[Supplement] The change of the trigger mechanism
A. The incunabula
The controlled-respiration equipment "Controller" which was practicalized to the 1940-1950s was a meaning, the machine to be automatically ventilated by, and was called another name "Automatic ventilator". The manufacturer such as Engstrom(1954), Bang(1953), Blease(1956), Beaver(1953), Barnet(1958), Drager(1953) was born one after another this time. In the second half of the 1950s, "Assister" to make the beginning and the active-ventilation of the intake effort of the patient synchronize with already with the trigger mechanism was practicalized and a trigger formula with a variety since then was proposed.
B. The new gusset tic prime
It was liked by "Assister" and the new Mattick method which makes a gas pressure a driving-source was adopted because the reaction of the trigger mechanism was quick. However, it is the machine which depends on the mechanical circuit, e.g. Bennett PR-2(1957-), Bird mark in the controlling mechanism 4 In (1959-), with the inevitability of the tectonically, it was rather the operation form which is near the volume trigger, not being a pure pressure trigger.
C. The beginning of the electric-control
Bennett MA-1(1967-), Engstrom which controls the machine of the new Mattick method finally in the fast charge feeling 2000(1974-) , The machine of Elema-Schonandor Servo-900(1970-) and so on appeared As for these many, the simple and sure pressure trigger formula with the electrical switch which is stored by the change of the circuit internal pressure was adopted. To make a circuit internal pressure cause a change by the intake effort, the full closure of the patient circuit is necessary. This didn't become a problem at all in the CMV(ASSIST/CONTROL) ventilation and was if anything evaluated as the favorable mechanism in popularization of PEEP. Even the technique to use PEEP could be suggested to the degree where there is not interference to raise sensitivity.
D. The popularization of SIMV
As the SIMV method became popular with the equipment of Siemens Servo-900B(1976-) and Drager UV-1(1978-), MRT CV-2000(1975-), Bennett MA-2(1978-) and so on, a wide range of mechanisms of the demand valve and the continuous flow, the reservoir bag and so on appeared for the spontaneous-respiration and also the equipment which combined these appeared. The demand valve method is the fault which the pressure trigger formula and the affinity are good for but many 有意"NI"吸 feeling work volumes are important to compared with the continuous flow method, being. On the other hand, the continuous flow method absorbs the change of the circuit internal pressure by the intake effort and has the fault to interfere with the start of the pressure trigger by. As for the SIMV machine in these times, it adopted a pressure trigger formula but most faced "a dilemma", the continuous flow mechanism for the reduction of the intake work volume and the trigger sensitivity in SIMV. CV-2000 was doing the plan of the desperateness to secure substantial sensitivity, stopping a continuous flow in the trigger window period to 姑息的.
E. The rise of the flow trigger formula
On the other hand, at the equipment which used a continuous flow mechanism specifically as the fundamental solution method of this "dilemma", " flow trigger mechanism " which makes a flow rate and intake quantity an index was introduced. (Strictly, it should express with the flow rate trigger, the quantity trigger.) In Bourns Bear-2(1985-), it made the flow rate of gas the temperature change of the thermistor, BOC CPU-1(1982-) sensed that the plastic ball of the style which is all over the body runs by the optical senser, Engstrom Erica(1981-) changed a flow rate into the pressure gap using Venturi tube and got a flow trigger signal. As for the ideally, the flow trigger formula is more excellent than the pressure trigger formula. Until a trigger is done in the former about the reason, as for the patient, because it is possible to breathe in gas freely, the intake work volume is a small thing compared with the pressure trigger formula. However, the temporal delay didn't result to be in the technology in those days compared with the pressure trigger formula because the low flow rate could not be detected and to have absolute advantage to the pressure trigger formula. However, because PSV didn't become popular, at this point, it didn't become a problem so. In these times, the compromise-method which introduced the advantage of "the continuous flow method where there are few intake work volumes which do a trigger" and "most of the maximal flows and moreover the demand method where there are few gas consumption and exhalation breathing resistances" was contrived. It passes a few bias flows beforehand to the demand mechanism and it is the mechanism which detects the beginning of the spontaneous-respiration in the flow trigger formula. This mechanism resembles in CPU-1, Bear-2, Erica, equal and is seen. It is Bennett to the others Like 7200(1984-), it used a pressure trigger formula for the general ventilation of CMV and SIMV, PSV "NADO" and in Flow by which is 変法 of the continuous flow method, the model which uses a style quantity ー trigger formula, too, appeared.
