Bag-mask ventilation is a fundamental skill in airway management. Nearly all patients undergoing general anaesthesia require bag-mask ventilation for a period after the induction of intentional apnoea. It is considered one of the safest and least invasive modes of ventilation, serving both as a means of pre-oxygenation during induction and as a bridge to definitive airway establishment. Outside the operating room, effective bag-mask ventilation is also essential in situations such as cardiac arrest, trauma resuscitation, and emergency care. Inadequate ventilation may result in insufficient oxygenation and hypoxia, which in turn can lead to irreversible hypoxic–ischaemic brain injury [1]. Proper positioning is critical for effective bag-mask ventilation. In 1936, Sir Ivan Magill recommended the sniffing position to optimise laryngeal exposure during direct laryngoscopy [2]. This position combines flexion of the neck on the chest (~35°) with extension at the atlantoaxial joint (~15°), theoretically aligning the oral, pharyngeal, and laryngeal axes to facilitate visualisation of the glottis and easier intubation. Predicting the likelihood of difficult mask ventilation and intubation is equally important. Factors associated with increased difficulty include obesity, advanced age, edentulous state, reduced neck mobility, short neck, higher Mallampati score, and airway obstruction. Early recognition of these predictors allows anaesthesiologists to anticipate challenges and prepare appropriate strategies. Several mask ventilation techniques have been described [4–6]. • One-hand C–E technique (conventional technique): The non-dominant hand forms a “C” with the thumb and index finger placed around the mask, applying downward pressure, while the middle, ring, and little fingers perform mandibular lift, resembling an “E.” • Two-hand C–E technique: Both hands are used to form a seal, with the thumbs and index fingers encircling the mask while the remaining fingers provide mandibular lift. Ventilation is performed by an assistant. • Thenar eminence (TE) technique: Both thenar eminences press downward on the mask while the four fingers of each hand pull the jaw upwards towards the mask. Although effective, this may cause airway obstruction at the oropharyngeal level, which can be overcome by using an oropharyngeal airway. A modified thenar eminence (MTE) technique has been proposed to improve mask ventilation during induction of general anaesthesia. In this approach, the thumbs oppose the mask at the level of the chin to facilitate mouth opening, while the thenar eminences maintain mask seal. The middle, ring, and little fingers pull the mandible forwards and upwards, thereby avoiding chin lift and maintaining airway patency. This technique combines the advantages of a two-hand seal with reduced risk of airway compression. Conventional teaching recommends the one-hand C–E technique as the first-line method, escalating to a two-hand technique if ventilation remains inadequate. However, even two-hand methods may not consistently achieve adequate tidal volumes due to air leaks, airway compression, or submandibular pressure. Modifications such as the thenar eminence technique have therefore been explored. While several manikin-based studies have compared the C–E and TE techniques, results remain conflicting. Importantly, limited clinical studies have evaluated these techniques in real patient populations. The primary objective of the present study was to compare the efficacy of conventional mask ventilation with the modified thenar eminence technique during induction of general anaesthesia, measured by expired tidal volume (VTe) within the first minute following administration of a muscle relaxant. The secondary objectives were to compare peak airway pressure (Pmax), end-tidal carbon dioxide (ETCO₂), and oxygen saturation (SpO₂) between the two techniques.

