European Journal of Cardiovascular Medicine

Airway management remains one of the most fundamental aspects of anaesthetic practice, and difficult airway scenarios continue to be a significant cause of morbidity and mortality in both elective and emergency surgical settings. The Fourth National Audit Project (NAP4) conducted by the Royal College of Anaesthetists and the Difficult Airway Society revealed that complications of airway management were the leading causes of anaesthesia-related deaths, with inadequate assessment and planning identified as major contributing factors.¹ The ability to predict a difficult airway preoperatively is therefore of paramount importance, as it enables anaesthesiologists to formulate effective management strategies, prepare appropriate equipment, and avert potentially life-threatening complications. The American Society of Anaesthesiologists (ASA) defines a difficult airway as a clinical situation in which a conventionally trained anaesthesiologist experiences difficulty with facemask ventilation, tracheal intubation, or both. The incidence of difficult airway varies widely in the literature, ranging from 1.5% to 13% for difficult laryngoscopy, 1.2% to 3.8% for difficult intubation, and 0.05% to 0.35% for failed intubation — reflecting heterogeneity in patient populations, definitions of difficulty, and varying practitioner experience.²

Numerous clinical predictors and bedside tests have been developed for preoperative identification of potentially challenging airways. These include the Mallampati classification, thyromental distance, sternomental distance, mouth opening, neck mobility, upper lip bite test, and the Wilson risk score, among others. However, no single test has demonstrated adequate sensitivity and specificity to be used in isolation; a combination of tests is therefore recommended to improve predictive accuracy.³ The Modified Mallampati Test, one of the most widely used instruments, was initially described by Mallampati in 1985 and later modified by Samson and Young. A meta-analysis by Lundstrøm et al. found that it demonstrated a sensitivity of 55% and specificity of 84% for predicting difficult intubation — highlighting both its moderate utility and its limitations as a standalone assessment.⁴ The thyromental distance has been found to have sensitivity of 20–62% and specificity of 82–99%, while the sternomental distance, mouth opening, and neck mobility each carry their own predictive values and limitations.⁵

Diabetes mellitus, a prevalent chronic condition particularly among the elderly, introduces additional complexities to airway management. The concept of "diabetic stiff joint syndrome" or "limited joint mobility syndrome" — arising from non-enzymatic glycosylation of collagen in joints due to chronic hyperglycaemia — can reduce mobility of the atlanto-occipital joint, affecting neck extension and, consequently, the laryngoscopic view. Erden et al. demonstrated a higher incidence of difficult intubation in diabetic patients compared to non-diabetics, with a significant correlation between diabetes duration and degree of airway difficulty.6 The palm print sign, which assesses small joint mobility in the hand as a surrogate for atlanto-occipital joint mobility, has shown promise in predicting difficult intubation specifically in diabetic patients. Vani et al. reported a sensitivity of 75% and specificity of 85% for this test in the diabetic population.7 Against this background, the present study was undertaken to evaluate and compare the efficacy of different airway assessment tests — the Upper Lip Bite Test, Modified Mallampati Score, Palm Print Sign, and neck range of movement — in predicting difficult airways specifically among elderly diabetic and non-diabetic patients undergoing elective surgery under general anaesthesia. By focusing on this demographic, the study aims to provide evidence-based guidance for anaesthesiologists and contribute to the development of tailored airway assessment protocols for these high-risk groups.

This cross-sectional interventional comparative study was conducted at the Department of Anaesthesiology, R.L. Jalappa Hospital and Research Centre, Sri Devaraj Urs Medical College, Tamaka, Kolar, from May 2023 to March 2025, following approval from the Institutional Ethics Committee. A total of 184 patients were enrolled — 92 elderly diabetic (Group 1) and 92 elderly non-diabetic (Group 2) — using a consecutive, consenting, convenience sampling method. Patients aged ≥60 years of either sex, scheduled for elective surgery under general anaesthesia with endotracheal intubation, with known or absent diagnosis of diabetes mellitus, were included. Patients unfit for general anaesthesia and those undergoing emergency surgeries were excluded. The sample size was calculated based on a prior study comparing palm print sign with Modified Mallampati Test, using 80% power, 5% significance level, and an expected difference in sensitivity of 17.6%, yielding 92 patients per group.

