Question 19

College answer

 Ensure optimal treatment of the underlying cause of respiratory failure where possible, e.g.

• Diuretics and CPAP for acute pulmonary oedema

• Bronchodilators for asthma 
 
1. Optimise pre-oxygenation/ intra procedure oxygenation

• Longer time of pre-oxygenation  

• Use of PSV or CPAP pre-intubation (peak Pi not >15 cmH2O recommended)

• Nasal prong and/or high-flow oxygenation during intubation (e.g. THRIVE or simple prongs at 15l/min)

• Monitoring end tidal oxygen; target FeO2 >80% 
 
2. Minimising time to first breath

• Positioning  (essential point to mention)

• Ramping (or similar) achieving tragus-sternal angle in horizontal plane Important in obese patient

• Experienced operator

• Equipment ready (expect candidate to have fall-back equipment such as VL, bougies, second generation LMA. No specific right or wrong re which device they should use first)

• Use of rapidly acting skeletal muscle relaxant (or use of spontaneously breathing technique e.g. LA) • Monitoring for intra-tracheal placement of ETT; capnography

• Ventilator set up with appropriate settings for immediate use including FiO2 1.0 and appropriate level PEEP, Vt and inspiratory airway pressure  

• Teamwork management – clear roles in primary and backup plans

• NB: Delay with use of video-laryngoscopy 
 
3. Rescue strategies

• Plan A, Plan B, Plan C

• Preparations for supraglottic and infraglottic rescue (more credit if specific algorithm is mentioned e.g. Vortex, DAS) 
 
4. Optimise cardiac output for improved V/Q matching

• Judicious fluid loading

• Vasopressors (e.g. Nor-adrenaline, metaraminol)

• Awareness of fall in output with induction of anaesthesia and institution of IPPV

• Invasive arterial pressure monitoring 
 

Discussion

The details of this answer are explored in the chapter on the prevention of hypoxia during airway management. For a proper literature reference, the time-poor candidate is directed to  "Preoxygenation and prevention of desaturation during emergency airway management" by Weingart and Levitan (2011).

Positioning

• Head up 20-25° (especially valuable in the obese patients)

Denitrogenation

• 100% FiO₂
• Deep breaths × 8
• Or, 3-4 minutes of breathing the oxygen-rich mixture
• The effect is enhanced by positive airway pressure
• There is no benefit in extending this period beyond 4 minutes

Positive pressure

• Use NIV unless contraindicated
• PEEP 5-10 cm H₂O
• Not to exceed 25 cm H₂O
• Alternatively, use a PEEP valve on the bag-valve mask

Minimisation of metabolic demands

• Use generous amounts of muscle relaxant
• The use of non-depolarising agents is preferred, as fasciculations can increase the total body oxygen demand 

Anticipation of hypoxia

• Preparation of staff and equipment for rapid desaturation

Apnoeic oxygenation

• Continued application of CPAP during the apnoeic period (i.e. while waiting for optimal intubating conditions)
• Use of bag-valve mask to gently ventilate the patient, promoting flow of fresh oxygen into the FRC

Preparation for failure

• Extend invitation to ENT or senior anaesthetic staff to be present at the intubation
• Make surgical airway equipment easily available