Split Nasopharyngeal Airway, a Tracking Tool for Fibreoptic Nasotracheal Intubation: A Randomised Controlled Study

1. Professor and Ex Head, Department of Anaesthesiology and Critical Care, Pt. B.D. Sharma PGIMS, Rohtak, Haryana, India. 2. Ex Senior Resident, Department of Anaesthesiology, Pt. B.D. Sharma PGIMS, Rohtak, Haryana, India. 3. Associate Professor, Department of Anaesthesiology, Pt. B.D. Sharma PGIMS, Rohtak, Haryana, India. 4. Senior Professor, Department of Anaesthesiology, Pt. B.D. Sharma PGIMS, Rohtak, Haryana, India. 5. Senior Resident, Department of Anaesthesiology, Pt. B.D. Sharma PGIMS, Rohtak, Haryana, India. 6. Resident, Department of Radiodiagnsis, BJMC and GCRI, Ahmedabad, Gujarat, India. 7. Resident, Department of Anaesthesiology and Critical Care, Pt. B.D. Sharma PGIMS, Rohtak, Haryana, India.

Abstract

Introduction: Managing a challenging airway in awake, sedated, or anaesthetised patients has made Fibreoptic Intubation (FOI) using a flexible Fibreoptic Bronchoscope (FOB) a mainstay in clinical practice.

Aim: To evaluate and compare fibreoptic nasotracheal intubation with or without Split Nasopharyngeal Airway (SNPA) as a conduit, focusing on time taken, ease of insertion, and haemodynamic changes.

Materials and Methods: This randomised controlled study was conducted at the Department of Anaesthesiology and Critical Care, Pt. B.D. Sharma, PGIMS, Rohtak, Haryana, India, on 80 patients who were randomly allocated into two groups: Group CL (the control group without SNPA) and Group NP (with SNPA). Both groups were induced with general anaesthesia, and nostrils were prepared for FOB. In Group CL, a well-lubricated FOB was inserted into the selected nostril without using SNPA, and endotracheal intubation was performed. In Group NP, an appropriately sized SNPA was lubricated and inserted into the selected nostril. The fiberscope was passed through the SNPA, the vocal cords were visualised, and the SNPA was removed before railroading the preloaded tube through the vocal cords to confirm correct placement. The time taken for bronchoscopy and intubation, ease of insertion, haemodynamic parameters, and bleeding were recorded in both groups. The data was coded, entered, and analysed using Statistical Package for the Social Sciences (SPSS) version 20.0. A significance level was set at a p-value ≤0.05.

Results: Demographic data, including age and gender distribution, mean weight, height, Body Mass Index (BMI), and airway parameters such as Mallampati grading, neck circumference, inter-incisor distance, and ASA grading, were standardised. There was no significant difference between the CL and NP groups regarding these parameters. The time taken for FOB and intubation in Group CL was 2.59±0.96 minutes and 3.61±1.04 minutes, respectively, compared to 1.87±0.91 minutes and 2.51±0.86 minutes in Group NP (p-value=0.001). The time taken to visualise the glottis was also shorter in the NP group (6.70±13.97 minutes) compared to the CL group (24.02±13.06 minutes), which was significant. Fibreoptic bronchoscopy was considered easy in 16 patients (40%) in Group CL and 27 patients (67.5%) in Group NP (p-value=0.04). The increase in mean arterial blood pressure was significantly higher in Group CL than in Group NP just after the insertion of the FOB into the nasopharynx (p-value=0.05).

Conclusion: Fibreoptic nasotracheal intubation through an SNPA is less time-consuming and results in easier intubation. It causes less trauma to the nasal passage and leads to fewer haemodynamic variations in terms of mean arterial pressure and heart rate. Hence, SNPA is a better method for facilitating FOI compared to intubation without it.

