Endotracheal intubation of obese patients may be difficult due to impaired oral manipulations resulting from fatty tissue accumulation in the cheeks and palate, hypertrophy of tonsils, upward shift of the larynx, and decreased mouth opening. Additionally, difficult manipulations with a laryngoscope are likely to be associated with reduced mobility of the neck, whose circumference is markedly larger and elevation of the thoracic cavity, which hinder the manoeuvres with a handle. The percentage of failures during intubations of obese patients reaches 13% [1]. Direct laryngoscopy intubation attempts may also lead to a variety of traumatic mechanical complications due to excessive force used to visualize the laryngeal opening.  

The currently used laryngoscopes with straight (Magill) and bent (Macintosh) blades were introduced in the 20ties of the previous century. Their modifications over time were not significant, and new designs were mainly to solve difficult intubation-related problems. An example of a classic (Macintosh) laryngoscope modification used for difficult intubation is the McCoy laryngoscope with a mobile blade, suitable for cases in which the flat epiglottis obscures the superior laryngeal aperture.

A new device for endotracheal intubation – the AirTraq optical laryngoscope (Fig. 1) was launched in 2007 and combines the properties of a laryngoscope, rigid probe or fibre-optic guide. It is a disposable device, which visualizes the larynx through the eyepiece with an optical system.

The endotracheal tube is placed in the AirTraq channel with a built-in light source (batteries last for 90 min of work) and an anti-fog system (to prevent misting over of a distal lens in the oral cavity). For these reasons, the device should be set up 30 sec before the intubation. Like in fiberoscopy, special solutions are used to prevent fogging of the optical system tip.

The AirTraq laryngoscope may be used in cases of potential difficulties to provide a patent airway with conventional laryngoscopes, e.g. morbid obesity, limited mobility of the neck,  narrow mouth opening, post-traumatic conditions involving the face and cervical spine, and in some other special cases. The device is recommended for anticipated and unanticipated difficult intubations. Traditional endotracheal tubes are used with the AirTraq laryngoscope; the armoured tubes may also be applied. The tube size depends on the type of laryngoscope:  regular size devices – 7.0-8.5 endotracheal tubes, small size devices – 6.0-6.5. The latest version is designed for infants. Insertion of the AirTraq laryngoscope to the oral cavity requires extremely small mouth opening: 18 mm for regular versions and 16 mm for small devices.

The aim of the study was to compare the usefulness of the AirTraq and classical Macintosh laryngoscopes for endotracheal intubation in morbidly obese patients.  

METHODS

The study, approved by the Ethical Committee, was carried out among adult patients with III degree obesity (BMI>39 kg m-2) anaesthetized for elective surgical procedures. Patients were randomly (single-blind method) allocated to the AirTraq group or Macintosh group. The AirTraq optical laryngoscope (Prodol, Spain) with the camera transmitting the view from its tip to a monitor or the traditional laryngoscope with the Macintosh blade, size 3 (Timesco, UK) were used.

Endotracheal intubation was performed after standard induction of general anaesthesia using propofol 1.5-2 mg kg-1, rocuronium 1 mg kg-1 and fentanyl 0.25 µg. Having obtained 100% block of neuromuscular conduction (TOF stimulation), intubation was attempted. The time required to insert the endotracheal tube was measured and the number of patients requiring additional manoeuvres to improve visualization of the laryngeal opening or insertion of the tube to the trachea was recorded. In patients with the optical laryngoscope, such manipulations included: changes of insertion direction, elevation of the epiglottis with the laryngoscope tip or tilting of the patient`s head backwards. In patients with the classical Macintosh laryngoscope, additional manoeuvres included the use of a guide-wire or changes of blade sizes.

The results were statistically analysed. Intergroup parameters were compared using the Student’s t test for independent unpaired variables. Statistical significance was assumed at p<0.05.  

RESULTS

The study was performed in 68 patients; the AirTraq group consisted of 36 and the Macintosh group of 32 patients. BMI values were 43.4±6.8 kg m-2 and 43.3±5.5 kg m-2, respectively. Demographic characteristics of the two groups were comparable.

The intubation time using the AirTraq optical laryngoscope was 29±11 sec and was significantly shorter compared to the Macintosh group – 49±27 sec. The number of additional manoeuvres required for improving visualization of the laryngeal aperture or insertion of the endotracheal tube was over twice lower for the AirTraq device (19% vs 50%).

In the Macintosh group, guide-wires were necessary in 14 cases and changes of the blade size (to larger) in two cases (Table 1). There were no traumatic complications following endotracheal intubation observed in either group.

DISCUSSION

In some cases, preoperative assessment of intubation conditions based on the Mallampati score differs from the real conditions found on direct laryngoscopy [2]. Moreover, in obese patients, we are often faced with problems related to narrow mouth opening, which in a conscious patient is often very good (Mallampati grade 1 or 2) whereas passive opening (after anaesthetics) is insufficient.

