Glottic visibility for laryngeal surgery: Tritube vs. microlaryngeal tube: A randomised controlled trial

Abstract

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.

Fig. 1

CONSORT flow diagram. FCV, flow-controlled ventilation; MLT, microlaryngeal tube; VCV, volume-controlled ventilation.

Fig. 2

Representative videolaryngoscopic photographs of a Tritube with an outer diameter of 4.4 mm (a) and a microlaryngeal tube with an outer diameter 8.2 mm (b) after endotracheal placement. Dashed lines indicate defined total laryngeal areas, dotted lines indicate concealed areas; (c) concealment of laryngeal structures for the study groups as boxplot, indicating median, interquartile range and full range.

Fig. 3

Subjective evaluation of surgical conditions on a four point rating scale for total study cohort (a), for patients treated by ear, nose and throat consultants (b), and for patients treated by ear, nose and throat residents in training (c). A χ² test was used to determine a P value. MLT, microlaryngeal tube, inner diameter 6.0 mm.

Fig. 4

Inspiratory plateau pressure, difference of plateau pressure and positive endexpiratory pressure (ΔP), respiratory system compliance and change in end-expiratory lung volume for volume-controlled ventilation and flow-controlled ventilation. Boxplots indicate median, interquartile range and full range. Outliers indicated by black crosses and defined as data points outside median ± 1.5 interquartile range.