Difficult airway, Endotracheal tube, Fibreoptic bronchoscope, Fibreoptic intubation

To manage a challenging airway in awake, sedated, or anaesthetised patients, flexible FOI has become a mainstay. Its role is well recognised in guidelines for managing both anticipated and unanticipated difficult airways (1),(2),(3),(4). The nasal approach for FOI is often easier, as less angulation is required to enter the larynx compared to the oral technique; additionally, the tongue does not interfere with insertion in the nasal route (5). However, the use of a rigid tracheal tube with a sharpened Murphy eye may increase the risk of nasopharyngeal injury and nasal bleeding. When the lumen of the tube abuts the pharyngeal mucosa, moderate to severe haemorrhage, retropharyngeal laceration, and perforation can occur (6),(7).

To facilitate FOI through either the nasal or oral route, various channels have been employed, including intubating oral airways, laryngeal mask airways, intubating laryngeal masks, endotracheal tubes, and nasopharyngeal airways. The nasopharyngeal airway (Table/Fig 1) can be modified to serve as a conduit for FOI by being vertically split in a spiral or zigzag fashion, allowing for its removal before passing the endotracheal tube (8),(9). Unexpected difficulties encountered during tracheal intubation may result in hypoxia and pulmonary aspiration. Therefore, several methods have been developed to predict difficult airways, which are particularly important for critically ill patients, as any delays during intubation and multiple attempts at laryngoscopy are associated with increased complications, including hypoxaemia, hypotension, arrhythmia, and even cardiac arrest (10). Use of a bronchoscope can be a lifesaving measure, alleviating major complications related to the airway and tracheostomies (11).

Given that fibreoptic nasotracheal intubation is associated with the aforementioned complications, the present study aimed to identify an ergonomic method of intubation in terms of ease of insertion and time taken for the procedure. Primary outcome measures include the time taken for nasotracheal intubation and ease of insertion. Secondary outcome measures include any trauma or bleeding that may occur, as well as haemodynamic changes.

Material and Methods

This randomised controlled study was conducted in the Department of Anaesthesiology and Critical Care at Pt. B.D. Sharma PGIMS, Rohtak, Haryana, India. The study period was from February 2020 to March 2021, following approval from the Institutional Ethics Committee (IEC/Th/19/Anst12). Informed and written consent was obtained from all patients. This trial was registered under the Clinical Trial Registry-India (CTRI) with the number CTRI/2020/07/026519.

Inclusion criteria: Patients aged between 18 and 60 years of either sex, belonging to American Society of Anaesthesiologists (ASA) physical status I and II, who underwent elective surgery under general anaesthesia where nasotracheal intubation is indicated were included in the study.

Exclusion criteria: Patients with obesity (BMI >30 kg/m²), hypertension, cardiac disease, pregnancy, any coagulation disorder, or obstructed nasal passages were excluded from the study.

Sample size calculation: A minimum of 35 patients was required in each group for the study. However, considering potential errors and dropouts, the sample size was increased to 40 per group. The sample size was calculated based on a study by Meena RK et al., which reported a duration of intubation of 79.76±11.88 seconds and 44.15±7.77 seconds in two groups, using α=0.05 and β=0.2 (12). The primary objective of this study was time-based.

The following formula was used for sample size calculation:

N=(r+1)(Z_α/2+Z_1-β)²σ²/rd²

where Z_α/2 is the critical value of the normal distribution at α/2 (e.g., for a confidence level of 95%, α is 0.05, and the critical value is 1.96), Z_β is the critical value of the normal distribution at β (e.g., for a power of 80%, β is 0.2, and the critical value is 0.842). The assumed difference of the mean (d) is 1.33, and the standard deviation (σ) is 2.

Study Procedure

To facilitate FOI through the nasal or oral route, various conduits have been used, including intubating oral airways, laryngeal mask airways, intubating laryngeal masks, endotracheal tubes, and nasopharyngeal airways. The nasopharyngeal airway can be modified to serve as a conduit for FOI by splitting it vertically in a spiral or zigzag fashion, which allows for easier removal before passing the endotracheal tube (8),(9).