On the day prior to surgery, all patients underwent a detailed pre-anaesthetic evaluation. Demographic data including age, gender, weight, height, BMI, ASA physical status, and comorbidities were recorded. Preoperative airway assessment included the Upper Lip Bite Test (ULBT), classified as Class I (lower incisors bite upper lip with mucosa totally invisible), Class II (mucosa partially visible), and Class III (lower incisors fail to bite upper lip) — with Classes II–III considered predictive of difficult intubation. The Modified Mallampati Score (MMS) was assessed with the patient seated, head neutral, mouth fully open, and tongue protruded without phonation; Grades III–IV were considered predictive of difficulty. The Palm Print Sign (PPS) was graded 0 to 3 based on visible phalangeal areas on ink imprint, with Grades 2–3 considered predictive. Neck range of movement was assessed and categorised as <80°, near 90°, or >100°.

On the day of surgery, standard monitoring was established, intravenous access secured, and preoxygenation with 100% O₂ for 3–5 minutes was performed. Anaesthesia was induced with standard agents and an appropriate muscle relaxant. Direct laryngoscopy was performed by an experienced anaesthesiologist using a Macintosh blade with the patient in the sniffing position. The laryngeal view was graded using the Cormack-Lehane (CL) system: Grades I–II classified as easy visualisation, and Grades III–IV as difficult visualisation of the larynx. Parameters recorded intraoperatively included mask ventilation quality, time taken for intubation, number of intubation attempts, and any alternative methods employed. Statistical analysis was performed using SPSS version 20.0. Categorical variables were expressed as frequencies and analysed using the Chi-square test; continuous variables as mean ± SD. A p-value <0.05 was considered statistically significant. Diagnostic accuracy was evaluated by calculating sensitivity, specificity, PPV, NPV, and accuracy for each airway test

This study evaluated 184 patients — 92 elderly diabetic and 92 elderly non-diabetic — undergoing elective surgery under general anaesthesia at R.L. Jalappa Hospital and Research Centre, Kolar, over 18 months. The following tables summarise the key findings. Demographic comparability was established between the two groups before analysis of airway parameters.

This study evaluated 184 patients — 92 elderly diabetic and 92 elderly non-diabetic — undergoing elective surgery under general anaesthesia at R.L. Jalappa Hospital and Research Centre, Kolar, over 18 months. The following tables summarise the key findings. Demographic comparability was established between the two groups before analysis of airway parameters.

Table 1: Demographic Profile and Baseline Characteristics

The demographic profiles were comparable between groups for age, gender, and BMI. No statistically significant differences were found. However, diabetic patients showed a higher proportion of ASA III status (43.5% vs. 23.9%) and a greater prevalence of obesity, reflecting the systemic burden of diabetes. Gender distribution was identical across both groups, effectively eliminating it as a confounding variable [Table 1].

Table 2: Preoperative Airway Assessment Findings

The preoperative airway assessment revealed strikingly significant differences between groups in ULBT and PPS, while MMS did not differ significantly [Table 2]. Class III ULBT — indicative of restricted mandibular mobility — was present in 38.0% of diabetic patients versus only 4.3% of non-diabetic patients (p<0.001), reflecting the impact of diabetes-related glycosylation on temporomandibular joint and periodontal tissue integrity. Difficult Palm Print Sign grades (3–4) were found in 26.1% of diabetic patients compared to 7.6% of non-diabetic patients (p=0.001), consistent with limited joint mobility syndrome. Neck extension did not differ significantly between groups.

