Medical ventilators
First Claim
1. A method of operating a medical ventilator to generate a variable pressure in the airways of a patient, with respiratory fresh gas being continuously delivered during an expiration phase of each breathing cycle, comprising the steps of:
- initially setting the pressure to obtain a desired value of the volume of gas ventilating the lungs of the patient, which value is to be controlled;
measuring the total volume of expired gas flowing in the ventilator away from the patient during the expiration phase;
measuring the volume of respiratory fresh gas delivered by the ventilator during the expiration phase;
subtracting the measured volume of respiratory fresh gas from the measured total volume of expired gas to calculate the volume of gas expelled from the lungs of the patient;
detecting in the calculated value of the volume of gas ventilating the lungs of the patient any change from the desired value; and
adjusting the pressure generated by the ventilator in response to the change in the value of the volume of gas ventilating the lungs of the patient so as to maintain the volume of gas ventilating the lungs of the patient at the desired value.
1 Assignment
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Accused Products
Abstract
A medical ventilator comprises a ventilator duct having an inlet for respiratory fresh gas. The pressure at which the respiratory fresh gas is supplied to the patient is determined by a driving jet disposed in the ventilator duct at a distance from the inlet so that an intervening column of gas acts as a pneumatic piston. The supply of driving gas to the jet is initially set by a regulator to obtain a desired value of a respiratory parameter, such as the volume of gas ventilating the patient'"'"'s lungs during the breathing cycle. The volume of gas expelled from the patient'"'"'s lungs is monitored during operation by detecting means and the regulator is adjusted by a servomotor in response to any change in the measured parameter in order to maintain the parameter at the desired value.
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Citations
10 Claims
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1. A method of operating a medical ventilator to generate a variable pressure in the airways of a patient, with respiratory fresh gas being continuously delivered during an expiration phase of each breathing cycle, comprising the steps of:
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initially setting the pressure to obtain a desired value of the volume of gas ventilating the lungs of the patient, which value is to be controlled; measuring the total volume of expired gas flowing in the ventilator away from the patient during the expiration phase; measuring the volume of respiratory fresh gas delivered by the ventilator during the expiration phase; subtracting the measured volume of respiratory fresh gas from the measured total volume of expired gas to calculate the volume of gas expelled from the lungs of the patient; detecting in the calculated value of the volume of gas ventilating the lungs of the patient any change from the desired value; and adjusting the pressure generated by the ventilator in response to the change in the value of the volume of gas ventilating the lungs of the patient so as to maintain the volume of gas ventilating the lungs of the patient at the desired value. - View Dependent Claims (2)
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3. A medical ventilator, comprising:
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a controller for initially setting the pressure of respiratory fresh gas, which is continuously supplied, to obtain a desired value of the volume of gas expelled from the lungs of a patient during an expiration phase of a breathing cycle, which value is to be controlled; a measuring apparatus for measuring the value of the volume of gas expired from the lungs of the patient during subsequent operation of the ventilator comprising; a first measuring device arranged to measure the total volume of expired gas flowing away from the patient in the ventilator during the expiration phase, the first measuring device generating a first measurement signal in response to the measured total volume; a second measuring device arranged to measure the volume of respiratory fresh gas delivered by the ventilator during the expiration phase, the second measuring device generating a second measurement signal in response to the measured volume of respiratory fresh gas; and a subtracting device for subtracting the second measurement signal from the first measurement signal to generate a resultant measurement signal significant of the volume of gas expelled from the lungs of the patient; a detector responsive to the resultant measurement signal for detecting any change in the measured value of the volume of gas expired from the lungs of the patient from the desired value; and an adjustment device for adjusting the controller in response to a detected change in the measured value of the volume of gas expired from the lungs of the patient in order to vary the pressure of respiratory fresh gas supplied by the ventilator so as to maintain the volume of gas expired from the lungs of the patient at the desired value. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10)
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Specification