Randomisation was performed using a computer-generated sequence of random numbers, and selected patients were randomly allocated to one of the following two equal groups: the Classic group (Group CL, n=40)-classic nasal fibreoptic bronchoscopic intubation without using a nasopharyngeal airway-and the NP group (Group NP, n=40)-nasal fibreoptic bronchoscopic intubation using a split nasopharyngeal airway (Table/Fig 2).

Preanaesthetic assessment was conducted for all patients a day prior to surgery, which included evaluating their general condition, body build, weight, height, heart rate, non invasive arterial blood pressure, and respiratory rate. A thorough systemic and airway examination was performed (Mallampati grading, neck circumference, inter-incisor gap). Routine investigations were advised, and both nostrils were examined for patency. The purpose and protocol of the study were explained to the patients, and informed written consent was obtained. Patients were kept fasting and premedicated.

In the operating theatre, standard vital monitors were attached, and an intravenous line was secured. Preoperative nebulisation with 4% lignocaine was administered. Both nostrils were prepared by instilling two drops of 0.1% xylometasoline hydrochloride solution. The length of the longitudinally split nasopharyngeal airway (Portex) was measured from the ala nasi to the ear lobule to select the appropriate size. In the other nostril, a nasopharyngeal airway (Portex) of size 5 was inserted for paraoxygenation. Preoxygenation with 100% oxygen was performed. Patients were premedicated with glycopyrrolate (0.005 mg/kg) followed by fentanyl (2 μg/kg), and induction of anaesthesia was achieved with propofol (2 mg/kg). Muscle relaxation was facilitated with vecuronium (0.1 mg/kg). Anaesthesia was maintained with sevoflurane in 65% N₂O and 35% O₂. Intubation was performed through the selected nostril, while paraoxygenation with three litres of oxygen was provided through the nasopharyngeal airway (Portex) in the other nostril. End-tidal carbon dioxide was monitored throughout the process. If oxygen saturation fell below 94% at any point during the procedure, the patient was ventilated with 100% oxygen.

In Group CL (Fibreoptic bronchoscopic intubation without using a nasopharyngeal airway, NPA): After mounting the tracheal tube over the flexible FOB, a well-lubricated FOB was inserted directly into the selected nostril and advanced. When the carina was seen, the endotracheal tube was then advanced into the trachea over the scope, and the FOB was removed while monitoring the position of the endotracheal tube.

In Group NP (Fibreoptic bronchoscopic intubation with a split nasopharyngeal airway): A lubricated split nasopharyngeal airway was inserted into the selected nostril. After mounting the tracheal tube over the flexible FOB and under all aseptic precautions, the FOB was inserted through the nasopharyngeal airway into the same nostril. Oxygenation was continued through a size 5 Portex nasopharyngeal airway in the other nostril. The scope was advanced until the carina was visible. The split nasopharyngeal airway was then removed by an assistant, and the endotracheal tube was advanced into the trachea over the scope. The FOB was gently removed through the tracheal tube while monitoring the position of the endotracheal tube.

Additional confirmation of tracheal intubation was performed using capnography and bilateral auscultation. The times for fibreoptic bronchoscopy and intubation were noted in both groups. Haemodynamic parameters, i.e., heart rate and mean arterial pressure, were monitored throughout the procedure. Any response of hypertension or tachycardia was defined as a rise of more than 20 percent from baseline and was treated with a bolus of injection propofol (10-20 mg intravenously). Nasal bleeding was managed with nasal drops of xylometasoline (0.1% solution), application of local pressure, and gentle suctioning. At the end of the surgery, residual neuromuscular block was antagonised with intravenous injection of glycopyrrolate (0.01 mg/kg) and neostigmine (0.05 mg/kg). Upon completion of the surgery and emergence from general anaesthesia, the patient was extubated and transferred to the Post-Anaesthesia Care Unit (PACU) for observation.

