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 vent may be higher than PEEP on vent settings
• Differences in PEEP with “expiratory hold” and PEEP set on vent 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), Low 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

Settings

• Ventilation (Settings)
• Ventilation (Weaning)
• Ventilation (Strategies)

See Also

• Noninvasive Ventilation
• Ventilator Desaturation
• Deterioration After Intubation (DOPE)
• EBQ:ARDSnet