Ventilator Settings

  • Peak Inspiratory Pressure (PIP or Ppeak):
    • Is the maximum pressure in the airways:
      • At the end of the inspiratory phase:
        • This valve is often displayed:
          • On the ventilator screen
    • Since this value is generated during a time of airflow:
      • The PIP is a determined by both:
        • Airway resistance and
        • Compliance
    • By convention:
      • All pressures in mechanical ventilation:
        • Are reported in “cm H2O”
          • It is best to target a PIP:
            • Of less than 35 cm H2O
  • Plateau Pressure (Pplat):
    • Is the pressure that remains in the alveoli:
      • During the plateau phase:
        • During which there is a:
          • Cessation of air flow, or with a breath-hold
    • To calculate this value:
      • The clinician can push:
        • The “inspiratory hold” button:
          • On the ventilator
    • The plateau pressure:
      • Is effectively the pressure at the alveoli with each mechanical breath, and:
        • Reflects the compliance in the airways:
          • To prevent lung injury:
            • The Pplat should be maintained:
              • At less than 30 cm H2O
  • Positive End Expiratory Pressure (PEEP):
    • Is the positive pressure:
      • That remains at the end of exhalation
    • This additional applied positive pressure:
      • Helps prevent atelectasis:
        • By preventing the end-expiratory alveolar collapse
    • PEEP is usually set at:
      • 5 cm H2O or greater:
        • As part of the initial ventilator settings
    • PEEP set by the clinician:
      • Is also known as extrinsic PEEP, or ePEEP:
        • To distinguish it from:
          • The pressure than can arise with air trapping
        • By convention:
          • If not otherwise specified:
            • “PEEP” refers to ePEEP
  • Intrinsic PEEP (iPEEP), or auto-PEEP:
    • Is the pressure that remains in the lungs:
      • Due to incomplete exhalation:
        • As can occur in patients with:
          • Obstructive lung diseases
    • This value can be measured by:
      • Holding the “expiratory pause” or “expiratory hold” button on the mechanical ventilator
  • Driving pressure (∆P):
    • Is the term that describes the:
      • Pressure changes that occurs during inspiration, and:
        • Is equal to the difference between:
          • The plateau pressure and PEEP (Pplat – PEEP):
            • For example:
              • A patient with a Pplat of 30 cm H2O and a PEEP of 10 cm H20:
                • Would have a driving pressure of 20 cm H2O
                  • In other words:
                    • 20 cm H2O would be the pressure that extered to expand the lungs
  • Inspiratory time (iTime):
    • Is the time allotted to deliver:
      • The set tidal volume:
        • In volume control settings, or
      • The set pressure:
        • In pressure control settings
  • Expiratory Time (eTime):
    • Is the time allotted to fully exhale:
      • The delivered mechanical breath
  • I:E ratio, or the inspiratory to expiratory ratio:
    • Is usually expressed as 1:2, 1:3, etc
    • The I:E ratio can be set:
      • Directly, or indirectly on the ventilator by changing the:
        • Inspiratory time
        • The inspiratory flow rate, or
        • The respiratory rate
    • By convention:
      • Decreasing the ratio means:
        • Increasing the expiratory time:
          • For example:
            • 1:3 is a decrease from 1:2:
              • Just like 1/3 is less than 1/2
  • Peak inspiratory flow:
    • Is the rate at which the breath is delivered:
      • Expressed in L/min:
        • A common rate is 60 L/min
    • Increasing and decreasing the inspiratory flow:
      • Is a means of indirectly affecting the I:E ratio:
        • A patient with a respiratory rate set at 20, who is not overbreathing:
          • Has three seconds for each complete cycle of breath:
            • If you increase the inspiratory flow:
              • The breath is given faster, and that leaves more time for exhalation:
                • Thus, inspiratory flow indirectly changes the I:E ratio
  • Tidal volume (TV or VT):
    • Is the volume of gas:
      • Delivered to the patient with each breath
    • The tidal volume is best expressed in both:
      • Milliliters (ex: 450mL) and
      • Milliliters/kilogram (ex: 6 mL/kg) of predicted body weight
    • Clinicians can choose to set the ventilator:
      • In a volume control mode:
        • Where the tidal volume:
          • Will be constant for each breath
      • In pressure control modes:
        • The pressure is constant:
          • But the tidal volume is an independent variable, and:
            • Will vary slightly with each breath:
              • Regardless:
                • Every mode of ventilation delivers a tidal volume
  • Respiratory rate (RR or f, for “frequency”):
    • Is the mandatory number of breaths:
      • Delivered by the ventilator per minute
    • However:
      • It is important to be mindful that:
        • The patient can breathe over this set rate, and therefore:
          • One must report both:
            • Your set RR and
            • The patient’s actual RR
              • Both of these values can found on the ventilator screen
      • In addition:
        • It is important to remember that the RR is a key factor in determining time for exhalation:
          • For example:
            • If a patient has a RR of 10 breaths per minute (bpm):
              • He will have 6 seconds per breath; ((60 seconds/min) / 10 bpm = 6 sec/breath)
            • A RR of 20 bpm:
              • Only allows 3 seconds for the entire respiratory cycle
  • Minute ventilation (VĖ, Vė, or MV ):
    • Is the ventilation the patient receives in one minute
    • It is calculated as the:
      • Tidal volume multiplied by the respiratory rate (TV x RR), and:
        • Expressed in liters per minute (L/min)
    • Most healthy adults:
      • Have a baseline minute ventilation of:
        • 4 L/min to 6 L/min
    • But critically ill patients:
      • Such as those attempting to compensate for a metabolic acidosis:
        • May require a minute ventilation of:
          • 12 L/min-15 L/min, or even higher:
            • To meet their demands
  • Fraction of inspired oxygen (FiO2):
    • Is a measure of the oxygen delivered by the ventilator during inspiration:
      • Expressed at a percentage
    • Room air contains 21% oxygen
    • A mechanical ventilator:
      • Can deliver varying amounts of oxygen:
        • Up to 100%

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