The following observations were recorded:

1. The time duration for glottic visualisation, fibreoptic bronchoscopy, and intubation was recorded (in minutes):
- T0=At insertion of the NPA
- T1=At insertion of the FOB
- T2=At visualisation of the glottis
- T3=At visualisation of the carina
- T4=At completion of intubation

The time to visualise the glottis for the CL group is calculated as (T2-T1), which is the time taken from the insertion of the FOB (T1) to the visualisation of the glottis (T2). In the NP group, it is also calculated as (T2-T1), taken from the insertion of the FOB into the split nasopharyngeal airway (T1) to the visualisation of the glottis (T2).

Total duration for fibreoptic bronchoscopy: In the CL group, the duration is calculated as (T3-T1), which is taken from the insertion of the FOB at T1 to the visualisation of the carina at T3. In the NP group, the duration is (T3-T0), taken from the insertion of the split nasopharyngeal airway at T0 to the visualisation of the carina at T3.

2. Haemodynamic changes:
Heart rate and mean arterial pressure were recorded at the following time intervals:
- TBL: Heart rate, mean arterial blood pressure, and oxygen saturation were recorded just before the procedure, specifically three minutes after the administration of vecuronium.
- TNP: Time just after the insertion of the nasopharyngeal airway in the NP group.
- TA: Time just after the insertion of the FOB into the nasopharynx.
- TB: Time just after the insertion of the FOB through the glottis into the trachea.
- TC: Time just after the insertion of the tracheal tube into the trachea.

3. Ease of insertion of the FOB (10):
- Not difficult: Upon initial introduction, the fiberscope is already aligned for good visualisation of the vocal cords, requiring little or no manipulation of the tip of the scope.
- Moderately difficult: Moderate manipulation of the fiberscope in all directions is necessary to locate the vocal cords.
- Difficult: Extensive manipulation of the fiberscope in all directions is often required, sometimes necessitating changes in the operator’s position, to identify the vocal cords.

4. Nasal bleeding assessment:

Any nasal bleeding was graded as ‘mild’ if it did not obscure the view of the FOB, and ‘severe’ if it was sufficient to obscure the view.

Statistical Analysis

The data were recorded and entered into a Microsoft Excel spreadsheet. Descriptive statistics were reported using percentages, means, and standard deviations. Quantitative clinical indicators were compared between two groups using an unpaired t-test, while qualitative data in two or more groups were compared using the Chi-square test. Analysis was conducted using SPSS version 20.0 (IBM SPSS Statistics Inc., Chicago, Illinois, USA) Windows software. The level of significance was set at p-value≤0.05.

Results

Demographic data, including age distribution, gender distribution, mean weight, height, and body mass index (Table/Fig 3), as well as airway parameters like Mallampati grading, neck circumference, inter-incisor distance, and ASA grading (Table/Fig 4), were standardised, and no significant differences were observed between the CL and NP groups regarding these parameters.

(Table/Fig 5) demonstrates that the mean time taken for glottic visualisation was shorter in the NP group compared to the CL group, and this difference was statistically significant (p-value=0.001). The time taken for FOB and FOI was also shorter in the NP group compared to the CL group, and this finding was statistically significant (p-value=0.001), as illustrated in (Table/Fig 6),(Table/Fig 7), respectively.

FOB was easier in the NP group than in the CL group, and this difference was statistically significant (p-value=0.04), as shown in (Table/Fig 8).

(Table/Fig 9) presents a comparison of haemodynamic changes, including mean heart rate at baseline (TBL), just after the insertion of the Nasopharyngeal Airway (NPA) (TNP), just after the insertion of the FOB into the nasopharynx (TA), into the glottis (TB), and into the trachea (TC). These changes were comparable in both groups (p-value>0.05). (Table/Fig 10) demonstrates the mean values of Mean Arterial Pressure (MAP) at different time points and shows that the MAP just after the insertion of the FOB into the nasopharynx (TA) in the CL group was higher than in the NP group, with a statistically significant difference (p-value=0.05). Mean MAP at other time points was comparable in both groups (p-value>0.05).

