Seventeen adult patients with large mediastinal masses requiring general anesthesia underwent awake intubation followed by continuous video bronchoscopy recordings of the compromised portion of the airway during staged induction. Assessments of changes in anterior–posterior airway diameter relative to baseline (awake, spontaneous ventilation) were performed using the following patency scores: unchanged = 0; 25 to 50% larger = +1; more than 50% larger = +2; 25 to 50% smaller = −1; more than 50% smaller = −2. Assessments were made by seven experienced bronchoscopists in side-by-side blinded and scrambled comparisons between (1) baseline awake, spontaneous breathing; (2) anesthetized with spontaneous ventilation; (3) anesthetized with positive pressure ventilation; and (4) anesthetized with positive pressure ventilation and neuromuscular blockade. Tidal volumes, respiratory rate, and inspiratory/expiratory ratio were similar between phases.
No significant change from baseline was observed in the mean airway patency scores after the induction of general anesthesia (0 [95% CI, 0 to 0]; P = 0.953). The mean airway patency score increased with the addition of positive pressure ventilation (0 [95% CI, 0 to 1]; P = 0.024) and neuromuscular blockade (1 [95% CI, 0 to 1]; P < 0.001). No patient suffered airway collapse or difficult ventilation during any anesthetic phase.
These observations suggest a need to reassess prevailing assumptions regarding positive pressure ventilation and/or paralysis and mediastinal mass–mediated airway collapse, but do not prove that conventional (nonstaged) inductions are safe for such patients.
- There is a serious concern that muscle paralysis and positive pressure ventilation of a patient with a large mediastinal mass may worsen the compressed airway segment and lead to an inability to ventilate
- Classic teaching is that maintaining spontaneous breathing is safer and preserves airway patency compared to positive pressure ventilation and/or paralysis
- However, there is a lack of evidence to support such a notion
- This prospective, single-center, observational study measured the dynamic change in the anterior–posterior diameter of the segment of the compressed central airway during staged induction of 17 adult patients with large mediastinal masses
- The compression of the central airway in a semisitting position did not worsen after muscle paralysis or muscle paralysis plus positive pressure ventilation compared with that occurring during awake, spontaneous breathing