Open AccessArticle Mismatch Between Preoperative Airway Assessment and Unanticipated Difficult Tracheal Intubation: A Retrospective Case–Control Study Chanatthee Kitsiripant Chanatthee Kitsiripant 1,*, Wilasinee Jitpakdee Wilasinee Jitpakdee 1, Maliwan Oofuvong Maliwan Oofuvong 1, Pannawit Benjawaleemas Pannawit Benjawaleemas 1, Nussara Dilokrattanaphichit Nussara Dilokrattanaphichit 1, Wipharat Juthasantikul Wipharat Juthasantikul 1, Pannipa Phakam Pannipa Phakam 1, Qistina Yunuswangsa Qistina Yunuswangsa 1 Polathep Vichitkunakorn Polathep Vichitkunakorn 2 1 Department of Anesthesiology, Faculty of Medicine, Prince of Songkla University, Hat Yai 90110, Thailand 2 Department of Family Medicine and Preventive Medicine, Faculty of Medicine, Prince of Songkla University, Hat Yai 90110, Thailand * Author to whom correspondence should be addressed. Healthcare 2026, 14(12), 1619; https://doi.org/10.3390/healthcare14121619 (registering DOI) Submission received: 4 May 2026 / Revised: 6 June 2026 / Accepted: 8 June 2026 / Published: 9 June 2026 Highlights What are the main findings? Most cases of unanticipated difficult tracheal intubation occurred in patients without obvious high-risk findings on routine preoperative airway assessment. Intubation difficulty became evident during laryngoscopy, characterized by poor visualization, repeated intubation attempts, and frequent escalation to advanced airway techniques. What are the implications of the main findings? Routine preoperative airway assessment may not reliably identify all patients who subsequently experience difficult intubation. Difficult intubation may become apparent only during laryngoscopy despite apparently normal preoperative assessment findings. Abstract Background/Objectives: Unanticipated difficult airway remains a critical patient safety concern in perioperative care. Despite routine preoperative assessment, difficult intubation may still occur in patients without obvious high-risk findings. This study aimed to evaluate perioperative factors associated with unanticipated difficult intubation and to examine the relationship between preoperative assessment and intraoperative intubation difficulty in routine clinical practice. Methods: This retrospective case–control study included adult patients undergoing general anesthesia with tracheal intubation between 2015 and 2020 at a tertiary care hospital. Unanticipated difficult intubation was defined as requiring ≥3 intubation attempts without documented preoperative suspicion of difficult airway. Patients with anticipated difficult airway or preoperative mechanical ventilation were excluded. A total of 95 cases and 429 controls were analyzed. Associations were explored using multivariable logistic regression. Results: Among 524 patients, cases more frequently had ASA physical status III and airway/neck/oral deformity. Notably, intubation difficulty became evident only at laryngoscopy, characterized by poorer visualization, increased intubation attempts (median 4 vs. 1), and frequent escalation to video laryngoscopy. Severe laryngoscopic views (Cormack–Lehane grade III–IV: 74.8% vs. 3.0%) were markedly overrepresented among cases. In multivariable analysis, ASA III and airway deformity remained independently associated with unanticipated difficult intubation. The model demonstrated modest discrimination (AUC 0.685). Conclusions: Unanticipated difficult intubation was uncommon but clinically important and frequently became apparent only during airway management. Although several associated factors were identified, routine bedside airway assessment alone may not reliably predict all cases of intraoperative difficult intubation. These findings highlight the limitations of routine bedside airway assessment in identifying all patients who subsequently experience difficult intubation and support the need for improved strategies to identify patients at risk. Keywords: airway management; difficult airway; intubation; patient safety; perioperative care; quality of care 1. Introduction In routine clinical settings, this discrepancy between preoperative assessment and intraoperative airway difficulty represents a critical patient safety gap. Intubation difficulty may only become apparent during laryngoscopy, when visualization is inadequate and airway management must be rapidly escalated. In addition to anatomical factors, physiological conditions and perioperative context may influence airway management outcomes, further limiting the reliability of preoperative prediction. Therefore, this study aimed to evaluate perioperative factors associated with unanticipated difficult intubation and to examine the gap between preoperative airway assessment and intraoperative difficult intubation in routine clinical practice. 