(Table/Fig 11) presents a comparison of nasal bleeding, indicating that the majority of patients experienced no nasal bleeding. Twelve patients in the CL group and seven patients in the NP group had mild nasal bleeding, while one patient in the CL group experienced severe nasal bleeding, and there were no cases of severe bleeding in the NP group.

Discussion

In the present study, the mean time for glottic visualisation in the NP group was 6.7003±13.97 minutes, compared to the CL group, which had a mean time of 24.02±13.06 minutes. This difference was statistically significant (p-value=0.001). The mean total time for fibreoptic bronchoscopy for the CL and NP groups was 2.59±0.96 minutes and 1.87±0.91 minutes, respectively, and the difference was also found to be significant (p-value=0.001). The mean total time taken for fibreoptic intubation in the CL group was 3.61±1.04 minutes, while in the NP group it was 2.51±0.86 minutes, which was statistically significant between the two groups (p-value=0.001). This was attributed to the use of a split nasopharyngeal airway (NPA) as a conduit, which resulted in fewer attempts and less manipulation during nasal fibreoptic bronchoscopy and intubation. The appropriate length of the nasopharyngeal airway helps maintain airway patency in relaxed patients and improves the view of the larynx, allowing the tip of the FOB to be positioned directly in front of the laryngeal inlet. This improved view facilitates the maneuvering of the bronchoscope tip into the trachea, making nasal intubations less traumatic and reducing the time required for the procedure. Additionally, the NPA can be used for supplemental oxygenation during episodes of desaturation. Thus, it was observed that the use of a split nasopharyngeal airway is a safe and effective tool for reducing the time needed to visualise the larynx and perform tracheal intubation.

Regarding ease of insertion, in the present study, fibreoptic bronchoscopy was not difficult for 16 patients (40%) in the CL group and for 27 patients (67.5%) in the NP group. It was moderately difficult for 23 patients (57.5%) in the CL group and for 12 patients (30%) in the NP group. It was found to be difficult for one patient (2.5%) in each group. Overall, fibreoptic bronchoscopy was easier in the NP group compared to the CL group, and the difference was statistically significant (p-value=0.04). The nasopharyngeal airway can achieve the goal of maintaining airway patency while also positioning the scope tip near the laryngeal inlet, facilitating the process of laryngeal visualisation and intubation, even in challenging situations. The anatomically correct curvature of the nasopharyngeal airway places the FOB tip directly over the laryngeal inlet, contributing to a higher success rate of intubation.

The mean heart rate in the present study was comparable in both groups at baseline, just after the insertion of the FOB into the nasopharynx, glottis, and trachea (p-value>0.05). This may be attributed to the topical application of lignocaine. The mean mean arterial pressure (MAP) just after the insertion of the FOB into the nasopharynx in Group CL was 94.08±8.517 mmHg, while in Group NP it was 89.93±10.164 mmHg, showing a statistically significant difference between the two groups (p-value=0.05). The mean MAP values at baseline and just after the insertion of the FOB into the nasopharynx, glottis, and trachea were comparable in both groups (p-value>0.05). This difference can be attributed to the stressful stimulation caused by the stiff FOB cable in direct contact with the upper airway mucosa during its passage in Group CL. In contrast, in Group NP, the prior insertion of the soft and pliable nasopharyngeal airway reduced sympathetic stimulation since the FOB cable moved within the inserted split nasopharyngeal airway.

Ahmed AM et al., also conducted a study on intubation in anaesthetised and paralysed patients. They found that the time duration to visualise the larynx and achieve intubation was shorter in the group using the split nasopharyngeal airway as a conduit compared to the classic fibre optic nasal intubation group, with a statistically significant result (p-value<0.05). They also noted that MAP increased only during the insertion of the FOB until the visualisation of the larynx, measuring 100.57±4.69 mmHg in the group using classic nasal fibreoptic intubation, compared to 99.90±4.58 mmHg in the group using the split nasopharyngeal airway (p<0.001) (13).

