Surgery – Respiratory method or device – Means for supplying respiratory gas under positive pressure
Patent
1997-03-12
1999-07-13
Weiss, John G.
Surgery
Respiratory method or device
Means for supplying respiratory gas under positive pressure
12820421, 12820418, 600529, A61M 1600
Patent
active
059212381
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The present invention relates to a pressure-controlled breathing aid.
Breathing aid devices--or ventilation devices--currently used in mechanical ventilation can be divided into two main groups, namely volumetric devices characterized by the supply of a specified volume in each respiratory cycle, and pressure-controlled devices characterized by the provision of a specified pressure in each respiratory cycle.
Volumetric devices have the advantage of guaranteeing a specified breathed volume, but they have major disadvantages. In particular, they expose the patient to risks of barotrauma as they tend to apply pressure which increases at the end of insufflation. Furthermore, the patient risks not being matched to the device in the sense that the respiratory reflexes of the patient can appear at different times from those at which the volumes imposed by the device finish being supplied.
On the contrary, pressure-controlled devices allow better synchronization of the patient with the device and avoid the risk of barotrauma since the maximum pressure supplied is known in advance. On the other hand, the volume supplied to the patient in each cycle and the breathed volume are not guaranteed.
The purpose of the present invention is to propose a breathing aid device which combines the advantages of both of the known ventilation modes discussed above.
According to the invention, the pressure mode breathing aid device, comprising means for supplying breathable gas to an inspiratory branch of a patient circuit at an inspiratory pressure, is characterized by: breathed volume lower than the command, and to reduce the inspiratory pressure in the case of a breathed volume higher than the command.
Thus, the pressure is adjusted in a direction tending to provide the predetermined volume applied as a command. In this way a volume is guaranteed without taking the risk of increasing the pressure in an uncontrolled manner, nor of creating the particular risk of mismatch between the breathing timing of the patient and that of the device. In particular, the invention is perfectly compatible with devices of the type described in FR-A-2 695 830 in which the device detects the respiratory reflexes of the patient in order to change from inspiratory phases to expiratory phases and viceversa.
In order to prevent any risk of barotrauma, it is advantageous to provide means of setting a maximum predetermined pressure which the pressure applied to the patient will not be able to exceed even if the volume supplied is insufficient.
It is also advantageous to provide a signalling device or other alarm detecting the simultaneous occurrence of insufficient volume and the setting of the pressure at its maximum predetermined value, in order to signal this situation of the device's inability to provide the breathed volume set as a command.
In the framework of the present invention, the expression "breathed volume" is used to denote both the volume of the breathable gas inspired or expired per unit time and the volume or quantity of gas inspired or expired per breathing cycle.
Preferably, the adjustment means apply to the inspiratory pressure a pressure variation which is equal in percentage to the difference between the inspiratory volume and the command.
However, in the case where an extreme value of pressure is predetermined and if the application of such a variation would result in exceeding the extreme value, the new inspiratory pressure is made equal to the extreme value of the pressure.
Other features and advantageous of the invention will furthermore emerge from the following description relating to non-limitative examples.
In the accompanying drawings:
FIG. 1 is a block diagram of a first embodiment of the device according to the invention;
FIG. 2 is an operational flowchart of the regulating means of the device of FIG. 1; and
FIGS. 3 and 4 are two block diagrams similar to FIG. 1 but relating to two embodiments of the device according invention.
In the example shown in FIG. 1, the breathing aid device comprises a patient circui
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Nellcor Puritan Bennett France Developpement
Srivastava Virendra
Weiss John G.
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