Ventilator high pressures

High Pressure Alarms

Skill One-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.

Skill Two- Determine Airway Resistance

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

Skill Three-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 dlow returns to baseline
• Treat with decreased vent rate and increased expiratory time.

Skill Four-Measuring 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- inhaler 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- lowerVt
  • Pneumothorax- Chest Tube
  • Pneumonia- Antibiotics