High frequency oscillatory ventilator and respiratory measurement system
First Claim
1. A ventilator apparatus for providing assistance in breathing to a living subject, comprising:
- a low compliance patient circuit tube having a first end and a second end;
means mounted to said patient circuit tube for providing fresh gas into said patient circuit tube and for exhausting exhaled gas out of said patient circuit tube;
an endotracheal tube intubated in the subject coupled to said first end of said patient circuit tube;
a pump for generating tidal volumes having an outlet coupled to said second end of said patient tube, said pump further comprising,a closure having a cavity area, said closure including said pump outlet and an opening for communication with said cavity area,a piston and a rolling seal covering said opening, said piston and said rolling seal allowing a relatively slow leak from said cavity area,means for oscillating said piston, anda flexible membrane provided within said cavity area between said pump outlet and said piston, said membrane dividing said cavity area into a first cavity between said membrane said outlet and a second cavity between said membrane and said piston, said membrane preventing communication of gas between said tube and said second cavity; and
wherein gas pressure developed in said patient circuit tube communicates to said first cavity deflecting said membrane towards said second cavity, wherein gas displaced by said membrane displacement in said second cavity escapes through said slow leak, wherein when said oscillating means oscillates said piston, said flexible membrane oscillates correspondingly generating tidal volumes through said patient circuit tube and said endotracheal tube.
1 Assignment
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Accused Products
Abstract
A high frequency oscillatory ventilator for infants and adults using feedback control to maintain either the desired tidal volume or pressure delivered to the subject. The inspiratory to expiratory time ratio of the ventilator is variable. The ventilator corrects the measured pressure for arbitrarily-sized endotracheal tubes and calculates the actual pressure or tidal volume delivered to the subject. The ventilator also separates the source of the tidal volume oscillations from the patient circuit with a flexible membrane or diaphragm, allowing transmission of oscillating tidal volumes while blocking mean airway pressures. The patient circuit is flexible, but fabricated from low-compliance material to minimize the loss of tidal volume. The ventilator uses feedback control of the exhaust flow to maintain mean airway pressure in the presence of an independently controlled bias flow. Further, a respiratory impedance measurement system is built into or connected to the patient circuit which monitors changes in lung mechanics while the patient is connected to the high frequency ventilator without changing mean airway pressure or removing the patient from the ventilator.
120 Citations
25 Claims
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1. A ventilator apparatus for providing assistance in breathing to a living subject, comprising:
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a low compliance patient circuit tube having a first end and a second end; means mounted to said patient circuit tube for providing fresh gas into said patient circuit tube and for exhausting exhaled gas out of said patient circuit tube; an endotracheal tube intubated in the subject coupled to said first end of said patient circuit tube; a pump for generating tidal volumes having an outlet coupled to said second end of said patient tube, said pump further comprising, a closure having a cavity area, said closure including said pump outlet and an opening for communication with said cavity area, a piston and a rolling seal covering said opening, said piston and said rolling seal allowing a relatively slow leak from said cavity area, means for oscillating said piston, and a flexible membrane provided within said cavity area between said pump outlet and said piston, said membrane dividing said cavity area into a first cavity between said membrane said outlet and a second cavity between said membrane and said piston, said membrane preventing communication of gas between said tube and said second cavity; and wherein gas pressure developed in said patient circuit tube communicates to said first cavity deflecting said membrane towards said second cavity, wherein gas displaced by said membrane displacement in said second cavity escapes through said slow leak, wherein when said oscillating means oscillates said piston, said flexible membrane oscillates correspondingly generating tidal volumes through said patient circuit tube and said endotracheal tube. - View Dependent Claims (2, 3, 4, 5)
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6. A ventilator apparatus for providing assistance in breathing to a living subject, comprising:
