B2. Airway maintenance, respiratory systems, anaesthetic machine

From greek.doctor

Airway management

There are several things which must be taken into account regarding airway management during perioperatively:

  • What is the patient’s body shape and airway anatomy? Will it make intubation difficult?
  • Has the patient fasted?
  • Are muscle relaxants needed?
  • Will the surgery influence the anaesthesia somehow?

If the patient hasn’t fasted before surgery, for example during an emergency, the stomach is regarded as full, and rapid-sequence intubation (RSI, also called crash induction) and the Sellick-manoeuvre is needed. The Sellick-manoeuvre involves placing pressure on the cricoid cartilage to compress the oesophagus and prevent aspiration.

  1. All equipment which will be and may be necessary are prepared
  2. The patient is preoxygenated with 100% oxygen
  3. The Sellick-manoeuvre is applied
  4. Anaesthesia and paralysis is induced simultaneously with succinylcholine and an IV anaesthetic
  5. The patient is rapidly intubated after step 3
  6. The Sellick-manoueuvre is stopped

Mask ventilation is avoided, as this would increase the risk of aspiration.

Airway devices

An airway can be maintained with various tools:

  • Face mask
  • Nasopharyngeal (Wendl) tube
  • Oropharyngeal (Guedel) tube
  • Combitube
  • Laryngeal mask
  • I-gel tube
  • Endotracheal tube (ET)
  • Coniotomy – if mask ventilation and intubation fails (difficult airway)

The most frequently used airway is the ET tube. Signs of a successful intubation include:

  • Direct visualisation of the tube passing between the vocal cords
  • Auscultation of breathing sounds bilaterally
  • Observation of chest movements

Anaesthetic machine

The primary function of the anaesthetic machine is to provide adequate amounts of oxygen and anaesthetic agent under controlled conditions, and to prevent the patient from inhaling their own exhaled air. It has three parts:

  • Gas delivery system – delivers a mixture of inhaled anaesthetics, oxygen, and air
    • CO2 – absorber containing soda lime
    • Reservoir bag – provides a gas reservoir and allows us to evaluate the patient’s spontaneous ventilation
    • Vaporizer – adds the anaesthetic
  • Ventilator
  • Monitor

The machine contains one-way valves which prevent the patient from inhaling their own exhaled air.