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

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

Introduction

In conventional practice for retromolar intubation, endotracheal tube (ET) is bent. This leads to compression of the inner diameter of the tube which in turn reduces airflow. Furthermore, conventionally ETs are stabilised in position using inflated tracheal cuff. Elastic sticky tapes around the exit pose hindrance for surgical procedures on the face. Surgical manipulation and maxillomandibular fixation may lead to compression, damage or accidental extubation of ET. We have developed a modified ET dedicated to retromolar intubation with innovative means for tube stabilisation to solve these problems.

Materials and Methods

To study the efficacy of the tube, a comparative in vitro study was done on mannequins. Null hypothesis of no change in air pressure and oxygen concentration in bent conventional ET versus modified ET was formulated. Comparison was done on the basis of the peak air pressure (PEP) and oxygen concentration, which was checked using air-gas monitor.

Results

The mean PEP was found to be 24.29 psi with standard deviation (SD) of 9.54 in sequentially bent conventional tube. This was found to be only 10.35 psi with SD of 3.22 in modified ET. Oxygen delivery was found to be 3.96 L/min in bent conventional tube, which was 5.22 L/min in modified tube. Both the findings were statistically significant.

Discussion

Modified retromolar tube (PUNTUBE) has been found to be efficient in maintaining low PEP while delivering more oxygen as compared to bent conventional tube. Novel mode of tube stabilisation in the form of PUNSTAB is an easy and effective way of tube stabilisation.

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

Tracheal tubes are routinely used in adults undergoing elective surgery. The size of the tracheal tube, defined by its internal diameter, is often generically selected according to sex, with 7-7.5 mm and 8-8.5 mm tubes recommended in women and men, respectively. Tracheal diameter in adults is highly variable, being narrowest at the subglottis, and is affected by height and sex. The outer diameter of routinely used tracheal tubes may exceed these dimensions, traumatise the airway and increase the risk of postoperative sore throat and hoarseness. These complications disproportionately affect women and may be mitigated by using smaller tracheal tubes (6-6.5 mm). Patient safety concerns about using small tracheal tubes are based on critical care populations undergoing prolonged periods of tracheal intubation and not patients undergoing elective surgery. The internal diameter of the tube corresponds to its clinical utility. Tracheal tubes as small as 6.0 mm will accommodate routinely used intubation aids, suction devices and slim-line fibreoptic bronchoscopes. Positive pressure ventilation may be performed without increasing the risk of ventilator-induced lung injury or air trapping, even when high minute volumes are required. There is also no demonstrable increased risk of aspiration or cuff pressure damage when using smaller tracheal tubes. Small tracheal tubes may not be safe in all patients, such as those with high secretion loads and airflow limitation. A balanced view of risks and benefits should be taken appropriate to the clinical context, to select the smallest tracheal tube that permits safe peri-operative management.

Nasolaryngeal Distances in the Adult Population and an Evaluation of Commercially Available Nasotracheal Tubes

BACKGROUND

Preformed nasal endotracheal tubes (NETs) come with a predefined insertion depth due to their curved design. While size indication refers to internal diameter, there is a considerable variability in the corresponding lengths and proportions of same-sized tubes of different manufacturers which is probably based on the lack of data of nasolaryngeal distances (NLDs) in the adult population. Choosing the best-fitting NET is therefore difficult and carries the risk of endobronchial intubation or, on the contrary, cuff inflation at the vocal cord level. The aim of this study was to develop a prediction model for NLD and a selection guide to choose the appropriate NET based on a radiographic description of NLD in comparison to the measurements of available NETs of several manufacturers.

METHODS

After institutional ethics board review, 388 computed tomography (CT) scan images of head, neck, and upper thorax in a heterogeneous adult cohort were included. Mean distances from the nares to the lower border of the thyroid cartilage were measured. NETs from different manufacturers were measured and compared to the NLD derived from the radiographic analysis. The patients' sex, body height, and weight were considered as possible covariates in quantile regression models for predicting the NLD.

RESULTS

Data from 200 patients were analyzed. NLD was associated with sex, body height, and weight. A simple quantile regression model using the body height as the only covariate sufficed to achieve accurate predictions of NLD. Validation on independent test data showed that 92.8% of the NLD predictions were closer than ±20 mm to the observed NLD values. Measurements of equal-sized NETs varied considerably in outer diameter, proportion, the nasopharyngeal part, and guide marks. Length differences of the bend-to-cuff distance, containing the anatomically NLD, ranged between 218 and 270 mm at same sizes.

CONCLUSIONS

A reliable prediction of NLD can be obtained simply by body height, using the formula (Equation is included in full-text article.). As manufacturers' tube lengths vary substantially, additional information about the bend-to-cuff distance as corresponding tube section would allow for more accurate tube selection.

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

Background

Clinicians sometimes encounter resistance in advancing a tracheal tube, which is inserted via a nostril, from the nasal cavity into the oropharynx during nasotracheal intubation. The purpose of this study was to investigate the effect of neck extension on the advancement of tracheal tubes from the nasal cavity into the oropharynx during nasotracheal intubation.

Methods

Patients were randomized to the ‘neck extension group (E group)’ or ‘neutral position group (N group)’ for this randomized controlled trial. After induction of anesthesia, a nasal RAE tube was inserted via a nostril. For the E group, an anesthesiologist advanced the tube from the nasal cavity into the oropharynx with the patient’s neck extended. For the N group, an anesthesiologist advanced the tube without neck extension. If the tube was successfully advanced into the oropharynx within two attempts by the same maneuver according to the assigned group, the case was defined as ‘success.’ We compared the success rate of tube advancement between the two groups.

Results

Thirty-two patients in the E group and 33 in the N group completed the trial. The success rate of tube passage during the first two attempts was significantly higher in the E group than in the N group (93.8% vs. 60.6%; odds ratio = 9.75, 95% CI = [1.98, 47.94], p = 0.002).

Conclusion

Neck extension during tube advancement from the nasal cavity to the oropharynx before laryngoscopy could be helpful in nasotracheal intubation.

Trial registration

ClinicalTrials.gov Identifier NCT03377114, registered on 13 December 2017.