detecting the onset of the inspiratory phase includes:
determining a patient flow difference (QpatientQref), where Qpatient is the current patient flow from the first flow signal and Qref is a reference patient flow determined from the first flow signal at a start of a trigger window;
determining a patient pressure difference (PrefPpatient), where Ppatient is the current patient pressure from the first pressure signal and Pref is a reference patient pressure determined from the first pressure signal at a start of a trigger window;
determining the patient’s inspiratory effort as a product of a patient flow difference and the pressure difference;
summing the patient’s inspiratory efforts accumulated over a time interval; and
triggering the inspiratory flow responsive to the sum of the patient’s inspiratory efforts over the time interval exceeding a threshold.
25. The method according to claim 24, wherein the time interval has a fixed duration.
26. The method according to claim 21, wherein detecting the onset of the inspiratory phase includes:
determining a patient pressure difference (PrefPpatient), where Ppatient is the current patient pressure from the first pressure signal and Pref is a reference patient pressure determined from the first pressure signal at a start of a trigger window;
determining a delayed patient pressure difference, where the length of the delay is selected so as to account for an inherent physiological delay between the onset of a pressure drop and a rise in patient flow occurring at a beginning of inspiration;
determining a product of a current patient flow from the first flow signal and the delayed patient pressure difference as the patient’s inspiratory effort;
summing the patient’s inspiratory efforts accumulated over a time interval; and
triggering the inspiratory flow responsive to the sum of the patient’s inspiratory effort exceeding a threshold.
27. The method according to claim 21, further comprising detecting onset of an expiratory phase of a patient’s breathing cycle for cycling from providing the inspiratory flow to allowing an expiratory flow of breathing gas from the exhaust assembly based on such a patient’s expiratory effort, wherein detecting the onset of the expiratory phase is determined based on both the first flow signal and the first pressure signal.
28. The method according to claim 27, wherein detecting the onset of the expiratory phase includes:
determining a patient flow difference (QrefQpatient), where Qpatient is the current patient flow from the first flow signal and Qref is a reference patient flow determined from the first flow signal at a start of a cycling window;
determining a patient pressure difference (PpatientPref), where Ppatient is the current patient pressure from the first pressure signal and Pref is a reference patient pressure determined from the first pressure signal at the start of the cycling window;
determining the patient’s expiratory effort as a product of the patient flow difference and the patient pressure difference; and
cycling from providing the inspiratory flow to allowing an expiratory flow of breathing gas from the exhaust assembly responsive to the patient’s expiratory effort exceeding a threshold.
29. The method according to claim 27, wherein detecting the onset of the expiratory phase includes:
determining a patient pressure difference (PpatientPref), where Ppatient is the current patient pressure from the first pressure signal and Pref is a reference patient pressure determined from the first pressure signal at a start of a cycling window;
delaying a patient flow from the first flow signal to determine a delayed patient flow;
determining a product of the current patient pressure difference and the delayed patient flow as the patient’s expiratory effort;
summing the patient’s expiratory efforts accumulated over a time interval; and
cycling from providing the inspiratory flow to allowing an expiratory flow of breathing gas from the exhaust assembly responsive to the sum of the patient’s expiratory effort exceeding a threshold.
30. The method according to claim 27, wherein detecting the onset of the expiratory phase includes:
determining a patient flow difference (QrefQpatient), where Qpatient is the current patient flow from the first flow signal and Qref is a reference patient flow determined from the first flow signal at a start of a cycling window;
determining a patient pressure difference (PpatientPref), where Ppatient is the current patient pressure from the first pressure signal and Pref is a reference patient pressure determined from the first pressure signal at the start of the cycling window;
determining the patient’s expiratory effort as a product of the patient flow difference and the patient pressure difference;
summing the patient’s expiratory efforts accumulated over a time interval; and
cycling from providing the inspiratory flow to allowing an expiratory flow of breathing gas from the exhaust assembly responsive to the sum of the patient’s expiratory efforts over the time interval exceeding a threshold.
31. The method according to claim 30, wherein the time interval has a fixed duration.
32. The method according to claim 21, wherein the controller cycles from providing the inspiratory flow to allowing an expiratory flow of breathing gas from the exhaust assembly by comparing patient flow determined from the first flow signal against a cycle threshold flow and cycles responsive to the patient flow falling below the cycle threshold flow.
33. The method according to claim 32, further comprising:
monitoring patient pressure, via the first pressure signal, at an end portion of the inspiratory phase;
monitoring patient flow, via the first flow signal, at a beginning portion of the expiratory phase;
determining whether the system cycled too late based on the monitored patient pressure at the end portion of the inspiratory phase determining whether the system cycled too early based on the monitored patient flow at the beginning portion of the expiratory phase; and
adjusting the cycle threshold flow for a next breathing cycle responsive to a determination that the system cycled too early or too late.
