SIMV(Synchronized Intermittent Mandatory Ventilation)
1. The concept and the purpose
IMV is the method where only the number which was decided to 1 minute in the condition of the spontaneous-respiration mode sends an active-ventilation. SIMV is the way of making this active-ventilation synchronize with the spontaneous-respiration (It is A/C(ASSIST/CONTROL), sCMV in case of synchronizing with all spontaneous-respirations and active-ventilation's being 送気ed).
However, in the reduction of the effort by intake of voluntary of making up the lack of voluntary air quantity of ventilation after making the spontaneous-respiration and the mechanical active-ventilation of the patient be compatible, it is the purpose of SIMV. SIMV in addition to the volume ventilation to do in PCV and BIPAP, VAPS, PLV, AutoFlow, Pressure Relief, too, is recently done by the active-ventilation.
(Reference 3) The SIMV synonym
The synonym of SIMV includes IDV(Intemittent Demand Ventilation) and IAV(Intemittent Assist Ventilation) but they are not a popular term.
(Reference 4) In SIMV, PSV is common sense?
At the recent resuscitator for the adult, that SIMV which uses a continuous flow isn't considered and to add PSV to the spontaneous-respiration of SIMV become common sense. However, it is the mainstream that, because it was difficult technically, wins a trigger signal in the resuscitator for the newborn baby in the method which for a long time does IMV with the continuous flow. It becomes for the spontaneous-respiration of the newborn baby to have been able to be recently taken by the improvement of the technology and newborn baby however, PTV to make synchronize with the spontaneous-respiration is becoming mainstream. Because the respiratory center is immature, sometimes becoming a hyperventilation when helping in A/C, the newborn baby sometimes manages in SIMV(Pressure) without PSV, too.
2. The component
SIMV alternately arranges the tense which sends an active-ventilation to the (1) intake trigger and the tense of the (2) spontaneous-respiration in the temporal axes. There is tense which is called a trigger window in the former and the duration is called trigger window time. Generally, only taking is sent by the active-ventilation into the trigger window time and in the tense of the spontaneous-respiration, the spontaneous-respiration is possible freely from 0 times to continuously more than one time. The time which adjusted two pieces of these tense is SIMV cycle. In the SIMV cycle time, it is possible to compute at the 60-second/SIMV number of times. Incidentally, to distinguish between the active-ventilation and the spontaneous-respiration exists only in the concept of SIMV.
(1) The active-ventilation
New volume ventilation (volume ventilation with Flow Augumentation, volume ventilation with wave forom control) and pressure ventilation (PCV, BIPAP, Pressure Relief) and moreover the pressure and fusing ventilation (VAPS, volume ventilation with Pressure Augumentation, PLV, AutoFlow) is used for the thing except conventional mechanical active-ventilation (CMV) in the volume ventilation by the method of the active-ventilation.
(2) The spontaneous-respiration
When usual, CPAP was used for the spontaneous-respiration but it is the mainstream that, recently, uses PSV except the low-end machine of the part. The resuscitator for the newborn baby sometimes uses HFV, too.
3. The control system
(1) The controlling mechanism
a) The new Mattick circuit-system
In the past, the mechanism which is controlling in SIMV with the new Mattick circuit like CV-2000, too, existed. It will be the limit of the mechanism which it is possible to control.
(2) The logic circuit method
The circuit which does a ligical decision by the connection structure of hard can be composed. -900 C of Servo, MA-2 do SIMV using this.
(3) MPU (The microprocessor)
MPU operates with the software which was written in the ROM. The recent resuscitator is doing SIMV by the processing by MPU. However, the judgement is possible immediately and it is possible for the version to rise about the complicated condition easily of the ROM exchange.
2) The operating principle
At present, some different methods are practicalized by the setting method of the trigger window.
a) The trigger window time fixation method (The partial period method, European plan)
(Figure ; SIMV (fixed time method))
It is the method which provides a fixed trigger window in the time for the part of the SIMV cycle. It is used for the model which is mainly made in the Europe. It sends an active-ventilation to the spontaneous-respiration which was detected (the trigger) in the window period. Generally, because it is shorter in the trigger window time than in one piece of intake expiration time (the CMV cycle time), an active-ventilation is never continuously sent the twice above the above to one trigger window. If a spontaneous-respiration isn't detected by the trigger window, an active-ventilation is sent with the ending. PSV (if established) is added to the spontaneous-respiration which was detected by the trigger window overtime.
(1) The characteristic of the fixed time method
As the characteristic of the fixed time type, the shorter the trigger window time is, as for the looseness of the timing (the interval) which an active-ventilation is stored in, the ventilation which was more rarely stable is sustained but the frequency with the sent active-ventilation which doesn't synchronize with the spontaneous-respiration is high. It synchronizes with the spontaneous-respiration to the extent that the trigger window time is long oppositely but the fault that the timing (the interval) of the active-ventilation is loose clarifies. This phenomenon isn't conspicuous if there are few predetermined numbers of SIMV but when the predetermined numbers are many, it becomes a problem. Therefore, in the model to use SIMV of this method for, the thing with little SIMV number of times which it is possible to set is a characteristic.
