AutoFlow, PRVC(Pressure Regulated Volume Control)
1. The concept and the purpose (Figure ; AutoFlow)
PCV is the ventilation of the pressure control type but if doing PCV pressure in the self-regulation to become a setting air quantity of ventilation, it can provide the active-ventilation of the ]—Ê type by the ventilation of the ironhand type. It is possible to fuse with the high level in the advantage of PCV and the advantage of CMV in this way. This try was commercialized by Siemens Servo-300, being first and was named PRVC. In PRVC, it was the category of the substitution of sCMV persistently but the Drager Inc. made (ventilating-pressure self-regulation type PCV) OBJ (DO and to replace with the conventional quantity ventilation) available by the modes of all ventilation such as A/C, SIMV, EMMV in Evita4. This is named AutoFlow. Whatever tense AutoFlow is because it is made with BIPAP system, because it is possible to ventilate a patient freely, theoretically, it doesn't wake up Fighting. SIMV however, after that, in sold Servo i, PRVC became available. Of AVEA and VELA of the VIASIS Inc. however, PRVC can be used by all modes.
2. The component
1) The way of the early stage ventilation
In PRVC, it is 10‡pH.2It gropes about the PCV pressure to begin from the test ventilation of the O and for the air quantity of ventilation to become a set value. AutoFlow however, it seems that it is using the technique to be same but details aren't published.
2) The decision procedure with PCV pressure
The specific processing method differs in AutoFlow and PRVC, but it is based on the compliance in either of future ventilation and fixes the following ventilating-pressure.
3) The intake time
There is not theory which anyone consents to about the way of fixing best intake time but it is possible to be classified as follows by it.
a) It makes the intake time of patient breathing an index.
(1) It uses the value which is longer sufficiently than the intake time of the patient.
0LPM in the intake time end, the intake flow rate becomes a negative condition in some cases. This situation can do an air quantity of ventilation in the maximum if it is the way of thinking which is the same as adding an intake pose to CMV and is the same ventilating-pressure. Also, it is favorable about the oxygenation ability, too. However, in the synchronism with the spontaneous-respiration, it is bad.
(2) It uses the value which is the same as the intake time of the patient.
It is the idea to make to have the time that the air quantity of ventilation doesn't increase even if the extension of the lung prevails sufficiently and extends intake time any more and best. It is the way of making a synchronism and a ventilation efficiency with the spontaneous-respiration compromise. In the intake time of the patient, the difficulty accompanies to make a synchronism and a ventilation efficiency best because it isn't always always constant. This can be solved if setting intake time, being rather long and setting the value which is near zero in Flow Cycle but the machine which can set Flow Cycle is only AVEA and VELA.
(3) It uses the value which is shorter than the intake time of the patient.
All PSV are this situation. In other words, it has priority over a synchronism with the spontaneous-respiration and it approves the decline of the ventilation efficiency. It is possible to use the hand that AVEA and VELA end intake early by setting Flow Cycle to rather many, too.
b) It uses physiological average.
Generally, it is in the safest setting, but the bottom of the positive pressure type artificial-ventilation which is different from the natural ventilation and there is not security with this best value in the distemperedness. It uses a value in about 1 second if being an adult if saying on the average. However, there is a side for which it is difficult to reflect a difference among individuals.
c) It uses the value which maximizes oxygenation ability.
It uses a maximum value in the range which doesn't cause an evil by Auto-PEEP. It doesn't consider a synchronism with the spontaneous-respiration. It makes consequential and "SEDE-SIYON" is indispensable.
(4) The forcible-stop condition
The condition that the active-ventilation aborts is in the present situation only when the airway pressure reaches a peak pressure alarm. Limitation by the measurement taking air quantity of ventilation and the beginning of the expiration during the intake time aren't considered. But, there is a model which Flow Cycle can be set to, too.
(5) The start-up speed of intake
It is the same as the problem by PSV.
3. The control system
PRVC is the application of PCV and PCV level is adjusted only by the control of the intake valve. The pressure doesn't run away even if the airway pressure becomes above the set value with the spontaneous-respiration of the patient. Because AutoFlow is the application of BIPAP, the control of the expiration valve plays an important role more than the function of the intake valve. Because PCV pressure is made by the cooperation of both valves, it is relieved from the expiration valve even if it rises above the set-pressure.
4. The modification element
1) Filtering processing by the ventilating-pressure
Basically, as for the ventilating-pressure of AutoFlow, PRVC, the following ventilating-pressure is fixed based on the compliance which was calculated by the future ventilation. This method doesn't cause hinderance at all at the test lung, but sometimes, the change of the ventilating-pressure is remarkable in case of continuing ventilation and when applying to the living body, it doesn't sometimes become valid ventilation, too. This is because the shaking and the resuscitator which occurs from the feedback system of the living body act mutually each other and the change of the ventilating-pressure is amplified. Generally, it hangs the ventilating-pressure which was won in the calculation to prevent such a phenomenon on the filter and it makes absorb a change. Specific filtering processing fact isn't published by the most cases, the corporate secret. However, the advantages and disadvantages of filtering processing is the important point which fixes the reliability of AutoFlow, PRVC.