Table 3: Intraoperative Airway Outcomes

Intraoperatively, difficult laryngoscopy was encountered significantly more often in diabetic patients — 34.8% versus 17.6% (p=0.010) — representing nearly a twofold higher incidence [Table 3]. Prolonged intubation time (>1 minute) was also significantly more frequent in diabetic patients (10.9% vs. 3.3%, p=0.048). Multiple intubation attempts were required in 33.7% of diabetic patients versus 23.9% of non-diabetic patients, though this difference did not reach statistical significance (p=0.140). Despite the higher rate of difficult laryngoscopy, mask ventilation was similarly easy in both groups (p=0.082), suggesting that the factors predisposing diabetic patients to difficult laryngoscopy do not equivalently affect ventilation. Video laryngoscopy was utilised more frequently in diabetic patients (6.5% vs. 3.3%), though this was not statistically significant (p=0.066).

Table 4: Diagnostic Accuracy of Airway Tests for Difficult Laryngoscopy

*p<0.05 statistically significant. PPV: Positive Predictive Value; NPV: Negative Predictive Value

The diagnostic accuracy analysis [Table 4] reveals a striking differential performance of airway assessment tests between the two groups. In diabetic patients, the ULBT demonstrated the highest sensitivity (90.6%) with excellent specificity (90.0%), establishing it as the most reliable predictor of difficult laryngoscopy in this population. The MMS achieved perfect specificity (100%) and a PPV of 100% in diabetic patients, making it a highly specific confirmatory test. The PPS showed good specificity (95.0%) with moderate sensitivity (65.6%). In non-diabetic patients, MMS led with the highest sensitivity (75.0%), while ULBT and PPS had low sensitivity but near-perfect specificity (98.7% each), making them useful for rule-in rather than rule-out purposes in this group. Across all patients combined, all three tests demonstrated statistically significant correlation with difficult laryngoscopy (p<0.001).

The present study provides evidence that elderly diabetic patients face a significantly higher incidence of difficult airway management compared to non-diabetic patients of comparable age. The demographic profiles of both groups were well matched, with no significant differences in age (65.95 ± 6.52 vs. 67.41 ± 5.92 years, p=0.112), gender distribution (55.4% males in both groups, p=1.000), or BMI (22.04 ± 4.24 vs. 21.27 ± 3.34 kg/m², p=0.172). These findings are consistent with those reported by Prakash et al. in their study on airway assessment in the Indian elderly population.8 Although the BMI difference was not statistically significant, the higher prevalence of obesity in diabetic patients (8.7% vs. 1.1%) aligns with the well-established association between type 2 diabetes and excess adiposity. The higher proportion of ASA III patients among diabetics (43.5% vs. 23.9%, p=0.066) reflects the greater systemic burden of diabetes, as highlighted in the comprehensive review by Hashim and Thomas.9 The Modified Mallampati Score did not differ significantly between groups (p=0.635), contrasting with findings by Erden et al. who reported a significantly higher prevalence of difficult Mallampati grades in diabetic patients.10 However, in terms of predictive accuracy, MMS demonstrated excellent specificity (100%) and good sensitivity (75.0%) in diabetic patients, confirming its established value as validated by Shiga et al. in their meta-analysis.11.

The most striking preoperative finding was the highly significant difference in ULBT results, with Class III ULBT present in 38.0% of diabetic patients versus only 4.3% of non-diabetic patients (p<0.001). This directly reflects the impact of glycosylation-induced stiffness on the temporomandibular joint and periodontal tissues. For predicting difficult laryngoscopy, ULBT demonstrated the highest sensitivity (90.6%) and specificity (90.0%) in diabetic patients, outperforming both MMS and PPS — a finding consistent with the work of Begum et al. who reported ULBT sensitivity of 91.1% in geriatric patients,12 and Khan et al. who similarly observed higher Class III ULBT prevalence in diabetic patients.13The Palm Print Sign was significantly more abnormal in diabetic patients (difficult grades in 26.1% vs. 7.6%, p=0.001), corroborating the concept of systemic limited joint mobility syndrome in diabetes. Its predictive accuracy (sensitivity 65.6%, specificity 95.0% in diabetic patients) aligns with the findings of Vani et al. and Nadal et al., who reported comparable values in their respective diabetic cohorts.14 In non-diabetic patients, MMS was the most sensitive predictor (75.0%), while ULBT and PPS offered excellent specificity but low sensitivity, indicating their utility as confirmatory rather than screening tools in this group. These differential performances across the two groups underscore that diabetes-specific physiological changes — particularly glycosylation of collagen in joints and connective tissues affecting the atlanto-occipital, temporomandibular, and cricothyroid joints — create a unique pattern of airway difficulty that warrants a tailored multi-test approach, as advocated by Roth et al. in their Cochrane systematic review.15

