Noninvasive Ventilation

Aka: Noninvasive Ventilation, Noninvasive Mechanical Ventilation, Non-Invasive Positive Pressure Ventilation, NIPPV

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II. Contraindications

  1. See Advanced Airway Indications
  2. Respiratory Failure or apnea
    1. Cardiopulmonary Arrest
    2. Comatose patient
  3. Airway protection
    1. Status Epilepticus
    2. Upper airway tenuous with risk of complete obstruction
    3. Uncontrolled Gastrointestinal Bleeding
    4. Intractable Emesis
    5. Facial Trauma, Burn Injury or recent surgery
  4. Other factors
    1. Uncooperative or Agitated Patient despite anxiolysis
    2. Patient unable to synchronize with BIPAP delivered breaths
    3. Hemodynamic instability

III. Indications

  1. See Endotracheal Intubation Preoxygenation
  2. Hypoxemic Respiratory Failure or Inadequate oxygenation (CPAP or BIPAP)
    1. Cardiogenic Pulmonary Edema
    2. Congestive Heart Failure exacerbations
  3. Hypercarbic Respiratory Failure or Inadequate ventilation (BIPAP)
    1. Chronic Obstructive Pulmonary Disease exacerbations
  4. Immunocompromised patients
    1. Early initiation of Noninvasive Ventilation reduces intubation risk
      1. Adda (2008) Crit Care Med 36(10): 2766-72 [PubMed]
    2. Non-intubated Immunocompromised patients have lower mortality
      1. Related to risk of Ventilator-Associated Pneumonia
  5. Other indications with mixed efficacy or inadequate studies
    1. Asthma
    2. Pneumonia (including mild to moderate pneumocystis Pneumonia)
    3. Acute Lung Injury (Acute Respiratory Distress Syndrome)
    4. Thoracic Trauma
    5. Cystic Fibrosis associated Respiratory Failure

IV. Precautions

  1. Start Noninvasive Ventilation early, before severe respiratory Fatigue occurs
    1. When starting Supplemental Oxygen, consider whether Noninvasive Ventilation would be a better choice
  2. Prepare the machine in advance of patient arrival (e.g. EMS radio report)
    1. Plug in the Bipap or Cpap machine
    2. Attach to wall oxygen
    3. Attach mask to machine
    4. Set initial FIO2 to 100%
    5. Set initial Inspiratory pressure (IPAP) to 10-15 H2O, and expiratory pressure (EPAP) to 5 H2O

V. Physiology

  1. Pressures required to allow inspiration must equal the airway pressures to overcome
    1. Ventilator pressures (CPAP, BIPAP) allow for lower respiratory Muscle pressures (work of breathing)
  2. Pressures required to allow inspiration
    1. Respiratory Muscle Pressures or work of breathing (pMuscle)
    2. Ventilator pressures (pApplied)
  3. Airway pressures to overcome
    1. Airway elastance with a predilection for airway collapse (pElastance)
    2. Airway resistance such as that due to bronchospasm or inflammation (pResistance)
    3. Airway impedance to flow from other factors such as anatomy in Sleep Apnea (pThreshold)
  4. Positive Airway Pressures
    1. Expiratory Positive Airway Pressure (EPAP) or Positive End-Expiratory Pressure (PEEP)
      1. Maintains open airways to provide oxygenation
      2. CPAP only supplies continuous pressure at this level
      3. BIPAP provides this pressure between ventilations
    2. Inspiratory Positive Airway Pressure (IPAP)
      1. Pressure Support Ventilation during inspiration provides a Tidal Volume (IPAP-EPAP) and clears CO2
      2. BIPAP provides this pressure during ventilations

VI. Adverse Effects

  1. Gastric insufflation
    1. Increases work of breathing (against a distended Stomach)
    2. Risk of Vomiting and aspiration
    3. Abdominal Compartment Syndrome is a rare associated complication
    4. Avoid BIPAP inspiratory pressures >20 cm H2O
  2. Mask malplacement effects
    1. Nasal or facial ulcerations
  3. Decreased Cardiac Output
    1. Results from decreased Preload related to increased intrathoracic pressure
    2. Manage with increased fluid Resuscitation
  4. Barotrauma
    1. Pneumothorax may occur at higher pressures

