Basic principles

  • Oxygenation: determined by MAP and FiO2; MAP mostly derived from PEEP
  • Minute Ventilation: determined by RR and TV; use RR as primary tool for CO2 manipulation
  • MAP = mean airway pressure
  • PEEP = positive end expiratory pressure
  • TV = tidal volume
  • RR = respiratory rate
  • IT = inspiratory time
  • PS = pressure support
  • FiO2 = fraction of inspired oxygen
  • PIP = peak inspiratory pressure
  • Plateau Pressure = airway pressure measured at end inspiration with inspiratory hold maneuver (helps to differentiate cause of high PIP) (PIP – pause pressure)
  • Auto PEEP = airway pressure measured after expiratory hold maneuver (detects air trapping)
  • SIMV = Synchronized intermittent mandatory ventilation

Pay attention to minute ventilation at all times and monitor exhaled TV. Exhaled TV less than inhaled TV suggest air leak in the respiratory system.

SIMV PRVC with PS is the PICU preferred mode. Pressure Regulated Volume Control (PRVC) is where breaths are pressure generated with a decelerating flow pattern.

Set

  1. TV = typically 6-8 cc/kg; adjust for chest wall excursion, breath sounds and PIP
  2. RR = usually 10-30 breaths/min; adjust for age, ETCO2, pCO2 (younger patients need faster rates)
  3. PEEP = 5-12 cm H20; adjust for FiO2, CXR (higher PEEP needed for sick lungs)
  4. IT = 0.4-1; adjust for age (lower iT for younger patients)
  5. PS = usually 10 cm H20, common range 6-14; adjust for desired work of breathing, lower PS makes pt work harder
  6. FiO2 = 21-100%; adjust for saturations (FiO > 60% toxic)

Variable PIP - must follow trends of PIP, typically values in the 20s, concerning if > 30 cm H20

Plateau Pressure should be < 28 always

Important differences between modes of ventilation

SIMV PC w/ PS
Pressure Control Ventilation
Peak Inspiratory Pressure is set.
Tidal Volume is variable.

  • Must follow trends
  • Goal to be returning > 6-8 cc/kg

Better in the presence of an air leak in the respiratory system
Normal PIP < 25 cm H2O

Flow in this mode of ventilation is decelerating.

SIMV VS w/ PS
Volume Control Ventilation
Tidal Volume is set.
PIP is variable.

  • Must follow trends
  • Concerning if PIP is high (> 30 cm H2O)

Flow in this mode of ventilation is constant.

Pressure Support Mode
Spontaneous Mode
Pt triggers ALL breaths
Target TV is > 5-6 cc/kg
PS assists pt to overcome resistance of vent circuit/ETT tube
Often used to help determine if pt is ready for extubation