Nigerian Journal of Basic and Clinical Sciences

: 2022  |  Volume : 19  |  Issue : 1  |  Page : 34--38

Success rate of endotracheal intubation: A comparison of direct laryngoscopy and intubating laryngeal mask airway

Usman Nasir1, Salahu Dalhat2, Mamuda Atiku2, Abdullahi Mustapha2, Adesope Saheed2, Ahmad Adam3, Abdullahi Mohammad2, Ahmed Ado2,  
1 Department of Anaesthesia, Abubakar Tafawa Balewa University, Bauchi, Nigeria
2 Department of Anaesthesia, Aminu Kano Teaching Hospital, Kano, Nigeria
3 Department of Anaesthesia, Turai Umar Yaradua Maternity and Children Hospital, Katsina, Nigeria

Correspondence Address:
Dr. Salahu Dalhat
Department of Anaesthesia, Aminu Kano Teaching Hospital, Kano


Context: Direct laryngoscopy (DL) remains the most popular method of endotracheal intubation despite the availability of easier methods like intubating laryngeal mask airway (ILMA)—a blind intubation aid with a high success rate of intubation even when employed by novices. Aim: This study compared the overall success rate of intubation using ILMA and DL during elective surgeries requiring intubation. Study Design: This was a comparative randomized study. Patients and Methods: Following the institutional ethical approval, 86 American Society of Anaesthesiologists physical status (ASA) I and II patients were randomized into DL and ILMA groups. Each received intravenous fentanyl 2 μg/kg, glycopyrrolate 4 μg/kg, intravenous propofol 3 mg/kg, suxamethonium 2 mg/kg to a maximum of 100 mg. Intubation was with DL in the first group and ILMA in the second group. Anesthesia was maintained with isoflurane and muscle relaxation with atracurium. The overall success rate, the success rate at the first attempt of intubation, time for intubation, and airway complications were assessed. Statistical analysis: Data were analyzed using the Statistical Package for Social Sciences (SPSS) version 21.0. The quantitative variables were analyzed using the Student's t-test and qualitative using the Chi-square test. A P value less than 0.05 was considered significant. Results: The success at insertion was 100% in the DL group and 95.3% with ILMA at the first attempt (P = 0.15). The success rate of intubation at the first attempt was 100 and 79.1% in the DL and ILMA groups, respectively. The mean time for intubation was 19.93 ± 6.17 and 46.54 ± 11.63 s in DL and ILMA, respectively (P = 0.001). Six patients (14%) had airway complications in the ILMA group. Conclusion: The overall success rate of intubation via ILMA is comparable to that of DL. In patients with normal airways, DL remains a comparatively faster and easier technique to secure the airway with tracheal intubation than ILMA.

How to cite this article:
Nasir U, Dalhat S, Atiku M, Mustapha A, Saheed A, Adam A, Mohammad A, Ado A. Success rate of endotracheal intubation: A comparison of direct laryngoscopy and intubating laryngeal mask airway.Niger J Basic Clin Sci 2022;19:34-38

How to cite this URL:
Nasir U, Dalhat S, Atiku M, Mustapha A, Saheed A, Adam A, Mohammad A, Ado A. Success rate of endotracheal intubation: A comparison of direct laryngoscopy and intubating laryngeal mask airway. Niger J Basic Clin Sci [serial online] 2022 [cited 2023 Feb 5 ];19:34-38
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Full Text


Endotracheal intubation, the optimal method of securing the airway, has had different ways by which it can be achieved. Over the years, direct laryngoscopy (DL) and intubation have been widely accepted and practiced. They have relatively become the “yardstick” over which other intubation techniques are measured. This is despite the fact that seemingly “easier and safer” techniques like the use of intubating laryngeal mask airway (ILMA), the I-gel, laryngeal mask airway (LMA) CTrach, Airtraq (an airway device that incorporates an LCD screen, a fiberoptic feature, and a disposable plastic blade) exist.[1],[2]

The first direct visualization of the vocal cords was performed by Alfred Kirstein of Germany in 1895. He used an esophagoscope which he had modified for that purpose and called it the “autoscope”.[3] Jackson Chevalier and Janeway Henry independently were instrumental in modifying the laryngoscope and popularizing the widespread use of DL.[3],[4]

The introduction of the LMA into modern anesthetic practice in 1987 represented a major advancement in airway management. It is an airway and ventilator device. It is midway in design between the facemask and the endotracheal tube.[5] The LMA offers an alternative and has become a means of securing the airway during a resuscitation although it does not offer full protection against regurgitation and aspiration.

