Surgery – Respiratory method or device – Means for supplying respiratory gas under positive pressure
Reexamination Certificate
2000-12-29
2003-06-24
Lo, Weilun (Department: 3761)
Surgery
Respiratory method or device
Means for supplying respiratory gas under positive pressure
C128S204180
Reexamination Certificate
active
06581597
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an artificial respiration apparatus and in particular, to a high-frequency oscillation (HFO) artificial respiration apparatus.
2. Description of Related Art
FIG. 11
shows a conventional HFO artificial respiration apparatus
200
. An inhale gas containing a high concentration of oxygen flows from an oxygen supply port
201
via a three-way branching pipe
202
to a patient X and to an exhaust end. The inhale gas flows normally at flow rate from 10 to 30 [l/min] and 60 [l/min] at maximum, to which a high frequency oscillating air pressure is applied by an oscillating air pressure urging block
203
for oxygen supply into lungs of the patient X. Here, the average pressure applied to the lungs of the patient X is controlled by an open degree of a rubber valve of an exhale valve
204
provided at an exhaust opening of exhale gas. The oscillating air pressure has an oscillation frequency (hereinafter, referred to as ventilation frequency) adjusted by rpm of a rotary valve
206
of the oscillating air pressure urging block
203
and an amplitude adjusted by an output of a blower
205
.
Here, explanation will be given on the principle of the oxygen supply in this HFO artificial respiration apparatus
200
. Firstly, when the inhale gas supplied to a patient X is subjected to a HFO air pressure, the pressure amplitude of the inhale gas causes a small-amount ventilation (gas exchange like convection) with respect to the gas (hereinafter, referred to as an exhale gas) containing carbon dioxide in the lungs of the patient X and the dispersion of the inhale gas due to oscillation causes the inhale gas to enter the lungs via an in-trachea tube
207
, which in turn causes the exhale gas to go out of the lungs (up to the mouth of the patient). The subsequent inhale gas performs the aforementioned ventilation and functions to send the exhale gas from the lungs to the exhale gas exhaust opening. Thus, it is possible to maintain a constant oxygen concentration in the lungs of the patient X.
The aforementioned HFO artificial respiration apparatus
200
has three basic parameters which can be set by a user (doctor) according to the state of a patient: (1) inner pressure of a patient circuit from the oxygen supply port to the patient X (5 to 15 [cmH
2
O] (490 to 1470 [Pa]), (2) oscillation amplitude of the high frequency oscillating air pressure (output of the blower
205
), and (3) ventilation frequency of the oscillating air pressure (3 to 15 [Hz]). There are also additional parameters: the inhale gas amount supplied to a patient X and the oxygen concentration of the inhale gas. The basic parameters are controlled according to the state of the patient X so as to obtain an optimal respiration condition.
(1) When it is necessary to increase the oxygen partial pressure (PaO
2
) in the artery blood of the patient X, the average inner pressure of the patient circuit is increased.
(2) In order to reduce the carbon dioxide partial pressure (PaCO
2
) in the artery blood, the amplitude of the high frequency oscillating air pressure is increased.
(3) The inherent ventilation frequency increasing the ventilation efficiency of the HFO artificial respiration differs depending on each of the patients X as well as on the state of a patient X. Accordingly, the ventilation frequency is controlled so as to be in the vicinity of such an inherent ventilation frequency.
The ventilation frequency is initially determined by the weight of the patient X and adjusted so as to obtain resonance with the body of the patient X to increase the gas (oxygen) diffusion effect, which in turn enables to obtain an effective gas exchange (between the oxygen and the carbon oxide). In general, the ventilation frequency is set to about 15 [Hz] for new-born babies, and to 3 to 10 [Hz] for children and grown-ups.
This ventilation frequency is usually fixed to a constant value unless a sudden change of the state of the patient X is observed. Accordingly, the respiration condition is normally adjusted by the parameters (1) and (2) alone.
On the other hand, when the PaO
2
is excessively reduced or the PaCO
2
is excessively increased due to a change of the state of the patient X, this means that a change has occurred in the ventilation frequency inherent to the patient X and it is not sufficient to adjust the parameters (1) and (2). That is, the ventilation frequency should be adjusted.
Here,
FIG. 12
shows the relationship between the ventilation frequency and the ventilation amount at a time for the lungs of the patient X when the output of the blower
205
of the oscillating air pressure urging block
203
is fixed to a drive upper limit in the HFO artificial respiration apparatus
200
. As shown in
FIG. 2
, in the HFO artificial respiration apparatus
200
, as the ventilation frequency is changed, the ventilation amount at a time is also changed. This is because a change of the ventilation frequency causes a change of the degree of the gas turbulence. For example, when the ventilation frequency is reduced, the flow resistance in the patient circuit is also reduced, and when the ventilation frequency is increased, the flow resistance is also increased.
Accordingly, in the aforementioned conventional example, if the ventilation frequency is reduced while maintaining the blower output constant, the ventilation amount at a time is abruptly increased. Even when the ventilation frequency is reduced only by 1 [Hz], the ventilation amount at a time may be excessively increased.
In order to evade this, the operator (doctor) of the HFO artificial respiration apparatus
200
should slightly reduce the output of the blower
205
by visual observation before changing the ventilation frequency. Moreover, the operator cannot know accurately how much the output of the blower
205
need be reduced. That is, it is difficult to maintain the ventilation amount at a time at a constant value when changing the ventilation frequency.
SUMMARY OP THE INVENTION
It is therefore an object of the present invention to provide a HFO artificial respiration apparatus capable of suppressing the change of the ventilation amount at a time when changing the ventilation frequency without requiring a complicated operation.
The high-frequency oscillation (HFO) artificial respiration apparatus according to the present invention comprises: an inhale gas introduction block for supplying an inhale gas containing oxygen to a patient; a patient-side path for guiding the inhale gas from the inhale gas introduction block to the patient, an oscillating air pressure urging block for applying an oscillating air pressure having a shorter cycle than a respiration cycle of the patient, to the inhale gas flowing in the patient-side path, an exhaust path for exhausting an exhale gas containing carbon dioxide exhaled from the patient; and a controller for controlling the oscillating air pressure urging block. The oscillating air pressure urging block includes an oscillation amplitude regulator for regulating an amplitude of the oscillating air pressure and a frequency regulator for regulating an oscillation frequency of the oscillating air pressure.
The controller includes an input block for accepting setting inputs for specifying an oscillation frequency of the oscillating air pressure and a ventilation amount at a time for the lungs of the patient and an operation control block for controlling the frequency regulator and the amplitude regulator according to the inputs. The operation control block has a ventilation amount maintaining function for controlling an amplitude based on the amplitude regulator in such a manner that the ventilation amount at a time for the lungs of the patient is maintained at a constant value when the oscillation frequency of the frequency regulator is changed by the setting inputs.
With this configuration, an operation of the apparatus enters an oscillation frequency of the oscillating air pressure
Greenblulm & Bernstein, P.L.C.
Lo Weilun
Patel Mital
Suzuki Motor Corporation
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