Study Design: This was a hospital-based prospective observational study. Study Setting and Duration: The study was conducted in the Department of Anaesthesiology, Government Medical College, Thiruvananthapuram, after obtaining approval from the Institutional Ethics Committee (IEC). Data collection was carried out over a period of 12 months. Study Population: The study included adult patients scheduled for elective surgeries under general anaesthesia in the Department of Anaesthesiology. Inclusion Criteria: Patients aged 18–55 years. Patients belonging to ASA physical status I–III. Patients providing written informed consent. Exclusion Criteria: Patients unwilling to participate. Patients with a known allergy to any of the study drugs. Sample Size: Sample size was calculated using the formula: N=((Z_(α/2)+Z_(1-β) )^2 (S_1^2+S_2^2))/(("µ" _1-"µ" _2 )^2 ) At 90% confidence interval and 90% power: α = 0.05, Z_(1-α/2)= 1.96 β = 0.10, Z_(1-β)= 1.28 S_1(SD of expired tidal volume, modified thenar eminence) = 55 S_2(SD of expired tidal volume, conventional technique) = 50 "µ" _1= 370, "µ" _2= 313 Substituting the values: Sample size = 18 per group. However, a total of 110 participants were recruited, as mask ventilation was routinely performed during induction of general anaesthesia. Sampling Technique: All consecutive eligible patients were included until the required sample size was achieved. Study Variables: Exposure variables: Gender, ASA physical status, Mallampati score, age, BMI, height, weight. Outcome variables: Expired tidal volume (VTe), peak airway pressure (Pmax), end-tidal carbon dioxide (ETCO₂), oxygen saturation (SpO₂), and ease of ventilation. Study Procedure: After pre-anaesthetic evaluation, fasting guidelines were followed, and oral premedication was administered as per protocol. On the day of surgery, patients were randomly allocated into two groups: Group C: Mask ventilation using the conventional E–C technique. Group M: Mask ventilation using the modified thenar eminence (MTE) technique. Standard ASA monitors (ECG, pulse oximetry, non-invasive blood pressure) were applied, and baseline vitals were recorded. Patients were preoxygenated with 100% oxygen at 10 L/min for 3 minutes. Anaesthesia induction was achieved with propofol 2 mg/kg IV, followed by lignocaine 2 mg/kg IV and rocuronium 1 mg/kg IV. In both groups, patients were positioned in the sniffing position with head extension and jaw thrust applied. In Group C, ventilation was performed using the one-hand E–C technique. In Group M, the modified thenar eminence technique was applied. In this method, both thumbs were placed over the lower jaw to open the mouth, while the thenar eminences secured the mask on the face. The remaining fingers provided mandibular lift without chin lift, thereby maintaining mouth opening and ensuring a tight mask seal. Initial breaths were allowed to stabilise tidal volumes. Parameters (VTe, Pmax, ETCO₂, SpO₂) were recorded over five consecutive breaths, and the average was taken for analysis. Ease of ventilation was assessed using a Likert scale: Easy (1), Moderate (2), and Difficult (3). Data Collection and Analysis: Data were collected using a structured proforma. Statistical analysis was performed using SPSS version 27 (Chicago, USA). Categorical variables were presented as frequencies and proportions, while continuous variables were expressed as mean ± standard deviation. The chi-square test was used for categorical comparisons, and the independent t-test was used for quantitative variables. A p-value <0.05 was considered statistically significant. Ethical Considerations: Approval from the Institutional Ethics Committee was obtained prior to study initiation. Written informed consent was obtained from all participants. Privacy and confidentiality were strictly maintained. No additional financial burden was placed on the patients.

A total of 110 patients were enrolled; however, data from 5 patients were incomplete, leaving 105 patients (Group C = 50, Group M = 55) for analysis. Table 1. Baseline Characteristics of Participants Variable Group C (n=50) Group M (n=55) Test statistic p-value Age (years), Mean ± SD 45.85 ± 9.45 47.10 ± 10.88 t = 1.082 >0.05 Age group <30 / 30–50 / >50 15 (30.0%) / 23 (46.0%) / 12 (24.0%) 12 (21.8%) / 27 (49.1%) / 16 (29.1%) χ² = 1.524 >0.05 Gender (Male:Female) 36:14 (72.0%:28.0%) 32:23 (58.2%:41.8%) χ² = 3.485 >0.05 ASA-PS I / II / III / IV 23/17/7/3 25/18/9/3 χ² = 2.984 >0.05 Presence of comorbidities 26 (52.0%) 33 (60.0%) χ² = 0.876 >0.05 The baseline demographic and clinical variables were comparable between the two