Methods and apparatus for treatment of respiratory disorders
Methods and apparatus for treating a respiratory disorder, m one aspect, include an apparatus that delivers backup breaths at a sustained timed backup rate that is a function of the patient's spontaneous respiratory rate. Other aspects include apparatus that delivers backup breaths at a rate that gradually increases from a spontaneous backup rate to a sustained timed backup rate or, alternatively, apparatus that oscillates a treatment pressure in antiphase with the patient's spontaneous respiratory efforts when a measure indicative of ventilation is greater than a threshold. Other aspects include apparatus configured to treat Cheyne-Stokes respiration by computing the treatment pressure so as to bring a measure indicative of ventilation of the patient towards a target ventilation that is dependent on the measure indicative of ventilation or, alternatively, by periodically elevating the treatment pressure to a high level for a short time.
1 . An apparatus for treating a respiratory disorder in a patient, the apparatus comprising:
a pressure generator configured to generate a supply of air at a positive pressure to an airway of the patient;
a sensor configured to generate sensor data representing a property of the supply of air; and
a controller configured to:
control the pressure generator to generate the supply of air at a positive treatment pressure that is approximately constant throughout a breathing cycle of the patient so as to provide a CPAP therapy;
compute a measure indicative of ventilation of the patient from the sensor data, the measure indicative of ventilation is a total amount of gas being exchanged by a respiratory system of the patient; and
repeatedly compute the positive treatment pressure so as to bring the measure indicative of ventilation towards a target ventilation that is dependent on the measure indicative of ventilation,
wherein, to compute the positive treatment pressure, the controller is configured to increase the positive treatment pressure by detecting when the measure indicative of ventilation exceeds the target ventilation and to decrease the positive treatment pressure by detecting when the measure indicative of ventilation falls below the target ventilation.
2 . The apparatus for treating the respiratory disorder of claim 1 , wherein the controller is further configured to compute the target ventilation as a high proportion of, but less than, a typical recent value of the measure indicative of ventilation.
3 . The apparatus for treating the respiratory disorder of claim 1 , wherein the controller is further configured to control the pressure generator to periodically elevate the positive treatment pressure to a high level for a short time, the high level being high enough and the short time being long enough to induce a central apnea in the patient.
4 . The apparatus for treating the respiratory disorder of claim 1 , wherein to compute the positive treatment pressure, the controller is configured to operate a control process selected from a group of control processes consisting of: proportional control, proportional-integral control, proportional-differential control, and proportional-integral-differential control, and discrete control.
5 . The apparatus for treating the respiratory disorder of claim 1 , wherein the measure indicative of ventilation is half an absolute value of respiratory flow rate.
6 . The apparatus for treating the respiratory disorder of claim 5 , wherein the controller is further configured to filter the absolute value of respiratory flow rate by a low-pass filter.
7 . The apparatus for treating the respiratory disorder of claim 5 , wherein the measure indicative of ventilation is an estimate of gross alveolar ventilation.
8 . The apparatus for treating the respiratory disorder of claim 1 , wherein the measure indicative of ventilation is broadly proportional to an actual ventilation of the patient.
9 . The apparatus for treating the respiratory disorder of claim 8 , wherein the measure indicative of ventilation is a peak respiratory flow rate over an inspiratory portion of the breathing cycle.
10 . The apparatus for treating the respiratory disorder of claim 1 , wherein the measure of ventilation is oxygen saturation.
11 . The apparatus for treating the respiratory disorder of claim 1 , wherein the controller is configured to repeatedly compute the positive treatment pressure based on comparing an apnea/hypopnea index with a first threshold value, and, based on the comparison, further comparing an airway patency index to a second threshold and/or comparing a flow limitation index to a third threshold.
12 . The apparatus of claim 1 , wherein, to compute the positive treatment pressure, the controller is configured to increase the positive treatment pressure proportionally to a difference between the measure indicative of ventilation and the target ventilation when the measure indicative of ventilation exceeds the target ventilation.
13 . The apparatus of claim 1 , wherein, to compute the positive treatment pressure, the controller is configured to decrease the positive treatment pressure proportionally to a difference between the measure indicative of ventilation and the target ventilation when the measure indicative of ventilation falls below the target ventilation.
