II. Definitions

  1. Auto-PEEP (Breath Stacking, Dynamic Hyperinflation, Intrinsic PEEP)
    1. Breath Stacking occurs when inadequate expiratory time before next breath (esp. Obstructive Lung Disease)
    2. Breath Stacking builds increased intrathoracic pressure and prevents right heart filling
  2. Plateau Pressure
    1. Plateau pressures should be kept <30 cm H2O (especially in ARDS) to prevent Barotrauma
      1. Contrast with Peek pressures which reflect only the airway pressures needed to expand lung
    2. Check by depressing inspiratory hold button
      1. Measures pressure at the alveoli immediately before expiration

III. Precautions

  1. Heed Ventilator Alarms
    1. Treat as critical incident that needs rapid response and evaluation
    2. If problem cannot easily be detected
      1. Disconnect Ventilator
      2. Provide bag-valve-mask PPV while troubleshooting
      3. Provide High Flow Oxygen (with PEEP Valve if needed)
  2. High Peak pressure and Ventilator Alarms
    1. High peak pressure alone cannot distinguish cause
      1. Plateau pressure must be obtained to understand cause, and direct management
    2. High airway resistance (e.g. Asthma, mucous plugging) can result in exceeding inspiratory peak pressure
      1. The Ventilator stops ventilating and alarms immediately when peak pressure exceeds the pressure limit
      2. Pressure limit set too low for current peak pressures results in hypoventilation (with hypercarbia risk)
      3. Pressure limit typically defaults to 40 cm H2O but can be increased if peak pressure is high
    3. However plateau pressure (alveolar pressure) is a risk of Barotrauma, NOT peak pressure
      1. To obtain plateau pressure, press and hold the "inspiratory hold/pause" button through a ventilation
      2. Plateau pressure >30 cm H2O (Barotrauma risk)
        1. Consider causes of increased plateau pressures
          1. ET in right mainstem
          2. Pneumothorax
          3. Increased Lung Volumes with alveolar overdistention
          4. Abdominal Distention with thoracic compression
          5. Decreased chest wall compliance
        2. Start by decreasing Tidal Volume
        3. Decreasing Respiratory Rate may also decrease pressure if Breath Stacking (Auto-PEEP)
      3. Plateau pressure <30 cm H2O (despite increased peak pressure)
        1. Consider increasing the Ventilator pressure limit (caution!)
        2. Reduce airway resistance (suctioning, check ET Tube position, Bronchodilators)
          1. Consider kinked tubes, mucous pluggings
          2. Consider additional bronchodilation for Asthma or COPD
  3. References
    1. Weingart in Majoewsky (2013) EM:Rap 13(1): 6-7
    2. Orman and Mallemat in Herbert (2015) EM:Rap 15(10): 13-16

IV. Causes: Auto-PEEP (Breath Stacking, Dynamic Hyperinflation, Intrinsic PEEP)

  1. Intrinsic PEEP (Auto-PEEP) is generated by the patient and Ventilator
    1. Contrast with extrinsic PEEP that is intentionally set and generated by Ventilator
  2. Auto-PEEP occurs with Breath Stacking
    1. Inadequate expiratory time before next breath (esp. Obstructive Lung Disease)
    2. Breath Stacking builds increased intrathoracic pressure and prevents right heart filling
    3. Increased Lung Volumes result in over-stretch and secondary lung injury
    4. Patients with hyperinflated lungs are also unable to trigger a ventilated breath
  3. Check by depressing Ventilator expiratory hold button
    1. Auto-PEEP is present if the end-expiratory pressure exceeds the VentilatorPEEP setting
    2. Flow-Time waveform will remain below baseline at the end of expiration
      1. https://litfl.com/intrinsic-peep/
  4. Measures to decrease Breath Stacking and Auto-PEEP
    1. Optimize Obstructive Lung Disease (e.g. Bronchdilator nebulizer treatments)
    2. Increase expiratory time
      1. Decrease Respiratory Rate
      2. Decrease inspiratory time (increase inspiratory flow rate)
      3. Decrease Tidal Volume
    3. Decrease Tachypnea (triggered breaths) by treating pain and anxiety
      1. Ketamine 0.3 mg/kg (sub-dissociative doses)
      2. Fentanyl
      3. Benzodiazpeines

