METHOD FOR DETERMINING THE RESISTANCE OF THE RESPIRATORY SYSTEM OF A PATIENT
First Claim
1. A method for automatically determining the resistance of the respiratory system of a spontaneously breathing intubated patient, wherein the method is conducted with or without assisted ventilation and includes an occlusion period at the start of inspiration, the method comprising:
- measuring flow (V′
) and airway pressure (Paw) as a function of time;
determining the airway pressure at the end of the occlusion period as end of occlusion airway pressure (Paw(tc)=Poccl);
analyzing a time dependence of the flow starting at the end of the occlusion period to determine a transition time (td) at which the slope of the flow changes from a first high value to a second lower value, and/or analyzing a time dependence of the airway pressure starting at the end of the occlusion period to determine the transition time (td) at which the slope at the airway pressure changes from a first high value to a second lower value, or by detecting an increase of the airway pressure over a predetermined threshold value to determine the transition time (td);
determining the flow at the transition time as transition time flow (V′
(td)=V′
peak) and determining the airway pressure at the transition time as transition time pressure (Paw(td));
calculating the resistance on the basis of the ratio of an estimated driving pressure at the transition time (Pdrv(td)) and the transition time flow (V′
peak), wherein the value of the transition time driving pressure (Pdrv(td)) is calculated as sum of the transition time airway pressure (Paw(td)) and a muscular effort pressure (Pmus(td)) at the transition time, which muscular effort pressure (Pmus(td)) is extrapolated based on a predetermined time dependence of muscular effort pressure (Pmus(t)) during the occlusion period and based on value of the end of occlusion airway pressure (Poccl).
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Accused Products
Abstract
A method for automatically determining the resistance of the respiratory system of a spontaneously breathing intubated patient. The method includes measuring flow (V′) and airway pressure (Paw) as a function of time; determining the airway pressure at the end of the occlusion period as end of occlusion airway pressure Paw(tc)=Poccl; analyzing a time dependence of the flow starting at the end of the occlusion period to determine a transition time td at which the slope of the flow changes from a first high value to a second lower value, and/or analyzing a time dependence of the airway pressure starting at the end of the occlusion period to determine a transition time td at which the slope at the airway pressure changes from a first high value to a second lower value, or by detecting an increase of the airway pressure over a predetermined threshold value to determine the transition time td; determining the flow at the transition time as transition time flow V′(td)=V′peak and determining the airway pressure at the transition time as transition time pressure Paw(td); and calculating the resistance on the basis of the ratio of an estimated driving pressure at the transition time Pdrv(td) and the transition time flow V′peak, wherein the value of the transition time driving pressure Pdrv(td) is calculated as sum of the transition time airway pressure Paw(td) and the muscular effort Pmus(td) at the transition time, which muscular effort Pmus(td) is extrapolated based on a predetermined time dependence of Pmus(t) during the occlusion period and based on value of the end of occlusion airway pressure Poccl.