Following the success of the classic LMA, a newer modification called the ILMA was introduced in 1997 with some superior features that give it an edge at achieving intubation, including an anatomically curved rigid airway tube, a rigid handle/guiding ramp, and an epiglottic elevator,[2] and has since been accepted for use in difficult airways.[6] The use of ILMA for intubation eliminates the need for head and neck? manipulation, thus, giving it an edge over rigid laryngoscopy, especially in cases of unsuspected, suspected, or confirmed c-spine injury, and hence, a reduced risk of complete transection of the spinal cord during use.

An impaired vision at laryngoscopy due to blood or secretions unlike in DL may not deter intubation when using ILMA as it is a blind procedure and does not require visualization of the glottis.[7] However, DL has the advantage of direct glottis visualization, and hence, visualization of the endotracheal tube (ETT) passing in between the vocal cords, thus confirming tube placement, so also blood and secretions altering view at DL could be suctioned and cleared to improve the view.

The ILMA is said to be easier to insert and also has a high success rate with a better learning curve as against rigid laryngoscopy.[3],[8] The success rate of intubation via the ILMA in first-time users of the device is high as seen in the study by Malhotra et al.,[9] who reported a 91.6% ILMA intubation success rate in their study. Another study by Nileshwar et al.[10] found a 74.2% (23/31) success rate in the first or second attempt at intubation with the use of ILMA. The ILMA has been incorporated into the difficult airway algorithm and has been used with great success in cases of a difficult airway.[11],[12]

Despite the high success rate for intubation while using ILMA, its better learning curve, its usefulness in patients with c-spine injury, and its usefulness for intubating patients with difficult airways, the use of ILMA to achieve intubation is still not widely practiced. This study, therefore, compared the success rate of the frequently used DL for achieving endotracheal intubation with that of ILMA.

 Patients and Methods

Eighty-six ASA I and II patients aged between 18 and 50 years scheduled for elective surgeries requiring general anesthesia with endotracheal intubation and relaxant technique at a tertiary institution were included in this prospective randomized study. The hospital's ethical committee clearance was obtained (ref no. AKTH/MAC/SUB/12A/P3/VI/2238). The study lasted over 7 months and all the patients who participated in the study had the informed consent signed. The patients with anticipated or confirmed difficult airway, obesity ( Body Mass Index (BMI) >30 kg/m2), risk of vomiting and/or aspiration, and full stomach were excluded from the study.

The patients enrolled in the study were randomly allocated to one of the two groups by a research assistant. Eighty-six (86) pieces of uniformly sized sheets of paper were labeled group A (DL) or group B (ILMA) with 43 each representing the two study groups. These papers were folded and shuffled in a large box. Each patient was made to pick one folded sheet of paper from the box and hand it over to the research assistant (a designated resident doctor). The investigator was blinded at this point.

The patients were reviewed a day before surgery. History and a thorough physical examination including an airway assessment were carried out. The patient's age, sex, weight, height, and other demographic parameters were recorded, and the available baseline investigations were reviewed including full blood count (FBC) and serum electrolytes. The patients were each assigned a physical status using the ASA classification

Informed consent was obtained and the patients were instructed to fast according to the ASA fasting guidelines.

In the theater, an anesthetic machine safety checklist was performed. The resuscitation equipment and drugs were made readily available. On arrival of the patient in the operating room, each patient was positioned supine on the operating table and connected to a multi-parameter patient monitor and the baseline vital signs (non-invasive systolic, diastolic, and mean arterial blood pressures, heart rate, respiratory rate, arterial saturation of oxygen, and electrocardiograph) were recorded. An intravenous access was secured using a size 16 G cannula for fluid and drug administration. Intravenous fentanyl 2 μg/kg and intravenous glycopyrrolate 4 μg/kg were administered 4 min before induction, and the patient was pre-oxygenated for 5 min. Intravenous propofol 3 mg/kg, followed by suxamethonium 2 mg/kg to a maximum of 100 mg was used for induction and to facilitate intubation, respectively. The airway management in both groups was carried out by a single investigator who was experienced and proficiently trained, while the research assistant (a dedicated resident doctor) was responsible for carrying out the timing and other entries on the data collection form.