F. The popularization of PSV
Servo-900C(1980-)、Engstrom ERICA(1981-)、Bear-5(1986-)、Bennett 7200(1984- ) , Feeble intake however, the performance which does a trigger without the sure and moreover temporal delay became necessary in earnest when equipped with equal "DE" PSV, and Ohmeda CPU-1(1988-), Bear-3(1989-) and so on, too, were equipped with PSV in the addition and PSV began to be used by the general clinician In the conventional flow trigger mechanism, the mystery gar became a problem and the sensitive pressure trigger formula which used a half conductor sensor (the impedance changes when adding a stress to the silicon crystal ; the sensor which applied a piezo resistance effect) attracted attention again. For example, because it was the flow rate trigger which used a mechanical sensor in Ohomeda CPU-1 but it supported PSV, in Advent(1989-) of the improvement machine, it was changed into the pressure trigger formula by the half conductor sensor.
G. The improvement of the sensor technology
In the automotive industry, because it supported the experience of oil crisis (1973) or emission control, it was done in the activeness of research "GAGA" which attempts for the combustion efficiency of the internal combustion engine to improve. For the fuel control to keep the mix proportion of correct aerial fuel into this, the development of the high-precision inspired-gas quantity measuring equipment was included. Specifically, to control the highest level, the air volume with 1 induction stroke must be able to be correctly measured about each cylinder. At fuel injection equipment (EGI) around the early stages, the flow measurement mechanism of the flap type was used. This is Servo It took the movement of the flap which changes according to the flow rate in the flag which is in 900 flow transducers and the similar principle out with the analog-signal. Regular readjustment was required to this. The output of the EGI the fast response, the physical strength, the low price, the durableness, the calibration are free, for which and then, it is easy to make a rigorization and the flow measurement mechanism of developing into the digital from being analog, too, more in the digital processing was demanded. It responded to these severe requests and in the 1980s, Hot wire type, Vortex type, 等, a various flow transducer were practicalized. As well as these technologies of ( Note ; that the practical example to these resuscitators is as follows, too ) with which the control valve of the liquid-rocket engine which was developed by NASA and the control technique of the various chemical industry, the mechatronics technology which is produced in mass with the AV equipment and then a microprocessor technology are compound and it are used for
1. The Vortex type
The turbulent flow occurs behind the obstacle which was installed, that the style was all over the body and Karman vortex occurs but the number of these whirlpools is proportional to the flow rate. The sensor which applied this principle is called Vortex type. It is applied to Mitsubishi Motors's fuel control system ECI and Bear-5. But, there is a fault which can not be measured because the whirlpool doesn't occur in the area with few flow rates.
2. The Hot wire type
The sensor by which a heated inoculating needle was cooled according to the flow rate of air and it changed impedance but applied this is Hot wire type. Nissan Motor's fuel control system ECCS and Bennett It is applied to 7200, Drager Evita. The Hot film type, too, is the same principle. Of the infant 用 and the thing for the adult must be used by the problem in the scalableness range.
3. The flow rate expectation type by the valve position
In fuel control system PGM-FI in Honda Technical Research Institute, it is the pressure amplitude of the place around the throttle valve and the one of the throttle valve. It reads the flow rate to have supported this from the aperture from the program and it is doing (Note ; the basic-patent is Bosch Inc.) a flow measurement but in the principle which is the same as this, Hamilton Amadeus and Drager Evita are measuring an intake flow rate by the pressure gap of the place around the intake valve and the aperture of the valve. This method is highly precise and the scalableness range, too, is wide. Even if it says that a recent resuscitator flow measurement of the side of intake is almost done by this method, 過言 is not.
