Oral submucosal fibrosis (OSMF) is a chronic premalignant disease of oral cavity[1]. Tobacco and betel quid chewing are the major causative factor leading to restricted mouth opening as it is related to development of OSMF. OSMF is characterized by juxta epithelial fibrosis of oral cavity leading to limited mouth opening, which causes difficulty in laryngoscopy and difficulty in intubation[2]. The consumption of tobacco and betel quid is very common in our area comprising of 25% to 30% of general population in both sex [3]. The occurrence and severity of OSMF depends on the duration and frequency of tobacco consumption and also plays a modifying role for its malignant transformation.

Initially presentation of OSMF includes ulceration and dryness of the mouth and later followed by fibrosis of the oral mucosa. It is important during pre-anesthetic checkup to ask for habit of tobacco chewing along with the duration and frequency since OSMF can cause unanticipated difficult intubation[4].

Direct laryngoscope can be considered if the patient is having minimum inter incisal  distance (IID) of more than 3 cm, which is essential for introducing the laryngoscope blade to permit the direct laryngoscopy [5]. Only patients with inadequate mouth opening comprising MPG III & IV and IID between 3 cm to 5cm were included in our study. No literature data is available regarding chances of successful direct laryngoscopy in patients with OSMF with regard to minimum inter incisal distance.

In this study we have analyzed the difficulty of intubation in patients with OSMF by comparing the Modified Mallampati Grade with the Cormack Lehane Score during direct laryngoscopy along with other clinical parameters like inter incisal distance, thyromental distance and sternomental distance to predict the added difficulty in intubation of OSMF patients [5].

AIMS AND OBJECTIVES

This study aims to evaluate airway management strategies in patients with Oral Submucosal Fibrosis (OSMF) undergoing general anaesthesia, focusing on predicting and managing difficult intubation effectively. The objectives are to review the airway characteristics of patients, to assess the appropriate airway management techniques based on preoperative findings, to correlate preoperative airway assessment parameters with the difficulty encountered during direct laryngoscopy, to analyse the success rate and challenges of intubation techniques and postoperative complications related to airway management in these patients.

After approval from institutional ethical committee, Rajkot (Outward No. PDUMC/IEC/1258/2019 dated 24/01/2019) written informed consent was obtained from all the patients. This prospective, observational study was conducted at PDU Government Medical College and Hospital with fifty adult patients (aged 15-65 years) diagnosed with oral submucosal fibrosis (OSMF) undergoing elective surgery under general anaesthesia (GA). This study includes patients of age between 15 – 65 years with mouth opening between 3-5 cm, history of tobacco/betel nut chewing, and Modified Mallampati Grade (MPG) III or IV. Mouth opening <3 cm, patients with edentulous/ missing both upper and lower incisors, patients undergoing emergency surgeries or requiring rapid sequence intubation, presence of neck/oral tumours, malformations, burns, or scars affecting airway management are excluded from study.

Before day of surgery, all patients underwent a detailed pre-anaesthetic evaluation, including history, physical examination, investigations (ECG, chest X-ray, laboratory tests). They were also assessed for Clinical Airway Parameters using:

• Modified Mallampati Classification (MPG) (Grade I-IV): based on oropharyngeal visibility
• Inter-Incisor Distance (IID): Measured as the distance between upper and lower incisors; <5 cm indicated difficult intubation
• Thyromental Distance (TMD): measured from thyroid notch to mentum; <6 cm suggested difficult airway
• Sternomental Distance (SMD): measured from chin to sternal notch; <12 cm predicted intubation difficulty

All clinical assessments were done by a single doctor who was blinded to the study. All patients received Tab. Alprazolam 0.5 mg and Tab. Ranitidine 150 mg the night before surgery to alleviate anxiety and control gastric acidity. On the day of surgery, monitoring with ECG, NIBP, and SpO₂ was initiated pre-induction and continued throughout the perioperative period. A difficult airway cart was kept ready, including Macintosh & McCoy blades, bougie, stylet, LMA, I-gel, Truview Video Laryngoscope, Fiberoptic Bronchoscope, and a Tracheostomy set, ensuring preparedness for any airway difficulties. Premedication with Inj. Glycopyrrolate, Inj. Ondansetron, Inj. Ranitidine, and Inj. Diclofenac Sodium. Induction was carried out using Inj. Thiopentone Sodium (6 mg/kg) and Inj. Succinylcholine (2 mg/kg) was given iv stat after check ventilation. Laryngoscopy was performed using a Macintosh blade in the sniffing position, and glottic visibility was assessed using the Cormack-Lehane grading system (Grade I-IV). Cases of difficult intubation (CL III & IV) were managed using external laryngeal manipulation, stylet, bougie-assisted intubation, Truview video laryngoscopy or fiberoptic intubation.