In the DL group, after achieving loss of verbal communication and jaw relaxation, with the head and neck in the sniffing position, the patient's mouth was opened as wide as possible using the scissors technique, and DL was performed with size 3 or 4 Macintosh laryngoscope and intubation was achieved with a polyvinyl chloride (PVC)-cuffed endotracheal tube of appropriate size (size 7.0 or 7.5 mm for females, and size 8.0 or 8.5 mm for males), as this would increase the chances of successful intubation and decrease the incidence of airway trauma. Intubation was regarded as successful if there was adequate chest movement and capnographic confirmation.

In the ILMA group, an appropriately sized ILMA (size 4 for those weighing more than 75 kg, size 3 for those weighing less than 75 kg) was selected and cuff checked for leaks and deflated completely against a hard surface. KY-jelly was applied to the convex surface of the mask. After achieving loss of verbal communication and jaw relaxation, with the head and neck in a neutral position, the ILMA was inserted using the standard technique as follows: The handle was held and inserted into the patient's mouth, then pushed against the hard palate and posterior pharyngeal wall, following the curve of the tube and the arc of the palate, until it was in position and the was cuff inflated with 20–30 mL of air (size 3: 20 mL; size 4: 30 mL).

The successful placement was adjudged by the ventilatory ability including adequate chest wall movement and capnography during manually assisted ventilation. If the airway patency was not maintained, the adjustment of ILMA as well as the patient's head was carried out. This was followed by the insertion of lubricated customized size 7.0, 7.5, or 8.0 mm straight-cuffed silicone endotracheal tube via the ILMA gently without applying undue force. If no resistance was felt, the cuff was inflated and the breathing circuit was reconnected.

If resistance was felt, the ILMA was adjusted using the following maneuvers: pull-up or push-down, rightward or leftward rotation, or even change to another ILMA size, and these were recorded in the proforma as markers of difficulty. Capnographic confirmation of the tracheal tube placement was done. Then, the ILMA was removed over the endotracheal tube and air entry with the endotracheal tube was reaffirmed. When tracheal intubation was not achieved after three attempts, the patients were intubated with conventional DL.

During intubation, a maximum of three attempts were allowed and a maximum limit of 90 s from picking the device to connecting the Endotracheal tube (ETT) to the anesthetic machine was allowed for each attempt, monitored by the research assistant using a stopwatch.

In both the study groups, anesthesia was maintained with 33% oxygen in the air with isoflurane 1–2% mixture; intravenous atracurium 0.5 mg/kg was used as a muscle relaxant with top-up doses at 30-min intervals. At the end of the surgery, the posterior pharynx was gently suctioned, the residual neuromuscular blockade was reversed with a mixture of intravenous glycopyrrolate 10 μg/kg and neostigmine (0.05 mg/kg), and with the return of airway protective reflexes and swallowing reflex, the patient was extubated.

The ease of intubation was assessed by recording the number of attempts required to intubate the patient's trachea and the degree of manipulation needed to achieve the intubation. The time taken for intubation was defined as the time interval between the introduction of the device (ILMA or laryngoscope) into the patient's mouth and confirmed successful tracheal tube placement. This was measured by the research assistant using a stopwatch.

The data obtained were analyzed using the Statistical Package for Social Sciences (SPSS) version 21.0 manufactured by IBM and headquartered in Armonk, New York. The quantitative variables were summarized using measures of central tendency (mean) and measures of variation (standard deviation) and were analyzed using Student's t-test. The qualitative variables were analyzed using the Chi-square test and summarized as frequencies and percentages. P values less than 0.05 were considered statistically significant.


Eighty-six ASA I and II patients between the ages of 18 and 50 years, who had consented to elective surgeries requiring general anesthesia with endotracheal intubation and relaxant technique, were studied.

[Table 1] represents the demographic and physical profile of the patients in the two groups and the results are comparable. Overall, the mean age was 35.71 ± 9.25 (mean ± standard deviation), while the mean age in the DL group was 36.95 ± 9.22 years, the mean age in the ILMA group was 34.47 ± 9.22 years, P: 0.214. The mean BMI in the DL group was 25.90 ± 1.75 and 26.48 ± 2.06 in the ILMA group with P = 0.167. The male to female ratio was 46:40 (P = 0.665). The patients who had Mallampati I or II and ASA I or II were comparable in the two groups with P values of 0.665 and 0.372, respectively.{Table 1}

In [Table 2], the number of attempts before successful device insertion is shown. There was a 100% (all 43 patients) success at insertion in the DL group, and 95.3% (41 patients) with ILMA insertion at the first attempt. The remaining 4.7% (two patients) in the ILMA group achieved success on the second attempt. The P value was 0.152, hence, the two groups are comparable.{Table 2}