VII. Management: Approach to Non-Invasive Positive Pressure Ventilation Selection

  1. Hypoxemic Respiratory Failure (Inadequate oxygenation)
    1. Concepts
      1. Increase oxygen delivered to the lung (FIO2) or
      2. Increase mean airway pressure (or Positive End-Expiratory Pressure, PEEP)
    2. Interventions
      1. Continuous Positive Airways Pressure (CPAP)
      2. High Humidity High Flow Nasal Oxygen (HHFNC)
      3. In practice, BIPAP is often used in these cases
    3. Monitoring
      1. Pulse Oximetry (preferred, reflects Oxygen Delivery to tissue)
      2. ABG with pO2
    4. Targets
      1. Target 90-96% Oxygen Saturation (88-92% in COPD and Obesity Hypoventilation Syndrome)
    5. Conditions
      1. Cardiogenic Pulmonary Edema
      2. Congestive Heart Failure exacerbations
    6. Maximum CPAP settings above which intubation should be considered (see below)
      1. Expiratory Positive Airway Pressure (EPAP) > 12-15 cm H2O
      2. Delivered FIO2 >60%
  2. Hypercarbic Respiratory Failure (Inadequate ventilation)
    1. Concepts
      1. Minute Ventilation = TV * RR
      2. Increase Tidal Volume (TV) or
      3. Increase Respiratory Rate (RR)
    2. Interventions
      1. Bilevel Positive Airway Pressure (BiPap)
    3. Monitoring
      1. ABG or VBG (pH and pCO2)
      2. etCO2
    4. Targets
      1. Do not attempt to fix acid-base abnormalities initially (Permissive hypercapnea is preferred)
      2. Allow a wider range of pH (7.2 to 7.5) in most patients
      3. Maintain normal pCO2 (35-45 mmHg) in Increased Intracranial Pressure, pregnancy, severe Pulmonary Hypertension
    5. Conditions
      1. Chronic Obstructive Pulmonary Disease exacerbations
      2. BIPAP may be used for any of the Hypoxemia cases as well instead of CPAP
        1. Includes CHF (without increased risk of Myocardial Infarction)
        2. Vital (2013) Cochrane Database Syst Rev 5:CD005351 +PMID:18646124 [PubMed]
  3. References
    1. Mallemat and Runde in Herbert (2015) EM:Rap 15(2): 7-8
    2. Internet Book of Critical Care (EMCRIT.org)
      1. https://emcrit.org/ibcc/guide/

VIII. Protocol: Indications for intubation (failed Noninvasive Ventilation)

  1. See Bilevel Positive Airway Pressure (BIPAP) for re-evaluation based on ABG criteria
  2. Based on re-evaluation clinical criteria including Arterial Blood Gas at 1-2 hours and at 4-6 hours
  3. Major Criteria (based on COPD cohort)
    1. See Advanced Airway indications
    2. Respiratory arrest (despite noninvasive Ventilator back-up rate)
    3. Gasping for air
    4. Loss of consciousness with respiratory pauses
    5. Agitation requiring sedation
    6. Heart Rate <50 bpm and loss of alertness
    7. Hemodynamic instability with systolic Blood Pressure <70 mmHg
  4. Minor Criteria (2 of the following, based on COPD cohort)
    1. Respiratory Rate >35 breaths/minute (at any time)
    2. Respiratory Rate >20-25/minute (after one hour of Noninvasive Ventilation)
    3. pH <7.30 and decreased from onset
    4. PaO2 <45 mmHg despite Supplemental Oxygen
    5. Decreased Level of Consciousness or worsening encephalopathy
  5. References
    1. Hoo (2012) Noninvasive Ventilation, Medscape EMedicine,
      1. http://emedicine.medscape.com/article/304235-overview#aw2aab6b5

IX. References

  1. Martin and Hall (2015) Crit Dec Emerg Med 29(2): 11-8
  2. (2016) Mechanical Ventilation, Fundamental Critical Care Support, SCCM, p. 61-92

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