Difficult intubation is one of the most significant issues anesthesiologists deal with occasionally. Among these, craniomaxillofacial deformities face the biggest challenge in intubation and make an anticipated difficult airway [1].

There are several strategies to approach these patients and each technique has unique benefits that should be used with experience [2]. Nowadays, the utilization of the conventional fiber-optic nasal intubation method in which the nasal tube is inserted in one step after visualization of the vocal cords by a flexible fiber-optic laryngoscope without the use of any facilitating techniques has proven to be a difficult task [3]. Fiberoptic bronchoscope (FOB) nasal intubation-aiding devices were originally designed to keep the airway patent by passing the relaxed redundant collapsible pharyngeal structure obstructing the airway. Attaching a nasal airway to a breathing circuit as a tool to assist or control ventilation is a very helpful trick in challenging airway management situations [4-6].

Inserting a tube nasally to or near the larynx has the advantage of keeping the airway patent as well as carrying the FOB tip immediately in front of the laryngeal inlet facilitating the process of laryngeal visualization and intubation without bloody secretions, especially in critical cases in which direct visualization is most challenging [7].

In the present study, the authors performed FOB nasal intubation as classically done (classical “CL” group) and thorough tube first (tube first “TF” group) comparing the effectiveness and safety in each group.

The sample size was calculated using PASS 11.0 and based on a study carried out by Shoukry et al.,2018. revealed that forty subjects were needed, twenty in each group, to detect a difference of 6.2 between the null hypothesis that both group means are 92.6 and the alternative hypothesis that the mean of group II is 86.4 with estimated group standard deviations of 3.1 and 3.8 and with a significance (alpha) of 0.00500 using a two-sided two-sample t-test. The sample size was inflated by 10% to account for attrition in prospective studies.

This study enrolled 40 patients who were randomly allocated to two groups, either the classic technique group (CL group) or the tube first technique group (TF group). Both groups (20 patients each) were comparable regarding demographic data (Table 1).

Compared to the TF group, the CL group showed a significantly higher heart rate at the 2nd and 3rd minutes after induction with p values 0.0048 & 0.004, respectively (Table 2). Moreover, the mean arterial blood pressure was significantly higher at the 2nd and 3rd minutes after induction with p-values 0.0001 & 0.0028, respectively (Table 3). Meanwhile, there is a statistical elevation in the TF group in SpO2 compared to the CL group during the second minute only without a statistically significant difference at the first and third minute of oxygen saturation assessment (Table 4). The TF group showed a statically shorter time from inserting the fibreoptic till viewing the vocal cord T1 (p=< 0.0001), and also the total procedure time from inserting the fibreoptic till its removal is shorter when compared to the CL group T2 (p=< 0.0001) (Table 5). There were no significant differences between both groups regarding the total incremental dose of propofol consumed during the procedure (Table 6).

Fig. (1). The CONSORT flow diagram.

Classical nasal fiberoptic intubation is commonly used in difficult airway intubation. The technique requires a relatively long time of intubation with difficulty in visualizing the glottis, which increases the patient’s discomfort [3]. Hence, there is continuous research for the appropriate approach using various facilitating devices such as nasopharyngeal airways, and intubating laryngeal masks to achieve minimal duration of fiberscope with rapid glottic visualization in different airway procedures.

In this study, we compared the safety and efficacy of the first tube technique as a conduit for nasal fibreoptic intubation versus the classic technique in terms of hemodynamic effects and duration of the procedure.

Safety was assumed as regards the hemodynamics measured during the procedure and with no complications and monitored as secondary outcomes.

As regard efficacy being measured by time as a primary outcome.

Baseline characteristics were similar in both groups, including age, sex, weight, height, body mass index, preoperative hemodynamics, and oxygen saturation. This could reflect a fair and balanced randomization. TF group showed a faster time from inserting the fibreoptic till viewing the vocal cords and also the total procedure time from inserting the fibreoptic till its removal is shorter when compared to the CL group (37.15±3.87 and 64.25±8.28 vs. 55.05±4.52and 88.25±5.49 seconds, respectively; p < 0.0001). Our results are in agreement with Mohammadzadeh et al. [8], that compared the classic and tube-first techniques by inserting the nasal tube into the nasopharynx till mark 18 in Iranian patients. It was thought that at 18 cm, the endotracheal tube reached a location near the vocal cords and served as a tool to help optimize the fiberscope as it is guided through the nasal cavity and toward the vocal cords. Both TI and T2 were significantly reduced in the tube first group (65.2 ± 33.2 and 87.1 ± 41.0 seconds, respectively) compared to the classic group (151.0±56.5 and 176.2±56.3 seconds, respectively). However, Mohammadzadeh et al. [8] found the power to detect a difference in the success rate of the tube first compared to the classic technique to be only 16% due to their small sample size. In our study, we didn’t need facilitation maneuvers such as head flexion or jaw thrust, or tongue retractors, thus, we had shorter times and this may be attributed to the use of the nasopharyngeal device through the other nostrils, also we were not committed to a fixed mark for the tube due to the large variation and discrepancy of various maxillofacial procedures.