2. Materials and Methods 2.1. Study Design and Setting This retrospective case–control study was conducted at a tertiary teaching hospital in Southern Thailand between January 2015 and December 2020. The study was reported in accordance with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines. 2.2. Ethical Approval Ethical approval was obtained from the Human Research Ethics Committee of the Faculty of Medicine, Prince of Songkla University (approval number 63-560-8-1). The requirement for informed consent was waived due to the retrospective nature of the study. All data were anonymized prior to analysis. 2.3. Study Population and Definitions Adult patients (≥18 years) undergoing general anesthesia with endotracheal intubation for elective or emergency surgery were screened. Patients receiving preoperative mechanical ventilation were excluded. Among the remaining eligible patients, 168 met the study definition of difficult intubation based on retrospective review of perioperative records. These patients were subsequently classified according to whether preoperative suspicion of difficult intubation had been documented before induction of anesthesia. Seventy-three patients with documented preoperative suspicion were classified as anticipated difficult intubation and excluded. The remaining 95 patients, who met the difficult intubation criteria without documented preoperative suspicion, were classified as unanticipated difficult intubation and constituted the case group. 2.4. Case and Control Selection Cases were defined as patients with unanticipated difficult intubation. Controls were selected from patients without documented intubation difficulty during the same study period. 2.5. Airway Management Context All patients included in the study underwent general anesthesia with tracheal intubation. Tracheal intubation was performed by anesthesia providers with varying levels of experience, including anesthesiology residents under supervision, nurse anesthetists, and attending anesthesiologists. The choice of intubation technique and airway device, including the use of direct or video laryngoscopy, was based on routine clinical judgment rather than a standardized airway management protocol. 2.6. Data Collection and Variables Data were retrospectively extracted from electronic medical records and anesthetic records and curated into a structured dataset for analysis. Preoperative airway assessment variables routinely documented in clinical practice included Mallampati classification, thyromental distance, interincisor gap, upper lip bite test, neck mobility, dentition status, history of difficult airway, and the presence of airway/neck/oral deformity. Airway/neck/oral deformity referred to clinically documented structural abnormalities that could potentially affect airway alignment or laryngoscopic visualization, including congenital craniofacial abnormalities, prior head and neck surgery, cervical structural abnormalities, limited mouth opening, or visible anatomical distortion identified during routine perioperative assessment. Collected demographic and clinical variables included age, sex, body mass index, ASA physical status, and relevant comorbidities (e.g., obstructive sleep apnea, tumors, trauma, and prior head and neck radiation). Perioperative variables included urgency and category of surgery (non-operating room anesthesia [NORA], neurosurgical/orthopedic surgery, ophthalmic/minor superficial surgery, otolaryngology surgery, thoracic/vascular surgery, and abdominal surgery), selected laboratory abnormalities potentially reflecting severe systemic illness or perioperative physiological instability (including coagulopathy and hypocalcemia), airway device usage, intubation provider, laryngoscopic view (Cormack–Lehane grade), number of tracheal intubation attempts, airway-related complications, and escalation of airway management techniques during intubation. NORA procedures referred to anesthetic care provided outside the conventional operating room environment, including interventional radiology suites, gastrointestinal endoscopy units, cardiac catheterization laboratories, and other procedural areas requiring anesthesia care. Airway management was performed according to routine clinical judgment rather than a standardized airway management protocol. Intubation attempts were performed by providers with varying levels of experience, including residents under supervision, attending anesthesiologists, and nurse anesthetists. Video laryngoscopy was available during the study period but was primarily used as a rescue or escalation device rather than as a routine first-line intubation technique. Only variables consistently available in both cases and controls were included in the analysis. Additional supporting data regarding study variables are available in the Supplementary Materials (Table S1). 