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a low compliance patient circuit tube having a first end and a second end; bias flow means mounted to said patient circuit tube having an inlet for providing fresh gas into said patient circuit tube and an exhaust outlet for exhausting exhaled gas from said patient circuit tube; pumping means coupled to said first end of said patient circuit tube for generating tidal volumes; an endotracheal tube mounted to said second end of said patient circuit tube and intubated in the subject; a first pressure transducer mounted on said bias flow means for measuring pressure within said patient circuit tube; means coupled to said bias flow means for minimizing any transmission of oscillations to said patient circuit tube; means coupled through said means for minimizing to said bias flow means exhaust outlet for varying said pressure within said patient circuit tube; and means coupled to said means for varying said pressure and said first pressure transducer for controlling said varying means to maintain a predetermined mean value of said pressure. - View Dependent Claims (7, 8, 9, 10, 11, 12)
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13. An apparatus for measuring the mechanical properties of the respiratory system of a living subject, comprising:
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a patient circuit tube having a first end and a second end; a first pressure transducer mounted at a first location a on said patient circuit tube for measuring the pressure within said patient circuit tube at said first location a; a second pressure transducer mounted at a second location b on said patient circuit tube for measuring the pressure within said patient circuit tube at said second location b, said second location b being a predetermined length from said first location a; an endotracheal tube intubated in the subject having an input coupled to said second end b of said patient circuit tube, and an output represented as x, said patient circuit tube and said endotracheal tube having a known four-pole acoustic characteristic [Ka ] between said first location a and said output x, said patient circuit tube and said endotracheal tube having a known four-pole acoustic characteristic [Kb ] between said second location b and said output x, pumping means mounted to said first end of said patient circuit tube having an input for oscillating said pumping means according to a signal received on said input; a random noise generator for providing a frequency band limited random signal to said pumping means input; means coupled to said first and second pressure transducers for monitoring the measured pressures at said first location a and said second location b during each inspiratory cycle, for determining the power spectral densities Pa and Pb of the pressures at said first location a and said second location b, respectively, using fast Fourier transform, and for calculating Ua, Ub, Px and Ux from the following equations;
##EQU2## where Px is the power spectral density of the pressure at said output x of said endotracheal tube, and Ua, Ub and Ux are the power spectral densities of volume flow at said first location a, said second location b and said endotracheal tube output x, respectively. - View Dependent Claims (14, 15, 16, 17)
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18. A ventilator apparatus for providing assistance in breathing to a living subject, comprising:
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a patient circuit tube having a first end and a second end; bias flow means mounted on said patient circuit tube for providing fresh gas into and for exhausting exhaled gas out of said patient circuit tube; a first pressure transducer mounted at a first location a on said patient circuit tube for measuring pressure within said patient circuit tube at said first location a; a second pressure transducer mounted at a second location b on said patient circuit tube for measuring pressure within said patient circuit tube at said second location b, said second location b being a predetermined distance from said first location a; an endotracheal tube intubated in the subject having an input coupled to said second end of said patient circuit tube, and an output represented as x, said patient circuit tube and said endotracheal tube having a known four-pole acoustic characteristic [Ka ] between said first location a and said output x, said patient circuit tube and said endotracheal tube having a known four-pole acoustic characteristic [Kb ] between said second location b and said output x; pumping means having an outlet coupled to said first end of said patient circuit tube for generating sinusoidal tidal volumes; means coupled to said first and second pressure transducers and to said pumping means for monitoring said measured pressures at said first location a and said second location b over each inspiratory cycle, for determining the power spectral densities Pa and Pb of the measured pressures at said first location a and second location b, respectively, using fast Fourier transform, for calculating Ux from the following equations;
##EQU3## where Px is the power spectral density of the pressure at said output x of said endotracheal tube, and Ua, Ub and Ux are the power spectral densities of volume flow at said first location a, said second location b and said endotracheal tube output x, respectively, and for calculating the delivered tidal volume VT for each inspiratory cycle at said output x by solving for Ux, calculating the inverse Fourier transform of Ux to determine the volume flow ux (t) at said output x and integrating the volume flow ux (t) over each inspiratory cycle; andwherein said monitoring, determining and calculating means controls said pumping means to maintain the delivered tidal volume VT at a predetermined level. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25)
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Specification