Khalifa [9] compared awake nasotracheal intubation using the classic technique of video-scopic nasotracheal intubation and the tube first technique in which a lubricated nasal tube was introduced first into the nasopharynx until mark 18 in males and 16 in females acting as a conduit for the new disposable video-scope (scope 2). Both TI and T2 were significantly reduced in the tube first group (156.0 ± 0.81 and 198.6 ± 0.82 seconds, respectively) compared to the classic group (201.6 ± 1.15 and 244.8 ± 1.15 seconds). Furthermore, the tube-first approach decreased the scope twisting and the resulting traumatization of the upper airway, which increased the overall success rate of intubation with the tube-first approach. It was going the same with our study using the tube as a conduit, the difference was that we used the tube first technique in sedated patients not awake.

Syal et al. [10], compared the classic technique with a modified tube first technique by inserting the nasal tube into the nasopharynx until mark 15 in wakeful Indian patients. The tube crossed the nasopharynx, and its tip stood above the larynx, acting as a conduit to guide the tip of the scope through the glottis. This provided an appropriate space for manipulation. Both TI and T2 were significantly reduced with the modified tube first approach (108.6 ± 43.1 and 128.8 ± 43.7 seconds, respectively) compared to the other methods (142 ± 49.2and and 164.80 ± 48 seconds, respectively). Also, he did the technique in awake patients, but we used the same technique with sedation.

With the classic procedure, advancing the tube after glottis viewing might be challenging. Technical issues and a failure rate of 1% to 10% have been documented even in the best hands of experienced practitioners [11, 12]. The bronchoscope camera might become contaminated with nasal and oropharyngeal secretions [3]. Additionally, the gap between the tube and the fiberscope was thought to be the main cause of the difficulty in moving the tube over the fiberscope. This gap caused the tube to deviate in a direction that could damage the nearby anatomical structures like the esophagus, arytenoid cartilage, pyriform fossae, or epiglottis [13]. Additionally, the use of muscle relaxants or anesthesia causes the oropharyngeal muscles to paralyze, which causes the tongue and epiglottis to collapse back onto the posterior wall of the throat [5, 14]. The epiglottis has been reported as a common site of obstruction during nasotracheal intubation [5]. As a result, there isn't much space left for inserting the tube into the trachea [15, 16]. Thus, the tube-first technique could lessen the bronchoscope twisting and provide easier glottis viewing compared to the classic procedure.

Our study had a shorter time of intubation in both techniques than the previous research of Mohammadzadeh et al. [8] despite being done by junior staff under the supervision of an expert, we didn't need facilitation maneuvers such as head flexion or jaw thrust, or tongue retractors This may be attributed to the clinical condition of some patients where our patients were ASA class I-II, the use a nasopharyngeal device through the other nostril provided the advantage of both providing a state of deep sedation with inhalational anesthesia also preventing upper airway obstruction that might occur while using muscle relaxant. Furthermore, the frequent suctioning that was performed could have led to the clearing of the secretion and less fogging of the camera. These findings may oppose those of Khalifa [9] as he used a disposable fiberscope without suction for ASA class I-III patients who required careful and gentle manipulation. Some burn patients had limited mouth opening and restricted neck manipulation, which explains the prolonged time of intubation taken.

We did not find any cases of desaturation, and all patients had mean oxygen saturation above 90%. We found a statistical elevation in the tube first group compared to the classic group during the second assessment time, but it was of no clinical significance. Moreover, we found no statistically significant difference at the first and third time of oxygen saturation assessments. Syal et al. [10] reported a desaturation rate of just 3.3% with the modified tube first approach compared to a significantly higher frequency of up to 26.7% with the classic technique. This could be related to the use of sedatives and anesthetics that might collapse the upper airway. According to Law et al. [11], partial or total airway obstruction accounts for 5% of problems connected to awake fiberoptic bronchoscopy.

Meanwhile, the heart rate and mean arterial blood pressure were significantly increased with the classic technique compared with the tube first technique. Hemodynamic excitation was observed with the classic technique rather than with the tube-first technique. This could be explained in light of the research conducted by Mohamed El-Tawansy et al. [17]. They compared the classic technique to the split nasopharyngeal airway device that was inserted before the bronchoscope. The inserted fiberoptic bronchoscope shaft caused stressful excitation of the upper airway, mostly because - in the classical technique - the shaft is in direct contact with the airways for a considerable time during its journey.

One of the limitations of using this technique is that it limits the maneuvering of FOB, especially in some traumatic maxillofacial cases and also it needs careful preparation of the nose although we didn’t experience complications such as nasal bleeding.

Among patients with difficult airway intubation undergoing general anesthesia, we found the Tube-First intubation approach was quicker and safer compared to the classical intubation technique.

Quicker (1ry outcome): measured by the time.

Safer (2ry outcome): measured by the hemodynamics during the procedure.