To assess the impact of advanced airway imaging (3D CT reconstruction and virtual endoscopy of airway) on airway management in adult patients undergoing head and neck cancer surgeries under general anaesthesia: Randomised controlled study (3D-ARC Study: 3D Airway Reconstruction for Cancer airway management)

Abstract

Background and Aims:

Traditional airway assessment methods likely miss findings, resulting in unanticipated difficult airways. Surgeons routinely do computed tomography (CT) scans of head and neck cancer patients to determine the extent and resectability of the disease. We used these images for 3-dimensional CT (3D CT) reconstruction to provide additional airway-related information to the anaesthesiologist and studied its impact on airway management.

Methods:

We randomly allocated 60 patients into two groups to formulate the airway management plan: Group A (Conventional airway assessment) and Group B (Conventional airway assessment along with 3D CT findings). A CT reporting format was prepared based on a literature review after discussion with radiologists and airway experts. In the case of luminal obstruction, a virtual endoscopy video was also created. These findings were shown to the anaesthesiologist managing the airway, and any change in the primary plan was noted. The primary outcome was the total time required for successful airway management. Secondary outcomes included the number of attempts, number of alternative techniques, other manoeuvres required, incidence of failed intubation, and any complications. Data were analysed using the SPSS statistics software.

Results:

The airway management time between both groups was comparable, with a median difference of 0 [95% confidence interval (CI): −14, 20; P = 0.752]. Among the manoeuvres used, optimal external laryngeal manipulation (OELM) was required more in Group A (P = 0.007). Both groups had no difference in the number of attempts (P > 0.99), number of alternative techniques (P = 0.052), and complications (P > 0.99). There was a significant change in the endotracheal tube size after CT findings were shown (P < 0.001). It aided in selecting the preferred side of the nostril for nasotracheal intubation (kappa = 0.545, showing moderate agreement between before and after CT groups). As per the feedback from anaesthesiologists who rated 3D CT on a Likert scale, it was considered beneficial for airway assessment.

Conclusion:

3D CT reconstruction and virtual endoscopy can be a valuable method of airway assessment.

INTRODUCTION

Airway management remains challenging in cancer patients, especially those undergoing head and neck cancer surgeries. Traditional clinical tools such as history and examination are insufficient and likely to miss significant findings in the airway in such cases, such as delineating the exact location and nature of the tumour and the extent to which it causes narrowing or distortion of the airway lumen.[1] Various imaging modalities available that can aid in airway assessment are X-ray, ultrasonography (USG), computed tomography (CT), magnetic resonance imaging (MRI), and flexible nasoendoscopy.[2] Patients with head and neck cancer undergo CT scanning as it provides detailed information on anatomical distortion and the site and extent of the tumour, with a shorter acquisition time than MRI.

Routinely, CT images are obtained in the axial plane and reconstructed in sagittal and coronal planes by using thin-section images. However, 3D reconstruction provides more comprehensive measurements and an understanding of the abnormality in the airway. In addition, 3D CT-virtual endoscopy (CTVE) has been used to offer 3D imaging of the airway, which aids in viewing intraluminal surfaces.[1,3,4,5,6,7,8,9] It is a valuable technique for airway assessment as it provides the airway’s intraluminal geography, including supraglottic, glottic, and subglottic features. Emerging reports emphasise the usefulness of advanced airway imaging (3D CT reconstruction and virtual endoscopy of the airway) to understand airway anatomy for difficult airways.

The primary objective of this study was to evaluate the impact of preoperative airway assessment with advanced airway imaging (3D CT reconstruction and virtual endoscopy of the airway) on airway management in terms of total airway management time in adult patients undergoing head and neck cancer surgery under general anaesthesia. The secondary objective was to evaluate the impact of preoperative airway assessment with advanced airway imaging (3D CT reconstruction and virtual endoscopy of the airway) on manoeuvres required, number of alternative techniques used, total number of attempts, complications, and failed intubation in adult patients undergoing head and neck cancer surgery under general anaesthesia.

