Probability Distribution of Times for Selective Lobar Intubation and Ventilation Using a Novel Subglottic Airway Device: A Mannequin Study.

introductionAcute respiratory distress syndrome (ARDS) is characterized by significant heterogeneity in lung mechanics, leading to ventilation-perfusion mismatch and potential for ventilator-induced lung injury. Selective lobar ventilation offers a tailored approach for managing the impact of such heterogeneity by isolating and ventilating specific lung regions. However, its clinical feasibility, particularly the time needed for intubation, has not been established. This study evaluated the time required for selective lobar intubation and ventilation using a novel airway device in a high-fidelity mannequin. The primary hypothesis was that procedural times would follow a log-normal probability distribution. A secondary hypothesis was that the probability of the procedure exceeding five minutes would be less than 5% at the 95% upper confidence limit, if a log-normal distribution were suitable.

methodsThis was a prospective observational study conducted at a university simulation center. Clinicians were invited to perform endotracheal intubation, followed by selective endobronchial intubation of the left lower lobe on an AirSim Advance Bronchi X mannequin (TruCorp Ltd., Lurgan, UK). Participants used a "tube-thru-tube" technique with video laryngoscopy and fiberoptic bronchoscopy, guided by stepwise visual instructions. Data collected included the total time from tube insertion to successful selective lobar ventilation and the participant's self-reported number of intubations performed in the previous year. The fit of procedural times to log-normal and other distributions was assessed using the Shapiro-Wilk and Pearson chi-square tests.

resultsAmong all 52 participants, there was a poor fit to a log-normal distribution (P = 0.0040). However, the six participants who performed less than five endotracheal intubations in the preceding year had significantly longer times (P = 0.0006). Among the other 46 clinicians, procedural times showed a strong fit to a log-normal distribution (Shapiro-Wilk W = 0.98, P = 0.73), superior to normal or Weibull distributions. The mean time for successful selective lobar intubation was 2.26 minutes. No participant exceeded a five-minute threshold. Utilizing the log-normal model, the calculated 95% upper confidence limit on the probability of exceeding five minutes was 0.02%.

conclusionsThis simulation shows that procedure times for selective lobar ventilation follow a log-normal distribution. This statistical predictability is essential for quantitatively evaluating safety and for designing future clinical trials, including novel ARDS therapies with selective lobar ventilation. The confirmation of the log-normal distribution for an advanced airway task can be applied to other assessments of intubation times to make quantitative comparisons (e.g., ratios of means) and to calculate probabilities of exceeding tolerance limits.