You are preparing to intubate a morbidly obese patient for respiratory failure.
Describe the strategies for minimising hypoxaemia in the period immediately pre- and post-intubation.
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
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
Denitrogenation
Positive pressure
Minimisation of metabolic demands
Anticipation of hypoxia
Apnoeic oxygenation
Preparation for failure
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