METHODS

After ethics approval from the Institutional Ethics Committee (vide reference number: IECPG-525/23.09.2021, dated 24.09.2021) and trial registration at Clinical Trials Registry-India (CTRI) (vide registration number: CTRI/2022/01/039126, dated 4 January, 2022, accessible at www.ctri.nic.in), this randomised controlled study was conducted between January 2022 and July 2023. The study was carried out by the principles of the Declaration of Helsinki (2013) and Good Clinical Practice guidelines. Adult patients (age >18 years) scheduled for head and neck cancer surgery (lip, oral cavity, nose, paranasal sinus, oropharynx, hypopharynx, salivary glands, nasopharyngeal, thyroid, tracheal, laryngeal cancers) having CT scans within 4 weeks of scheduled surgery were included. Patients with the presence or plan of tracheostomy before surgery were excluded. Patients were explained about the study protocol, and written informed consent was obtained for participation in the study and use of the patient data for research and educational purposes.

A thorough pre-anaesthetic check-up with history, physical examination, and standard preoperative investigations was performed on all patients. The clinical assessment of the airway included mouth opening, modified Mallampati class, mandibular protrusion, thyromental distance, sternomental distance, neck circumference, neck length, and neck movements. El-Ganzouri’s risk index[10] was calculated.

Patients were randomly allocated using computer-generated random numbers (using https://www.randomizer.org/) into two groups to formulate a perioperative airway management plan. Opaque-sealed envelopes with sequential numbers were used for allocation concealment, and further airway assessment was done according to the patient’s group allocation. Blinding was not feasible as the person managing the airway was aware of the group. Airway management time was objectively defined and measured by an independent observer unaware of the group. Patients were randomly assigned to Group A (n = 30), in which conventional airway assessment was done by history, clinical examination, and routine imaging), and Group B (n = 30), in which 3D CT reconstruction was done in addition to conventional airway assessment. In cases in which anatomical distortion of the airway or narrowing of the airway lumen was observed, a virtual endoscopy video was created 1 cm above and 1 cm below the site of anatomical distortion.

As per routine protocol, the CT scan was acquired with the patient in a supine position and head and neck in a neutral position, supported by a headrest cushion for the scan. Specific manoeuvres were used for obtaining CT scans for certain malignancies, such as protruding tongue in the case of tongue malignancies and puffing cheek for buccal mucosa cancers. CT images were obtained in the axial plane and reconstructed in sagittal and coronal planes by using thin-section images. Scans were acquired following intravenous (IV) administration of non-ionic, low osmolarity iodinated contrast 1–1.5 mL/kg, and a scan was acquired in the venous phase. A radiologist did a 3D CT reconstruction with images acquired by CT scan. In cases where anatomical distortion or narrowing of the airway lumen was observed, a virtual endoscopy video was created with the same software, 1 cm above and 1 cm below the site of anatomical distortion. Based on a literature review and discussions with radiologists and anaesthesiologists, the various parameters and airway measurements were enumerated in the CT reporting annexure/form for airway assessment [Supplementary Table 1].[11,12,13,14,15,16,17,18] Tomographic parameters identified from the literature were evaluated for content relevance, and a panel of experts did content analysis to select accurate, appropriate, and interpretable parameters. The template was then run in real time on patients, and each measurement was objectively defined to finalise the CT reporting form.

Supplementary Table 1.

CT reporting format showing various parameters on CT to be reported for airway assessment. (Few procedures of measurement are from published literature[11,12,13,14,15,16,17,18])