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Citations
19 Claims
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1. A method for automatically determining the resistance of the respiratory system of a spontaneously breathing intubated patient, wherein the method is conducted with or without assisted ventilation and includes an occlusion period at the start of inspiration, the method comprising:
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measuring flow (V′
) and airway pressure (Paw) as a function of time;determining the airway pressure at the end of the occlusion period as end of occlusion airway pressure (Paw(tc)=Poccl); analyzing a time dependence of the flow starting at the end of the occlusion period to determine a transition time (td) at which the slope of the flow changes from a first high value to a second lower value, and/or analyzing a time dependence of the airway pressure starting at the end of the occlusion period to determine the transition time (td) at which the slope at the airway pressure changes from a first high value to a second lower value, or by detecting an increase of the airway pressure over a predetermined threshold value to determine the transition time (td); determining the flow at the transition time as transition time flow (V′
(td)=V′
peak) and determining the airway pressure at the transition time as transition time pressure (Paw(td));calculating the resistance on the basis of the ratio of an estimated driving pressure at the transition time (Pdrv(td)) and the transition time flow (V′
peak), wherein the value of the transition time driving pressure (Pdrv(td)) is calculated as sum of the transition time airway pressure (Paw(td)) and a muscular effort pressure (Pmus(td)) at the transition time, which muscular effort pressure (Pmus(td)) is extrapolated based on a predetermined time dependence of muscular effort pressure (Pmus(t)) during the occlusion period and based on value of the end of occlusion airway pressure (Poccl). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for automatically determining the elastance (E) of the respiratory system of a spontaneously breathing intubated patient, wherein said method is conducted with or without assisted ventilation and includes an occlusion period at the start of inspiration, wherein said method comprises:
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a) determining the resistance (K) of the respiratory system with or without assisted ventilation and including an occlusion period at the start of inspiration by; measuring flow (V′
) and airway pressure (Paw) as a function of time;determining the airway pressure at the end of the occlusion period as end of occlusion airway pressure (Paw(t)=Poccl); analyzing a time dependence of the flow starting at the end of the occlusion period to determine a transition time (td) at which the slope of the flow changes from a first high value to a second lower value, and/or analyzing a time dependence of the airway pressure starting at the end of the occlusion period to determine the transition time (td) at which the slope at the airway pressure changes from a first high value to a second lower value, or by detecting an increase of the airway pressure over a predetermined threshold value to determine the transition time (td); determining the flow at the transition time as transition time flow (V′
(td)=V′
peak) and determining the airway pressure at the transition time as transition time pressure (Paw(td));calculating the resistance on the basis of the ratio of an estimated driving pressure at the transition time (Pdrv(td)) and the transition time flow (V′
peak), wherein the value of the transition time driving pressure (Pdrv(td)) is calculated as sum of the transition time airway pressure (Paw(td)) and a muscular effort pressure (Pmus(td)) at the transition time, which muscular effort pressure (Pmus(td)) is extrapolated based on a predetermined time dependence of muscular effort pressure (Pmus(t)) during the occlusion period and based on value of the end of occlusion airway pressure (Poccl);b) measuring the inspiratory volume as a function of time; c) determining the airway pressure (Paw(t)) during the occlusion period (tb<
t<
tc) as a function of time (Paw(t));d) extrapolating the airway pressure during the occlusion (Paw(t)) with occlusion period (tb<
t<
tc) data to the time when the inspiratory volume reaches a predetermined volume (tc) to obtain an extrapolated airway pressure (Pextr(te));e) subtracting the extrapolated airway pressure (Pextr(te)) from the ventilator pressure (Paw(te)) to obtain an estimated driving pressure (Pdrv(te)); f) calculating the resistive pressure (Pres(te)) at the predetermined inspiratory volume (⅔
VT) using the measured flow at that inspiratory volume and the resistance value determined in step a), and subtracting the resistive pressure (Pres(te)) from the estimated driving pressure (P−
extr(te)) to determine the elastic pressure (Pel(te)), and determining the elastance on the basis of the ratio of elastic pressure (Pel(te)) to the predetermined inspiratory volume (V(te)). - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. A method for determining a resistance of a respiratory system of a patient, the method comprising the steps of:
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inhaling through a breathing apparatus; blocking a flow through the breathing apparatus at a start of said inhaling, said blocking being performed during an occlusion period; measuring flow through the breathing apparatus during said inhaling as a function of time; measuring airway pressure in the breathing apparatus during said inhaling as a function of time; determining the airway pressure at an end of the occlusion period (Poccl); determining a transition time (td) during said inhaling and after the occlusion period, the transition time being determined by one of, determining a time when a slope of the flow changes from a first high value to a second lower value, determining a time when a slope of the airway pressure changes from a first high value to a second lower value, and determining a time when the airway pressure increases above a predetermined threshold; determining the flow at the transition time td as V′
peak;determining the airway pressure at the transition time td as Paw(td); determining muscular pressure at the transition time (Pmus(td)) by extrapolation of the airway pressure during the occlusion period; calculating a driving pressure at the transition time (Pdrv(td)) by adding Paw(td) and Pmus(td); calculating the resistance of the respiratory system based on a ratio of Pdrv(td) to V′
peak.
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Specification