Pressure Control Ventilation
-Pressure is set and volume delivery changes. Varies as lung characteristics change (Cst & Raw) in other words- the ventilator provides a constant pressure to the Pt during inspiration
-All breaths are time or patient triggered, pressure targeted, and time cycled
Pressure Control Ventilation
Advantages
-Allows a set max pressure
-Set pressure reduces the risk of overdistention
Pressure Control Ventilation
-Disadvantages
-Volume delivery varies with the Pts lung characteristics
-Clincians may be less familiar with the pressure control ventilation -Vt and minute ventilation (Ve) decrease when lung characteristics deteriorate
-Considered a lung protective strategy and reduces risk of barotrauma
-Used when peak pressure are of primary concern- above 50 ccH20 or plateau pressure approaches 35 cmH2O in volume ventilation
-Due to a decrease in lung compliance -If peak pressures are high for temporary reasons, pressure control ventilation is not needed, simply receive the cause of higher peak pressure -Brinchconstriction- bronchdilator -Secretions- suctioning
-No Vt setting, only pressure setting
-Must set exhaled Vt alarms as volume can change quickly with change in lung compliance
Increases Compliance= same PIP (increased Vt)
Decreased C = same as PIP ( decreased Vt) the lungs are stiffer and harder to ventilate
Increased RAW= same PIP (decreased Vt)
Decreased RAW = Same PIP (increased Vt)
-Determining Vt in pressure ventilation
-Measure Pplat and baseline pressure after initial volume targeted breath
-Check Vt and adjust initiating pressure ventilation at low pressure -If Pplate is not available, the peak pressure from VC-CMV minus 5 cm H2O (PIP - 5 cm H2O) can be used as starting point -If volume readings are not available, an initial pressure of 10-15 cmH2O with the close monitoring of volume measurement and adjustment/ titrate as appropriate to achieve Vt. -Goal is < 35cmH2O -All other parameters (f, I:E, sensitivity, FiO2, peak flow, ect_ are set in the same manner as volume control ventilation
Pressure Controlled Inverse Ration Ventilation
-Not a true mode of ventilation
-The inspiration time (Ti) is set longer than the expiration time (Te)- inverse I:E ratio -Normally expiratory time is greater than inspiratory time
-Lungs that are stiff and non compliant, a short inspiratory time may be insufficient to deliver all the inspired gas
-Prolonging Ti allows for greater and better distribution of gases in the lungs
-Improves oxygenation and gas exchange, decreases PIP and PEEP levels
Pressure Controlled Inverse Ration Ventilation
Recommended for
-ARDS
-Severe restrictive lung disease in general -Pts requiring high FiO2(>60) and peep (>15 ccH2O) -High PIP (>50 cmH2O) -Low PaO2 with decreases compliance
Pressure Controlled Inverse Ration Ventilation
I:E ratio
-Start with I:E ratio of 2:1 or greater
-Quite uncomfortable for Pts and may require sedation or paralysis to allow ventilator to control breathing pattern
-Open loop
-Open loop- you tell the vent what to do and the vent does it
-traditional modes of MV -PC,AC,SIMV,PSV
-Closed Loop-
-Closed Loop- You tell the vent what to do and the vent does it, then interrupts data and the vent dictates what to do next
-Advanced modes and the future of MV -PRVC, VAPS, ASV, PVA,MMV
Airway Pressure Release Ventilation (APRV)
-A form of spontaneous breathing at a positive pressure level
-Otherwise known as: Bilevel, Biphase, or TCAV (time controlled adaptive ventilation) -Similar to CPAP -Simulates pressure control with an inverse I:E ratio
Airway Pressure Release Ventilation (APRV)
oxygenation tool
-Utilzes long inspiratory time to improve alveolar recruitment and maximize gas exchange by improving gas distribution= improved oxygenation
-In other words- this is CPAP (think oxygenation) with a release of pressure (think CO2 elimination) with the goal of recruitment
Airway Pressure Release Ventilation (APRV)
Long level, short level
-A longer level (CPAP) or P-high which allows for alveolar recruitment with enough pressure to open the lungs without overdistention (T-high)
-A very short level (release phase) or P-Low which does not allow for full exhalation… remember FRC. The purpose for low level or release phase is to allow for CO2 elimination (T-Low)
Airway Pressure Release Ventilation (APRV)
-Indications
-Acute lung injury
-ARDS -Extensive Atelectasis
Airway Pressure Release Ventilation (APRV)
-Setting
-P-high key inspiratory pressure
-P low - low baseline pressure that is minimally maintained upon exhalation -T high, number of seconds allotted to the inspiratory phase -T-low number of seconds allotted for the exhalation phase -Both levels are time triggered and time cycled -P high and P low indicate the levels of pressure administered -T high and T low describes the time spent in high and low airway pressures
-Two uses for APRV
-Rescue- spontaneous breathing isn’t necessary
-TCAV= Time controlled adjective ventilation -Recruitment (non resume) - emphasis on using CPAP to recruit, spontaneous is available
APRV
-Intail setting for rescue
-P high - set at plateau pressure if possible, if not available- 20-30 cmH2O
-Best to keep P high below 35 cmH2O -T high 4.0- 6.0 seconds -P low - 0 cmH2O -T-low .2-.6 seconds
APRV
-Intial setting for recruitment
-P high set plateau pressure of possible, if not available 15-30 cmH2O
-Best to keep P high below 35 cmH2O -T high 4.0- 6.0 seconds -P low - 0 cmH2O -T-low .2-.6 seconds
-Improving ventilation in APRV
- Decrease PaCO2
-P high increase in 2-5 cmH2O increments (up to 30, maybe 40 with low compliance)
-T high decrease to create more drops
-Improving ventilation in APRV
-Increase PaCO2
-P high decrease in 2-5 cmH2O increments if oxygenation status is acceptable
-T high increases slowly in increments of .5-2 seconds
-Improving oxygenation in APRV
-increase PaO2
-P high increase in 2-3 cmH2O increments -T high increase by .5-.2 seconds, along with P high increases -T low decrease in .1 second increments
-Weaning APRV
-1.) Wean FiO2 first
-Target is less than 50 -2.)” drop and stretch
APRV Weaning
Drop and Stretch
-does the simultaneously
-Drop P high decrease in 2-5 c,H2) increments until is less than equal to 10 but only after FiO2 <50% and oxygenation is stable for 2 hours -Stretch, T high increase in .5 seconds increments up to 15 seconds -Each drop should be done every two hours - if done too quickly, a;veoli may collapse -Goal is to progress towards pure CPAP by decreasing P high and increasing T high ( drop and stretch) -Once P high is lowered to 10 cmH2O and T high reaches 15 seconds, switch to CPAP 10 cmH2O with PS 5-10
