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