Bag Mask Ventilation

BMV Basics

Anesthetic machines come with several elements

1. Mask - forms a seal on the mouth. A good seal allows accurate reading of ETCO2 and ETO2 (to assess pre-oxygenation)
2. Circuit - the tubing that connects the mask to the ventilator
3. Bag - acts as a gas reservoir and allows delivery of breaths during BMV
4. APL valve - adjusts the blow off pressure available in the circuit
5. Bag to Vent Switch (if applicable)

BMV Adjuncts

Oropharyngeal Airway

Useful for maintaining airway patency Sizing: corner of mouth to angle of mandible Contraindications: must be inserted carefully pediatrics (due to incompletely formed hard palate)

Nasopharyngeal Airway

Also known as a nasal trumpet Used to maintain airway patency Sizing: tip of nose to earlobe Contraindications: Basal skull fracture, patients likely to have epistaxis (relative)

Laryngeal Mask Airway

A supraglottic (does not pass below vocal cords) airway device which can be used to maintain an airway under anesthesia or in an emergency situation. These devices do not provide the level of seal that an ETT does

Indications

• anesthetic cases with:
  • good access to the airway (to swap to ETT, if needed)
  • positioning amenable to low airway pressures
  • generally, no laparopscopic component
• Patients at risk of laryngospasm/bronchospasm
  • less invasive and provoking than an ETT
  • if laryngospasm does occur, LMA will not ventilate
• Emergency airway access and inability to intubate

  Contraindications

  Patient Factors

• Severe GERD
• Obesity
  • due to higher pressures required for ventilation
• Patients at risk of aspiration
  • non-fasted patients
  • patients with delayed gastric emptying

    Surgical

• laparoscopic (generally)
• shared airway with limited access to manage airway

  Sizing

  These are weight based and vary by type LMA

Endotracheal Tube

Placement

Standard endotracheal tubes are placed below the level of the vocal cords under direct vision. On x-ray, the tube tip should sit 2-4 cm above the carina. A rule of thumb for the depth of tube is: $Depth = 3\times Tube~Diameter$

Sizing

Tube diameter is generally selected with the following rule for cuffed tubes: $Tube~Diameter = (age + 4)/4$

Cuff inflation

Cuff pressure should be 20-30 cm H2O to prevent mucosal ischemia An adequate seal between the cuff and the trachea can be assessed by looking at the inspired tidal volume and comparing it to the expired tidal volume.

Specialized Endotracheal Tubes

RAE tubes

Stands for: Ring, Adair, Elwyn Characteristic bend removes tube and circuit from surgical field Useful in: Sinus surgery, facial surgery Special considerations: Fixed length from bend to tip of tube can impair proper tube placement below glottis

Nasal RAE

Special Considerations:

• Fixed length from bend to tip of tube can impair proper tube placement below glottis

  EVAC Tubes

  Standard endotracheal tube with a suction port above the level of the glottis Useful for endotracheal tube care in the ICU environment (or if the patient is likely to need ICU care)