Of the resuscitator of the same manufacturer however, being unclear in the ideal trigger window time, different time is used. For example, in CV-3000, it is 1 second and in CV-4000, it is 1.5 seconds. Drager Evita however, trigger window time is changed into 頻回 every version.
(2) The problem of the fixed time method
(a) The cross-ply with intake quantity
Active-ventilation quantity is made voluntary intake quantity in the cross-ply and the lung capacity becomes excessive when the trigger window opens and an active-ventilation is 送気ed by the inspiratory-phase of the spontaneous-respiration.
(b) The psychological block of voluntary expiration
When the expiration of the spontaneous-respiration starts in the eve of the trigger window, the trigger window time ends while the expiration doesn't end and an active-ventilation is 送気ed.
To solve (a) in Evita, it gives only the ullage of the spontaneous-respiration by the active-ventilation from the trigger window beginning time. Delaying for a maximum of 3 seconds in the beginning of the trigger window if there is a spontaneous-respiration (expiration intake however however) in CPU-1 when the trigger window begins to solve (a)(b) But, the SIMV number of times decreases from the set value only for this time. While is in 0.3 seconds, it doesn't do an active-ventilation immediately after there is a spontaneous-respiration to reduce (a)(b) in Elvira and Erica, after the.
(c) The SIMV number of times isn't kept.
Above-mentioned CPU-1 decreases. Drager Evita before Engstrom Erica, Elvira and Ver.8 increases. Because the trigger window time ends compulsorily at the same time as the active-ventilation begins, the trigger window time reduces this, the SIMV cycle time draws in only about the part and the SIMV number of times increases than the set value according to this.
(3) The way of deciding that it does the time of the fixed time method
(a) The model which uses a fixed value
CPU-1 and CV-3000 are 1 second and CV-4000 is 1.5 seconds.
(b) The model which uses CMV cycle time
Trigger window time is set at the 60-second/CMV number of times. It is adopted in Servo-900, Servo-300 and Hamilton Amadeus, Veola.
(c) The model which uses SIMV and the CMV number of times
The one which decides trigger window time automatically by these set values This was used for Evita before Ver.8.
(d) The model which makes SIMV cycle time a standard
20-30% of the general SIMV cycle time is set. It is 25% in E-150, E-200, Erica, Elvira and in KV-5, it is 20%.
b) The trigger window time variable method (The span method, U.S. term) (Figure ; SIMV (variable-time method))
The 2nd method is the method to assume that all of the SIMV cycle times are a trigger window. It is often used for the model which is made in the U.S.. An active-ventilation is sent to the spontaneous-respiration which was detected first in this period. At the same time, the trigger window ends and PSV is added to the spontaneous-respiration after that. Therefore, in this method, in the trigger window time, it isn't constant. Then, if a spontaneous-respiration isn't detected, an active-ventilation is sent simultaneously with the beginning of the following SIMV cycle. It continues that the active-ventilation came off in this case in the last time with CONTROL, ASSIST in the following SIMV cycle to replenish. In this method, in spontaneous-respiration (PSV), when continuing, the following trigger window is actually abridged to the following SIMV cycle. Bear-3, Bear-5, Benette 7200ae, Adult-Star, Bird It is used for 8400 and 6400.
(1) The characteristic of the variable-time method
The characteristic of this method is the point where the active-ventilation which synchronized with this as far as a spontaneous-respiration was done with the trigger is sent. Also, as for the SIMV number of times, a predetermined number is always kept. But, when there are few predetermined numbers of SIMV, looseness isn't avoided in the interval which an active-ventilation is stored in.
On the other hand, when there are many predetermined numbers of SIMV, SIMV can be used instead of CMV(Assist/Control) because it operates smoothly. Generally, at the resuscitator which adopted this method, the number of times setting by CMV and SIMV is done with the same control and the range with the SIMV number of times which it is possible to set is wide.
(2) The problem of the variable-time method
It is a special case but when the cycle time of the spontaneous-respiration is longer than the SIMV cycle time, the SIMV number of times has decreased.
c) The other time regulation method
In Evita after Ver.11, it was fixed on 5 seconds which much exceed CMV cycle time more. SIMV with equal to or more than 12 times operates as the variable-time method and hereinafter operates as 変法 of the fixed time method if being. A characteristic of this method is near the variable-time method and there is it to cancel the fault that the interval is loose.
4. The advantage and the fault of SIMV
The coexistence compatibility of both can be realized by that the SIMV method which is being "DURE" is false and dividing the active-ventilation which the healer intends and the free spontaneous-respiration of the patient by the temporal axes. The degree of the active-ventilation can be freely set by the setting of the SIMV number of times and it is an advantage. However, there is a fault which can not side because it isn't possible to expect when an active-ventilation is 送気ed from the view point of the patient. When receiving an active-ventilation, it is easier for the back of the trigger to pull out power and not to be against 送気 of gas. On the other hand, when PSV is added, 送気 of gas interrupts the back of the trigger when there is not intake in the enough negative pressure. The patient can not judge by the attitude of which of the passive or active target he should come in touch with the ventilation which starts at now. Therefore, SIMV is improper for "the patient who tries to cooperate with the mechanical artificial respiration" and the idea, "to use the ventilation law which helps all patient intake is kind" such as PSV and A/C(Pressure), PAV, too, is born.