Questions on Mechanical Ventilators - page 2

Hello:) I need help with answering the questions for my vent training certification. I'll appreciate any help you can give. Please if you know of any websites that can help a newbie, pls send it... Read More

  1. Visit  912smith profile page
    1
    i need help with 3 questins concerning a ventilator.
    1) In the SIMV mode, all patient breaths are delivered by the ventilator.
    true or false

    2) The amount of pressure needed to keep the lungs from totally collapsing after exhalation is peak inspiratory pressure (PIP).
    true or false

    3) The secondary low-pressure alarm may alert the caregiver that the tubing may be kinked.
    true or false
    icuRNmaggie likes this.
  2. Visit  GilaRRT profile page
    0
    Quote from 912smith
    i need help with 3 questins concerning a ventilator.
    1) In the SIMV mode, all patient breaths are delivered by the ventilator.
    true or false

    2) The amount of pressure needed to keep the lungs from totally collapsing after exhalation is peak inspiratory pressure (PIP).
    true or false

    3) The secondary low-pressure alarm may alert the caregiver that the tubing may be kinked.
    true or false
    How about you tell us what you think the answers and why, then we can discuss. Sorry, I'm not going to give you answers without any discussion.
  3. Visit  zcoq72mehs profile page
    0
    I could be wrong, but in regard to:
    i need help with 3 questins concerning a ventilator.
    1) In the SIMV mode, all patient breaths are delivered by the ventilator.
    true or false

    2) The amount of pressure needed to keep the lungs from totally collapsing after exhalation is peak inspiratory pressure (PIP).
    true or false

    3) The secondary low-pressure alarm may alert the caregiver that the tubing may be kinked.
    true or false

    1. simv stands for synchronized intermittent mandatory ventilation. It has a minimal rate, say simv12. This minimal rate will be delivered by the ventilator, no matter what (think of it as a back-up rate). Now.......let us say the patient decides to take a breath on their own......the machine synchronizes with the patient breath request, and gives the volume of air per its settings (perhaps a tidal volume of 700cc or whatever). It is synchronized. It is intermittent because it gives the breaths at the minimal rate AND the patient's own breath request rate (this prevents 'air hunger' if you will, prevents anxiety that you can not breathe on your own, and will help you with the breath via delivering the volume). It is mandatory, because once that patient initiates the breath, it is going to give that mandatory volume, and mandatory minimal back-up rate.

    2. peak inspiratory pressure is probably not what you are looking for to prevent lung collapse. Peak inspiratory pressure varies (ards or wet lungs, bronchoconstriction, obstrucive process, whatever).......you dont want it to get too high cause you could cause a pneumothorax, in uncuffed cases, possible abdominal distention, etc., ntm trauma to the lungs. You dont want your mean airway pressures to be high over prolonged periods of time, and the PIP is part of that equation.

    Instead, I believe you are looking for PEEP--positive end expiratory pressure. This can be 5cm h2o or whatever the pulmonologist and RT think is optimal based on serial abg's, clinical condition, etc etc., but frequently it is somewhere between 5 to 10. This positive end expiratory pressure maintains airway pressure in the lungs, preventing the alveoli from collapsing, thus allowing maximal time for respiratory exchange (which includes the diffusion of gases, oxygen and carbon dioxide in particular), and thus providing optimal clinical condition.


    3. 'low pressure' alarms are usually a result of low pressure......thus, a LEAK......the gases are escaping somehow, thus reading low pressure. If the tube was KINKED, the pressures should be HIGH, cause the ventilator attempts to cycle, and there is an obstruction to the gas flow, causing the pressures to increase, setting off high pressure alarms.


    that is my take on it anyway. hope it helps. and, i am not an expert, so be forewarned. i am just a nurse. Really you should ask your respiratory therapist.

    yes, i did read that blue textbook 20years ago (egans respiratory care), and i have worked with lots of ventilators, but i never had a single inservice. just self-taught stuff.
  4. Visit  zcoq72mehs profile page
    0
    also, just to be clear.......simv does not have to deliver the 700cc in all settings.......assist control, also labeled CMV (albeit nearly incorrectly and confusingly, as that stands for controlled mandatory ventilation, wherein you are not supposed to be allowed to take your own breaths......it can be used for sedated and paralyzed cases), WILL deliver that exact volume, however...........

    so, simv can allow the patient to take their own breaths between the backup rate, with NO guaranteed volume delivered by the machine.............

