Surgery – Respiratory method or device – Means for supplying respiratory gas under positive pressure
Patent
1994-10-13
1996-05-28
Burr, Edgar S.
Surgery
Respiratory method or device
Means for supplying respiratory gas under positive pressure
12820328, 12820421, 12820518, A61M 1600
Patent
active
055201725
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to an anesthetic machine.
A distinction is made in medical technology between anesthetic machines and ventilation systems.
Pure ventilation systems have been disclosed, for example, in the form of respiratory support machines as described, for example, in DE 38 20 043 A1, DE 37 12 389 A1 or EP 0 112 979 B1. Ventilation machines or respiratory support machines are used to ventilate patients before or after an operation in cases where the patient's own ability to breathe is insufficient.
By contrast, an anesthetic machine is used for the specific treatment of the patient during an operation. In the case of major surgical interventions, the anesthesia is, as a rule, carried out as so-called inhalation anesthesia. In this case, the patient is supplied by an anesthetic machine with the anesthetic gas mixture which is composed of oxygen, laughing gas and a vaporized anesthetic. At the same time, a ventilation is carried out. An anesthetic/ventilation machine is described, for example, in EP 0 058 706 B1.
The prior art relevant to the present invention is explained in detail in FIGS. 6 to 13 to improve understanding hereinafter.
As depicted in FIGS. 6 to 8, a known anesthetic machine 1 is essentially composed of three main groups, namely an anesthetic apparatus 2, a ventilation part 3 and an anesthetic system 4. The anesthetic apparatus 2 with a high-pressure gas supply is used to produce a fresh gas flow 5, i.e. an anesthetic gas mixture composed of oxygen, laughing gas and the anesthetic agent. The fresh gas 5 is passed continuously or intermittently into the anesthetic system 4.
The anesthetic system 4 represents the central functional unit of an anesthetic machine with which the actual gas exchange between the machine and the patient is brought about. Depending on the degree of unconsciousness, i.e. the depth of anesthesia, the gas exchange is achieved by the patient in the form of spontaneous breathing or, if spontaneous breathing ceases, by a mechanical or manual ventilation. In this case the ventilation takes place by the additional ventilation part 3.
The anesthetic systems 4 in use at present can be differentiated, depending on the reuse of the gas which is exhaled by the patient 6 and returned to the anesthetic system, into three different basic types which are depicted in FIGS. 6 to 8.
In the "half-open anesthetic system" depicted in FIG. 6, the gas which is exhaled and flows from the patient 6 back into the anesthetic system 4 through line 7 is not reused but completely removed from the system through the anesthetic gas extractor 8. The amount of gas (respiratory gas 9) required by the patient must be supplied to the anesthetic system 4 as fresh gas 5 from the anesthetic apparatus 2 via supply line 10. The gas supply line 10 is called the inspiratory branch and the gas removal line 7 is called the expiratory branch.
In the so-called "half-closed anesthetic system" depicted in FIG. 7, part of the exhaled gas is reused, i.e. the amount of gas (=tidal volume) supplied for inspiration by the patient consists partly of previously exhaled expiratory gas and only partly of fresh gas. A circulation 11 for this purpose is drawn as dotted line in FIG. 7, i.e. the expiratory gas from the expiration line 7 goes in one part to the anesthetic gas extractor 8 and in the other part (arrow 12) back to the inspiratory branch 10. This use of the expiratory gas makes it possible to achieve a considerable saving of fresh gas and simultaneously a conditioning of the inspiratory respiratory gas. The conditioning of the respiratory gas 9 in this case takes place by mixing the fresh gas 5 with the expiratory gas which has 100% humidity and a temperature of 37 degrees Celsius. The conditioning accordingly results in a warming and a moistening of the inspiratory respiratory gas. The smaller requirement for fresh gas 5 also makes an impact in terms of costs.
In the so-called "closed anesthetic system" depicted in FIG. 8, the expired respiratory gas 9' in the expiration line 7 is
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Burr Edgar S.
Raciti Eric P.
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