Sno.	Parameter	Procedure of measurement	Images
1. [fig a]	Thickness of tongue[11]	Measured as the maximum thickness of the tongue at the level of the soft palate’s tip measured in the mid-sagittal section[11]
2. [fig a]	Thickness of the submental region[11]	Subcutaneous tissue from the skin to the mylohyoid muscle in mid sagittal section[11]
3. [fig a]	Hyomental distance[11,12]	Distance from the lower aspect of the hyoid to the inferior aspect of the mentum[11,12]
4. [fig b]	Depth of epiglottis at the level of the mid-hyoid bone[11]	Measured at the base of epiglottis at the level of vallecula through mid-hyoid to the skin
5. [fig c]	Thyrohyoid distance[11]	Measured between the inferior aspect of the hyoid and the superior aspect of thyroid cartilage[11]
6.	Pre-epiglottic fat attenuation	Present/absent
7. [Fig d]	Depth of arytenoid cartilage[11]	Depth of arytenoid cartilage from the skin at the level of insertion of vocal cords[11]
8. [Fig d]	Fat pad thickness at the thyroid cartilage[11]	Measured as the maximum distance from skin to thyroid cartilage[11]
9. [Fig d]	Distance from uvula to posterior pharyngeal wall[13]	Minimum distance from the uvula to the posterior pharyngeal wall measured at the level of dens[13]
10. [Fig d]	Distance from the base of the tongue to the posterior pharyngeal wall[13,14]
11. [Fig e]	Length of epiglottis[15]
12. [Fig e]	Distance from epiglottis to posterior pharyngeal wall[14] a) Tip of the epiglottis to the posterior wall b) Base of the epiglottis to the posterior wall
13. [Fig f]	Neck anteroposterior diameter[16]	The shortest anteroposterior distance through the centre of the cricoid cartilage on the lowest axial section of the cricoid[16]
14. [Fig g]	Distance from membrane to vallecula[16]	Measured from the midpoint of the thyrohyoid membrane between the hyoid bone and laryngeal prominence to the closest concave point of the vallecula[16]
15. [Fig h]	Anteroposterior dimension at the level of vocal cords	a) Total distance from the anterior vertebral line to the thyroid cartilage b) Retropharyngeal soft tissue c) Airway shadow
16	Intraluminal narrowing site	Nasal cavity/nasopharynx/oropharynx/hypopharynx/supraglottis/glottis/infraglottis/trachea/bronchi
17	Intraluminal narrowing extent	Length from proximal to distal end of narrowing measured in mm
18 [Fig i]	Residual patent airway	The anteroposterior and transverse diameter of the patent airway measured at the site of narrowing of the airway
19 [Fig j]	Airway lumen above vocal cords	Distance from anterior to posterior boundary of larynx in sagittal view above the vocal cords
20 [Fig j]	Airway lumen below vocal cords	Distance from anterior to posterior boundary of larynx in sagittal view below the vocal cords
21 [Fig k]	Tracheal diameter	Measured 1 cm above the carina
22 [Fig l]	Left bronchial diameter (if available)	Measured 1 cm below the carina left bronchi
23 [Fig l]	Right bronchial diameter (if available)	Measured 1 cm below the carina in right bronchi
24 [Fig m]	Nasal spur	Present/Absent
25 [Fig n]	Deviated nasal septum	Present/Absent
26	Side of the nostril selected for intubation	Right/Left nostril selected based on patency, spur/deviated nasal septum[17]
27 [Fig o]	Right nasal cavity diameter	Minimum distance between inferior concha and nasal septum right side[18]
28 [Fig o]	Left nasal cavity diameter	Minimum distance between inferior concha and nasal septum left side[18]

On the day of surgery, in the preoperative holding area, the anaesthesiologist was asked about the primary plan of airway management (technique and equipment of tracheal intubation, selection of nostril, size and type of the endotracheal tube, any adjuncts to be used, and size of nasopharyngeal/oropharyngeal airways if needed) based on the conventional assessment. Then, for patients belonging to Group B, 3D CT findings as per the CT reporting format [Supplementary Table 1] and a virtual endoscopy video recorded on a laptop/desktop were shared with the concerned anaesthesiologists. Any change in the primary plan of perioperative airway management after showing 3D CT findings in Group B, and the final airway management plan executed inside the operating theatre for both groups, was noted.

In the operating theatre, standard monitors [5-lead electrocardiogram (ECG), non-invasive blood pressure, and pulse oximeter (SpO₂)] were attached, and a peripheral IV line was established. Anaesthesia management was done according to institutional protocol at the discretion of the anaesthesiologist, and the technique was noted. The anaesthesiologist managing the airway was the same as assessing the airway preoperatively. All the airway management in both groups was performed by experienced anaesthesiologists who had performed at least 50 flexible fibreoptic bronchoscope/video laryngoscope/direct laryngoscope-guided intubations in head and neck cancer patients. The anaesthesia was maintained with sevoflurane in an oxygen: air mixture to maintain a minimum alveolar concentration (MAC) of 1.2. Minute ventilation was controlled to maintain normocapnia [end-tidal carbon dioxide (EtCO₂): 35-45 mmHg). Best view to obtaining a percentage of glottis opening (POGO)[19] in the case of video laryngoscopy, Cormack Lehane (CL) grading in case of direct laryngoscopy,[20] and time to glottic view (the time from the beginning of the insertion of the equipment till the optimal glottic view)[21] were noted. Haemodynamic parameters (mean blood pressure and heart rate) were noted pre-induction, starting laryngoscopy/fibreoptic, post-intubation, and every minute for 10 minutes.

