|Year : 2016 | Volume
| Issue : 1 | Page : 27-33
Airway management for morbidly obese patients: a comparative study between fiberoptic bronchoscopes and intubating laryngeal masks
Hala M.S. Eldeen MD , Aboelnour Elmorsy Badran, Mona A Hashish, Doaa G Diab
Anasthesiology Department, Mansoura University Hospital, Mansoura, Egypt
|Date of Submission||12-Jun-2014|
|Date of Acceptance||19-Oct-2014|
|Date of Web Publication||17-Mar-2016|
Hala M.S. Eldeen
Anasthesiology Department, Mansoura University Hospital, Mansoura
Source of Support: None, Conflict of Interest: None
Obesity is an epidemic disease that continues to increase in most countries. It is estimated that more than 30% of the adult population is obese. Airway management in morbidly obese adults may be a challenge to anesthesiologists due to anatomical and physiological changes that affect obese patients. The intubating laryngeal mask airway (ILMA) is a new device specifically designed to be an effective ventilator device and blind intubation guide in patients with normal and abnormal airways. The aim of this study was to compare the effectiveness and the safety of the ILMA technique with fiberoptic intubation (FOI) in obese patients with an anticipated difficult intubation.
Patients and methods
Eighty morbidly obese adult patients of either sex, aged 18-60 years, with BMI more than 40 kg/m 2 , with anticipated difficult intubation, and ASA physical status I-III, were scheduled for elective bariatric abdominal surgery, which required tracheal intubation and general anesthesia, in Mansoura University Hospital. Patients were randomly allocated into two groups: the FOI and the ILMA group. Randomization of the groups was performed by a computerized method, with 40 patients in each group. Anesthesia was induced with intravenous propofol 2-3 mg/kg of ideal body weight and fentanyl (2 mg/kg). Anesthesia was maintained with a propofol infusion (10 mg/kg/h). Patient characteristics such as age, sex, BMI, and the ASA class, heart rate and noninvasive blood pressure (NIBP), oxygen saturation, the success or failure rate, the number of attempts, and the duration of the successful attempt were all recorded.
Patients in the ILMA and the FOI groups were comparable to each other regarding the duration of intubation and the success rate. However, complications were significantly lower in the ILMA group than in the FOI group.
ILMA may be a good alternative device for FOI for tracheal intubation in morbidly obese patients.
Keywords: fiberoptic intubation, intubating laryngeal mask airway, obese patients
|How to cite this article:|
Eldeen HM, Badran AE, Hashish MA, Diab DG. Airway management for morbidly obese patients: a comparative study between fiberoptic bronchoscopes and intubating laryngeal masks
. Ain-Shams J Anaesthesiol 2016;9:27-33
|How to cite this URL:|
Eldeen HM, Badran AE, Hashish MA, Diab DG. Airway management for morbidly obese patients: a comparative study between fiberoptic bronchoscopes and intubating laryngeal masks
. Ain-Shams J Anaesthesiol [serial online] 2016 [cited 2021 Apr 11];9:27-33. Available from: http://www.asja.eg.net/text.asp?2016/9/1/27/178876
| Introduction|| |
Obesity is an epidemic disease that continues to increase in most countries. It is estimated that more than 30% of the adult population is obese  . The National Health And Nutrients Examination Society (NHANES) classified obesity into grade I overweight as a BMI of 25 kg/m 2 or higher, grade II obesity as a BMI of 30 kg/m 2 or higher, grade III morbid obesity as BMI > 40 kg/m 2 , and grade IV as BMI55 kg/m 2 , with significant comorbid conditions  . Morbid obesity is associated with an increased prevalence of diseases, including hypertension, coronary heart disease, congestive heart failure, stroke, type II diabetes, and obstructive sleep apnea syndrome. Airway management in morbidly obese adults may be a challenge to the anesthesiologist due to anatomical and physiological changes that affect obese patients, including difficulty with mask ventilation, rapid oxygen desaturation, and altered pharmacokinetics  . The intubating laryngeal mask airway (ILMA) is a new device specifically designed to be an effective ventilator device and blind intubation guide in patients with normal and abnormal airways  . ILMA represents a major advance in airway management and has been incorporated into difficult airway algorithms  . The ILMA has been used successfully in patients with difficult airways, including patients in whom fiberoptic intubation (FOI) failed ,, .