    CMV, which should be labeled AC for assist control, DOES give that prescribed volume with every patient breath request.........

    SIMV allows for a lower minute averaged mean airway pressure for the patient........which is something you want.........because when the patient breathes, it doesnt have to push 700cc, and give all that pressure to achieve that 700cc volume.

    CMV/AC WILL always give that 700cc volume, thereby producing higher averaged mean airway pressures.


    sorry about that...........

    it is just that simv on some ventilators can do some tricky stuff.......you CAN make it do certain stuff..........

    But, in the traditional, old-fashioned sense.......SIMV all by itself will only give the 12breaths of 700ml, allow the patient to breath on their own more if they wish, without giving them 700ml, but instead just allowing however much they can inhale on their own (300ml or whatever).

    hope that is clear as mud.



    ventilators have become most complex nowadays, being both volume controlled, pressure controlled, bilevel controlled, cpap controlled, allow talking with cuff deflation, etc etc etc............
  5. Visit  GilaRRT profile page
    0
    I am not sure I track you on the lower minute averaged pressure always being something you want? You have other options such as pressure controlled ventilation and "hybrid" modalities such as VC+ (PB 840) or PRVC (Servo-i) that will work with AC. SIMV has many pitfalls that must be appreciated. Increased work of breathing can occur with SIMV among other problems. The pros and cons of each mode must be considered; however, SIMV is not a mode I would often consider for a variety of patients.
  6. Visit  GreyGull profile page
    0
    Quote from 912smith
    i need help with 3 questins concerning a ventilator.
    1) In the SIMV mode, all patient breaths are delivered by the ventilator.
    true or false
    This question can either be a trick question on an RT exam or a poorly written question on a nursing quiz.
  7. Visit  zcoq72mehs profile page
    0
    Quote from GreyGull
    This question can either be a trick question on an RT exam or a poorly written question on a nursing quiz.
    probly a question on RT exam of some sorts. I wouldnt necessarily say it is a trick question (it wants you to think it thru), but it could definitely be written better.
  8. Visit  zcoq72mehs profile page
    0
    Quote from GilaRN
    I am not sure I track you on the lower minute averaged pressure always being something you want? You have other options such as pressure controlled ventilation and "hybrid" modalities such as VC+ (PB 840) or PRVC (Servo-i) that will work with AC. SIMV has many pitfalls that must be appreciated. Increased work of breathing can occur with SIMV among other problems. The pros and cons of each mode must be considered; however, SIMV is not a mode I would often consider for a variety of patients.
    I am not an RT or pulmonogist. It is just my opinion based on my experience. I do not know why YOU would desire higher peak airway pressures over lower airway pressures if you had a choice and the immediate clinical results are the same. It is usually not a 'goal' of the pulmonologist to WANT higher mean averaged airway pressures as it can have deliterious effects. If your experiences are different, please do expound as to why your pulmonogist and/or RT department desires higher mean averaged airway pressures as a desired goal over NOT having to have them, as to educate me and others, please.

    Pressure controlled ventilation is just that--it delivers a pressure, no guaranteed volume (in its purest sense. remember, their are algorithms used by these ventilators now which can make changes based on results, ntm other modalities that can be implemented, which is why i had to post twice in regard to simv. but, in isolation, there is no guaranteed volume). Just because you have pressure controlled ventilation does not mean you somehow want or desire HIGHER averaged mean airway pressures vs. achieving the necessary clinical outcome without needing those higher airway pressures. Generally speaking, we try to achieve the desired goals while keeping in mind the mean airway pressure/peak airway pressure--as in not letting them go higher unnecessarily, as it is not a goal/desirable.

    Yes, SIMV can have an increased work of breathing--depending on the clinical situation, you may want this. You dont usually want to go from assist control to extubation. We want to exercise the diaphragm, see the results, make adjustments, etc. Many times the next logical step from AC is SIMV to do just that--to increase the work of breathing as a step in a process that makes one closer to the extubation process, ntm mean airway pressures.

    But all this is really academic--i didnt want to just answer the question without trying to assist with the thinking process as to why the questions were being posed. There are rarely absolutes in the medical profession, and situations can present themselves that may dictate a change from the standard intervention. The use of the word 'always' was probably a mistake, hindsight, but i would like an exposition as to why you feel that it could be a desired goal to have a higher one than one could achieve without having that said higher one considering its possible harmful effects.

