Role of tube size and intranasal compression of the nasotracheal tube in respiratory pressure loss during nasotracheal intubation: a laboratory study

Abstract

BackgroundSmall nasotracheal tubes (NTTs) and intranasal compression of the NTT in the nasal cavity may contribute to increasing airway resistance. Since the effects of size, shape, and partial compression of the NTT on airway resistance have not been investigated, values of airway resistance with partial compression of preformed NTTs of various sizes were determined.MethodsTo determine the factors affecting the respiratory pressure loss during the nasotracheal intubation, physical and fluid dynamics simulations were used. The internal minor axes of NTTs in the nasal cavity of intubated patients were measured using dial calipers. In physical and fluid dynamics simulations, pressure losses through the tubular parts, compressed parts, and slip joints of NTTs with internal diameters (IDs) of 6.0, 6.5, 7.0, 7.5, and 8.0 mm were estimated under partial compression.ResultsThe median internal minor axes of the 7.0- and 7.5-mm ID NTTs in the nasal cavity were 5.2 (4.3–5.6) mm and 6.0 (4.2–7.0) mm, respectively. With a volumetric air flow rate of 30 L/min, pressure losses through uncompressed NTTs with IDs of 6.0-, 6.5-, 7.0-, 7.5- and 8.0-mm were 651.6 ± 5.7 (6.64 ± 0.06), 453.4 ± 3.9 (4.62 ± 0.04), 336.5 ± 2.2 (3.43 ± 0.02), 225.2 ± 0.2 (2.30 ± 0.00), and 179.0 ± 1.1 Pa (1.82 ± 0.01 cmH2O), respectively; the pressure losses through the slip joints were 220.3 (2.25), 131.1 (1.33), 86.8 (0.88), 57.1 (0.58), and 36.1 Pa (0.37 cmH2O), respectively; and the pressure losses through the curvature of the NTT were 71.6 (0.73), 69.0 (0.70), 64.8 (0.66), 32.5 (0.33), and 41.6 Pa (0.42 cmH2O), respectively. A maximum compression force of 34.1 N increased the pressure losses by 82.0 (0.84), 38.0 (0.39), 23.5 (0.24), 16.6 (0.17), and 9.3 Pa (0.09 cmH2O), respectively.ConclusionPressure losses through NTTs are in inverse proportion to the tubes’ IDs; greater pressure losses due to slip joints, acute bending, and partial compression of the NTT were obvious in small NTTs. Pressure losses through NTTs, especially in small NTTs, could increase the work of breathing to a greater extent than that through standard tubes; intranasal compression further increases the pressure loss.

Comparative Analysis of Peak Air Pressure and Oxygen Flow between Conventional and Modified Endotracheal Tube for Retromolar Intubation (PUNTUBE)- An In Vitro Study

“…These additional features in tube, such as sharp bends and slip joints, cause obvious increases in the pressure loss. [ 5 ] According to Hagberg, wire ligature when used to secure the ET externally can deform the tube by compressing the inner diameter of the tube. [ 6 ] Most common oral tube stabilising methods include tube fastener or adhesive tapes placed around the tube.…”

Tracheal tube size in adults undergoing elective surgery – a narrative review

“…Obstruction may also be secondary to external forces causing collapse or kinking of the tracheal tube. Smaller tubes are more deformable [27] and prone to external compression [28] than larger tubes. For example, a size 8.0-mm tube requires three times as much force to reshape it than a size 6.0-mm tube.…”

“…Differences between a size 8.0 mm and 6.0 mm cuffed oral tracheal tube (Shiley TM , Covidien, Hi-Lo tracheal tube, Mansfield, MA, USA). (a) tube length (b) cuff diameter when inflated to a pressure of 25 cm H 2 o without resistance (c) residual cuff volume when inflated with 10 ml of air (d) cuff length.Smaller tubes are more deformable[27] and prone to external compression[28] than larger tubes. For example, a size 8.0-mm tube requires three times as much force to reshape it than a size 6.0-mm tube.…”

Effect of neck extension on the advancement of tracheal tubes from the nasal cavity to the oropharynx in nasotracheal intubation: a randomized controlled trial

“…Anesthesiologists sometimes encounter resistance in the advancement of a tracheal tube inserted via a nostril from the nasal cavity to the oropharynx before introducing a laryngoscope during nasotracheal intubation. This resistance might be caused by a large-sized tracheal tube compared to the nasal cavity [1] or blockage by the posterior wall of the nasopharynx. Clinicians can easily detect the former as a cause of resistance and resolve the problem by changing to a smaller tube.…”