groups. The mean age of participants was 45.85 ± 9.45 years in Group C and 47.10 ± 10.88 years in Group M, with no statistically significant difference (t = 1.082, p > 0.05). Gender distribution showed a predominance of males in both groups (72.0% in Group C vs. 58.2% in Group M), but the difference was not statistically significant (χ² = 3.485, p > 0.05). ASA physical status classification was also similar, with nearly half of patients in ASA I (46.0% in Group C and 45.5% in Group M), and a small proportion in ASA IV (6.0% and 5.5% respectively). Comorbidities were present in 52.0% of Group C and 60.0% of Group M, with no significant difference (χ² = 0.876, p > 0.05). These findings confirm that the two groups were homogeneous at baseline, eliminating confounding bias. Table 2. Distribution of Comorbidities Comorbidity Group C (n=50) Group M (n=55) Type 2 Diabetes Mellitus (T2DM) 3 (6.0%) 7 (12.7%) Hypertension + T2DM 10 (20.0%) 8 (14.5%) T2DM + HTN + COPD 1 (2.0%) 1 (1.8%) T2DM + HTN + CAD 1 (2.0%) 3 (5.5%) Hypothyroidism (± T2DM) 2 (4.0%) 2 (3.6%) Other multiple comorbidities 8 (16.0%) 12 (21.8%) None 24 (48.0%) 22 (40.0%) The spectrum of comorbidities was broadly similar between the groups. Type 2 diabetes mellitus (T2DM) was the most frequent comorbidity, observed in 6.0% of Group C and 12.7% of Group M participants. Hypertension in combination with T2DM was also common (20.0% in Group C vs. 14.5% in Group M). Other conditions such as hypothyroidism, COPD, dyslipidaemia, and coronary artery disease were reported in both groups, often in combination with diabetes or hypertension. Notably, nearly half of Group C (48.0%) and 40.0% of Group M had no comorbid illnesses. Statistical comparison revealed no significant difference in the overall distribution of comorbidities (χ² = 0.876, p > 0.05), indicating that systemic illness burden was similar across groups. Table 3. Comparison of Expired Tidal Volume (VTe) VTe (mL) Group C (n=50) Group M (n=55) 455–460 19 (38.0%) 12 (21.8%) 461–465 4 (8.0%) 5 (9.1%) 466–470 17 (34.0%) 11 (20.0%) >470 10 (20.0%) 27 (49.1%) Mean ± SD 464.6 ± 6.44 469.9 ± 7.89 t value –5.081 p < 0.01 Expired tidal volume showed a clear and significant difference between groups. In Group C, the majority of participants (38.0%) had VTe in the range of 455–460 mL, and only 20.0% achieved values greater than 470 mL. In contrast, almost half of Group M (49.1%) recorded VTe >470 mL, while 21.8% fell in the 455–460 mL range. The mean expired tidal volume was 464.6 ± 6.44 mL in Group C compared with 469.9 ± 7.89 mL in Group M. This difference was statistically significant (t = –5.081, p < 0.01), confirming that the modified thenar eminence technique provided superior ventilation in terms of tidal volume delivered. Table 4. Comparison of Ventilatory Parameters (Pmax, ETCO₂, SpO₂) Parameter Group C (Mean ± SD) Group M (Mean ± SD) t value Pmax (cm H₂O) 18.32 ± 3.86 19.87 ± 4.08 –3.318 ETCO₂ (mmHg) 30.47 ± 2.95 32.17 ± 2.64 –4.974 SpO₂ (%) 98.17 ± 1.59 98.71 ± 1.42 –3.622 Additional ventilatory parameters also showed better outcomes with the modified thenar eminence technique. The mean peak airway pressure (Pmax) was slightly higher in Group M (19.87 ± 4.08 cm H₂O) compared to Group C (18.32 ± 3.86 cm H₂O), and this difference reached statistical significance (t = –3.318, p < 0.05). End-tidal CO₂ (ETCO₂) values were significantly greater in Group M (32.17 ± 2.64 mmHg) than in Group C (30.47 ± 2.95 mmHg) (t = –4.974, p < 0.01), suggesting more effective alveolar ventilation. Oxygen saturation (SpO₂) also showed a favourable profile, with Group M averaging 98.71 ± 1.42% compared to 98.17 ± 1.59% in Group C (t = –3.622, p < 0.05). Together, these findings highlight that the modified technique not only improved tidal volume but also enhanced oxygenation and ventilation efficiency. Table 5. Summary of Key Outcomes Outcome Group C (n=50) Group M (n=55) p-value Mean VTe (mL) 464.6 ± 6.44 469.9 ± 7.89 <0.01 % with VTe >470 mL 20.0% 49.1% <0.05 Mean Pmax (cm H₂O) 18.32 ± 3.86 19.87 ± 4.08 <0.05 Mean ETCO₂ (mmHg) 30.47 ± 2.95 32.17 ± 2.64 <0.01 Mean Pmax (cm H₂O) 18.32 ± 3.86 19.87 ± 4.08 <0.05 Mean ETCO₂ (mmHg) 30.47 ± 2.95 32.17 ± 2.64 <0.01 SpO₂ ≥ 98% 64.0% 80.0% <0.05 The consolidated outcome analysis underscores the superiority of the modified thenar eminence technique. Nearly half of Group M (49.1%) achieved VTe >470 mL compared with just 20.0% in Group C (p < 0.05). Mean expired tidal volume was significantly higher in Group M (469.9 ± 7.89 mL) than in Group C (464.6 ± 6.44 mL) (p < 0.01). Pmax and ETCO₂ values were also higher in Group M, both reaching