RESISTANCE CHARACTERISTICS OF ULTRATHIN-WALLED AND CONVENTIONAL ENDOTRACHEAL TUBES FOR NEONATES

Background: Kolobow introduced the concept of an ultrathin-walled endotracheal tube (UT-ETT) in 1994. (Biomed Instrument Technol 1994;28:123). Commercially available UT-ETT have recently become available (T-Wall, Vital Signs, Totowa, NJ). We evaluated the resistance characteristics of conventional ETT and new UT-ETT in the laboratory.

Methods: The resistance of three samples of each ETT (conventional ETTs: 3 mm ID, 4.3 mm OD; 3.5 mm ID, 4.9 mm OD; and 4 mm ID, 5.6 mm OD and UT-ETT 3.6 mm ID, 4.3 mm OD) were measured using a RT-200 analyzer (Allied Products, St Louis, MO). The ETTs were cut to the same length 13 cm that included the connector. Each ETT was position in the same curvature using a clay template. Inspiratory resistance was measured at flow rates of 3, 3.25, 3.5, 3.75, 4, 5, 6, 7, 8, 9, 10, and 20 L/min. In the second part of the evaluation the ETTs were attached to a test lung (Michigan Instruments, Grand Rapids, MI) with C 0.01 L/cm H2O, R 50 H₂O /L/s. Spontaneous breathing was simulated with a tidal volume of 12 ml and peak inspiratory flow of 2 L/min. Flow, volume, and pressure was measured at a point between the ETT and the test lung using a CO2SMO Plus respiratory monitor (Novametrix Medical Systems, Wallingford, CT) at a rate of 100x/s. Data was saved to the hard drive of a personal computer then exported to an Excel (Microsoft, Redmond, WA) spreadsheet for further analysis. Pressure volume curves were constructed allowing for qualitative evaluation of imposed inspiratory work.

Results: For the same OD, the UT-ETT results in lower resistance and lower work of breathing. Compared to the 3.0 ID ETT the UT-ETT produced 54-56% less resistance at flows of 1-10 L/min.

Conclusions: The new UT-ETT provides lower resistance and reduced work of breathing at the same OD (same risk of tracheal damage). Future clinical trials should evaluate any impact.