Positive Pressure Ventilation

Aka: Positive Pressure Ventilation, Bag Valve Mask, Bag Valve Mask Ventilation, Ambu Bag, Anesthesia Bag, PEEP Valve, Impedance Threshold Device, ResQPOD, MOANS Mnemonic, ROMAN Mnemonic

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II. Indications: Positive Pressure Ventilation

  1. Respiratory Failure
  2. Cardiopulmonary Resuscitation
  3. Conscious Sedation

III. Contraindications: Relative (Exercise caution)

  1. Severe facial Trauma
  2. Open eye injuries
  3. Oral cavity with foreign body

IV. Precautions: Difficulat Bag Valve Mask Ventilation

  1. Mnemonic: MOANS
    1. Mask seal (e.g. beard)
    2. Obstruction
    3. Older Age
    4. No teeth (replace dentures for Bag Valve Mask Ventilation)
    5. Stiff lungs requiring increased Ventilatory pressures (Asthma, COPD, ARDS, term pregnancy)
  2. Mnemonic: ROMAN
    1. Radiation to Neck or Restricted Lung Excursion (Asthma, COPD, ARDS, pumonary edema)
    2. Obesity or Obstruction or Obstructive Sleep Apnea
    3. Mask Seal (e.g. beard), Mallampati or Male gender
    4. Age >55 years
    5. No Teeth (replace dentures for Bag Valve Mask Ventilation)

V. Device: Flow-inflating bag (Anesthesia Bag)

  1. Mechanism
    1. Requires compressed oxygen source to fill
  2. Advantages
    1. Preferred for Newborn Resuscitation
    2. Lung Compliance can be felt on squeezing bag
    3. Can deliver free-flow 100% oxygen
  3. Disadvantages
    1. Requires a tight facial seal
    2. Higher risk of over-inflating lung (use manometer)
    3. Technically more difficult to learn to use
  4. Technique
    1. Set oxygen supply flowmeter to 5-10 L/min
    2. Adjust bag volume with flow-control valve

VI. Device: Self-inflating bag (Bag-valve mask or Ambu Bag)

  1. Aduncts (see below)
    1. PEEP Valve
    2. Impedance Threshold Device (e.g. ResQPOD)
  2. Mechanism
    1. Bag fills spontaneously after being squeezed
  3. Advantages
    1. Does not require an oxygen source
    2. Easier to learn to use
  4. Disadvantages
    1. Can not deliver free flow oxygen
      1. Place Nasal Cannula 15 lpm below mask to deliver continuous oxygen
    2. Delivered oxygen is diluted with room air entrained through the exhalation port
      1. Apply a PEEP Valve to increase Oxygen Delivery
  5. Oxygen Delivery with ventilation (Bag-Valve Mask)
    1. No Oxygen Source
      1. Delivers 21% Oxygen (Room air)
    2. Without Oxygen Reservoir
      1. Delivers 30-80% Oxygen at 10 LPM flow
    3. With Oxygen Reservoir (required for high oxygen flow)
      1. Delivers 60-95% Oxygen at 10-15 LPM flow
      2. Delivers oxygen if reservoir fills
  6. Pop-Off Valves (Bag Valve Mask)
    1. Usually set at 30-45 cm H2O
    2. Pop-off should be easily occluded on bags
      1. Higher pressures are needed during CPR
    3. Occlusion of the pop off valve
      1. Depress valve with finger during ventilation or
      2. Twist the pop-off valve into closed position
  7. Monitoring
    1. End-Tidal CO2
      1. Place device between bag and mask
      2. Confirms that delivered breaths are matched with CO2 exhalation
    2. Mask pressure gauge
      1. Available with some bag-valve masks via built-in gauge or via accessory port
      2. Ideally present to monitor delivered pressure with each gauge (prevents hyperinflation)
        1. Exercise caution, when a gauge is not present to avoid hyperinflation
      3. Target pressures
        1. Green zone: 20 mmHg (do not exceed 30 mmHg)
  8. Images
    1. Neonatal Ambu-Bag
      1. lungAmbuPeds250.png

VII. Device: Self-inflating Bag (Bag Valve Mask) Adjuncts

  1. PEEP Valves
    1. Put PEEP Valve on every bag-valve-mask
    2. PEEP Valves dramatically improve Oxygen Delivery
      1. One-way valve that blocks flow out of the exhalation port unless pressure exceeds set value (PEEP)
        1. PEEP keeps alveoli open between ventilations
      2. Blocks room air from entering the exhalation port (prevents dilution of supplied oxygen with room air)
        1. May set the PEEP Valve to 0, if only wish to raise delivered oxygen without applying PEEP
    3. Adverse Effects
      1. Increases risk in Hypotension of decreasing venous return (increases intrathoracic pressure)
    4. References
      1. Levitan (2013) Practical Emergency Airway Management Course
  2. Impedance Threshold Device (e.g. ResQPOD)
    1. May be indicated in CPR (but variable evidence)
    2. Attaches inline between positive pressure device (e.g. ambubag) and mask or ET Tube
    3. Assists in maintaining negative intrathoracic pressure which in turn increases venous return
    4. Associated with increased rate of Return of Spontaneous Circulation
      1. Aufderheide (2005) Crit Care Med 33(4): 734-40 [PubMed]
    5. However more recent studies showed no benefit
      1. Aufderheide (2011) N Engl J Med 365(9): 798-806 [PubMed]