V. Causes: Acute Respiratory Deterioration on Ventilator (DOPES Mnemonic)

  1. Dislodged or displaced Endotracheal Tube or deflated cuff
  2. Obstructed Endotracheal Tube (e.g. mucous plugging, blood in tube)
  3. Pneumothorax
  4. Equipment failure (Ventilator, tubing)
  5. Stacking of breaths (incomplete exhalation in Asthma or COPD)

VI. Causes: Acute Respiratory Deterioration on Ventilator (categorized by peak inspiratory pressure)

  1. Peak Inspiratory Pressure Decreased
    1. Air Leak
    2. Hyperventilation
  2. Peak Inspiratory Pressure Unchanged
    1. Pulmonary Embolism
    2. Extrathoracic problem
  3. Peak Inspiratory Pressure Increased
    1. Plateau Pressure unchanged: Airway Obstruction
      1. Aspiration
      2. Bronchospasm
      3. Secretions
      4. Endotracheal Tube obstruction
    2. Plateau Pressure increased (>30 cm H2O): Decreased Compliance (see management as above)
      1. Abdominal Distention
      2. Asynchronous breathing
      3. Atelectasis
      4. Auto-PEEP (inadequate expiration time with air trapping or stacked breaths, esp. Asthma)
        1. Tachypnea is primary problem with secondary excessive Respiratory Alkalosis
        2. Start by lowering Tidal Volume
        3. Consider decreasing Respiratory Rate to allow greater exhalation (reducing Breath Stacking)
        4. May also increase flow rates, to deliver Tidal Volume faster (longer expiration time)
      5. Pneumonia
      6. Pneumothorax
      7. Pulmonary edema

VII. Cause: Hypotension in the intubated Patient

  1. Tension Pneumothorax
    1. First consideration in a newly hypotensive patient on Mechanical Ventilation
    2. Emergent Needle Thoracostomy followed by Chest Tube
  2. Auto-PEEP (Breath Stacking, Dynamic Hyperinflation)
    1. Decrease Tidal Volume
    2. Increase expiratory time by decreasing Respiratory Rate or decreasing inspiratory time
  3. Increased intrathoracic pressure
    1. Volume Resuscitation
  4. Myocardial Infarction
    1. Consider serial Electrocardiogram and Troponin

VIII. Management: Trouble-Shooting Inadequate Ventilation or Oxygenation (DOTTS Mnemonic)

  1. Disconnect the Ventilator
    1. Listen over the ET Tube for hissing sound
    2. Hissing suggests release of hyperinflated air from Breath Stacking
    3. If hissing present
      1. Apply anterior chest pressure gently for 10 seconds to assist with further release of stacked air
  2. Oxygenation
    1. Connect Ambu Bag with 100% FIO2 and provide manual Positive Pressure Ventilation
      1. Attach PEEP Valve if >5 cm H2O (set to Ventilator setting)
    2. Assess lung compliance
      1. Difficult Positive Pressure Ventilation (PPV)
        1. Endotracheal Tube obstruction or airway obstruction (e.g. aspiration) OR
        2. Decreased lung compliance (e.g. acute pulmonary edema, Pneumothorax)
      2. Easy Positive Pressure Ventilation (PPV)
        1. Air leak (e.g. deflated ET cuff or dislodged tube)
  3. Tube Position or Function
    1. Compare tube position to prior reading
    2. Pass suction catheter via the Endotracheal Tube to relieve mucous plugging
  4. Tweak the Ventilator setting
    1. Consider Breath Stacking (Auto-PEEP)
    2. Consider lowering Respiratory Rate and Tidal Volume
  5. Sonography
    1. See Lung Ultrasound for Pneumothorax (Sliding Lung Sign)
    2. See Lung Ultrasound
    3. See Blue Protocol (Lichtenstein Dyspnea Evaluation by Ultrasound Protocol)
    4. See Volpicelli Dyspnea Evaluation with Ultrasound Protocol
    5. Unclear if Ultrasound can reliably determine ET position in relation to carina

IX. References

  1. Hamm (2018) Fundamental Critical Care Support Course Lecture, St Paul, MN, attended 4/26/2018
  2. Marino (1991) ICU Book, Lea & Febiger, p. 368
  3. Mallemat and Swadron in Herbert (2013) EM:Rap 13(12): 11
  4. Swaminathan and Mallemat in Herbert (2020) 20(7): 10-1
  5. Roginski, Hogan and Buscher (2020) Crit Dec Emerg Med 34(6): 17-27

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