Intubating laryngeal mask ventilation is the most basic, yet the most essential, skill in airway management in obese patients. It is the primary technique of ventilation before tracheal intubation or insertion of any airway device. Its most unique role, however, is as a rescue technique for ventilation when tracheal intubation fails or proves difficult. The ability to establish adequate laryngeal mask ventilation has, therefore, become a major branch point in any difficult airway algorithm  .
It is surprising that despite its life-saving role, laryngeal mask airway (LMA) has received little attention in the literature and book chapters addressing airway management.
Hence, the aim of this study was to compare the effectiveness and the safety of the ILMA technique with FOI in obese patients with an anticipated difficult intubation.
| Patients and methods|| |
This study was approved by the Local Ethics Committee, and written informed consent was obtained from all patients. Eighty adult morbidly obese patients aged 18-60 years, of both sex, with BMI more than 40 kg/m 2 , with an anticipated difficult intubation and ASA physical status I-III, were scheduled for elective bariatric abdominal surgery, which required tracheal intubation and general anesthesia. Patients were randomly allocated into two groups: the FOI or the ILMA groups. Randomization was performed using a random number table in balanced blocks of 20 (10 per group), with 40 patients in each group. Patients were excluded if they were younger than 18 years, had an American Society of Anesthesiologists physical status IV or V, had respiratory tract pathology, coagulation disorders, required a nasal route for tracheal intubation, or were at risk of regurgitation-aspiration (previous upper gastrointestinal tract surgery, known hiatus hernia, esophageal reflux, peptic ulceration, or not fasted). Lastly, anticipated impossible intubation cases were also excluded.
The patients' age, sex, BMI, thyromental distance, sternomental distance, Mallampati score  (grade I: visualization of the entire laryngeal aperture, grade II: visualization of only the posterior commissure of the laryngeal aperture, grade III: visualization of only the soft palate, grade IV: visualization of just the soft palate), mouth opening, and protrusion of the mandible were detected.
An intravenous 20-G cannula was inserted as intravenous access 20 min before the induction of anesthesia; before manipulation, the airway was topically anesthetized with 100 mg of 5% lignocaine sprayed into the posterior pharynx to decrease gagging during airway management with both techniques. Sedation by 0.03 mg/kg intravenous midazolam was given, atropine (0.02 mg/kg) also was given to all patients to reduce secretions that might affect visualization or insertion of the tube.
In the operating room, patients were monitored using an ECG, a pulse oximeter (SpO 2 ), noninvasive blood pressure (systolic, diastolic, and mean), and capnography to adjust the end-tidal CO 2 around 35-40 mmHg. Both devices were prepared for use before the induction of anesthesia, each on a side table near the anesthesia machine. In this research, a ﬁthroptic bronchoscope (FOB) of 4.0 mm outer diameter and ILMA sizes 3, 4, and 5 were prepared.
Preoxygenation through an adequately sized facial mask with 100% oxygen for 3-5 min was performed for all patients. Preoxygenation should be carried out in the head-up or sitting rather than the supine position.
Anesthesia was induced with intravenous propofol 2-3 mg/kg of ideal body weight and fentanyl (2 mg/kg). Anesthesia was maintained with propofol infusion (10 mg/kg/h) as required to obtain satisfactory intubation conditions.
Throughout the procedure, oxygen was administered continuously through a nasal cannula because nasopharyngeal oxygen insufflation in morbidly obese patients after the induction of anesthesia has also been shown to decrease the severity of desaturation after 4 min of apnea. Nasopharyngeal insufflation may therefore be useful during intubation attempts to buy more time; the insertion of ILMA or FOI was then performed according to randomization, and on failure of one method, as defined by three unsuccessful attempts, the alternative study method was performed. A total of three attempts using either ILMA or FOI were allowed for experienced anesthesiologists to intubate the patients. The attempt was aborted if oxygen saturation decreased to less than 93% or the attempt time exceeded 120 s since the experienced anesthesiologist started to intubate the patient. After the tracheal intubation was accomplished successfully, the tracheal tube was connected to the circle breathing system of the anesthesia machine. The lungs were then ventilated with intermittent positive pressure ventilation. Pressure-controlled ventilation was applied. Anesthesia was maintained with isoflurane in oxygen. A fresh gas flow of 1.5 l/min was used, and the ventilator settings and the isoflurane concentration were adjusted to maintain an end-expiratory carbon dioxide of 35-40 mmHg. Rocuronium was administered at the dose of 0.6 mg/kg for intubation then at the dose of 0.1 mg/kg for maintenance.