2.7. Statistical Analysis Statistical analyses were performed using R version 4.3.1 (R Foundation for Statistical Computing, Vienna, Austria) [ 21]. Continuous variables are presented as medians with interquartile ranges and categorical variables as counts with percentages. Between-group comparisons were performed using Student’s t-test or Mann–Whitney U test for continuous variables and the chi-square test or Fisher’s exact test for categorical variables, as appropriate. Univariable logistic regression was used to explore associations between candidate variables and unanticipated difficult intubation. Variables selected based on clinical relevance and univariable screening were entered into a multivariable logistic regression model. Collinearity was assessed prior to model construction. Results are reported as odds ratios (ORs) with 95% confidence intervals (CIs). A two-sided p-value < 0.05 was considered statistically significant. Model discrimination was evaluated using the area under the receiver operating characteristic curve (AUC). Given the retrospective observational design and limited number of outcome events, all analyses should be interpreted as exploratory and hypothesis-generating rather than confirmatory or intended for predictive model development. Missing or undocumented variables were categorized as “unknown” where appropriate in descriptive analyses. Multivariable regression analyses were performed using complete case analysis without multiple imputation. Sample size considerations were performed to estimate the approximate number of cases required for exploratory association analysis and feasibility assessment in the setting of a relatively low institutional incidence of unanticipated difficult intubation. An assumed odds ratio of 2.5 was selected based on effect sizes reported in prior observational airway studies. Under these assumptions, approximately 70 cases and 280 controls were estimated to provide 80% power at a significance level of 0.05. 4. Discussion Unanticipated difficult intubation in this study was uncommon but clinically significant and occurred predominantly in patients without identifiable risk on routine preoperative assessment. This finding reinforces consistent evidence that commonly used bedside airway assessment tools have limited discriminative ability, particularly when applied in isolation [ 10, 19, 22, 23]. The similarity of most routinely documented preoperative airway assessment findings between groups, contrasted with the marked differences observed in laryngoscopic view, intubation attempts, and the need for escalation to video laryngoscopy, illustrates the mismatch highlighted in the study title. Large observational studies have similarly demonstrated that difficult intubation may arise despite apparently normal preoperative findings [ 4, 5], highlighting the limitations of current airway prediction strategies in routine clinical practice. Evidence from major airway audits further indicates that serious airway complications frequently occur in unanticipated scenarios and are influenced by human and system factors beyond anatomical predictors alone [ 9]. Collectively, these findings suggest that unanticipated difficult intubation should be viewed as an important patient safety issue that extends beyond the limitations of preoperative prediction alone. In the present study, intubation difficulty was primarily revealed intraoperatively, characterized by poor laryngoscopic visualization and the need for escalation of airway techniques. The marked predominance of Cormack–Lehane grade III–IV views and repeated intubation attempts underscores that clinically relevant intubation difficulty often becomes evident only at the point of laryngoscopy. This observation highlights the limitations of preoperative assessment alone in identifying all cases of difficult intubation. Male sex showed a trend toward increased risk but did not reach statistical significance. Previous evidence suggests that sex-related anatomical differences may contribute to intubation difficulty; however, its predictive value remains inconsistent and context-dependent, and should therefore be interpreted with