The primary outcome was the total time required for successful airway management ‘total time from passage of the device into the oral cavity’[21] (for laryngoscope) and nostril for fibreoptic bronchoscope) till the first appearance of regular capnograph waveform. Secondary outcomes included the number of attempts (defined as all activities from introduction of the endotracheal tube into the nasal/oral cavity till it was taken out), number of alternative techniques, other manoeuvres required [tube rotation, use of Magill’s forceps, and optimum external laryngeal manipulation (OELM)], incidence of failed intubation [‘inability to site endotracheal tube after multiple attempts’],[13] the incidence of any airway morbidity[21]/complications [mucosal bleeding, blood on tube introducer/endotracheal tube, dental injury, lip injury, desaturation episode], or postoperative sore throat (POST score) 1 h after extubation. The numeric rating scale (NRS) of intubation was recorded based on the overall difficulty faced by the anaesthesiologist, with an increasing difficulty level from 0 to 10.

No prospective study has been performed in head and neck cancer patients to see the impact of advanced airway imaging (3D CT reconstruction and virtual endoscopy) on airway management. Thus, this study was a pilot, randomised study done on 60 patients. Data were analysed using the Statistical Package for the Social Sciences (SPSS) statistics software version 21.0 (Armonk, NY: IBM Corp., USA). Continuous variables were reported with mean (standard deviation) and median (25^th–75^th percentile, interquartile range). Categorical variables, such as the diagnosis distribution and type of surgery, were reported with numbers and percentages. An unpaired student t-test compared the two groups’ mean, age, weight, height, and body mass index (BMI). The Mann-Whitney U test was applied to compare ‘time to glottis view’[21] and ‘total airway management time’[21] (primary outcome) and neck length, neck circumference, thyromental distance (TMD), sternomental distance (SMD), El Ganzouri risk score, intraoperative The NRS) of intubation, and POGO between the two groups. The median difference and its 95% confidence interval (CI) were determined using the Hodges-Lehmann method for the primary outcome. The qualitative variables American Society of Anesthesiologists (ASA) physical status, dentition, modified Mallampati class, and intraoperative qualitative parameters were compared using the Chi-square or Fisher’s exact test. The complications and manoeuvres used were compared using Fisher’s exact test in both groups. The Wilcoxon signed-rank test was applied to compare the endotracheal tube size before and after CT, after CT and inside the operating theatre, and before CT and inside the operating theatre in the interventional group. The agreement between the airway management plan before CT, after CT, and inside the operating theatre was made using the Kappa statistic, considering ‘0.2–0.4 as fair agreement, 0.4–0.6 as moderate agreement, 0.6–0.8 as substantial agreement, and 0.8–1 as profound agreement’.[22] Kappa statistic was also used to compare the airway management plan before and inside the operation theatre in the control group. Descriptive statistics were used to report various airway CT parameters. We applied repeated-measures analysis of variance (ANOVA) to find the difference in haemodynamic parameters between the two groups.

RESULTS

In this study, 60 patients were randomly allocated into two groups [Figure 1]. The two groups’ demographic characteristics and El Ganzouri risk score[10] on clinical airway assessment were comparable (P > 0.05) [Tables 1 and 2]. Out of 30 patients, in 14 cases, a higher size of the endotracheal tube was selected based on 3D CT findings (P < 0.001). In only one case, the endotracheal tube size, as selected after CT findings, had to be changed to a smaller size (P > 0.99). The change in endotracheal tube size after showing 3D CT was significant (P < 0.001) with successful intubation in operation theatre [Table 3]. Fifty-seven cases were done with nasal intubation, of which 28 were assessed with conventional methods, and for 29 cases, CT reporting was used additionally. Six cases of spurs and 10 cases of deviated nasal septum were reported in CT. Nineteen patients had a right nasal cavity patent, 10 had a left nasal cavity patent, and one had similar patency on both sides. There was a change in the side of nostril selection for nasotracheal intubation in six patients based on 3D CT findings (kappa = 0.545, showing moderate agreement between before and after CT groups) [Table 4]. The type of equipment used for intubation (FOB/direct laryngoscope/McIntosh video laryngoscope/hyper angulated video laryngoscope) was changed in three patients in Group B (kappa = 0.818). The remaining airway management plan remained similar after showing 3D CT findings (kappa = 1, showing profound agreement) [Table 4].

Figure 1.

Consolidated Standards of Reporting Trials flow diagram

Table 1.