After completion of surgery and confirmation of spontaneous breathing with adequate tidal volume, reversal of anaesthesia was administered using iv Inj. Glycopyrrolate (0.004 mg/kg) and iv Inj. Neostigmine (0.05 mg/kg) to facilitate smooth extubation following thorough suctioning of secretions. Patients were monitored in post-anaesthesia care unit for 24 hours for any complications including sore throat, dysphagia, bleeding, mucosal trauma or dental injuries. Delayed complications such as airway edema or respiratory distress was also monitored. Patients complained of sore throat were treated with lozenges and ENT specialist consultation was arranged for any persistent airway-related issues.

This study was undertaken to assess the difficulty in intubation of the individuals with OSMF. Total Fifty patients were included in our study of either sex between the age of 15 to 65, posted for elective surgery under general anesthesia with endotracheal intubation. Only patients with inadequate mouth opening comprising MPG III & IV were included in our study.

We have analyzed the difficulty of intubation in patients with OSMF by comparing the Modified Mallampati Grade with the Cormack Lehane Score during direct laryngoscopy and the ease of intubation after giving muscle relaxants while providing general anesthesia. Along with MPG we have also assessed the other clinical parameters like inter incisal distance, thyromental distance, sternomental distance to predict the added difficulty in intubation of OSMF patients.

1.Demographics and Baseline Characteristics

As shown in figure 1, among the 50 patients with OSMF, majority of the patients belong to the age group between 20 to 65 years of age with history of tobacco chewing and reduced mouth opening due to OSMF.

Majority of patients had MPG III (80%) and MPG IV (20%), suggesting a high likelihood of challenging airway management. These findings highlight the importance of preoperative airway evaluation in guiding appropriate intubation strategies and optimizing patient safety.

Among 50 patients, 39 males and 11 females were there in our study. This implies that even though incidence of tobacco consumption is found in the female population, it is observed that incidence of OSMF was less in female compared to the male gender.

2. Airway Assessment and Predictors of Difficult Intubation

A thorough preoperative airway assessment was conducted to evaluate the predictors of difficult intubation among patients with oral submucosal fibrosis (OSMF). The assessment included Modified Mallampati Grading (MPG), Thyromental Distance (TMD), and Sternomental Distance (SMD), which are established clinical markers for predicting difficult laryngoscopy.

3. Laryngoscopy Findings and Intubation Difficulty

On direct laryngoscopy examination of 50 OSMF patients (Figure 4), 42% (21 patients) were found to have Cormack-Lehane (CL) Grade II, indicating easy intubation, while 54% (27 patients) had CL Grade III and 4% (2 patients) had CL Grade IV, signifying difficult intubation. This suggests that despite the anticipated airway challenges in OSMF patients, a subset of cases could still be managed successfully using conventional direct laryngoscopy.

When analyzed according to Modified Mallampati Grade (MPG), patients with MPG III had a 52% chance of easy intubation, whereas all patients with MPG IV required additional airway management techniques. As illustrated in table 1 among 40 patients with MPG III, 21 (52%) had easy intubation (CL II), while 19 (48%) required secondary airway adjuncts such as a stylet, bougie, or TruView video laryngoscopy for successful intubation. In contrast, all 10 patients with MPG IV had CL III or IV needed advanced intubation techniques (Table 1).

Overall, 58% of OSMF patients (29 out of 50) had difficult intubation (CL III & IV), while 42% had relatively easier intubation (CL II). These findings reinforce the correlation between MPG and CL grading, highlighting the importance of preoperative airway assessment in anticipating and planning for intubation difficulty in OSMF patients.

4. Intubation Attempts and Postoperative Complications

The number of intubations attempts and postoperative complications were analyzed to assess the ease of airway management and associated morbidity in patients with oral submucosal fibrosis (OSMF).

Figure 5 summarize the number of intubation attempts required for securing the airway. In MPG III cases (n=40), 37 patients (92.5%) were intubated on the first attempt, whereas 3 patients (7.5%) required a second attempt. In MPG IV cases (n=10), 8 patients (80%) were intubated on the first attempt, while 2 patients (20%) needed a second attempt. Among the 50 patients, the majority (90%) were successfully intubated in a single attempt, while 10% required a second attempt. These findings suggest that direct laryngoscopy is more likely to succeed in a single attempt in MPG III patients, whereas MPG IV patients tend to require additional intubation manoeuvres.

Figure 6 present the incidence of postoperative complications. Out of 50 patients, 46 (92%) did not experience any significant complications. However, 4 patients (8%) reported mild sore throat, which resolved within 4–8 hours with conservative management. No instances of voice change, bleeding, or airway trauma were observed. These findings indicate that while difficult airway management was anticipated in OSMF patients,

careful perioperative airway planning minimizes complications and ensures safe postoperative recovery.