4. The supersonic transit type
It is used for the expiration flow measurement of Servo i and Servo s. In the transmitter/receiver of the supersonic, it is established and it is measuring the difference of the propagation time of the supersonic among two to two back and forth at the aisle of fluid. If fluid doesn't have speed, there is not a propagation differential-time, but the propagation time draws in according to the current velocity about fluid and the supersonic of the direction and the opposite direction becomes long. By featuring, the wide measuring range and the high-precision can look forward to it, but to get a differential-time, the length among two becomes need and only the part has the fault that the sensor becomes big. There is one with the big exhalation-valve unit of Servo i and Servo s because of the length with measuring-unit.
5. The delta-pressure type
It installs an obstacle in the aisle, and it measures a pressure inclination among two of the back and forth and it measures a flow rate. It is used for the flow rate measurement by call feeling 測 of a lot of resuscitators such as the VYASIS Inc. and the Hamilton Inc.. Because it features and measuring range is limited, the resistance value sometimes uses the variable area film (variable orfice membrane) which the flow rate changes, too, but however, of the infant 用 and the thing for the adult must be used.
H The flow rate measurement technology prescribes the plan of the resuscitator.
The flow rate measurement technology sometimes fixes the basic mechanism and the specification, the feature of the resuscitator. For example, the flow transducer of the Vortex type is very firm and needs a quality control on it hardly. However, because it isn't possible to measure if not being above the flow rate which is constant, in Bear-5, 5LPM base flow is applied into the circuit. However, because the base flow lowered the sensitivity of the pressure trigger, the 圧測 fixed mechanism which used proximal pressure monitor tube "Proximal Airway Pressure Tube" on the measure became indispensable. However, the EMMV mechanism by the expiration expired volume per minute became possible thanks to the flow transducer with high reliability. The side of intake is measuring a flow rate by the valve aperture but Evita is using the flow transducer of the Hot wire type for the side of the expiration. However, it is of problem's there being in the thing, the durability which calibration "GA" needs at the Hot wire type equal "GA" cause and it isn't possible to have absolute trust to the information on the expiration air quantity of ventilation. Therefore, EMMV becomes the mechanism which made the expired volume per minute of intake an index necessitously. Evita At 4, it is using the unique flow trigger formula to have made demand sensitivity and trigger sensitivity be independent. However (the commonplace resemblance?), the base flow to think that should combine with the flow trigger mechanism isn't flowing. This is to process only by Fluothane Sir information on the side of intake. The expiration flow measurement of Servo i can simplify a patient circuit, not needing a special sensor even if it is a newborn baby mode, becoming applicable with one sensor from the newborn baby to the adult because the measuring range, too, is wide.
I. Future trigger mechanism
Because recently the flow measurement technology improved, the " float rigger " method which exceeds a conventional pressure trigger formula became possible. In Baby-log of the Drager Inc., the flow rate trigger could be done by the several-ml unit and a field, SIMV in the newborn baby, was pioneered newly. At present, the development competition of the resuscitator for the newborn baby which has PTV(Patient Triggered Ventilation) feature has started. The recent tendency about the trigger formula is in the direction where the auto trigger and the sensitive contradiction solve a flow rate condition by the complex-condition which combined a layer matter with the main constituent. For example, Drager Evita does in the trigger in the condition to have compounded a flow rate and pressure to ASB, BIPAP. Of Servo-300 of the Siemens Elema Inc. however, also, it does a trigger by the complex-condition with flow rate and pressure. The term, filtering algorithm, is remarkable recently. It is the technology which does an advanced "DEZITARUHUIRUTA-" place reason, removes a noise ingredient and cancels malfunction at the trigger in the gotten information. The resuscitator of above mentioned third generation is never exaggeration, saying being "the equipment to have embodied a technology of the side of the flownmeter by" even if it expresses. The resuscitator in the future seems not to be operation form, - cycle and the - generator method like the past, and the viewpoint to classify by the mechanism and the performance of the used technology of the side of the flownmeter seems to increasingly become important more.