Data were collected by the independent unblinded anesthesiologist using a data collection form, on which the following were recorded: age, sex, BMI, and the ASA class. Heart rate and NIBP and oxygen saturation before the induction of anesthesia (preinduction values) were considered as baseline, which compared with values obtained immediately after insertion (insertion time is the time from picking up the study device until the point at which satisfactory ventilation of the lungs was established) and immediately after intubation (intubation time is the time from the handling of the device until successful ventilation through the tracheal tube after removal of the devices), and then every 3 min for the first 10 min. Adverse events encountered during tracheal intubation (oxygen saturation < 90%, soft tissue trauma with bleeding, sore throat), the intubation profile such as the success or the failure rate, the number of attempts, and the duration of the successful attempts were all collected by the attending anesthesiologist.
The technique for ILMA insertion was performed as follows: one-handed rotational movement in the sagittal plane with the head supported by a pillow to achieve a neutral position. ILMA with an appropriate size (size 3 for those less than 70 kg and 4 or 5 for those more than 70 kg, respectively) was used for tracheal intubation. After local anesthesia was applied to the oropharynx, the induction of anesthesia, deflation of the ILMA cuff, and application of the lubricant on the posterior surface of the ILMA were completed, the ILMA was introduced into the oral cavity of the patients guided by a capnograph, and it was pressed along the palatopharyngeal curve and pushed further down till resistance was felt, in this case manual positive-pressure ventilation was attempted. If bag ventilation was adequate, guided by visible chest expansion, oxygen saturation greater than 95%, and end-tidal carbon dioxide ranging between 25 and 40 mmHg, the trachea was intubated with a tube of proper size. If resistance was felt or evidence of esophageal intubation during bag ventilation occurred, various modifications may be useful, such as the rotation technique or a fully or partially inflated cuff; if the tracheal intubation failed (more than three attempts), the cuff of the ILMA was deflated and the ILMA was removed and the trachea was intubated with another device.
In contrast, the FOBI technique was as follows: the scope was intended to be held and controlled by the right hand, while being advanced/withdrawn by the left hand.
This technique requires a thorough understanding of the equipment, which includes the following: a knowledge of optical principles to keep the intended target in the center of the image as you advance the scope, keeping the shaft fully extended all the time, insufflations of oxygen to help prevent tissue collapse in asleep patients, and preventing damage of the scope by not twisting the shaft with the left hand. The fiberoptic set was set up (i.e. a place for everything and everything in place). The FOB was connected to a video camera system. The FOB technique was performed through the oral approach with an Ovassapian airway. When an adequate level of anesthesia was obtained, the Jaw thrust maneuver was performed by an assistant to open the oropharyngeal space and facilitate the intubation; a well-lubricated FOB linked to a video camera system was passed smoothly through the airway till its tip located 3-5 cm above the carina to intubate the trachea with a tube of proper size. The correct position of the endotracheal intubation (ETT) was confirmed by bilateral chest auscultation and EtCO 2 .
The muscle relaxant was reversed by atropine at the dose of 0.02 mg/kg and neostigmine at the dose of 0.04 mg/kg, and then, tracheal extubation was performed.
Morbidly obese patients are at a higher risk of respiratory obstruction soon after extubation, Hence, it is essential that the patient is fully awake, responding to commands, and performing purposeful movements. Extubation over an airway exchange catheter should be strongly considered if a possible reintubation is likely to be difficult; the patient must be transferred to the recovery room sitting up at 45°, and humidified supplemental oxygen should be administered immediately, and chest physiotherapy commenced soon after the operation.
Data are presented as mean ± SD or median with 95% confidence interval for non-Gaussian variables. Comparison of two means was performed using the Student t-test, and comparison of two medians was performed using the Mann-Whitney U-test. Comparison of percentages was performed using the Fisher exact method. All comparisons were two-sided, and a P value less than 0.05 was considered significant.