Oral submucosal fibrosis (OSMF) is a chronic, progressive, and irreversible premalignant disorder characterized by fibrosis of the oral mucosa, leading to restricted mouth opening and increased airway-related challenges, particularly in tracheal intubation. The condition is strongly linked to betel nut and tobacco chewing, which are prevalent habits in India [6]. As fibrosis advances, the reduced inter-incisal distance (IID) can make difficulty in direct laryngoscopy and intubation, requiring alternative airway management strategies [7]. Direct laryngoscopy is considered the gold standard for tracheal intubation, yet patients with severe OSMF (MPG III & IV) often present with restricted mouth opening, rendering conventional intubation more difficult [8]. In such cases, fiberoptic-assisted intubation or TruView laryngoscopy is a viable alternative, whereas tracheostomy was reserved for extreme cases [9]. However, our study suggests that for patients with IID ≥3 cm, direct laryngoscopy with external laryngeal manipulation, a bougie, or a stylet can facilitate successful airway access without requiring advanced airway techniques.

In our study, the majority of patients (42%) were in the 36–45 age group, which aligns with previous epidemiological studies on OSMF prevalence [10]. The gender distribution (78% male, 22% female) was also consistent with existing literature [11], which attributes the higher prevalence in males [12].

A significant finding in our study was that long-term tobacco use (≥10 years) was strongly associated with higher Modified Mallampati Grades (MPG) and more difficult laryngoscopy (Figure2). This reinforces existing evidence that prolonged exposure to tobacco carcinogens exacerbates fibrosis and limits mouth opening which causes difficult airway scenario [13]. Notably, our study found that the frequency, composition and duration of tobacco exposure played a greater role in limited mouth opening (OSMF) that concurs with previous research [14].

Among our 50 study participants, 80% had MPG III and 20% had MPG IV, highlighting the high prevalence of airway compromise in OSMF patients (Figure 1). Direct laryngoscopy revealed that 58% had difficult intubation (CL III &IV), whereas 42% had easier intubation (CL II) (Table1). Notably, direct laryngoscopy was successful in 50% of MPG III patients but difficult in MPG IV patients, emphasizing the predictive role of MPG in anticipating airway difficulty [15]. Further, airway parameters such as thyromental distance (TMD) and sternomental distance (SMD) also showed a strong correlation with difficult intubation (Figure 3). Patients with TMD <6 cm and SMD <12.5 cm had a significantly higher incidence of CL III & IV, reinforcing their utility as preoperative screening tools [16].

In our study, 90% of patients were intubated successfully on the first attempt, while 10% required a second attempt (Figure 5). Among the MPG IV group, 20% required a second attempt, highlighting the need for adjunctive intubation techniques such as bougie-assisted intubation, TruView video laryngoscopy or fiberoptic intubation. These findings align with studies advocating video laryngoscopy for difficult airways, as it enhances glottic visualization and improves first-attempt success rates [17]. Postoperative complications were minimal, with only 8% of patients reporting mild sore throat, which resolved within 4–8 hours (Figure 6). No instances of airway trauma, bleeding, or dental injuries were recorded, underscoring the safety of direct laryngoscopy in carefully selected OSMF patients. Similar results have been documented in other studies emphasizing the importance of preoperative airway assessment and careful planning in reducing complications [18].

Our findings suggest that direct laryngoscopy remains a feasible option for OSMF patients with IID ≥3 cm, there might be role of iv induction agents (Inj. Thiopentone Sodium) and iv muscle relaxants (Inj. Succinylcholine) which attributes to improve mouth opening and easier direct laryngoscopy as anticipated difficult airway preoperatively. Other adjuncts like external laryngeal maneuvers, stylet, bougie or TruView laryngoscopy are also available. However, fiberoptic intubation is still preferred method in patients with IID <3 cm [19].

LIMITATION:

Limitations of our study was relatively small sample size (n=50). The role of iv muscle relaxants which helps in improving mouth opening resulting in easier direct laryngoscopy in OSMF patients which was in contrast to preoperative findings was not assessed. Evaluating the role of muscle relaxant in improving mouth opening requires further research. Additionally, self-reported tobacco history may have introduced recall bias, potentially underestimating cumulative exposure and its effects on airway difficulty. Future research with larger, multicentric studies could provide more definitive insights into airway management in OSMF patients.

In conclusion, our study highlights that direct laryngoscopy is possible in carefully selected oral submucosal fibrosis patients with IID ≥3 cm, but MPG IV patients consistently require alternative airway management strategies. Modified Mallampati classification, Inter-incisor distance, Thyromental Distance and Sternomental Distance remain reliable predictors of difficult intubation and preoperative planning with adjunct airway techniques significantly improves intubation success and reduces complications. By incorporating structured airway assessment and an individualized approach, safe and effective airway management can be achieved in patients with OSMF undergoing general anaesthesia.

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