caution [ 25]. Other variables, including tumor, prior head and neck radiation, metabolic abnormalities, and operator-related factors, were not independently associated with the outcome after adjustment. Resident involvement was not independently associated with unanticipated difficult intubation after adjustment; however, this finding should be interpreted cautiously given the exploratory nature of the analysis and the limited number of outcome events. The absence of statistically significant association for head and neck tumors or prior radiation exposure should not be interpreted as evidence of absence of effect, as these factors are well-recognized factors associated with difficult airway management in the previous literature. The present findings may instead reflect limited statistical power, interactions among variables, study-specific characteristics, or residual confounding inherent to retrospective observational analysis. These findings suggest that such factors may play a context-dependent rather than primary role, or that their effects are mitigated within structured clinical environments. Hypocalcemia and coagulopathy were included as exploratory perioperative variables because they may reflect severe systemic illness, trauma-related conditions, or physiological instability encountered during perioperative management. However, these variables are not established anatomical predictors of difficult intubation, and their observed associations should therefore be interpreted cautiously. Importantly, repeated intubation attempts in retrospective routine clinical practice may not exclusively reflect anatomical airway difficulty but may also be influenced by operator experience, device selection, situational urgency, and clinical context. Therefore, the observed difficult intubation events likely represent an interaction among anatomical, physiological, operator-related, and system-related factors rather than purely anatomical airway difficulty alone. In addition, videolaryngoscopy during the study period was primarily used as an escalation or rescue technique rather than a routine first-line device, which may have influenced intubation patterns and escalation pathways observed in the present study. The present study used a historical operational definition based primarily on repeated intubation attempts. Contemporary airway management concepts have evolved substantially and increasingly emphasize multidimensional airway difficulty, including physiological, situational, and human-factor components beyond anatomical intubation difficulty alone. Accordingly, the findings of the present study should be interpreted within the context of difficult tracheal intubation rather than the broader contemporary concept of difficult airway management. Despite identifying associated factors, the overall discriminative performance of the multivariable model was modest (AUC 0.685), emphasizing the inherent limitations of prediction in this setting. No single variable or combination of routinely available clinical factors appears sufficient for reliable identification of patients at risk. These findings underscore the importance of recognizing the limitations of routine bedside airway assessment and maintaining vigilance throughout airway management [ 27]. The reported AUC should be interpreted cautiously, as the present analysis was exploratory and not intended for predictive model development or clinical risk stratification. Given the retrospective observational design and relatively limited number of outcome events, the identified associations should be interpreted cautiously and considered exploratory and hypothesis-generating rather than causal. This study has several limitations. First, the retrospective design may introduce information bias and precludes causal inference. Second, airway assessment variables were derived from routine clinical documentation and may not have been assessed or recorded with complete standardization, potentially limiting the ability to capture subtle anatomical or physiological factors relevant to difficult intubation. Third, the unmatched observational design may permit residual confounding related to patient comorbidities, provider experience, surgical characteristics, and airway management strategy. Airway management was not standardized and reflected routine clinical practice. Variability in provider experience, airway device selection, and escalation strategies may therefore have influenced the observed outcomes independently of patient-related airway anatomy. Furthermore, this was a single-center study conducted in a