REDUCED AIRWAY-RESISTANCE AND WORK OF BREATHING DURING MECHANICAL VENTILATION WITH AN ULTRA-THIN, 2-STAGE POLYURETHANE ENDOTRACHEAL-TUBE (THE KOLOBOW TUBE)

Objectives: To compare dynamic pulmonary function studies using the ul trathin walled Kolobow endotracheal tube, with conventional endotrache al tubes of similar external diameter on rabbits during mechanical ven tilation. To test the hypothesis that the increased internal diameter of the Kolobow tube will result in decreased airway resistance and wor k of breathing. Design: Controlled animal study. Setting: Institutiona l animal research facility. Subjects: Adult female Dutch Belted rabbit s (n = 6), weighing 1.4 to 1.6 kg. Interventions: The animals were ini tially intubated with a conventional endotracheal tube (2.5-mm interna l diameter; 3.6-mm outer diameter); they were paralyzed and placed on a mechanical ventitator. Ventilatory settings were adjusted to obtain standard arterial blood gases: pH of 7.35 to 7.45; Pace, of 35 to 40 t orr (4.7 to 5.3 kPa), and Pao(2) of 90 to 100 torr (12.0 to 13.3 kPa). After the stabilization period, pulmonary function tests (PFTs) were measured (period 1), the conventional endotracheal tube was replaced w ith a Kolobow tube, and PFTs were measured again and recorded (period 2). While continuously monitoring tidal volume, the peak inspiratory p ressure was decreased to match the tidal volume measured during ventil ation with the conventional endotracheal tube. Once the desired tidal volume was reached, PFTs were recorded (period 3). Flows were unchange d during the experiment and the length of the endotracheal tubes was t he same for both the conventional and the Kolobow tube. Measurements a nd Main Results: Mean values of the airway resistance and work of brea thing from periods 1 and 3 were compared using the Student's t-test. T here was a 59% decrease in total airway resistance (p = .001) and 45% decrease in the work of breathing (p = .0006). Conclusions: The use of the ultrathin walled Kolobow endotracheal tube resulted in significan t decreases in airway resistance and work of breathing, which has the potential for improving the ventilatory mechanics in very small premat ure newborns.