EM Topic – Invasive Positive Pressure Ventilation

Control (aka cycle or limit)

Pressure-controlled: Breath determined by achieving a set peak inspiratory pressure (PIP)

  1. Pro: limits risk of barotrauma
  2. Con: if compliance of lung changes then hypo- or hyper ventilation may occur

Volume–controlled: Breath determined by delivering a set tidal volume

  1. Pro: better control of tidal volume
  2. Con: if compliance of lung is high then PIP may be high, risking barotrauma

Volume-Control Modes

Controlled Mechanical Ventilation:

  1. Ventilator delivers breaths at set rate, patient unable to breathe spontaneously
  2. For apnoeic, deeply sedated, muscle relaxed patients

Intermittent Mechanical Ventilation (IMV):

  1. Ventilator delivers breaths at set rate, but patient able to make unassisted breaths too

Assist/Control (A/C) Ventilation or Continuous Mechanical Ventilation (CMV):

  1. Ventilator has a back-up rate set, and delivers a breath if no patient-initiated breath in time period. Patients may breathe above the set rate, each breath will be assisted.
  2. Often used in ED patients

Synchronized Intermittent Mechanical Ventilation (SIMV):

  1. Similar to A/C mode, the ventilator has a back-up rate set, and delivers a breath if no patient initiated breath in time period. Patients may breathe above the set rate.
  2. However only the set rate of ventilator- or patient-initiated breaths are assisted to the full TV or PIP. Additional patient-initiated breaths above the set rate are not assisted.
  3. Often used in ED patients

Pressure-Control Modes

Positive End Expiratory Pressure (PEEP) & CPAP:

  1. Functionally similar
  2. PEEP is the term used in mechanical ventilation and CPAP during spontaneously breathing
  3. ↑FRC, maintains alveolar patency, ↑PO2, but may ↓CO at higher pressures

Pressure Support Ventilation (PSV):

  1. Spontaneous breathing by patient supported by attaining a set PIP on each breath
  2. PEEP may be added too, as well as a mandatory back up rate (usually via SIMV)

Indications

  1. Intubation – Failure of ventilation, oxygenation, loss of airway patency or protection.
  2. Failed NIV

Common Initial Settings

  1. Depends on underlying issues – Lung protection (most situations) or Obstructive lung dz
  2. Lung protection:
    1. Vol A/C or SIMV – VT 6-8ml/kg, Insp Flow 60-80ml/min, RR 12-20, I:E 1:2, FiO2 1.0 & PEEP 5cmH2O, Plateau Pressure<30cmH2O
  3. Obstructive lung dz:
    1. PSV mode – PIP<40cmH2O OR Vol A/C or SIMV – VT 8ml/Kg, Insp Flow 60-80ml/min. For both: RR 8-10, I:E 1:4-5, FiO2 1.0, PEEP 0-5cmH2O, Plateau pressure<30cmH2O

Complications

  1. Intubation trauma
  2. Barotrauma
  3. Air-trapping/intrinsic PEEP
  4. Nosocomial infections
  5. ↑WOB if asynchrony of breaths or poor trigger
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