Demographic parameters

Parameters	Group A (n=30)	Group B (n=30)	Mean difference (95% CI)	P
Age (years)	50.70 (8.03)	49.79 (9.47)	0.91 [−3.70, 5.52]	0.693
Gender: Male/Female (n)	23/7	24/6	−0.83 [−8.08, 6.42]	>0.99
Weight (kg)	61.93 (13.98)	62.77 (14.07)	−0.83 [−8.08, 6.42]	0.819
Height (cm)	161.87 (6.7)	163.1 (7.0)	−1.37 [−4.92, 2.19]	0.445
BMI (kg/m2)	23.51 (4.31)	23.60 (5.03)	−0.09 [−2.51, 2.33]	0.943
ASA I/II/III/IV (n)	22/8/0	19/10/1	-	0.580
Distribution of diagnosis in both groups
Ca tongue	3	3
Ca GBS	1	3
Ca buccal mucosa	16	13
Thyroid ca	1	1
Ca mandible	1	-
Ca maxilla	1	1
Ca central arch	-	1
Ca retromolar trigone	3	2
Ca alveolus	4	6
Type of surgery
CR, PMMC, MND	16	20
Thyroidectomy	1	1
Mandiblectomy	3	2
Maxillectomy	1	1
Glossectomy	3	3
WLE, flap, SOHND	2	1
WLE, MND	2	1
WLE, nasolabial flap, SSG, MND	2	-
Central arch resection	0	1

Data are presented as mean (standard deviation) or number of patients. BMI=Body mass index; ASA=American Society of Anesthesiologists; Ca=Carcinoma; CR=Composite resection; PMMC=Pectoralis major myocutaneous flap; MND=Major neck dissection; WLE=wide local excision; SOHND=Supraomohyoid neck dissection; SSG=split skin graft, GBS = Gingivobuccal sulcus

Table 2.

Clinical airway assessment parameters

Parameter	Group A (n=30)	Group B (n=30)	P
Mouth opening (cm)	2.73 (1.19)	2.25 (1.12)	0.116
Abnormal dentition (n)	14	6	0.007
Modified MPC I/II/III/IV (n)	0/9/4/17	1/0/4/25	0.004
Mandibular protrusion test  Class A/B/C (n)	16/14/0	14/14/2	0.587
Thyromental distance (cm)	6.8 [6.1–7]	7 [6.9–8.3]	0.034
Sternomental distance (cm)	14 [13–16.8]	14 [12.8–15.3]	0.689
Neck circumference	39.5 [34–41.8]	36.8 [35–39]	0.515
Neck length	10.3 [9–12]	11 [9–12]	0.873
Neck movement <90 deg/>90 deg	0/30	0/30	-
H/o previous difficult intubation questionable (n)	1	0	>0.99
H/o previous difficult intubation definite (n)	1	0	>0.99
H/o RT/CT/surgery (n)	2	4	0.670
El Ganzouri risk	3 [3–4]	4 [3–4]	0.507

Data are presented as mean (standard deviation) or numbers or median (interquartile range). MPC=Mallampati classification; RT=Radiotherapy; CT=Chemotherapy

Table 3.

Impact of 3D CT on endotracheal tube size selection in Group B

	Change		No change	P
	Increase	Decrease
ACT vs BCT	14	0	16	<0.001
OT vs ACT	0	1	29	>0.99
OT vs BCT	13	0	17	<0.001

Data are presented as numbers. BCT=Before showing CT findings (based on conventional assessment); ACT=After showing CT findings; OT=inside OT

Table 4.

Change in airway plan

	Concordance	Disconcordance	Proportion of change	Kappa
Group A
BCT vs OT (T)	29	1	1/30	0.936
BCT vs OT (T’)	30	0	0/30	>0.99
BCT vs OT (E)	30	0	0/30	>0.99
BCT vs OT (N)	29	1	1/30	0.936
BCT vs OT (ET)	30	0	0/30	>0.99
BCT vs OT (Ad)	30	0	0/30	>0.99
Group B after showing 3D CT findings
BCT vs ACT (T)	30	0	0/30	>0.99
BCT vs ACT (T’)	30	0	0/30	>0.99
BCT vs ACT (E)	27	3	3/30	0.818
BCT vs ACT (N)	24	6	6/30	0.545
BCT vs ACT (ET)	30	0	0/30	>0.99
BCT vs ACT (Ad)	30	0	0/30	>0.99