VIII. Device: Noninvasive Positive Pressure Ventilation (NIPPV)

  1. Bilevel Positive Airway Pressure (BiPAP)
  2. Continuous Positive Airways Pressure (CPAP)
  3. High Humidity High Flow Nasal Oxygen (HHFNC)

IX. Precautions

  1. Do not use Bag Valve Mask to deliver free flow oxygen
    1. Oxygen only flows when squeezing bag
    2. Use Bag Valve Mask with a PEEP Valve and Nasal Cannula at 15 lpm under mask to deliver oxygen
  2. Position patient for best ventilation (Oops Mnemonic, Levitan)
    1. Oxygen On
    2. Apply 15 lpm by Nasal Cannula under mask for Apneic Oxygenation
    3. Pull Mandible forward (Jaw Thrust maneuver)
    4. Sit patient up (to 20 degrees)
  3. Anticipate difficult mask ventilation (Mnemonic: MOANS)
    1. Mask seal (e.g. beard)
    2. Obstruction
    3. Older Age
    4. No teeth (replace dentures for Bag Valve Mask Ventilation)
    5. Stiff lungs requiring increased Ventilatory pressures (Asthma, COPD, ARDS, term pregnancy)
  4. References
    1. Difficult Airway Course
      1. http://www.theairwaysite.com

X. Technique

  1. Tidal Volume
    1. Term Newborns
      1. Administer 5-8 ml/kg (15 to 25 ml per ventilation)
      2. Bag volume: 200 to 750 ml (usually >450 ml)
    2. Adults and older children
      1. Administer 6-7 ml/kg (lower than prior recommendations for 10-15 ml/kg)
  2. Hold mask over face with one hand
    1. Mask should fit snugly
      1. Covers mouth, nose and chin
      2. Should not cover eyes
    2. Use C-E position
      1. Operator forms a "C" with their first 2 fingers applying pressure to seal mask over nose and mouth
        1. Thumb over the mask top (nose)
        2. Index finger over the mask bottom (mouth)
      2. Operator forms an "E" with their last 3 fingers under the jaw
        1. Use fingers to support the jaw, pulling the face into the mask
    3. Avoid submental pressure (risk of airway obstruction)
    4. Employ assistant when unable to obtain adequate seal with one hand
      1. Obese patients
      2. Patients with dentures (consider leaving dentures in for better mask fit)
      3. Facial hair
      4. Clinician with small hands or inadequate strength
  3. Head Tilt - chin lift (Avoid if Trauma!)
    1. Use Jaw Thrust maneuver in Trauma or suspected spine injury
    2. Infants/Toddlers
      1. Neutral sniffing position without hyperextension
    3. Children >2 years
      1. Anterior displacement of c-spine
      2. Folded towel under neck and head
  4. Observe for adequate ventilation
    1. Adequate chest rise
    2. No signs of gastric insufflation

XI. Protocol: Troubleshooting

  1. No chest rise:
    1. Reposition head
    2. Ensure mask is snug
    3. Lift the jaw
    4. Consider suctioning airway
    5. Consider equipment failure (always test before use)
      1. Test bag with hand occluding patient outlet
      2. Check for bag leak
      3. Check flow-control valve
      4. Check that oxygen line is connected
    6. Consider airway adjuncts
      1. Nasal Airway
      2. Oral Airway
  2. Avoid Stomach insufflation and gastric distention
    1. Apply cricoid pressure (Sellick maneuver)
      1. In unconscious infant or child
    2. Consider NG suction
  3. Sudden decrease in Lung Compliance
    1. Right main Bronchus intubation
    2. Obstructed Endotracheal Tube
    3. Pneumothorax

XII. Resources

  1. Bag-Valve-Mask Demonstration Video (NEJM)
    1. http://www.youtube.com/watch?v=08pxEGmBCGM

XIII. References

  1. Brown (2022) Walls Manual of Emergency Airway Management, LWW
  2. Mason and Levitan in Herbert (2018) EM:Rap 18(1):14
  3. Swaminathan and Weingart in Herbert (2019) EM:Rap 19(7):6-7

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