Surgery – Respiratory method or device – Means for supplying respiratory gas under positive pressure
Patent
1993-08-18
1997-04-15
Asher, Kimberly L.
Surgery
Respiratory method or device
Means for supplying respiratory gas under positive pressure
12820312, 12820422, A61M 1610, A62B 700, F16K 3102
Patent
active
056199864
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an apparatus for controlling the concentration of at least one component in a gas mixture in an anaesthetic system comprising an inhalation branch, a dosing unit for supplying the component, and a control unit for controlling the supply.
Such a device can be employed in inhalation anaesthetics, e.g. for controlling the concentration of the anaesthetic given to the patient in a gas mixture.
The invention also concerns a method for controlling the concentration of at least one component in a gas mixture in an anaesthetic system.
BACKGROUND ART
In the field of anaesthetics, the trend is towards increasingly refined, and thus expensive, anaesthetics. It has consequently become desirable to reduce the consumption thereof.
One way of reducing the consumption of anaesthetics is to use an anaesthetic system with total or partial re-inhalation. In total re-inhalation, no gas escapes from the system, and the patient is breathing essentially the same gas mixture all the time. The carbon dioxide exhaled by the patient is eliminated in a CO.sub.2 absorber, and oxygen and the anaesthetic are supplied to maintain the concentrations thereof at the desired level. In partial re-inhalation, only part of the exhaled gas mixture is inhaled again, and a certain amount of fresh gas mixture is instead supplied. The gas surplus is discharged during exhalation. If the consumption of anaesthetics is to be minimized, a system with total re-inhalation is the best option.
Controlling the concentration of anaesthetics in anaesthetic systems with re-inhalation is today often performed manually. The anaesthetist sometimes may consult a gas-concentration meter mounted in the anaesthetic system and serving to measure the concentration of the anaesthetic.
It is also known to control the concentration of the anaesthetic automatically by means of a computer.
WO 88/06904 discloses an apparatus for controlling the concentration of a component in a gas mixture given to the patient. The apparatus includes a patient circuit which consists of a circle system for re-inhalation, which has an inhalation branch and an exhalation branch. A gas-concentration meter for measuring the concentration of the component in the gas mixture is provided in the inhalation branch close to the patient and is connected to a computer. A desired-value transducer for setting the desired concentration of the gas component is also connected to the computer. With the aid of signals from the gas-concentration meter and the desired-value transducer, the computer controls a gas-dosing unit which is provided further away from the patient in the inhalation branch, to give the desired concentration of the gas component. Thus, this is a feedback control.
Both in manual and computer-controlled operation it is, however, difficult to rapidly and highly accurately adjust the concentration of the anaesthetic to the desired level.
This is, among other things, due to the fact that there may be a considerable discrepancy between the concentration of anaesthetic in the flow supplied to the breathing system and the concentration of anaesthetic in the gas mixture inhaled by the patient.
DISCLOSURE OF INVENTION
The object of the present invention is, therefore, to provide an apparatus which enables automatic and highly accurate adjustment to the desired value of the concentration of a component in the gas mixture in an anaesthetic system, there being but a brief time delay.
This object is achieved by an apparatus which is of the type mentioned in the introduction to this specification and which is characterized in that the dosing unit is adapted to supply the component to the inhalation branch at a point located ahead of a gas-concentration meter provided in said branch, and that the control unit is adapted to control the supply of said component as a function of the concentration measured by the gas-concentration meter and the flow rate of the gas mixture in the inhalation branch.
This apparatus enables accurate and rapid control of the c
REFERENCES:
patent: 3669134 (1972-06-01), Dobritz
patent: 4022234 (1977-05-01), Dobritz
patent: 4150670 (1979-04-01), Jewett et al.
patent: 4345612 (1982-08-01), Koni et al.
patent: 4399686 (1983-08-01), Kindlund et al.
patent: 4421113 (1983-12-01), Gedeon et al.
patent: 4509359 (1985-04-01), Gedeon et al.
patent: 4587967 (1986-05-01), Chu et al.
patent: 4702242 (1987-10-01), Broddner et al.
patent: 4770168 (1988-09-01), Rusz et al.
patent: 4903693 (1990-02-01), Yasue
patent: 4905685 (1990-03-01), Olsson et al.
patent: 4989597 (1991-02-01), Werner
patent: 5044361 (1991-09-01), Werner et al.
patent: 5049317 (1991-09-01), Kiske et al.
patent: 5094235 (1992-03-01), Westenkow et al.
patent: 5237990 (1993-08-01), Psaros et al.
patent: 5243973 (1993-09-01), Falb et al.
patent: 5423313 (1995-06-01), Olsson et al.
Ventilation inhomogeneity during controlled ventilation. Which index should be used? A. Larsson, et al., Journal of Applied Physiology 65 (1988):5, pp. 2030-2039.
"Pulmonary Blood Flow Determination with Selective Rebreathing or CO.sub.2 ", Linnarsson et al., Karolinska Institutet, pp. 39-48.
"Method to Deliver a Preset Inspired Concentration of Anesthetic Regardless of Degree of Rebreathing", Perhag et al., Anestheslology, V75, No. 3A, Sep., 1991, A1010.
Persson Janne
Werner Olof
Asher Kimberly L.
Werner Olof
LandOfFree
Method and apparatus for controlling the concentration of at lea does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for controlling the concentration of at lea, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for controlling the concentration of at lea will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-354224