The power of this clinical trial was calculated retrospectively using the G power analysis program version 3; using a post-hoc power analysis type II error protection of 0.05 and an effect size conversion of 0.8, a total sample size of 80 patients (40 patients in each group) produced a power of 0.79.
| Results|| |
Eighty patients were included in this study, with 40 patients in either the FOI group or the ILMA groups. Patient characteristics, including age, sex, body mass index (BMI), and ASA, had no significant differences in both groups [Table 1]. The heart rate showed no significant changes between the two studied groups during procedures [Figure 1], whereas MABP showed a significant decrease in ILMA at all times [Figure 2]. Both oxygen saturation and the tracheal intubation time had no significant changes between both groups [Figure 3] and [Figure 4]. The success rate was comparable in the two studied groups [Figure 5]. Regarding the complications, there were 4 patients in the FOI group compared with 2 patients in the LMIA group, who became desaturated, and 2 patients developed trauma and nasal bleeding in the first group compared with one in the second group; hence, the incidence of overall adverse events and oxygen desaturation were significantly higher in the FOI group compared with the ILMA group, regardless of the type of analysis [Table 2]. No patient had to be awakened or the surgery postponed.
|Figure 1: Basal and intraoperative heart rates (HRs) between the FOBI group and the intubating laryngeal mask airway (ILMA) group. Data are presented as mean ± S D.|
Click here to view
|Figure 2: Basal and intraoperative mean arterial pressure (MAP) between the FOBI group and the intubating laryngeal mask airway (ILMA) group. Data are presented as mean ± SD (P < 0.05). *Significant when compared with the ILMA gro up.|
Click here to view
|Figure 3: Arterial oxygen saturation (SpO2). Data are presented as mean ± SD. ILMA, intubating laryngeal mask airway|
Click here to view
|Figure 4: The duration of intubation in the two studied groups. Data are presented as mean ± SD (P < 0.05). ILMA, intubating laryngeal mask airway|
Click here to view
|Figure 5: The success rate of intubation in the studied groups. Data are presented in percentage (P < 0.05). ILMA, intubating laryngeal mask airway.|
Click here to view
| Discussion|| |
Management of the airway in morbidly obese patients is considered a significant challenge for anesthesiologists due to their relatively short, immobile neck, full cheeks, large tongue, and increased pharyngeal tissue mass  .
FOI is the standard of care for a predicted difficult airway management as stated by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway (2003).
However, in patients with difficult airways, the anesthesiologist has to achieve the best patient comfort, tolerability, and the best possible intubating conditions, while maintaining maximal patient safety during this procedure, avoiding stress, pain, and memorization; so, there are several challenges for the anesthesiologist to ensure a sufficient anesthesia level to obtain patient co-operation with a nonobstructing airway.
The ILMA was designed to help improve ventilation and tracheal intubation in both normal and difficult airways. The ILMA may provide a useful alternative to FOB in the management of the airway in morbidly obese patients  .
These airway devices would seem suitable to aid tracheal intubation in morbidly obese patients. Hence, the present study was designed to compare the effectiveness of the ILMA technique with FOBI in morbidly obese patients with anticipated difficult tracheal intubation.
The main result of this study was that in obese patients, the FOBI required a longer duration for tracheal intubation although it was not significant, and more maneuvers to optimize its position, which led to more postoperative complications compared with ILMA.
The results of the present study were in parallel to the results obtained by Joo and Rose  , who found that the incidence of successful tracheal intubation through ILMA was 97-99% for patients with a normal airway, which is close to our results.
Combes and colleagues prospectively compared the characteristics of airway management using ILMA in morbidly obese and lean patients. They showed that although it was not specifically designed for morbidly obese patients, when used by nonexpert anesthesiologists, ILMA can provide adequate ventilation and allows tracheal intubation in most of these patients  .
In addition, our results are in agreement with those of Pandit et al.  , who reported first intubation success rates in normal patients that were the same as in reports of patients with difficult airways, and also demonstrated that the total blind intubation time using ILMA was shorter than that with fiberoptic-guided intubation through ILMA in normal patients.
Frappier and colleagues assessed the usefulness of the Mallampati score alone or combined with other variables to predict difficult intubation using ILMA in morbidly obese patients. They studied 118 morbidly obese (BMI > 40 kg/m 2 ) patients, most of whom were female. The success rate, the number of attempts, and the total duration of the procedure were not different among patients with low-grade and high-grade laryngeal views. The time required for insertion of the ILMA was slightly longer in patients with high-grade laryngeal views. Failure of the technique was explained by the experience of the practitioner or airway characteristics. No adverse effects related to the technique were reported.
