Ventilator Troubleshooting

See Also

Definitions

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
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

Causes
Acute Respiratory Deterioration on Ventilator (DOPES Mnemonic)

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

Approach
High plateau pressure, High Peak pressure and Ventilator Alarms

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)
High peak pressure alone cannot distinguish cause
1. Plateau pressure must be obtained to understand cause, and direct management
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
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
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. Decrease Tidal Volume
  1. May decrease Tidal Volume as low as 4 ml/kg
  2. Risk of hypercapnia due to decreased Minute Ventilation
  3. However, permissive hypercapnia is preferred
3. Decrease PEEP
  1. Risk of decreased oxygenation and alveolar collapse
4. Increase Expiratory Time (e.g. shorter breaths or slower rate, decreases Auto-PEEP risk)
  1. Decreasing Respiratory Rate may also decrease pressure if Breath Stacking (Auto-PEEP)
  2. Risk of hypercapnia
5. Address reversible factors impeding Lung Compliance
  1. Increase Post-Intubation Sedation and Analgesia
  2. Consider chemical paralysis (e.g. Rocuronium, cistracuronium)
6. Consider changing Ventilator mode
  1. Change Ventilator to Pressure Cycled (PC) Ventilation
7. Pathology specific strategies
  1. Lung Injury
    1. Decrease Tidal Volume until plateau pressure <30 cm H2O
  2. Obstructive Lung (Breath Stacking)
    1. Decrease Respiratory Rate until plateau pressure <30 cm H2O
Plateau pressure <30 cm H2O (despite increased peak pressure)
1. Increased PIP with normal pPLAT reflects increased airway resistance
2. Reduce airway resistance (suctioning, check ET Tube position, Bronchodilators)
  1. Evaluate for Endotracheal Tube obstruction
    1. Consider kinked tubes
    2. Suction for mucous plugs
  2. Consider bronchospasm
    1. Consider additional bronchodilation for Asthma or COPD
  3. Evaluate for dessynchrony with Ventilator
3. Consider increasing the Ventilator pressure limit (caution!)
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

Approach
Auto-PEEP (Breath Stacking, Dynamic Hyperinflation, Intrinsic PEEP)

Intrinsic PEEP (Auto-PEEP) is generated by the patient and Ventilator
1. Contrast with extrinsic PEEP that is intentionally set and generated by Ventilator
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
Check by depressing Ventilator expiratory hold button
1. Auto-PEEP is present if the end-expiratory pressure exceeds the Ventilator PEEP setting
2. Flow-Time waveform will remain below baseline at the end of expiration
  1. https://litfl.com/intrinsic-peep/
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

Approach
Acute Respiratory Deterioration on Ventilator (categorized by peak inspiratory pressure)

Peak Inspiratory Pressure Decreased
1. Air Leak
2. Hyperventilation
Peak Inspiratory Pressure Unchanged
1. Pulmonary Embolism
2. Extrathoracic problem
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

Approach
Hypotension in the intubated Patient

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

Approach
Refractory Hypercapnic Respiratory Failure

Indications
1. Appropriate Ventilator settings with PaCO2 is higher than target (with pH<7.2
First increase Respiratory Rate (RR)
1. Exercise caution in Obstructive Lung Disease due to risk of Breath Stacking
Correct asynchrony ("bucking the vent")
1. Address Air Hunger (low Minute Ventilation or PEEP)
2. Address underlying causes (e.g. pain, anxiety, Alcohol Withdrawal)
  1. Increase Post-Intubation Sedation and Analgesia
Other measures
1. Correct Electrolyte disturbance (Hypokalemia, Hypophosphatemia)
2. Heliox (decreases lung hyperinflation)
3. Paralysis with Neuromuscular Blockade (e.g. Rocuronium, cistracuronium)
  1. Precaution: Requires Deep Sedation!
4. VV-ECMO

Approach
Refractory Hypoxemic Respiratory Failure

Precautions
1. Avoid hyperoxia
  1. Risk of difficult weaning, worsening shock, liver failure, bacteremia, increased mortality
2. Avoid corrective strategies that increase Breath Stacking
Troubleshoot the Ventilator
1. See DOPES Mnemonic as above
2. See Acute Respiratory Deterioration on Ventilator above
Increase oxygenation
1. Use ARDSNet Table to increase FIO2 in conjunction with PEEP
Other measures
1. Paralysis with Neuromuscular Blockade (e.g. Rocuronium, cistracuronium)
  1. Precaution: Requires Deep Sedation!
2. Prone Positioning
  1. As an alternative in resource limited areas, "good" lung may be positioned down (lateral decubitus)
3. Increased inspiratory time on Ventilator
4. VV-ECMO

Approach
Trouble-Shooting Inadequate Ventilation or Oxygenation (DOTTS Mnemonic)

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
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)
Tube Position or Function
1. Compare tube position to prior reading
2. Pass suction catheter via the Endotracheal Tube to relieve mucous plugging
Tweak the Ventilator setting
1. Consider Breath Stacking (Auto-PEEP)
2. Consider lowering Respiratory Rate and Tidal Volume
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

References

Hamm (2018) Fundamental Critical Care Support Course Lecture, St Paul, MN, attended 4/26/2018
Marino (1991) ICU Book, Lea & Febiger, p. 368
Mallemat and Swadron in Herbert (2013) EM:Rap 13(12): 11
Roginski, Hogan and Buscher (2020) Crit Dec Emerg Med 34(6): 17-27
Schaub, Peluso and Stull (2020) Crit Dec Emerg Med 34(9): 3-12
Swaminathan and Mallemat in Herbert (2020) 20(7): 10-1