Bag Valve Mask (BVM) Comprehensive Notes

Bag Valve Mask (BVM) Overview

Normal Breathing

Inhalation
  • Process: Inhalation involves expansion of the thoracic cavity due to contraction of the diaphragm and intercostal muscles.
  • Boyle's Law: As volume increases, pressure decreases, allowing air to enter the lungs. The equation representing this relationship is given by:
    P<em>1V</em>1=P<em>2V</em>2P<em>1V</em>1 = P<em>2V</em>2
  • Pressure Gradient: The negative pressure inside the thoracic cavity (less than atmospheric pressure) facilitates the inflow of air into the lungs.
Exhalation
  • Process: During exhalation, lungs recoil, and the intercostal muscles and diaphragm relax, leading to increased pressure in the thoracic cavity. Air exits the lungs through the exhalation port due to the pressure gradient, making exhalation a passive process.

Bag Valve Mask (BVM) Mechanics

Components of the BVM
  1. Squeezable Bag: This allows for manual ventilation.
  2. One-Way Valve: Prevents backflow of exhaled air.
  3. Face Mask: Ensures proper delivery of air to the patient.
Function
  • Operation: Compressing the bag opens the valve, delivering air to the lungs; releasing the bag allows passive exhalation. The bag refills with room air or oxygen during exhalation.
  • Indications:
    • Emergency ventilation for apnea, respiratory failure, or impending respiratory arrest.
    • When ET intubation or definitive airway control is not feasible.
    • Used as a “bail-out” manoeuvre during failed intubation attempts.

Special Considerations for Paediatrics

  • Head Size: Larger at the back, requiring specific positioning.
  • Facial Features: Softer tissue, necessitating careful mask fit.
  • Lung Size: Smaller lungs mean faster breathing rates.
  • Tongue Size: Larger tongue requires consideration to maintain airway.
Equipment Adjustments
  • Use a round face mask and a smaller bag to accommodate pediatric anatomy.

Airway Management Pillars

  1. Patency of the Upper Airway: Ensuring clear airflow.
  2. Protection Against Aspiration: Preventing foreign material from entering the lungs.
  3. Assuring Oxygenation and Ventilation: Maintaining adequate gas exchange.

Equipment for BVM Ventilation

  • Basic Supplies: Gloves, face mask, personal protective equipment.
  • Airway Tools: Oropharyngeal and nasopharyngeal airways, lubricating ointment.
  • Ventilation and Oxygen: BVM apparatus, PEEP valve, 100% oxygen source.
Key Specifications
  • Deliver approximately 6-7 mL/kg per breath (approx. 500 mL for an average adult).
  • Ventilation rate for a patient with a perfusing rhythm: 10-12 breaths per minute.

Successful BVM Ventilation Requirements

  1. Patent Airway: Clear of obstructions.
  2. Adequate Mask Seal: Ensures proper air delivery.
  3. Proper Ventilation Technique: Effective manual support with positive pressure.
  4. PEEP Valve: May be needed to enhance oxygenation.

Establishing a Patent Airway

Key Actions
  1. Management of Obstructions: Clear the oropharynx from the tongue, secretions, and foreign bodies.
  2. Positioning: Ensure proper alignment to maintain airway integrity.
  3. Use of Adjuncts: Employ nasopharyngeal or oropharyngeal airways as necessary.

Procedure and Technique for BVM Ventilation

  1. Position the Patient's Head: Sniffing position if cervical spine injury is not suspected.
  2. Seal the Face Mask: Use thumb and index finger to secure the mask, while maintaining airway with other fingers.
  3. Administer Ventilation: Use the second hand to squeeze the bag and ventilate the patient.

Assessment of Adequacy

  • Monitor:
    • Chest rise and fall
    • Bilateral air entry
    • Improvement in patient colour
    • Absence of air entering the stomach
    • Bag feel
    • SpO2 saturation levels

Contraindications for BVM Ventilation

  1. Complete upper airway obstruction.
  2. Risks of aspiration post-paralysis.
  3. Severe facial trauma and eye injuries.
  4. Presence of foreign materials like gastric contents in the airway.

Difficult Airway Indicators

  • Signs of potential difficulty include:
    • Upper airway obstruction
    • Edentulous patients
    • Patients with facial hair (beard)
    • Obese individuals
    • Elderly patients over 70
    • Facial burns or scars

Managing Difficult Airway

Techniques
  1. Optimize Positioning: Adjust airway to improve access.
  2. Triple Airway Manoeuvre: Includes head tilt, chin lift, and jaw thrust.
  3. Utilize Airway Adjuncts: Use oropharyngeal or nasopharyngeal airways to enhance airway patency.

Alternative Interventions if BVM Fails

  1. Laryngeal Mask Airway (LMA): A mask inserted over the larynx to facilitate ventilation.
  2. Cricothyroidotomy: Emergency procedure to create an airway in severe airway obstruction cases.

Complications of BVM Ventilation

  1. Hypo/Hyperventilation: Inadequate oxygenation due to improper ventilation rates.
  2. Gastric Insufflation: Inflation of the stomach due to improper seal or technique.
  3. Volutrauma: Lung injury from over-stretching.
  4. Barotrauma: Lung injury from excessive pressure.
  5. Aspiration Risk: Passage of foreign materials into the lungs.