Data are presented as numbers. BCT=Plan based on conventional assessment; OT=plan executed inside OT; ACT=After showing CT findings; T=Technique (awake/GA/sedation); T’=Technique (oral/nasal); E=Type of equipment; N=Side of nostril for intubation; ET=Type of endotracheal tube; Ad=Type of adjuvant. Concordance: (BCT vs OT) = number of pairs agreed with respect to airway management based on conventional assessment and inside OT in Group A. (BCT vs ACT)=number of pairs agreed with respect to airway management before CT and after CT in Group B. Disconcordance: (BCT vs OT) = number of pairs disagreed with respect to airway management based on conventional assessment and inside OT in Group A. (BCT vs ACT)=number of pairs disagreed with respect to airway management before CT and after CT in Group B. Kappa 0.2–0.4: fair agreement. 0.4–0.6: moderate agreement. 0.6–0.8: substantial agreement. 0.8–1: profound agreement

There was no significant difference in total airway management time (P = 0.752) [Figure 2] and time to glottis view (P = 0.637) in both groups. The median difference for total airway management time was 0.0 [95% confidence interval (CI): −14, 20], and time to glottic view was 0 [95% CI: −10.0, 10.0] as calculated by the Hodges-Lehmann method. Among the manoeuvres used, optimal external laryngeal manipulation (OELM) was significantly used in Group A (P = 0.007). Both groups had no difference in the number of attempts (P > 0.99), number of alternative techniques (P = 0.052), operators (P = 0.612), postoperative sore throat (P > 0.99), or complications (P > 0.99) [Table 5]. There was no case of failed intubation in either group.

Figure 2.

Comparison of the distribution of total airway management time (TAM) by using a box whisker plot between Group A and Group B

Table 5.

Intraoperative details of various study parameters

Parameters	Group A (n=30)	Group B (n=30)	P
Time to glottis view (s)	25 [14.3–50]	30 [15–40]	0.637
Airway management time (s)	60 [48.3–100]	80 [60–100]	0.75
Number of attempts 1/2/3 (n)	27/3/0	25/4/1	>0.99
Number of failed intubation (n)	0	0	-
Number of alternative techniques  1/2 (n)	30/0	25/5	0.052
Operators  1/2 (n)	29/1	27/3	0.612
Manoeuvres
OELM (n)	12	3	0.007
Jaw thrust (n)	9	6	0.371
Tube rotation (n)	12	13	0.793
Magills (n)	1	0	>0.99
Cuff inflation (n)	2	2	>0.99
Complications
Oedema (n)	2	2	>0.99
Blood on tube (n)	3	4	>0.99
Bleeding (n)	2	2	>0.99
Bronchospasm (n)	1	0	>0.99
Dental injury (n)	-	-	-
Lip injury (n)	-	-	-
Cuff rupture (n)	0	1	>0.99
Desaturation (n)	0	0	-
POST Grade I/II/III/IV (n)	26/4/0/0	26/4/0/0	>0.99
DL/CMAC/Dblade/FOB (n)	4/18/0/8	0/11/5/14	0.003
POGO	80 (70–90) n=18	75 (60–80) n=16	0.204
CL grade II	n=4	n=0
NRS	7 [5–8]	5 [4–7]	0.105
Extubation plan on table/ICU/tracheostomy/ICU over tube exchanger (n)	3/15/12/0	2/22/6/0	0.185

Data are presented as median (interquartile range) or numbers. OELM=Optimal external laryngeal manipulation; POST=Post operative sore throat; VL=Videolaryngoscope; DL=Direct laryngoscope; FOB=Fibreoptic bronchoscopy; NRS=Numeric rating scale

Four cases were done under direct laryngoscopy in Group A, and no cases in Group B. Eighteen cases were done with video laryngoscopy in Group A and 16 cases in Group B. The POGO score did not differ significantly in both groups (P = 0.204).

The NRS of intubation was higher in Group A compared to Group B (P = 0.105) [Table 5]. After receiving feedback from anaesthesiologists on 30 cases, 22 received a rating of 5, while six received a rating of 4 on the Likert scale for the benefit of 3D CT findings for airway assessment. There was no significant difference in haemodynamic parameters between the two groups at any time. The post-induction values were significantly higher than other time points for all the haemodynamic parameters, possibly due to the stress response Figures 3 and 4. Mean measurements of various CT parameters are mentioned in Supplementary Table 2. Dynamic manoeuvres such as puffing the cheek are done for CT scans in oral cavity tumours to visualise the mass.[23] One case of carcinoma buccal mucosa and gingivobuccal sulcus underwent CT with this manoeuvre. It resulted in fallacious measurements of tongue thickness, depth of epiglottis, and arytenoid as it was pulled up. The uvula opposed the pharyngeal wall, and ‘the distance from the base of the tongue to the posterior pharyngeal wall’[13,14] was narrowed. The airway lumen at the tip and base of the epiglottis was falsely reduced due to this manoeuvre. Hence, these measurements of this patient were excluded from the study.