    I do not know of any harmful effects by wanting to minimize peak and mean airway pressures for a given clinical situation/outcome.

    apparently you do...........

  9. Visit  GreyGull profile page
    0
    Breaths are delivered by the ventilator either by a controlled breath or a pressure supported breath but who or what initiated the breath is different. It would be rare today to not use a pressure supported breath with SIMV. In the Eagan book you read from over 20 years ago it may still have discussed the patient breathing spontaneously from a free flowing bag attached inline to the ventilator.
  10. Visit  zcoq72mehs profile page
    0
    Quote from 912smith
    i need help with 3 questins concerning a ventilator.
    1) In the SIMV mode, all patient breaths are delivered by the ventilator.
    true or false

    2) The amount of pressure needed to keep the lungs from totally collapsing after exhalation is peak inspiratory pressure (PIP).
    true or false

    3) The secondary low-pressure alarm may alert the caregiver that the tubing may be kinked.
    true or false
    Ok, i will try to be more direct now that all this info has been shared. Remember, i may be wrong.

    1. pure simv allows the patient to breath on their own, therefore false

    2. False. PEEP, positive end expiratory pressure, is used to prevent alveolar collapse. Inspiratory pressures are for inspiration, and should not directly be related to 'collapsing after exhalation' since it works with the inspiratory cycle, n ot the expiratory cycle of the equation.

    3. false. kinking something will cause an obstruction of gas flow, INCREASING pressure, setting off a high pressure alarm. low pressure alarms can be because gas is leaking someplace/somehow, usually.
  11. Visit  zcoq72mehs profile page
    0
    Quote from GreyGull
    Breaths are delivered by the ventilator either by a controlled breath or a pressure supported breath but who or what initiated the breath is different. It would be rare today to not use a pressure supported breath with SIMV. In the Eagan book you read from over 20 years ago it may still have discussed the patient breathing spontaneously from a free flowing bag attached inline to the ventilator.
    That is what i was talking about. In the clinical setting, SIMV is augmented. I mean, think about it.........we have a 7.0 ETT, all this circuit length to overcome.........pi r squared and length are related to resistance. In the clinical setting we are going to overcome this resistance thru implementation of other settings. But, simv in its purest sense allows the patient to breath on their own, in between, without guarantee-ing a set volume, thereby lowering the averaged mean airway pressures, exercising the diaphragm, building up phosphodiesterase levels, and a step in the weaning process as the clinical condition dictates.

    You and I know that SIMV in the clinical setting WILL be augmented as necessary.........you and i also know that cpap is sometimes used also, which is a lot more difficult than augmented simv..........and we then do serial abgs, assess clinical outcome, etc etc. all in an attempt to assess readiness for extubation or whatever.

    Even bipap is used on these ventilators nowadays.......again, more difficult to breathe than unaugmented simv.


    But, you CAN give SIMV wherein there is NO augmentation. We all need to get past this. In its purest sense, simv allows the patient to 'breathe on their own' so to speak.

    Overthinking the question is probly not a good idea just because we know that we dont necessarily implement simv without pressure support to overcome the beforementioned resistance formula to at least give them a similar environment as what it would be like to breathe on their own.
  12. Visit  GreyGull profile page
    0
    Quote from zcoq72mehs
    I do not know why YOU would desire higher peak airway pressures over lower airway pressures if you had a choice and the immediate clinical results are the same. It is usually not a 'goal' of the pulmonologist to WANT higher mean averaged airway pressures as it can have deliterious effects. If your experiences are different, please do expound as to why your pulmonogist and/or RT department desires higher mean averaged airway pressures as a desired goal over NOT having to have them, as to educate me and others, please.
    In some patients achieving a higher MAP might be desirable for oxygenation and this is obtained by manipulating the factors or setting that are part of the MAP equation. This will be within reasaon with the Plateau Pressure monitored clossed. The PIP and the Plateau pressure will give you an indication at to what the reason for the increased PIP might be. If the MAP is high and the goal of oxygenation still has not been achieved, time for a different mode or a different ventilator such as a HFOV. But even on the HFOV, the initial MAP setting will be at 2 (neonatal) - 5 cmH20 (adult) higher than the conventional ventilator.