34. A method of providing a flow of breathing gas to a patient comprising:
generating a flow of breathing gas;
providing the flow of breathing gas to a patient via a patient circuit;
controlling the flow of breathing gas delivered to a patient responsive to a control signal;
measuring the flow of breathing in the patient circuit and outputting a first flow signal indicative thereof;
measuring a pressure of the flow of breathing gas in the patient circuit and outputting a first pressure signal indicative thereof;
communicating gas from within the patient circuit to ambient atmosphere; and
activating a plurality of triggering mechanisms over an expiratory phase of a breathing cycle to increase a sensitivity to a patient initiated trigger as the expiratory phase of the breathing cycle progresses.
35. A system for providing a flow of breathing gas to a patient comprising:
a gas flow generator adapted to provide a flow of breathing gas;
a gas flow controller associated with the gas flow generator and adapted to control the flow of breathing gas delivered to a patient responsive to a control signal;
a patient circuit coupled to the gas flow generator and adapted to communicate the flow of breathing with an airway of a patient;
a flow sensor adapted to measure the flow of breathing gas in the patient circuit and to output a first flow signal indicative thereof;
a pressure sensor adapted to measure a pressure of the flow of breathing gas in the patient circuit and to output a first pressure signal indicative thereof;
an exhaust assembly adapted to communicate gas from within the patient circuit to ambient atmosphere; and
a controller that receives the first flow signal and the first pressure signal and outputs the control signal that controls the flow of breathing gas delivered to the patient circuit by the pressure generating system and, hence, the flow of breathing gas at a patient’s airway, wherein the controller detects onset of the expiratory phase of a patient’s breathing cycle for cycling the expiratory flow of breathing gas based on such a patient’s expiratory effort, which is determined based on both the first flow signal and the first pressure signal.
36. The system according to claim 35, wherein the controller:
determines a patient flow difference (QrefQpatient), where Qpatient is the current patient flow from the first flow signal and Qref is a reference patient flow determined from the first flow signal at a start of a cycling window;
determines a patient pressure difference (PpatientPref), where Ppatient is the current patient pressure from the first pressure signal and Pref is a reference patient pressure determined from the first pressure signal at the start of a cycling window;
determines the patient’s expiratory effort as a product of the patient flow difference and the patient pressure difference; and
cycles from providing the inspiratory flow to allowing an expiratory flow of breathing gas from the exhaust assembly responsive to the patient’s expiratory effort exceeding a threshold.
37. The system according to claim 35, wherein the controller:
determines a patient pressure difference (PpatientPref), where Ppatient is the current patient pressure from the first pressure signal and Pref is a reference patient pressure determined from the first pressure signal at a start of a cycling window;
delays a patient flow from the first flow signal to determine a delayed patient flow;
determines a product of the current patient pressure difference and the delayed patient flow as the patient’s inspiratory effort;
sums the patient’s inspiratory efforts accumulated over a time interval; and
cycles from providing the inspiratory flow to allowing an expiratory flow of breathing gas from the exhaust assembly responsive to the sum of the patient’s expiratory effort exceeding a threshold.
38. The system according to claim 35, wherein the controller:
determines a patient flow difference (QrefQpatient), where Qpatient is the current patient flow from the first flow signal and Qref is a reference patient flow determined from the first flow signal at a start of a cycling window;
determines a patient pressure difference (PpatientPref), where Ppatient is the current patient pressure from the first pressure signal and Pref is a reference patient pressure determined from the first pressure signal at the start of the cycling window;
determines the patient’s expiratory effort as a product of the patient flow difference and the patient pressure difference;
sums the patient’s expiratory efforts accumulated over a time interval; and
cycles from providing the inspiratory flow to allowing an expiratory flow of breathing gas from the exhaust assembly responsive to the sum of the patient’s expiratory efforts over the time interval exceeding a threshold.
39. The system according to claim 38, wherein the time interval is a fixed period of time.
40. A method of providing a flow of breathing gas to a patient comprising:
generating a flow of breathing gas;
providing the flow of breathing gas to a patient via a patient circuit;
controlling the flow of breathing gas delivered to a patient responsive to a control signal;
measuring the flow of breathing in the patient circuit and outputting a first flow signal indicative thereof;
measuring a pressure of the flow of breathing gas in the patient circuit and outputting a first pressure signal indicative thereof;
communicating gas from within the patient circuit to ambient atmosphere; and
detecting onset of the expiratory phase of a patient’s breathing cycle for cycling an expiratory flow of breathing gas based on such a patient’s expiratory effort, which is determined based on both the first flow signal and the first pressure signal.