Figure 3.

Mean arterial pressure before induction, at the time of laryngoscopy/fibreoptic bronchoscopic intubation, post-intubation, every minute till 10 min in both groups

Figure 4.

Heart rate before induction, at time of laryngoscopy/fibreoptic bronchoscopic intubation, post-intubation, every minute till 10 min in both groups

Supplementary Table 2.

CT parameters for airway assessment

Parameter	n	Median [range (IQR)] in cm	Mean[SD] in cm
Tongue thickness	29	7.1 [4.65–8.75 (6.8–7.6)]	7.1 [0.92]
Submental distance	30	1.5 [0.50–3.64 (1.3–1.7)]	1.5[0.60]
Hyomental distance	30	3.7 [1.87–6.50 (3.2–4.2)]	3.8[0.92]
Thyrohyoid distance	30	0.35 [0.10–1.29 (0.2–0.5)]	0.4[0.24]
Depth of epiglottis	30	3.4 [2–6 (3–4)]	3.5[0.77]
Depth of arytenoid	30	3.3 [3–4 (2.45–5.3)]	3.5[0.72]
The fat pad at the thyroid cartilage	30	0.8 [0.41–4.57 (0.5–1)]	1.0[0.92]
Uvula to posterior pharyngeal wall	28	1 [0.43–7.80 (0.6–1.2)]	1.34[1.7]
The base of the tongue to the posterior pharyngeal wall	30	1.4 [0.62–2.48 (1.2–1.7)]	1.4[0.40]
Length of epiglottis	30	2 [0.87–4 (1.7–2.4)]	2.1[0.58]
Base of epiglottis to posterior pharyngeal wall	30	1.7 [1.20–2.80 (1.5–2.4)]	1.74[0.32]
Anteroposterior diameter at neck	30	11.9 [9.2–16.46 (11–13)]	12.27[1.66]
Membrane to vallecula distance	30	1.9 [1–3 (1.5–2)]	1.94[0.54]
Anteroposterior dimension at the level of vocal cords total	30	4 [2–5 (3.5–4.2)]	3.83[0.72]
Airway shadow at the level of vocal cords	30	2 [1.5–2.2 (1–4)]	2.0[0.64]
Retropharyngeal soft tissue	30	1.3 [1.1–1.6 (0.93–2.41)]	1.78[0.35]
Airway lumen above vocal cords	30	1.9 [1.5–2 (1.04–3.05)]	1.78[0.41]
Airway lumen below vocal cords	30	2 [1.7–2 (1.4–2.8)]	1.97[0.33]
The minimum distance between the nasal septum and inferior concha left	30	0.9 [0.16–0.4 (0.8–1)]	0.93[0.26]
The minimum distance between the nasal septum and inferior concha right	30	1 [0.4–0.6 (0.88–1)]	0.97[0.17]
Tracheal diameter	10	1.47 [1.2–2.07 (1.37–1.8)]	1.565[0.28]

Data is expressed in both mean (standard deviation) and median [range (interquartile range)],, as this remains a hypothesis-generating study and for future research for the reported parameters

DISCUSSION

In this study, the addition of advanced airway imaging for airway assessment resulted in no significant difference in the total time required for successful airway management. The higher value of the ‘airway management time’[21] and ‘time to glottis view’[21] in the 3D CT group was because of a larger number of cases done with fibreoptic intubation in this group, which takes longer than intubation with laryngoscopy. There was less use of optimal external laryngeal manipulation, possibly due to the appropriate selection of airway management techniques after getting a better airway assessment with 3D CT. However, there was no significant difference in other manoeuvres, number of alternative techniques, number of attempts, airway morbidity/complications, and postoperative sore throat in both groups.

Surgeons routinely perform imaging on head and neck cancer patients to determine the extent of the tumour, and these images can guide the anaesthesiologist in formulating an airway plan. Gutierrez et al.[14] concluded that CT measurements help predict the difficult airway in patients with head and neck cancers.