Difficult laryngoscopy (CL Grade III–IV) was encountered in 34.8% of diabetic patients compared to 17.6% of non-diabetics (p=0.010), representing nearly a twofold higher incidence — closely aligned with rates reported by Nadal et al. (31.4% vs. 13.8%) in a comparable patient group.14 Prolonged intubation time (>1 minute) was significantly more frequent in diabetic patients (10.9% vs. 3.3%, p=0.048). Despite the higher difficulty of laryngoscopy, mask ventilation did not differ significantly between groups (p=0.082), a finding consistent with El-Orbany et al., who demonstrated that difficult mask ventilation and difficult laryngoscopy do not always share the same predictors.16 Video laryngoscopy was employed more frequently in diabetic patients (6.5% vs. 3.3%), consistent with the current trend toward proactive use of advanced airway tools in anticipated difficult airways, as supported by Aziz et al.17 Taken together, these findings reinforce the importance of routine multi-test preoperative airway assessment in elderly diabetic patients, with particular emphasis on ULBT and PPS as diabetes-sensitive predictors. Anesthesiologists should maintain a high index of suspicion and ensure availability of advanced airway management tools for this population.

This study provides substantial evidence that elderly diabetic patients carry a significantly higher risk of difficult airway management compared to their non-diabetic counterparts. Difficult laryngoscopy was encountered in 34.8% of diabetic patients versus 17.6% of non-diabetic patients (p=0.010), and prolonged intubation time occurred in 10.9% versus 3.3% (p=0.048). The pathophysiological basis lies in diabetes-induced glycosylation of collagen in connective tissues and joints, producing limited joint mobility syndrome that affects the temporomandibular joint, atlanto-occipital joint, and cervical spine — collectively restricting mouth opening, neck extension, and laryngeal visualisation during intubation. Significantly higher rates of Class III ULBT (38.0% vs. 4.3%, p<0.001) and difficult Palm Print Sign grades (26.1% vs. 7.6%, p=0.001) in diabetic patients highlight the systemic manifestations of this process and its direct relevance to preoperative airway evaluation.

Among the assessment tools evaluated, the Upper Lip Bite Test emerged as the most sensitive and specific predictor of difficult laryngoscopy in elderly diabetic patients (sensitivity 90.6%, specificity 90.0%), followed by the Modified Mallampati Score (sensitivity 75.0%, specificity 100%) and Palm Print Sign (sensitivity 65.6%, specificity 95.0%). In non-diabetic patients, the Modified Mallampati Score was the most sensitive predictor (75.0%). No single test was sufficient across both populations, underscoring the need for a comprehensive multi-test approach in preoperative assessment, particularly for elderly diabetic patients.

Anaesthesiologists managing elderly diabetic patients should maintain a high index of suspicion for difficult airways and routinely apply multiple bedside tests — with special emphasis on the ULBT and PPS. Adequate preparation, including availability of video laryngoscopes and other advanced airway management devices, should be ensured prior to induction. Future research should focus on developing composite, validated scoring systems specifically designed for elderly diabetic patients, and on investigating whether optimised glycaemic control and targeted perioperative interventions can mitigate the degree of airway difficulty in this high-risk population

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