14 . A method of treating a respiratory disorder in a patient, the method comprising:
controlling a pressure generator to generate a supply of air at a positive treatment pressure to an airway of the patient, wherein the positive treatment pressure is approximately constant throughout a breathing cycle of the patient so as to provide a CPAP therapy;
computing a measure indicative of ventilation of the patient from data representing a property of the supply of air, the measure indicative of ventilation is a total amount of gas being exchanged by a respiratory system of the patient; and
repeatedly computing the positive treatment pressure so as to bring the measure indicative of ventilation towards a target ventilation that is dependent on the measure indicative of ventilation,
wherein computing the treatment pressure comprises increasing the positive treatment pressure by detecting when the measure indicative of ventilation exceeds the target ventilation and decreasing the positive treatment pressure by detecting when the measure indicative of ventilation falls below the target ventilation.
15 . The method according to claim 14 , further comprising computing the target ventilation as a high proportion of, but less than, a typical recent value of the measure indicative of ventilation.
16 . The method according to claim 14 , further comprising controlling the pressure generator to periodically elevate the positive treatment pressure to a high level for a short time, the high level being high enough and the short time being long enough to induce a central apnea in the patient.
17 . The method according to claim 14 , wherein computing the positive treatment pressure comprises operating a control process selected from a group of control processes consisting of: proportional control, proportional-integral control, proportional-differential control, and proportional-integral-differential control, and discrete control.
18 . The method according to claim 14 , wherein the measure indicative of ventilation is half an absolute value of respiratory flow rate.
19 . The method according to claim 18 , further comprising filtering the absolute value of respiratory flow rate by a low-pass filter.
20 . The method according to claim 18 , wherein the measure indicative of ventilation is an estimate of gross alveolar ventilation.
21 . The method according to claim 14 , wherein the measure indicative of ventilation is broadly proportional to an actual ventilation of the patient.
22 . The method according to claim 21 , wherein the measure indicative of ventilation is a peak respiratory flow rate over an inspiratory portion of the breathing cycle.
23 . The method according to claim 14 , wherein the measure of ventilation is oxygen saturation.
24 . A non-transitory, tangible computer-readable storage medium having computer-executable instructions encoded thereon which, when executed by a processor, cause the processor to be configured to perform the method of claim 14 .
25 . The method according to claim 14 , wherein the positive treatment pressure is repeatedly computed based on comparing an apnea/hypopnea index with a first threshold value, and, based on the comparison, further comparing an airway patency index to a second threshold and/or comparing a flow limitation index to a third threshold.
26 . The method of claim 14 , wherein, to compute the positive treatment pressure, the controller is configured to increase the positive treatment pressure proportionally to a difference between the measure indicative of ventilation and the target ventilation when the measure indicative of ventilation exceeds the target ventilation.
27 . The method of claim 14 , wherein, to compute the positive treatment pressure, the controller is configured to decrease the positive treatment pressure proportionally to a difference between the measure indicative of ventilation and the target ventilation when the measure indicative of ventilation falls below the target ventilation.
28 . A CPAP therapy device that is configured to generate a supply of air at a positive treatment pressure that is approximately constant throughout a breathing cycle of a patient so as to provide a CPAP therapy, and repeatedly compute a positive treatment pressure of the supply of air to an airway of a patient so as to bring a measure indicative of ventilation of the patient towards a target ventilation that is dependent on the measure indicative of ventilation, the measure indicative of ventilation is a total amount of gas being exchanged by a respiratory system of the patient,
wherein, to compute the positive treatment pressure, a controller of the CPAP therapy device is configured to increase the positive treatment pressure proportionally to a difference between the measure indicative of ventilation and the target ventilation by detecting when the measure indicative of ventilation exceeds the target ventilation and to decrease the positive treatment pressure proportionally to the difference between the measure indicative of ventilation and the target ventilation by detecting when the measure indicative of ventilation falls below the target ventilation.
29 . The CPAP therapy device of claim 28 , wherein the device is configured to repeatedly compute the positive treatment pressure based on comparing an apnea/hypopnea index with a first threshold value, and, based on the comparison, further comparing an airway patency index to a second threshold and/or comparing a flow limitation index to a third threshold.