statistical significance (p < 0.05 and p < 0.01 respectively). Oxygen saturation ≥98% was recorded in 80.0% of Group M compared to 64.0% of Group C (p < 0.05). These results collectively establish that the modified thenar eminence technique yields superior ventilatory outcomes. The bar chart (Fig. 1) visually depicts the proportion of patients achieving VTe >470 mL in both groups. Only 20.0% of participants in Group C exceeded this threshold, compared with 49.1% in Group M. This marked difference highlights the clinical advantage of the modified thenar eminence technique in achieving higher expired tidal volumes during mask ventilation. The graphical representation strengthens the statistical findings, making the outcome differences readily apparent.49.1%

The present prospective observational study compared the efficacy of conventional mask ventilation (E–C technique) with the modified thenar eminence (MTE) technique during induction of general anaesthesia. The primary outcome measured was expired tidal volume (VTe), while secondary outcomes included peak airway pressure (Pmax), end-tidal carbon dioxide (ETCO₂), oxygen saturation (SpO₂), and ease of ventilation. The results demonstrated that the MTE technique produced significantly higher expired tidal volumes than the conventional E–C technique. Nearly half of the participants in Group M achieved VTe values above 470 mL compared to only 20% in Group C. The mean VTe was 469.9 ± 7.9 mL with the MTE technique versus 464.6 ± 6.4 mL with the E–C technique, a statistically significant difference. These findings highlight the superiority of the MTE technique in achieving greater ventilatory efficiency. Secondary outcomes further reinforced this trend. Pmax was slightly but significantly higher in Group M (19.9 ± 4.1 cm H₂O) compared to Group C (18.3 ± 3.9 cm H₂O). Similarly, ETCO₂ values were higher in Group M (32.2 ± 2.6 mmHg) than in Group C (30.5 ± 3.0 mmHg). Oxygenation was also better maintained in Group M, with 80% of participants achieving SpO₂ ≥ 98% compared to 64% in Group C. These results suggest that the modified technique not only improves tidal volume delivery but also contributes to more effective alveolar ventilation and oxygenation. Our findings are in agreement with previous studies. Appukuttan et al. [11] in a randomized cross-over trial found that the MTE technique provided a significantly higher expired tidal volume compared with the conventional technique (370 mL vs. 313 mL, p = 0.01). Similarly, Bharadwaj et al. [12] reported higher VTe values with the V–E (two-hand thenar eminence) technique compared to the C–E technique in obese patients, with mean values of 702 mL and 492 mL respectively (p ≤ 0.001). Fei et al. [13], in a study on obese apnoeic adults, demonstrated significantly greater VTe with the V–E technique (720 mL) compared to the C–E technique (371 mL, p < 0.001). Joffe et al. [14] also observed that two-handed techniques (including jaw thrust and TE) provided superior ventilation compared to single-handed methods. The mechanism underlying the effectiveness of the MTE technique may be explained by its ability to maintain airway patency. By combining firm mask seal with forward and upward mandibular displacement while keeping the mouth open, the technique increases retrolingual and retropalatal cross-sectional areas. This reduces airway resistance, minimises air leaks, and enhances gas exchange, explaining the observed improvements in VTe, ETCO₂, and SpO₂.

This prospective observational study confirms that the modified thenar eminence technique of mask ventilation is more effective than the conventional E–C technique during induction of general anaesthesia. The MTE technique yielded significantly higher expired tidal volumes, improved oxygenation, and better alveolar ventilation as indicated by higher ETCO₂ levels. It also provided favourable airway pressures and ease of ventilation. Given its advantages, the modified thenar eminence technique may be recommended as a reliable alternative to conventional mask ventilation, particularly in situations where adequate tidal volume is difficult to achieve. The study was limited to elective surgical patients without predictors of difficult airway. Patients were paralysed and studied under controlled conditions, which may not fully represent emergency or trauma scenarios. The study population included only adults with a normal body mass index, excluding paediatric and geriatric patients. Additionally, as an observational design, the study cannot establish causal relationships.

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