Glottic visibility for laryngeal surgery: Tritube vs. microlaryngeal tube

BACKGROUND: Good visibility is essential for successful laryngeal surgery. A Tritube with outer diameter 4.4 mm, combined with flow-controlled ventilation (FCV), enables ventilation by active expiration with a sealed trachea and may improve laryngeal visibility. OBJECTIVES: We hypothesised that a Tritube with FCV would provide better laryngeal visibility and surgical conditions for laryngeal surgery than a conventional microlaryngeal tube (MLT) with volume-controlled ventilation (VCV). DESIGN: Randomised, controlled trial. SETTING: University Medical Centre. PATIENTS: A total of 55 consecutive patients (>18 years) undergoing elective laryngeal surgery were assessed for participation, providing 40 evaluable data sets with 20 per group. INTERVENTIONS: Random allocation to intubation with Tritube and ventilation with FCV (Tritube-FCV group) or intubation with MLT 6.0 and ventilation with VCV (MLT-VCV) as control. Tidal volumes of 7 ml kg predicted body weight, and positive end-expiratory pressure of 7 cmH2O were standardised between groups. MAIN OUTCOME MEASURES: Primary endpoint was the tube-related concealment of laryngeal structures, measured on videolaryngoscopic photographs by appropriate software. Secondary endpoints were surgical conditions (categorical four-point rating scale), respiratory variables and change of end-expiratory lung volume from atmospheric airway pressure to ventilation with positive end-expiratory pressure. Data are presented as median [IQR]. RESULTS: There was less concealment of laryngeal structures with the Tritube than with the MLT; 7 [6 to 9] vs. 22 [18 to 27] %, (P < 0.001). Surgical conditions were rated comparably (P = 0.06). A subgroup of residents in training perceived surgical conditions to be better with the Tritube compared with the MLT (P = 0.006). Respiratory system compliance with the Tritube was higher at 61 [52 to 71] vs. 46 [41 to 51] ml cmH2O (P < 0.001), plateau pressure was lower at 14 [13 to 15] vs. 17 [16 to 18] cmH2O (P < 0.001), and change of end-expiratory lung volume was higher at 681 [463 to 849] vs. 414 [194 to 604] ml, (P = 0.023) for Tritube-FCV compared with MLT-VCV. CONCLUSION: During laryngeal surgery a Tritube improves visibility of the surgical site but not surgical conditions when compared with a MLT 6.0. FCV improves lung aeration and respiratory system compliance compared with VCV. TRIAL REGISTRY NUMBER: DRKS00013097.