tertiary teaching hospital, which may limit generalizability to other settings. Future prospective studies incorporating standardized airway assessment protocols, predefined documentation frameworks, and clearly defined airway management algorithms are warranted. Such studies may reduce information bias, improve consistency of data collection, and further clarify factors associated with unanticipated difficult intubation. Nonetheless, the large screened population and routine clinical setting provide clinically relevant insights into perioperative difficult intubation encountered in routine practice. Overall, these findings highlight the limitations of routine bedside airway assessment in reliably identifying all cases of intraoperative difficult intubation. While preoperative airway assessment remains an essential component of perioperative evaluation, routine bedside assessment alone may not reliably identify all patients who subsequently experience difficult intubation. 5. Conclusions Unanticipated difficult intubation is an uncommon but clinically important perioperative event. Although ASA physical status III and airway/neck/oral deformity were independently associated with unanticipated difficult intubation, most routinely documented preoperative airway assessment findings were similar between groups. These findings highlight the limitations of routine bedside airway assessment in identifying all patients who subsequently experience difficult intubation. While preoperative airway assessment remains an essential component of perioperative evaluation, it may not reliably identify all patients at risk of unanticipated difficult intubation. Supplementary Materials The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/healthcare14121619/s1, Table S1: Patient demographics and perioperative characteristics. Author Contributions Conceptualization, M.O. and P.B.; methodology, M.O.; software, M.O. and P.V.; validation, C.K. and Q.Y.; formal analysis, M.O.; investigation, Q.Y.; resources, P.V.; data curation, C.K., W.J. (Wilasinee Jitpakdee), N.D., W.J. (Wipharat Juthasantikul) and P.P.; writing—original draft preparation, C.K. and W.J. (Wilasinee Jitpakdee); writing—review and editing, C.K. and M.O.; visualization, M.O.; supervision, P.B.; project administration, M.O. All authors have read and agreed to the published version of the manuscript. Funding This research received no external funding. Institutional Review Board Statement The study was conducted in accordance with the Declaration of Helsinki, and approved by the Institutional Review Board of Faculty of Medicine, Prince of Songkla University (approval number 63-560-8-1) on 15 January 2021. Informed Consent Statement Patient consent was waived due to retrospective nature of the cohort study. Data Availability Statement The data presented in this study are available from the corresponding author upon reasonable request. The data are not publicly available due to privacy and ethical restrictions involving patient information. Conflicts of Interest The authors declare no conflicts of interest. Abbreviations The following abbreviations are used in this manuscript: ASA American Society of Anesthesiologists AUC Area under the curve CI Confidence interval IQR Interquartile range OR Odds ratio ROC Receiver operating characteristic References Lee, W.; Kim, H.; Kim, K.; Ro, Y.J.; Yang, H.S. Encountering unexpected difficult airway: Relationship with the intubation difficulty scale. Korean J. Anesthesiol. 2016, 69, 244–249. [] [ CrossRef] Crosby, E.T.; Cooper, R.M.; Douglas, M.J.; Doyle, D.J.; Hung, O.R.; Labrecque, P.; Muir, H.; Murphy, M.F.; Preston, R.; Rose, D.K.; et al. The unanticipated difficult airway with recommendations for management. Can. J. Anaesth. 1998, 45, 757–776. 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Baseline characteristics and preoperative airway assessment of the study population. Variables Unanticipated Difficult Intubation (n = 95) No Documented Intubation Difficulty (n = 429) p-Value Demographics Age (years), median (IQR) 54 (38.0–65.0) 52 (33.0–62.0) 0.262 Male sex 55 (57.9) 205 (47.8) 0.095 BMI (kg/m 2), median (IQR) 23.5 (19.3–26.2) 22.5 (19.1–25.7) 0.572 ASA physical status 0.015 - I 2 (2.1) 32 (7.5) - II 51 (53.7) 271 (63.2) - III 41 (43.2) 122 (28.4) - IV 1 (1.1) 4 (0.9) Airway-related conditions Airway/neck/oral deformity * 8 (8.4) 11 (2.6) 0.012 Tumor (airway-related) 12 (12.6) 39 (9.1) 0.389 History of head and neck radiation 3 (3.2) 4 (0.9) 0.116 OSA/snoring 15 (15.8) 66 (15.4) 1 Preoperative airway assessment Mallampati class III-IV 10 (10.5) 20 (4.7) 0.084 Thyromental distance < 3 FB 3 (3.2) 15 (3.5) 0.992 Inter-incisor gap < 3 cm 7 (7.4) 16 (3.7) 0.290 Limited neck mobility 3 (3.2) 8 (1.9) 0.241 Upper lip bite test class III 1 (1.1) 3 (0.7) 0.529 Perioperative factors Coagulopathy 1 (1.1) 2 (0.5) 0.452 Hypocalcemia 1 (1.1) 0 (0) 0.181 Surgical category 0.448 Non-operating room anesthesia (NORA) ** 13 (13.7) 53 (12.4) Neurosurgical/Orthopedic surgery 6 (6.3) 39 (9.1) Ophthalmic/Minor superficial surgery 12 (12.6) 75 (17.5) Otolaryngology (ENT) surgery 31 (32.6) 153 (35.7) Thoracic/Vascular surgery 11 (11.6) 33 (7.7) Abdominal surgery 22 (23.2) 76 (17.7) Data are presented as numbers (%); unless otherwise indicated. ASA, American Society of Anesthesiologists; BMI, body mass index; OSA, obstructive sleep apnea; IQR, interquartile range. * Airway/neck/oral deformity included clinically documented structural abnormalities potentially affecting airway alignment or visualization. ** NORA refers to procedures performed outside the conventional operating room environment, including interventional radiology suites, gastrointestinal endoscopy units, cardiac catheterization laboratories, and other procedural areas requiring anesthesia care. Table 2. Intraoperative airway management and laryngoscopic findings. Table 2. Intraoperative airway management and laryngoscopic findings. Variables Unanticipated Difficult Intubation (n = 95) No Documented Intubation Difficulty (n = 429) p-Value Laryngoscopic view (Cormack–Lehane) <0.001 - Grade I-II 23 (24.2) 407 (94.9) - Grade III-IV 71 (74.8) 13 (3.0) - Not recorded 1 (1.1) 9 (2.1) Airway difficulty and attempts Intubation attempts, median (IQR) 4 (3.0–5.0) 1 (1.0–1.0) <0.001 Airway device use <0.001 - Direct laryngoscopy 18 (18.9) 401 (93.5) - Video laryngoscopy 71 (74.7) 23 (5.4) - Advanced/rescue technique * 6 (6.3) 5 (1.2) Provider characteristics First-attempt provider (resident) 70 (73.7) 268 (62.5) 0.106 Experience < 5 years 90 (94.7) 400 (93.2) 0.631 Airway-related complications Emergency tracheostomy 1 (1.1) 1 (0.2) 0.331 Data are presented as numbers (%); unless otherwise indicated. IQR, interquartile range. * Advanced/rescue techniques include supraglottic airway devices, fiberoptic intubation, and other alternative airway strategies. Table 3. Multivariable logistic regression analysis of factors associated with unanticipated difficult intubation. Table 3. Multivariable logistic regression analysis of factors associated with unanticipated difficult intubation. Variable Adjusted OR (95% CI) p-Value ASA physical status III (vs. I–II) 4.85 (1.06–22.12) 0.042 Airway/neck/oral deformity 4.09 (1.43–11.66) 0.009 Male sex 1.56 (0.97–2.53) 0.069 Tumor (airway-related) 1.99 (0.88–4.54) 0.100 History of head and neck radiation 3.85 (0.75–19.80) 0.106 Coagulopathy or hypocalcemia 4.99 (0.58–43.20) 0.145 Resident as first-attempt provider 1.57 (0.93–2.66) 0.094 OR = odds ratio, CI = confidence interval. Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content. © 2026 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license. Share and Cite MDPI and ACS Style Kitsiripant, C.; Jitpakdee, W.; Oofuvong, M.; Benjawaleemas, P.; Dilokrattanaphichit, N.; Juthasantikul, W.; Phakam, P.; Yunuswangsa, Q.; Vichitkunakorn, P. Mismatch Between Preoperative Airway Assessment and Unanticipated Difficult Tracheal Intubation: A Retrospective Case–Control Study. Healthcare 2026, 14, 1619. https://doi.org/10.3390/healthcare14121619 AMA Style Kitsiripant C, Jitpakdee W, Oofuvong M, Benjawaleemas P, Dilokrattanaphichit N, Juthasantikul W, Phakam P, Yunuswangsa Q, Vichitkunakorn P. Mismatch Between Preoperative Airway Assessment and Unanticipated Difficult Tracheal Intubation: A Retrospective Case–Control Study. Healthcare. 2026; 14(12):1619. https://doi.org/10.3390/healthcare14121619 Chicago/Turabian Style Kitsiripant, Chanatthee, Wilasinee Jitpakdee, Maliwan Oofuvong, Pannawit Benjawaleemas, Nussara Dilokrattanaphichit, Wipharat Juthasantikul, Pannipa Phakam, Qistina Yunuswangsa, and Polathep Vichitkunakorn. 2026. "Mismatch Between Preoperative Airway Assessment and Unanticipated Difficult Tracheal Intubation: A Retrospective Case–Control Study" Healthcare 14, no. 12: 1619. https://doi.org/10.3390/healthcare14121619 APA Style Kitsiripant, C., Jitpakdee, W., Oofuvong, M., Benjawaleemas, P., Dilokrattanaphichit, N., Juthasantikul, W., Phakam, P., Yunuswangsa, Q., & Vichitkunakorn, P. (2026). Mismatch Between Preoperative Airway Assessment and Unanticipated Difficult Tracheal Intubation: A Retrospective Case–Control Study. 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