Normal ranges of all parameters were unavailable in the literature and, wherever available, were mentioned in CT reporting. Naguib et al.[13] and Hye Jin Kim et al.[16] reported the following measurements of CT in the difficult laryngoscopy group: length of epiglottis:[13] 2.1 (SD: 0.9) cm, vocal cords to posterior pharyngeal wall:[13] 1 (SD: 0.4) cm, distance between the tongue and posterior pharyngeal wall:[21] 1.6 (SD: 0.6 cm), distance between the tip of the uvula and posterior pharyngeal wall:[13] 1.3 (SD: 0.4) cm, neck anteroposterior diameter:[16] 11.7 (SD: 1.3) cm, and membrane to vallecula distance:[16] 2.5 (SD: 0.5) cm.

In our study, after showing 3D CT findings, a major change in the airway plan was seen in the size of the endotracheal tube and the selection of nostrils for nasotracheal intubation. Videolaryngoscopy is emerging as a standard of routine airway management in difficult airways. Due to its availability at our centre, plan A started with videolaryngoscope instead of direct laryngoscope in both the groups where laryngoscopy was indicated, considering all cases of head and neck cancer to be difficult airways. Hence, there was no significant change in the equipment used for intubation after sharing 3D CT findings. The only case where direct laryngoscopy was planned based on clinical airway assessment was a case of thyroid cancer. When the 3D CT findings and virtual endoscopy of luminal obstruction were shown, the plan was changed to a video laryngoscope, followed by successful intubation.

The identification of the nasal spur is paramount for nasotracheal intubation. After reporting a spur, deviated nasal septum, and a patent side of the nostril, the airway plan was changed to the more patent side of the nasal cavity. Grimes et al.[24] also concluded that there was a positive correlation between a difficult nostril assessed on CT and difficulty of intubation (P < 0.001). Their results also suggested that it should be routine to review CT scans to select the preferred nostril for intubation. Ahmad et al.[3] created virtual endoscopy videos for glottic and subglottic pathologies, compared real-life fibreoptic findings with the virtual endoscopy fly-through reconstruction, and found that the images correlated.

Our study had a few limitations. Most of the head and neck cancer cases were supraglottic, and no airway obstruction was found; hence, virtual endoscopy could not be studied extensively. Only one case of thyroid cancer had tracheal compression, for which a virtual endoscopy video was created that assisted an anaesthesiologist in changing the plan of intubation from direct laryngoscopy to videolaryngoscopy. Intubation difficulty score (IDS) could be calculated only for direct and video laryngoscopy cases, about 22 in Group A and 16 in Group B; the rest were done with fibreoptic bronchoscopy. In contrast to intubation with a laryngoscope,[11,15] difficult intubation with fibreoptic intubation has not been graded. As the distribution of cases was not similar in both groups, POGO, Cormack–Lehane grade, and IDS could not be compared due to the small sample size. Normal values of various CT parameters are not available in the literature. Furthermore, anaesthesiologists lack familiarity with these parameters; thus, further research is needed to establish standardised interpretations of various CT parameters.

CONCLUSION

Airway assessment with 3D CT reconstruction did not significantly impact airway management in terms of the total time required for successful airway management. However, it provided additional airway-related information to anaesthesiologists, mainly for nasal intubation and cases of luminal obstruction. Further studies are needed to ascertain the normal ranges of various CT parameters that predict difficult airways.

Statement on data sharing

De-identified data may be requested with reasonable justification from the authors (email to the corresponding author) and shall be shared after approval as per the authors’ Institution policy.

Supplementary material

This article has supplementary material and can be assessed at this link. Supplementary Material at http://links.lww.com/IJOA/A31.

Author contributions

SG: Concept, Design, Definition of intellectual content, data collection manuscript writing. ED: Concept, Design, Definition of intellectual content, data collection manuscript writing. RG: Concept, Design, Definition of intellectual content, data collection, manuscript writing. SB: Design, data collection, manuscript writing. SM: Design, data collection, manuscript writing. SJB: Design, data collection, manuscript writing. NG: Design, data collection, manuscript writing. VK: Design, data collection, manuscript writing.

Disclosure of use of artificial intelligence (AI)-assistive or generative tools

The AI tools or language models (LLM) have not been utilised in the manuscript, except that software has been used for grammar corrections.

Declaration of use of permitted tools

Nil.

Presentation at conferences/CMEs and abstract publication

None.

Conflicts of interest

Dr Rakesh Garg, who is one of the coauthors of this manuscript, is also the editor of the journal and was not involved in the decision-making for this manuscript, which was handled independently by another editor of the journal.

Funding Statement

Nil.