The number of attempts before intubation as presented in [Table 3] shows a 100% (all 43 patients) success rate of intubation at the first attempt using the DL compared to 79.1% (34 patients) while using the ILMA. The remaining 20.9% (9 patients) were successfully intubated at the second attempt, with a statistically significant P value of 0.002.{Table 3}

The incidence of airway complications was noted to be more in the ILMA group (14%, six patients), with all being airway trauma. The DL group had no complications recorded [Table 4] which was statistically significant (P = 0.002). This is shown in [Figure 1].{Table 4}{Figure 1}


This study was designed to compare DL and ILMA regarding the success of each device during the use and safety, taking into cognizance the time taken to intubate, the number of attempts before intubation, the first-attempt success rate at intubation, and overall success rate at intubation.

The results from this study show that the mean time taken for intubation was significantly longer in the ILMA group (46.54 ± 11.63 s) when compared with the DL group (19.93 ± 6.17 s). This trend in the intubation time was reported in another study under a similar setting as in this study. Kavitha et al.[13] compared the intubating condition and hemodynamics in the patients who had general anesthesia and were intubated with either an ILMA or standard DL. They found a significantly increased intubation time in their ILMA group (63.66 ± 14.10 s) when compared with the DL group (21.63 ± 3.61 s), with P values >0.05. Unlike in our study, where airway management was carried out by a single experienced investigator, the Kavitha et al.[13] study, however, did not indicate the level of experience of their investigator which could have affected their outcome.

Studies have also compared similar airway devices alongside others and yielded similar results. Kim YY et al.,[14] in addition to the ILMA and DL, also studied I-gel and Air-Q as intubation aids under simulated manikin studies. Their ILMA group still showed the longest intubation time among all four devices with a P value of 0.0083. The prolonged intubation time with ILMA could be explained by the fact that the ILMA-guided blind intubation process consists of three steps including insertion and confirmation of the ILMA position, insertion, and confirmation of the endotracheal tube placement, and then finally, the removal of the ILMA. All these are time-consuming as compared to the use of DL for intubation. It also could be attributed to the fact that the investigator in this study was proficiently trained with DL and has more experience with DL for intubation than with ILMA.

The overall success rate in this study was 100% in both groups making the two devices comparable in that aspect. This may be in part due to the thorough airway assessment with only patients with Mallampati I and II chosen for the study. The number of attempts before successful intubation was done in two stages (the number of attempts needed for successful device insertion, and subsequently, the number of attempts needed before successful intubation), these in addition to the number of adjustment maneuvers required before intubation (in the ILMA group) were a measure of the ease of intubation. For the device insertion, it was 100% at the first attempt using the DL with a subsequent 100% intubation at the first attempt, but in the ILMA group, there was a 95.35% first-attempt success rate at device insertion [Table 2], with the remaining 4.65% inserted at the second attempt. This was followed by a 79.07% first-attempt success at intubation, with the remaining 20.93% (nine patients) intubated during a second attempt. All the nine patients who required a second attempt at intubation in the ILMA group needed the pull-up adjustment maneuver to achieve success [Table 3]. These findings are consistent with certain studies,[15] which reported a first-attempt success rate in ILMA intubations varying between 72.0 and 86.7%. Even though these studies used the PVC tube both in the normal and reverse directions, their results were still in conformity with ours.

The incidence of airway complication (injury) was more in the ILMA group, occurring in 9 out of 43 patients (13.95%) as compared to the DL group with no airway injury recorded [Table 4]. As in this study, Kihara et al.,[16] who studied three intubating devices, concluded that ILMA results in higher incidences (8 of 50) of airway injury (mucosal injury and upper lip injury) compared to DL (0 of 50) and light wand (0 of 50). Kavitha et al.[13] also came to the same conclusion after comparing the ILMA and DL with more palatopharyngeal complications with the use of ILMA.

There was no association between the number of intubation attempts and mucosal injury probably due to the use of the specialized wire reinforced endotracheal tube that came with the ILMA, which has a soft and malleable rubber tip as compared to the commonly used stiff PVC tube. These results are like those of the previous studies,[17],[18] where higher airway complications were also seen in their ILMA groups.


We concluded that the overall success rate of intubation via the ILMA is comparable to that of the DL. However, in patients with normal airways, DL remains a comparatively faster technique to secure the airway with tracheal intubation than the ILMA, and the DL is still easier to use to intubate a patient than using the ILMA.

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Conflicts of interest

There are no conflicts of interest.


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