Ventilator high pressures

High Pressure Alarms

  • In volume control mode, (high)pressure alarm sounds. In pressure control mode (low) volume alarm sounds--BOTH signify similar problems and troubleshoot with the following 4 maneuvers.

Measure Peak Plateau Pressure

  • Need to measure peak plateau pressure P(Plat) not only peak airway pressure P(Peak).
    • Press and hold the “inspiratory hold” button-waveform shows peak pressure and then lower plateau.
  • P(Plat) >30 thought to be potentially injurious to lung.
  • P(Plat) reflects equilibration of airway pressures without flow, accounts for airway resistance.

Determine Airway Resistance

  • When airway resistance high, P(Peak)>> P(Plat)
    • Normal P(Peak)-P(Plat) < 5cm H2O
      • Airway resistance increased with: asthma, mucus plugging, small tube, tube kinking, tube obstructed

Eval for Dynamic Hyperinflation

  • Flow at end of expiration has not stopped, ie breath stacking, ie need more time to exhale and each breath adding volume to lungs
  • Consequence of dynamic hyperinflation
  1. Harder to trigger vent- dys-synchrony
  2. Increased dead space- hypoxic/hypercapneic
  3. Elevated intra-thoracic pressures decrease venous return
  • Look to make sure expiratory flow returns to baseline.

Measure Hyperinflation

  • If you suspect dynamic hyperinflation, perform “expiratory hold”, then PEEP on ventilator may be higher than PEEP on ventilator settings
  • Differences in PEEP with “expiratory hold” and PEEP set on ventilator suggest hyperinflation.

Management

High P(Peak), Low P(Plat)

  • Suggests increased airway resistance, not compliance problem
    • Kinked tube- pass suction catheter?
    • Mucus plug- pass suction catheter and suction
    • Bronchospasm- inhaled bronchodilators
    • Tube too small- swap tube

High P(Peak), High P(Plat)

  • Suggests decreased compliance, not an isolated resistance problem
    • Mainstem bronchus- pull back ETT, CXR?
    • Atelectasis- bronchoscopy
    • Cardiogenic Pulmonary Edema-diuretics vs inotropes
    • ARDS- lower Vt
    • Pneumothorax- Chest Tube
    • Pneumonia- Antibiotics

PEEP measured > PEEP Vent Setting

  • Suggests Dynamic Hyperinflation
    • Remove from vent, allow complete exhalation
    • Lower ventilator rate
    • Shorten I-time to change I:E around 1:4
    • Tidal volume 6-8mL/kg predicted body weight
    • Increase inspiratory flow rate to 60-80L/min to allow more exhalation time
    • Opioid sedation blunts intrinsic tachypnea
    • Treat bronchospasm

See Also

Mechanical Ventilation Pages

Authors:

Ross Donaldson