    OXYGENATION is proportional to MAP x FiO2

    MAP =

    (Ti x PIP)+(Te x PEEP)
    -------------------------------
    Ti + Te

    This equation assumes Pressure vs. Time is a square wave or a Pressure Control Mode.


    Ways to increase MAP
    1. Increase PEEP
    2. Increase PIP
    3. Increase Ti
    4. Increase RR
    5. Increase Flow

    Quote from zcoq72mehs
    Pressure controlled ventilation is just that--it delivers a pressure, no guaranteed volume (in its purest sense. remember, their are algorithms used by these ventilators now which can make changes based on results, ntm other modalities that can be implemented, which is why i had to post twice in regard to simv. but, in isolation, there is no guaranteed volume). Just because you have pressure controlled ventilation does not mean you somehow want or desire HIGHER averaged mean airway pressures vs. achieving the necessary clinical outcome without needing those higher airway pressures. Generally speaking, we try to achieve the desired goals while keeping in mind the mean airway pressure/peak airway pressure--as in not letting them go higher unnecessarily, as it is not a goal/desirable.
    Pressure controlled ventilation will give you a slightly higher MAP because it is a square wave delivery.


    Quote from zcoq72mehs
    Yes, SIMV can have an increased work of breathing--depending on the clinical situation, you may want this. You dont usually want to go from assist control to extubation. We want to exercise the diaphragm, see the results, make adjustments, etc. Many times the next logical step from AC is SIMV to do just that--to increase the work of breathing as a step in a process that makes one closer to the extubation process, ntm mean airway pressures.
    SIMV is rarely used for weaning today. The days of "decrease the rate of SIMV by one each day" are gone as we now wean patients quicker to reduce ventilator days. Each morning hospitals across the country may do a sedation vacation on a patient in the AC mode and place the patient into an SBT (Spontaneous Breathing Trial) which is Pressure Support. If the patient tolerates it, they may allow them to continue and even consider extubation at that time.
    Last edit by GreyGull on Dec 31, '10
  13. Visit  GreyGull profile page
    0
    Quote from zcoq72mehs
    That is what i was talking about. In the clinical setting, SIMV is augmented. I mean, think about it.........we have a 7.0 ETT, all this circuit length to overcome.........pi r squared and length are related to resistance. In the clinical setting we are going to overcome this resistance thru implementation of other settings. But, simv in its purest sense allows the patient to breath on their own, in between, without guarantee-ing a set volume, thereby lowering the averaged mean airway pressures, exercising the diaphragm, building up phosphodiesterase levels, and a step in the weaning process as the clinical condition dictates.

    You and I know that SIMV in the clinical setting WILL be augmented as necessary.........you and i also know that cpap is sometimes used also, which is a lot more difficult than augmented simv..........and we then do serial abgs, assess clinical outcome, etc etc. all in an attempt to assess readiness for extubation or whatever.

    Even bipap is used on these ventilators nowadays.......again, more difficult to breathe than unaugmented simv.


    But, you CAN give SIMV wherein there is NO augmentation. We all need to get past this. In its purest sense, simv allows the patient to 'breathe on their own' so to speak.

    Overthinking the question is probly not a good idea just because we know that we dont necessarily implement simv without pressure support to overcome the beforementioned resistance formula to at least give them a similar environment as what it would be like to breathe on their own.
    Why would you put anyone on SIMV without a pressure supported breath after you description of resistance?

    Do you know how you would appropriately set up SIMV? When would you place a patient on no spontaneous support at all? I am asking this only because of your given explanation of resistance. What is appropriate supported or PSV breaths? What do your RTs set the spontaneous Low Volume alarm at?

    SIMV and the PSV breaths generate two different flow patterns. You may also have the machine giving a VT of 700 and then as you are describing having a PSV of 0 or some only do 5 which may only generate a spontaneous breath of 50 ml.


    BIPAP is two different levels of pressure and has a very different flow and delivery from what SIMV is or even Pressure Support.

    The days of serial ABGs for ventilator weaning should also be a thing of the past. SpO2, MV and ETCO2 are what you need once you have established a baseline and that may only be required for a hard to wean patient. Even if you don't have ETCO2 you can still look at the minute volume and the work of breathing. Modern ventilators also do many of the calculations for you. It is very rare that we do an ABG for every mode, rate and FiO2 change today.


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