Ventilatory assistance for treatment of cardiac failure and cheyne-stokes breathing
First Claim
1. An apparatus for the treatment of cardiac failure, Cheyne-Stokes breathing or central sleep apnea, the apparatus comprising:
- a controllable source of breathable gas at positive pressure;
means for delivering said breathable gas at positive pressure to a subject'"'"'s airway;
means for deriving a measure of respiratory airflow of the subject; and
a servo-controller configured to accept an input variable and a reference quantity, and produce an output to bring the value of the input variable towards the value of the reference quantity;
wherein(i) said input variable is a measure of instantaneous ventilation, and(ii) said reference quantity is a percentage of a long-term measure of ventilation continuously derived as half the absolute value of the respiratory airflow, the long-term measure of ventilation being low-pass filtered with a time constant that is long compared with the lung-chemoreceptor delay in patients with Cheyne-Stokes breathing or central sleep apnea.
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Accused Products
Abstract
Method and apparatus for the treatment of cardiac failure, Cheyne Stokes breathing or central sleep apnea are disclosed. A subject is provided with ventilatory support Respiratory airflow is determined. From the respiratory airflow are derived a measure of instantaneous ventilation and a measure of longterm average ventilation. A target ventilation is taken as 95% of the longterm average ventilation. The instantaneous ventilation is fed as the input signal to a clipped integral controller, with the target ventilation as the reference signal. The output of the controller determines the degree of ventilatory support. A third measure of ventilation, for example instantaneous ventilation low pass filtered with a time constant of 5 seconds, is calculated. Ventilatory support is in phase with the subject'"'"'s respiratory airflow to the fuzzy extent that this ventilation is above target, and at a preset rate conversely.
34 Citations
14 Claims
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1. An apparatus for the treatment of cardiac failure, Cheyne-Stokes breathing or central sleep apnea, the apparatus comprising:
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a controllable source of breathable gas at positive pressure; means for delivering said breathable gas at positive pressure to a subject'"'"'s airway; means for deriving a measure of respiratory airflow of the subject; and a servo-controller configured to accept an input variable and a reference quantity, and produce an output to bring the value of the input variable towards the value of the reference quantity; wherein (i) said input variable is a measure of instantaneous ventilation, and (ii) said reference quantity is a percentage of a long-term measure of ventilation continuously derived as half the absolute value of the respiratory airflow, the long-term measure of ventilation being low-pass filtered with a time constant that is long compared with the lung-chemoreceptor delay in patients with Cheyne-Stokes breathing or central sleep apnea. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method of calculating a control signal, based on an obtained measure of a subject'"'"'s respiratory airflow, said signal being suitable for controlling the delivery of breathable gas at positive pressure to the subject'"'"'s airway in the treatment of cardiac failure, Cheyne-Stokes breathing or central sleep apnea, said method comprising:
a servo-control procedure accepting an input variable and a reference quantity, and producing said control signal as an output of the servo-control procedure, wherein the output is suitable for bringing the value of the input variable towards the value of the reference quantity;
wherein(i) said input variable is an obtained measure of instantaneous ventilation of the subject, and (ii) said reference quantity is a percentage of a long-term measure of ventilation continuously derived as half the absolute value of the respiratory airflow, the long-term measure of ventilation being low-pass filtered with a time constant that is long compared with the lung-chemoreceptor delay in patients with Cheyne-Stokes breathing or central sleep apnea.
Specification