Airway Management and Respiratory Physiology
Core concepts
Master the difficult-airway algorithm: assess, optimize, and have a plan A, B, C, D. Know predictors of difficulty (Mallampati, thyromental distance, mouth opening, cervical mobility, obesity, beard, prior radiation), and the difference between difficult mask ventilation, difficult laryngoscopy, and difficult intubation. Understand oxygen delivery and the oxyhemoglobin dissociation curve, the alveolar gas equation, and the effect of shunt versus dead space on oxygenation and ventilation. Know the physiology of preoxygenation, apneic oxygenation, and rapid-sequence induction. Recognize the presentation and management of laryngospasm, bronchospasm, and aspiration. Understand capnography waveforms and their meaning.
Traps in questions
- Assuming a Mallampati score alone predicts intubation difficulty; it predicts laryngoscopy but is imperfect.
- Confusing a cannot-intubate-cannot-ventilate scenario with a merely difficult laryngoscopy; the response differs.
- Forgetting that a normal oxygen saturation can coexist with a large shunt until late.
- Misreading a capnography trace: a sudden loss of waveform suggests disconnection or esophageal intubation, not bronchospasm.
- Overlooking that preoxygenation with 100% oxygen for 3 minutes or 8 vital-capacity breaths is adequate in most adults.
Worked example / rule of thumb
In a cannot-intubate-cannot-ventilate situation, insert a supraglottic airway and, if oxygenation fails, proceed to emergency front-of-neck access. Rule of thumb: the priority is oxygenation, not intubation; every step should restore or preserve oxygen delivery.
Exam framing
Stem questions often describe a desaturation after induction. The best answer addresses the most likely cause first (displacement, obstruction, esophageal placement) before escalating to a surgical airway.