2) The relation with the other pressure ventilation
AutoFlow is the new pressure/the quantity ventilation which is exchanged for the quantity type active-ventilation but to do relation with the other pressure ventilation how is unsolved. For example, in SIMV(AutoFlow)+PSV, that it should use the compliance value which is measured in PSV for the calculation of AutoFlow is unclear. If there is much SIMV number of times, the reliability seems to be better about the excluded one *of* the measured value in PSV. However, when little, because the interval which can be measured by the active-ventilation opens, to be as it excluded causes hinderance. As for such processing, too, the specific method is an unknown quantity. Actual Evita4 however, when there is little SIMV number of times, there is an impression that the change of the active-ventilation pressure is big. This algorithm is being regarded as being steadily improved in the future, too.
3) The minimum ventilating-pressure
Because it is operating for the taking air quantity of ventilation to converge on the constant value in the present situation, when there is more required amount (the taking air quantity of ventilation) of the patient than the setting, there is uneasiness which the ventilating-pressure has fallen to unnecessarily. For example, a thing with the active-ventilation pressure which is lower than with PSV pressure is sometimes observed in SIMV(AutoFlow), too. The compulsion pressure ventilation which is lower than the PSV pressure is after all the active-ventilation which doesn't have inevitability. Therefore, that the minimum active-ventilation pressure can be set seems to be important. Also, as for this, the patient ventilation which exceeds a setting taking air quantity of ventilation therefore is permissible.
5. The advantage and the fault
1) The range of the clinical application
In RPVC, the fault of PCV, that the air quantity of ventilation is responsible, is improved. However, PRVC around the early stages was the point which is the variation of sCMV(synchronizedCMV) only and clinical application was limited. The application range is wide because recent PRVC can be used by the mode of all ventilation to use an active-ventilation like AutoFlow.
2) The fusing of the European style and the America style
Of another meaning however, AutoFlow has meaning. It adds intake pose time, being general in the concept of CMV (the mechanical active-ventilation), but this decreases an extension disproportion at the lung and can improve oxygenation ability. However, because it brings about an exsufflation stop in the end-of-suction end condition for the patient who has voluntary ventilation, it is possible to cause Fighting. Generally, at the resuscitator which is made in Europe, a concept, synchronizedCMV to make CMV side with the spontaneous-respiration, is used for the compulsion quantity ventilation. It thinks that it is always added, being general in the intake pose time with CMV and the setting which saved an intake pose isn't too much considered. Generally, the synchronism with the spontaneous-respiration has the tendency not to consider too much and sCMV presupposes "SEDE-SIYON" which is certain degree of. On the other hand, in to be made in America, the ]—Ê type active-ventilation merely means volume ventilation (Assisted Volume Ventilation, Volume Assisted Breath, Mandatory(Volume) Breath, Assisted CMV) and being general, it sets an intake pose to it to choose it only at the necessary time by the option handling, not being indispensable. It adopts the mechanism by which intake above the use of the dwindling wave and the setting intake gas flow rate and the intake which exceeds setting intake time are permissible and it thinks much of the synchronism with the spontaneous-respiration plainly.
In the intake pose time of the narrow sense, it passes away because it massages with the intake pose, too, and also the intake time and it becomes possible when adding AutoFlow to make all of the intake time of the ]—Ê type active-ventilation. In other words, the volume ventilation which doesn't use the intake pose which the user who is made in America detests becomes possible with the European resuscitator. The mechanical active-ventilation gets to have flexibility to the spontaneous-respiration because the ventilation which exceeds the following setting intake gas flow rate is permissible in AutoFlow and also of what tense however, intake and the expiration are permissible. In other words, fuse here in CMV of the European style and the flexible America style concept of the volume ventilation in AutoFlow, being first.
3) The permission by the intake which exceeds a setting intake gas flow rate
Because the mechanism (flow supplementation and the pressure augumentation mechanism in the place to say in the Bear Inc.) by which the ventilation above the setting intake gas flow rate is permissible theoretically, too, is included in AutoFlow, there is not an evil that the airway pressure becomes a negative pressure even if the patient does intake beyond the setting intake gas flow rate at the time of the active-ventilation.
4) There is little Fighting.
As for another advantage of the mechanical active-ventilation which added AutoFlow, the exhalation-valve is an inspiratory-pressure and it is in the closed point. The expiration of the patient is possible even if it is during the intake time with it. On the other hand, the poor total pressure (150cmH to be of the exhalation-valve inside sCMV and in Assisted Volume Ventilation2Because it is closed at O degree ), during the intake time, the patient can not take a breath. In other words, in the active-ventilation which added AutoFlow, it is difficult for Fighting to happen.
5) The possibility to become the inspiratory-pressure which is higher than PCV
However, when the patient renounces an intake effort, because it works to maintain an air quantity of ventilation, the patient tends to neglect an intake effort and the average airway pressure tends to become high for its purpose to PRVC and AutoFlow. Also, because it works when will maintain an air quantity of ventilation compulsorily when there is too more setting quantity than the required amount of the patient, the evil that the airway pressure rises unnecessarily appears.