Meena RK et al., conducted a study that calculated the time taken from the insertion of the FOB into the nasal cavity until the inflation of the endotracheal tube cuff. They found that the time taken for intubation was longer in the group using only the endotracheal tube compared to the group using the nasopharyngeal airway as a conduit (p-value<0.001). They also concluded that MAP was significantly higher, with an increase of 13.68% in the group using the endotracheal tube compared to 1.73% in the group using the nasopharyngeal airway as a conduit for intubation (p-value<0.001). Furthermore, they observed that while introducing the fiberscope through the nasal tube or split nasopharyngeal airway, no bleeding was seen in 90% of the patients in the group using the split nasopharyngeal airway, compared to 52.6% in the group using the nasal ETT (p-value=0.002) (12).

The time taken for intubation in group NP was less compared to group CL. The mean MAP at baseline, just after the insertion of the FOB into the glottis, and when the trachea was reached, was comparable in both groups. In the present study, the majority of patients (75%) in both groups had no nasal bleeding, and this was not statistically significant (p-value=0.23). This outcome can be attributed to effective nasal preparation with xylometasoline nasal drops and the use of a split nasopharyngeal airway as a conduit. Only one patient in the CL group experienced severe nasal bleeding; he was excluded from the study and replaced by another participant (p-value>0.05).

Patil T et al., also conducted a study and found that the mean intubation time was shorter in patients who were awake and nasally intubated with a modified nasopharyngeal airway in situ compared to those without a nasopharyngeal airway, and this difference was statistically significant (p-value<0.05). This reduction in intubation time was due to the use of modified NPA as a conduit, which resulted in fewer attempts and less manipulation. They also observed similar results and concluded that the success rate of intubation and the number of attempts were significantly lower in patients who were nasally intubated with the modified NPA compared to those intubated without it (p-value<0.05). Additionally, they found that the incidence of epistaxis and trauma to the nasal mucosa was higher in the group without the NPA (33.6%) than in the group that was nasally intubated with the modified nasopharyngeal airway (11.2%), which was statistically significant (p-value<0.05) (9).

Limitation(s)

All nasal intubations were performed on healthy, anaesthetised, and paralysed patients; therefore, present study results may not be applicable to other populations. Patency of both nostrils was required in all cases. The study was not blinded, which may introduce bias. All nasotracheal fibreoptic intubations were performed using polyvinyl chloride, so the results of present study may not be applicable to endotracheal tubes made of other materials. Additionally, this clinical trial was limited to general anaesthesia and may not be applicable to awake fibreoptic intubation. Therefore, further studies are required in awake patients.

Conclusion

The success of FOI largely depends on the skills and experience of the anaesthesiologist. The use of a conduit can improve fibreoptic tracheal intubation. Present study concluded that fibreoptic nasotracheal intubation through a split nasopharyngeal airway takes less time and offers better ease of intubation, as the nasopharyngeal airway conforms to the anatomical curvature of the upper airway, providing a straight, aligned path. This approach causes less trauma to the nasal passage and facilitates nasal intubation. Additionally, there are fewer haemodynamic variations in terms of mean arterial pressure and heart rate. Hence, the split nasopharyngeal airway is a better method to facilitate FOI compared to intubation without it.

DOI and Others

DOI: 10.7860/JCDR/2024/69198.20234

Date of Submission: Mar 21, 2024
Date of Peer Review: May 01, 2024
Date of Acceptance: Jul 11, 2024
Date of Publishing: Nov 01, 2024

AUTHOR DECLARATION:
• Financial or Other Competing Interests: None
• Was Ethics Committee Approval obtained for this study? Yes
• Was informed consent obtained from the subjects involved in the study? Yes
• For any images presented appropriate consent has been obtained from the subjects. Yes

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EMENDATIONS: 10