Procedure

BiPap

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BiPap, Bilevel Positive Airway Pressure, Average Volume Assured Pressure Support, AVAPS

  • See Also
  1. Non-Invasive Positive Pressure Ventilation
  2. Mechanical Ventilation
  3. Continuous Positive Airways Pressure (CPAP)
  4. Positive End-Expiratory Pressure (PEEP)
  5. Acute Respiratory Failure
  6. High Humidity High Flow Nasal Oxygen (HHFNC)
  • Indications
  1. Acute Pulmonary Edema Management (Acute Heart Failure)
  2. Hypoxic Acute Respiratory Failure (Oxygenation failure)
    1. BIPAP is in practice typically used instead of CPAP
    2. COPD Exacerbation
    3. Asthma Exacerbation
    4. Severe Pneumonia
    5. Acute Respiratory Distress Syndrome
    6. Obesity Hypoventilation Syndrome
  3. Hypercarbic Acute Respiratory Failure (Ventilatory Failure)
    1. Bridge to or from Mechanical Ventilation (e.g. Delayed Sequence Intubation or Ventilator Weaning)
    2. Do-not-intubate Resuscitation Status
  • Contraindications
  1. See Non-Invasive Positive Pressure Ventilation
  2. See Advanced Airway Indications
  3. Respiratory Failure (requires intubation)
  4. Altered Level of Consciousness with increased aspiration risk
  5. Significant oral or airway secretions
  • Mechanism
  1. Noninvasive Positive Pressure Ventilation
  2. Similar to CPAP except offers two pressure levels instead of one continuous pressure
    1. Preset inspiratory airway pressure (IPAP)
    2. Preset expiratory airway pressure (EPAP)
  3. Oxygen Delivery is increased by expiratory pressure (EPAP) increase (similar to CPAP)
  4. Work of breathing is decreased
    1. BIPAP offers a greater assistance than CPAP in reducing the work of breathing
  5. Tidal Volume is related to the difference between inspiratory (IPAP) and expiratory (EPAP) pressures
    1. Tidal Volume increases as the difference between IPAP and EPAP increases
    2. In other words, the Tidal Volume is identical for IPAP/EPAP of 10/5 and 15/10
    3. The IPAP-EPAP difference allows BIPAP to ventilate (albeit without airway control)
    4. As the IPAP-EPAP delta increases and Tidal Volume increases, PaCO2 decreases
  • Approach
  • Sedation
  1. Allows for BIPaP tolerance
  2. Avoid Benzodiazepines if possible
    1. Risk of respiratory depression, confusion and paradoxical Agitation
  3. Typical agents used
    1. Dexmedetomidine
    2. Ketamine
    3. Fentanyl
    4. Haloperidol
  • Protocol
  • Start BIPAP settings
  1. Starting in an alert patient
    1. Allow patient to self-apply mask and start with 2-3 cm inspiratory pressure (IPAP)
    2. If oxygenation is adequate, expiratory pressure (EPAP) may be started at 0
    3. Gradually increase inspiratory pressure (IPAP) above EPAP to increase Tidal Volume
    4. Gradually increase expiratory pressure (EPAP) to maintain oxygenation
      1. EPAP is also increased to reduce Preload and Afterload in Cardiogenic Pulmonary Edema (see below)
  2. Inspiratory Pressure (IPAP)
    1. Start 10-15 cm H2O
    2. Maximum 20-25 cm H2O
      1. IPAP >20 cm H2O risks gastric distention with aspiration risk and decreased diaphragmatic excursion
    3. Persistent hypercapnea
      1. Increase inspiratory pressure (IPAP) in 2 cm H2O increments (to a maximum of 20-25 cm H2O)
      2. Keep expiratory pressure (EPAP) unchanged while increasing IPAP to increase Tidal Volume
        1. Increasing Delta (IPAP - EPAP) increases Tidal Volume, and decreases PaCO2
      3. Titrate Tidal Volumes to a maximum of 6-8 ml/kg
      4. Predict required new Minute Ventilation (MV = Tidal Volume * Respiratory Rate)
        1. MVnew = (PaCO2_now / PaCO2_goal) * MVcurrent
        2. Where the PaCO2_goal is 10 mmHg improved from current (e.g. 60 mmHg instead of 70 mmHg)
