You’re peacefully writing a note when you notice an incessant beeping from the back of your resus bay.  It’s not a monitor, it’s a ventilator.  What do you do? Press the silence button?  Call respiratory therapy?

As Dr. Weingart has said, ventilator alarms need to be treated like a code announcement.  Immediate assessment is necessary.  

The alarm most often triggered is the high airway pressure alarm.

Airway pressure is indicated by the peak pressure and = flow x resistance + alveolar pressure.  The most widely used upper limit for peak pressure is 35-40 cmH2O.  It’s important to prevent the trigger of these alarms because once triggered, many ventilators will cycle to expiration, resulting in a shortened inspiration and inappropriate tidal volume.  However, peak pressures don’t tell you much about the patient or the risk of barotrauma.

1) For that, you must measure the plateau pressure.  This reflects equilibration of airway pressures without flow, accounting for airway resistance; it estimates alveolar pressure. To measure this, press the inspiratory hold button for 0.5s.  Plateau pressures should be < 30.

2) Compare the peak pressure to the plateau pressure.

  • Peak pressure high, plateau pressure low/normal: suspect increased airway resistance or high inspiratory flow rates.
    • Kinked tube: pass suction catheter
    • Mucus plug: pass suction catheter and suction
    • Bronchospasm: inhaled bronchodilators, steroids
    • Tube too small: swap tube
    • Patient biting tube: oral airway, inc sedation
    • High insp flow: decrease rate
    • Condensation in tubing: replace tubing
    • Patient coughing: investigate etiology, inc sedation
  • Peak pressure high, plateau pressure high: suspect decreased lung compliance, not isolated resistance problems.
    • Mainstem bronchus: pull back ETT, ?CXR
    • Atelectasis: reposition patient, ?bronchoscopy
    • Pulmonary Edema: diuretics, nitrates, consider inotropes
    • ARDS: decrease VT by 1ml/kg increments (minimum = 4 ml/kg)
    • Pneumothorax: chest tube
    • Pneumonia: antibiotics
    • Pleural effusion/ascites: reposition patient, ?drainage
    • Trendelenberg: reposition patient

Although not always necessary, removing the patient from the vent and manually bagging can assist with determining whether the problem originates with the vent/circuit versus the ETT/patient.  Difficulty bagging implies the latter, while ease implies the former.  Just ensure that your bag is hooked up to oxygen and that you have a PEEP valve attached to apply the appropriate PEEP.

  • Life in the Fast Lane — High Airway and Alveolar Pressures; http://lifeinthefastlane.com/ccc/high-airway-and-alveolar-pressures/
  • EMCrit – How to Dominate the Ventilator; http://emcrit.org/wp-content/uploads/vent-handout.pdf
  • http://wikem.org/wiki/Ventilator_high_pressures
  • Morgan, Edward G., Maged Mikhail and Michael Murry. Clinical Anesthesiology, Fourth edition, 2006. McGraw Hill, Philadelphia. Pg. 82
  • Moon, Richard and Enrico Camporesi “Respiratory Monitoring”. Miller’s Anesthesia, Sixth edition, Ronald Miller (Ed), 2005, Elsiever, New York. Pg.1466.