They showed that ILMA was an effective airway device for ventilation and intubation in morbidly obese patients. They revealed successful tracheal intubation, with the majority on the first attempt. The total intubation success rate, mucosal damage, and the sore throat rate were similar to our results  .
Dhonneur and colleagues studied 104 morbidly obese patients (BMI > 40 kg/m 2 ) with the LMA CTrach and showed higher first intubation and total intubation success rates, but with a longer intubation time than ours. They demonstrated that in the LMA CTrach group, 49% of the patients required maneuvers for optimizing ventilation and the laryngeal view, resulting in the time to intubation prolonged by ~1 min when compared with direct laryngoscopy  .
Arslan et al.  concluded that ILMA results in shorter intubation times with fewer maneuvers and sore throat compared with the LMA CTrach in morbidly obese patients.
In patients with a difficult airway, the standard care involves FOI under spontaneous ventilation. FOBI has emerged as the gold standard for patients with a suspected or proven difficult airway; this finding was supported by the American Society of Anesthesia. However, FOI has some drawbacks such as oxygen desaturation, aspiration of the stomach content during prolonged attempts for tracheal intubation, tachycardia, hypertension, and life-threatening cases of airway obstruction that may require emergency surgical airway. FOBI has been associated with 55% incidence of patient discomfort. Hence, the challenge for the operator is to ensure a sufficient anesthesia level to obtain patient co-operation without airway obstruction  .
The success rate in the FOBI group was 92.5%, which was nearly similar to that (92%) achieved by Langeron et al.  .
In our work, intubation failure in the FOBI group might be attributed to multiple factors. Ineffective desiccation (dryness of the secretion by antisialagogue) caused the secretion to obscure the lens (secretions give a white-out image and blood gives a red-out image). Sometimes, suctioning through the working channel is time consuming and required external suctioning.
Optimization maneuvers used in the FOBI group include tongue pull, cleaning the lens against the nearby mucosa, withdrawal, cleaning and reinsertion, suctioning of secretion or blood, working-channel suctioning, and warm saline injection as an antifogging solution, and counterclockwise rotation. Another commonly used maneuver is called the Chandy maneuver. It consists of two sequential steps: the first is to use the handle to unfurl the epiglottis, and the second is the usage of the handle to lift, and not tilt, the laryngeal inlet away from the posterior pharyngeal wall. This helps to tighten the laryngeal seal and orient the laryngeal inlet in the center of view. This maneuver was rapidly and easily achieved with ILMA intubation than in the case of FOBI  .
Regarding complications, the incidence of desaturation was significantly higher in FOBI (10%) compared with ILMA (2.5%); this is parallel to the results of Wahba et al.  , who reported oxygen desaturation in 10% of the cases with FOBI. They attributed this desaturation to the presence of plenty of secretions.
Postoperative sore throat was reported in two cases (5%) in the FOBI group compared with one case with group ILMA  . This might be attributed to the manipulation of the airway.
Two patients in each group (5%) showed trauma and bleeding, and this might be due to excess maneuver during airway management. This incidence was comparable to that of Malik et al.  and Yildiz et al.  .
Finally, dealing with hemodynamics, Ali and his colleagues found that intubation using FOB produced lesser cardiovascular response than with DL. They attributed this to the direct stimulation of the mechanoreceptors at the base of the tongue, the epiglottis, and the pharyngeal muscles by the blade of the laryngoscope  .
The hemodynamic response to intubation using either DL or ILMA was also observed: 5 min after intubation, both the mean arterial pressure and the diastolic arterial pressure were significantly less in the ILMA group compared with the DL group  .
| Conclusion|| |
We conclude that ILMA may be a good alternative device for FOB for tracheal intubation in morbidly obese patients, with significantly fewer complications compared with FOB.
| Acknowledgements|| |
Conflicts of interest
| References|| |
Kristensen MS. Airway management and morbid obesity. Eur J Anaesthesiol 2010; 27:923-927.
Kuchta KF. Pathophysiologic changes of obesity. Anesthesiol Clin N Am 2005; 23:421-429, vi
Lottis S, Bellamy MC. Anaesthesia and morbid obesity. Br J Anaesth 2008; 8:151-156.
Brain AI. The laryngeal mask - a new concept in airway management. Br J Anaesth 1983; 55:801-805.
Benumof JL. Laryngeal mask airway and the ASA difficult airway algorithm. Anesthesiology 1996; 84:686-699.