  3. Expiratory Pressure (EPAP)
    1. Start 4-5 cm H2O
    2. Maximum 10-15 cm H2O
    3. Persistent Hypoxia
      1. Increase both inspiratory pressure (IPAP) AND expiratory pressure (EPAP) in increments of 2 cm H2O
      2. Both IPAP and EPAP must be increased the same amount to maintain the same Tidal Volume
    4. Cardiogenic Pulmonary Edema
      1. Increase expiratory pressure in tandem with inspiratory pressure (decreases Preload and Afterload)
  4. FIO2: 1.0 (100%)
    1. Titrate down to lowest level to maintain Oxygen Saturation >91% (or other patient specific parameter)
  5. Inspiratory to Expiratory Time (I:E)
    1. COPD
      1. Set Inspiratory to Expiratory Time (I:E) low for a shorter inspiratory time, allowing for adequate expiration
  6. Respiratory Rate (back-up)
    1. Start at 6 breaths/minute
    2. Respiratory Rate may be increased above patient's inherent rate in somnolent patient
      1. Higher Respiratory Rate is unlikely to be tolerated in the alert patient
    3. Note patient's Respiratory Rate while maintaining spontaneous respirations
      1. May need to match this if Mechanical Ventilation required
  7. Average Volume Assured Pressure Support (AVAPS)
    1. Analogous to pressure regulated volume control (PRVC) on mechanical Ventilators
    2. Available on some newer BiPap machines
    3. Allows for setting a Tidal Volume (TV) goal, and a range of IPAP settings that the machine can use to achieve that TV
    4. Indicated in hypercarbic Respiratory Failure, allowing for automatic titration of Tidal Volume based on patient respiratory effort
  1. Monitoring
    1. Clinical appearance
    2. Mental status
    3. Vital Signs
    4. Pulse Oximetry
    5. Venous Blood Gas (or Arterial Blood Gas)
    6. Ventilator changes may be made as often as every 15-30 minutes
  2. Clinical goals
    1. Respiratory Rate <30 breaths/min
    2. Tidal Volume (Vt) 6-8 ml/kg (Ideal Body Weight)
    3. Improved gas exchange
    4. Patient comfort
  3. Improved findings on Arterial Blood Gas (ABG) expected if BIPAP successful
    1. PaCO2 decreases by 8 mmHg or more
    2. pH increases by 0.06 or more
  4. Respiratory Failure findings suggesting need for Mechanical Ventilation
    1. PaCO2 >80 mmHg
    2. pH <7.25 mmHg
    3. Glasgow Coma Scale (GCS) <8
  5. Patient intolerance of BIPAP
    1. Consider low dose Ketamine (e.g. 0.5 mg/kg IV)
    2. Consider low dose anxiolysis with Lorazepam or similar Benzodiazepine
      1. Exercise caution to prevent respiratory depression
    3. Consider CPAP
      1. Less need of patient to synchronize their breaths
      2. CPAP has only a constant pressure, while BIPAP has inspiratory and expiratory pressure phases
  • Efficacy
  • Noninvasive positive airway pressure in respiratory distress
  1. CPAP and BIPAP have similar outcomes in respiratory distress
    1. Only BiPap (not CPAP) is effective however in hypercarbic Acute Respiratory Failure (Ventilatory failure)
  2. CPAP may be better tolerated in some cases
    1. No need to synchronize their breaths with different inspiratory and expiratory pressure phases
  3. Li (2013) Am J Emerg Med 31(9): 1322-7 [PubMed]
  • Adverse Effects
  1. See Non-Invasive Positive Pressure Ventilation
  • References
  1. (2016) Mechanical Ventilation, Fundamental Critical Care Support, SCCM, p. 61-92
  2. Hormann (1994) Eur J Anaesthesiol 11(1):37-42
  3. Mallemat and Runde in Herbert (2015) EM:Rap 15(2): 7-8
  4. Mallemat and Swaminathan (2023) EM:Rap, accessed 7/1/2023
  5. Martin and Hall (2015) Crit Dec Emerg Med 29(2): 11-8
  6. Soo Hoo in Mosenifar (2013) Noninvasive Ventilation, Medscape
    1. http://emedicine.medscape.com/article/304235