41. The method according to claim 40, wherein detecting the onset of the expiratory phase includes:
determining a patient flow difference (QrefQref), where Qpatient is the current patient flow from the first flow signal and Qref is a reference patient flow determined from the first flow signal at a start of a cycling window;
determining a patient pressure difference (PpatientPref), where Ppatient is the current patient pressure from the first pressure signal and Pref is a reference patient pressure determined from the first pressure signal at the start of a cycling window;
determining the patient’s expiratory effort as a product of the patient flow difference and the patient pressure difference; and
cycling from providing the inspiratory flow to allowing an expiratory flow of breathing gas from the exhaust assembly responsive to the patient’s expiratory effort exceeding a threshold.
42. The method according to claim 40, wherein detecting the onset of the expiratory phase includes:
determining a patient pressure difference (PpatientPref), where Ppatient is the current patient pressure from the first pressure signal and Pref is a reference patient pressure determined from the first pressure signal at a start of a cycling window;
delaying a patient flow from the first flow signal to determine a delayed patient flow;
determining a product of the current patient pressure difference and the delayed patient flow as the patient’s expiratory effort;
summing the patient’s expiratory efforts accumulated over a time interval; and
cycling from providing the inspiratory flow to allowing an expiratory flow of breathing gas from the exhaust assembly responsive to the sum of the patient’s expiratory effort exceeding a threshold.
43. The method according to claim 40, wherein detecting the onset of the expiratory phase includes:
determining a patient flow difference (QrefQpatient), where Qpatient is the current patient flow from the first flow signal and Qref is a reference patient flow determined from the first flow signal at a start of a cycling window;
determining a patient pressure difference (PpatientPref), where Ppatient is the current patient pressure from the first pressure signal and Pref is a reference patient pressure determined from the first pressure signal at the start of the cycling window;
determining the patient’s expiratory effort as a product of the patient flow difference and the patient pressure difference;
summing the patient’s expiratory efforts accumulated over a time interval; and
cycling from providing the inspiratory flow to allowing an expiratory flow of breathing gas from the exhaust assembly responsive to the sum of the patient’s expiratory efforts over the time interval exceeding a threshold.
44. The method according to claim 44, wherein the time interval is a fixed duration.
45. A system for providing a flow of breathing gas to a patient comprising:
a gas flow generator adapted to provide a flow of breathing gas;
a gas flow controller associated with the gas flow generator and adapted to control the flow of breathing gas delivered to a patient responsive to a control signal;
a patient circuit coupled to the gas flow generator and adapted to communicate the flow of breathing with an airway of a patient;
a flow sensor adapted to measure the flow of breathing gas in the patient circuit and to output a first flow signal indicative thereof;
a pressure sensor adapted to measure a pressure of the flow of breathing gas in the patient circuit and to output a first pressure signal indicative thereof;
an exhaust assembly adapted to communicate gas from within the patient circuit to ambient atmosphere; and
a controller that receives the first flow signal and the first pressure signal, wherein the controller detects onset of the expiratory phase of a patient’s breathing cycle, for cycling the system from providing the inspiratory flow to allowing an expiratory flow of breathing gas from the exhaust assembly, responsive to a patient flow determined from the first flow signal falling below the cycle threshold flow, wherein the controller monitors patient pressure, via the first pressure signal, at an end portion of the inspiratory phase to determine whether the system cycled too late and monitors patient flow, via the first flow signal, at a beginning portion of the expiratory phase to determine whether the system cycled too early, and wherein the controller adjusts the cycle threshold flow for a next breathing cycle responsive to a determination that the system cycled too early or too late.
46. A method of providing a flow of breathing gas to a patient comprising:
generating a flow of breathing gas;
providing the flow of breathing gas to a patient via a patient circuit;
controlling the flow of breathing gas delivered to a patient responsive to a control signal;
measuring the flow of breathing in the patient circuit and outputting a first flow signal indicative thereof;
measuring a pressure of the flow of breathing gas in the patient circuit and outputting a first pressure signal indicative thereof;
communicating gas from within the patient circuit to ambient atmosphere; and
detecting onset of the expiratory phase of a patient’s breathing cycle for cycling the system from providing the inspiratory flow to allowing an expiratory flow of breathing gas from the exhaust assembly, by comparing a patient flow determined from the first flow signal with a cycle threshold flow;
cycling the system from providing the inspiratory flow to allowing an expiratory flow of breathing gas from the exhaust assembly responsive to the patient flow falling below the cycle threshold flow;
determining whether the system cycled too late based on the patient pressure at an end portion of the inspiratory phase;
determining whether the system cycled too early based on the patient flow at a beginning portion of the expiratory phase; and
adjusting the cycle threshold flow for a next breathing cycle responsive to a determination that the system cycled too early or too late.