Brimacombe JR. Difficult airway management with the intubating laryngeal mask. Anesth Analg 1997; 85:1173-1175.
Joo H, Rose K. Fastrach - a new intubating laryngeal mask airway: successful use in patients with difficult airways. Can J Anaesth 1998; 45:253-256.
Parr MJ, Gregory M, Baskett PJ. The intubating laryngeal mask. Use in failed and difficult intubation. Anaesthesia 1998; 53:343-348.
Henderson JJ, Popat MT, Latto IP, Pearce ACDifficult Airway Society Difficult Airway Society guidelines for management of the unanticipated difficult intubation. Anaesthesia 2004; 59:675-694.
Mallampati SR, Gatt SP, Gugino LD, Desai SP, Waraksa B, Freiberger D, Liu PL. A clinical sign to predict difficult tracheal intubation: a prospective study. Can Anaesth Soc J 1985; 32:429-434.
Wahba SS, Tammam TF, Saeed AM. Comparative study of awake endotracheal intubation with Glidescope video laryngoscope versus flexible fiber optic bronchoscope in patients with traumatic cervical spine. Egypt J Anaesth 2012; 28:257-260.
Liu EH, Goy RW, Lim Y, Chen FG. Success of tracheal intubation with intubating laryngeal mask airways: a randomized trial of the LMA Fastrach and LMA CTrach. Anesthesiology 2008:108:621-626.
Joo HS, Rose DK. The intubating laryngeal mask airway with and without fiberoptic guidance. Anesth Analg 1999; 88:662-666.
Combes X, Sauvat S, Leroux B, Dumerat M, Sherrer E, Motamed C, et al. Intubating laryngeal mask airway in morbidly obese and lean patients: a comparative study. Anesthesiology 2005; 102:1106-1109; discussion 5A
Pandit JJ, MacLachlan K, Dravid RM, Popat MT. Comparison of times to achieve tracheal intubation with three techniques using the laryngeal or intubating laryngeal mask airway. Anaesthesia 2002; 57:128-132.
Frappier J, Guenoun T, Journois D, Philippe H, Aka E, Cadi P, et al. Airway management using the intubating laryngeal mask airway for the morbidly obese patient. Anesth Analg 2003; 96:1510-1515, table of contents.
Dhonneur G, Ndoko SK, Yavchitz A, Foucrier A, Fessenmeyer C, Pollian C, et al. Tracheal intubation of morbidly obese patients: LMA CTrach vs direct laryngoscopy. Br J Anaesth 2006; 97:742-745.
Arslan ZI, Özdamar D, Yildiz TS, Solak ZM, Toker K. Tracheal intubation in morbidly obese patients: a comparison of the Intubating Laryngeal Mask Airway™ and Laryngeal Mask Airway CTrach™. Anaesthesia 2012; 67:261-265.
Woodall NM, Harwood RJ, Barker GL. Complications of awake fibreoptic intubation without sedation in 200 healthy anaesthetists attending a training course. Br J Anaesth 2008; 100:850-855.
Langeron O, Semjen F, Bourgain JL, Marsac A, Cros AM. Comparison of the intubating laryngeal mask airway with the fiberoptic intubation in anticipated difficult airway management. Anesthesiology 2001; 94:968-972.
Verghese C. Laryngeal mask airway devices: three maneuvers for any clinical situation
. ???: McMahon Publishing; 2008. 30-31.
Tabari M, Alipour M, Ahmadi M. Haemodynamic changes occurring with tracheal intubation by direct laryngoscopy compared with intubating laryngeal mask in adults; a randomized comparison trial. Egypt J.
Malik MA, Subramaniam R, Churasia S, Maharaj CH, Harte BH, Laffey JG. Tracheal intubation in patients with cervical spine immobilization: a comparison of the Airwayscope, LMA CTrach, and the Macintosh laryngoscopes. Br J Anaesth 2009; 102:654-661.
Yildiz TS, Ozdamar D, Arslan I, Solak M, Toker K. The LMA CTrach™ in morbidly obese and lean patients undergoing gynecological procedures: a comparative study. J Anesth 2010; 24:849-853.
Ali L, Khurshid T, Boota M, et al
. Tracheal intubation; direct laryngoscopic oral intubation versus fiberoptic nasal intubations haemodynamic response. Professional Med J 2011; 18:407-410.
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2]