Ventillator Management
(Last Updated - 2/18/2009)

-Changing RR:
     Ex.) If Increase RR to 24 (old RR was 20):
          -Will increase ventillation by 24/20 = 6/5
          -Will decrease PCo2 by 1/6
          -PCo2 = 51
          -New PCo2 = 51 - (1/6 * 51) = ~42
          -Change in PCo2 will be ~10 (51 to 42)
          -Will change pH by 0.08 (will increase pH - old pH = 7.13)
          -New expected pH = ~7.21


-Equation:
        Current          Goal
     V_E * P_CO2 = V_E * P_CO2
     V_E = TV x RR

-Initiating Ventillation:
     Normal Goal TV's: 8 mL/kg

-Assist Control (AC):
     Assist --> Set the backup RR
     Control --> Set the TV
     -Patients may "breathe over the vent" (take more than the minimum set RR (assist) --> may lead to resp alkalosis --> may not be able to completely control ventillation esp if the patient is already adequately sedated
          -Can fix this problem with changing to SIMV / PSV mode

-SIMV / PSV:
     Control only --> Set the TV for a certain # of breaths only
     -The patient may take extra breaths but these extra breaths are on their own thru the resistance of the ET tube --> difficult breaths
          -Give PSV for these extra breaths to help with resistance breathing but with goal TV's lower than set TV's by control so that overall ventillation is reduced and this decreases resp alkalosis

-Paralytics:
     -Only use in the following circumstances:
          1) High-Demand Ventillation (basically uncomfortable ventillation):
               -Sepsis
               -Minute Ventillations >20
               -RR's >35
               -PEEP's >15
          2) Asthma Attacks --> to avoid air-trapping:
               -Normal respiration --> volumes @ end-inspiration and @ end-expiration are 0
               -Obstructive Airway Disease (Asthma / COPD) --> volumes @ end-inspiration are 0 but @ end-expiration they do not quite reach 0 so they air-trap
                    -If you ventillate them with high rates then you increase the air-trapping because they take longer to reach 0 at end-expiration than normal
                    -Program the RR's low (~10) to maximize end-expiratory return to 0

-Predicting Good Extubation Outcomes:
     Rapid Shallow Breathing Index (RSBI):
          RSBI = RR (bpm) / TV (L)
               < 105 --> Good predictor of successful extubation
               > 105 --> Good predictor of unsuccessful extubation


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