Our results confirm reports about high usefulness of the AirTraq laryngoscope in obese patients [3, 4, 5]. Similar studies in 106 obese patients carried out by Ndoko and colleagues [3] gave comparable results – the mean time to intubation with the optical device was 24 sec and with the traditional one – 56 sec (additionally, in the latter group, 6 patients required the use of AirTraq to make the intubation possible).  In our study, intubations were performed using the traditional laryngoscope; however, in almost half of the cases, the endotracheal tube guide was necessary. Although no traumatic complications were observed, the use of bigger strength or rigid guides always predisposes to such complications.

In seven patients intubated by us with the optical laryngoscope, additional manoeuvres were required to improve visualization of the laryngeal opening and insert the endotracheal tube. Similar difficulties and their management were reported in the available literature [4]. An obese patient should be placed in the neutral position – the head and neck in line [6]. During intubation with the AirTraq laryngoscope, just like in classical laryngoscopy, the semi-reclining position is recommended, which markedly facilitates the manipulations with the device [7]. Our observations also show that difficulties in visualization of the laryngeal opening after the insertion of the device are most often caused by too deep insertion. Visualization is improved with the same manoeuvres as those used during direct laryngoscopy: the insertion should be carried out in the vertical plane; movements that may cause the so-called “lever” of teeth ought to be avoided not to injure the teeth. Moreover, the procedure is easier once the mandible is raised with the other hand as reduced pressure on the laryngoscope facilitates its manipulations.

It should be remembered that when the optical laryngoscope is used, the endotracheal tube could not be manipulated. If the difficulties of tube insertion develop, we should try to localize the laryngeal opening in the middle of the visual field and not to manipulate the tube. On the other hand, to change the insertion direction, the entire device should be manipulated.  Dhonneur and colleagues [4] described the method of ”reverse” insertion of the AirTraq laryngoscope in obese patients enabling faster insertion of the device into the oral cavity, which is somewhat similar to the insertion of the oropharyngeal tube to the oral cavity. However, this method was not used in the present study.

Furthermore, the use of the AirTraq optical laryngoscope was described for endotracheal awake intubation of an obese patient. Generally, such a procedure is performed with a fiberoscope. It is worth stressing that the AirTraq laryngoscope may also be used for emergent difficult intubations in obese patients [9].

The AirTraq optical laryngoscope is additionally equipped with the video camera to observe the laryngeal aperture on a monitor [5,10]. The video camera is compatible with various types of monitors and may be connected with a computer. Thanks to video-laryngoscopy, the incidence of attempted intubation-related complications may be reduced: weaker force required for visualization of the laryngeal opening, smaller space  needed to insert the endotracheal tube into the trachea, less severe traumatization of the oral cavity, teeth and pharynx, lower incidence of pharyngeal and laryngeal reflexes. In the present study, the AirTraq laryngoscope with a built-in video camera was applied; its use was easy and convenient.

Our study is mainly of a practical value. The findings reveal that endotracheal intubation in obese patients should always be managed with the AirTraq optical laryngoscope. The device in question is also extremely useful in difficult intubation cases; thanks to its low price and easy application, the AirTraq may be an alternative for fiberoscopes.

CONCLUSIONS

The AirTraq optical laryngoscope enables faster and potentially less traumatic endotracheal intubation in obese patients compared to classical Macintosh laryngoscopy.

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REFERENCES

1.Gaszynski W, Strzelczyk J, Gaszynski T: Ocena przydatnosci testów klinicznych wkierunku rozpoznania prawdo-podobienstwa trudnej intubacji uotylych. Twój Magazyn Medyczny – Chirurgia 2003; 3: 50-54.

2.Gaszynski T: Standard clinical tests for predicting difficult intubation are not useful among morbidly obese patients. Anesth Analg 2004; 99: 956.

3.Ndoko SK, Amathieu R, Tual L, Polliand C, Kamoun W, El Housseini L, Champault G, Dhonneur G: Tracheal intubation of morbidly obese patients: atrial comparing performance of Macintosh and Airtraq laryngoscopes. Br J Anaesth 2008; 100: 263-268.

4.Dhonneur G, Ndoko SK, Amathieu R, Attias A, Housseini LE, Polliand C, Tual L: Aof two techniques for inserting the Airtraq laryngoscope in morbidly obese patients. Anaesthesia 2007; 62: 774-777.

5.Dhonneur G, Abdi W, Ndoko SK, Amathieu R, Risk N, El Housseini L, Polliand C, Champault G, Combes X, Tual L: Video-assisted versus conventional tracheal intubation in morbidly obese patients. Obes Surg 2008; 4: Epub on-line Springer nr 10.1007/s1 1695-008-9719-0.

6.Hirabayashi Y, Seo N: In-line head and neck position is preferable for tracheal intubation with the Airtraqlaryngoscope compared to the sniffing position. J Anesth 2008; 22: 189-190.

7.Gaszynski T, Gaszynski W: Ulozenie do intubacji ilucia centralnego uotylych. Anaesthesiol Intensive Ther 2004; 36: 223-224.

8.Uakritdathikarn T, Asampinawat T, Wanasuwannakul T, Yoosamran B. Awake intubation with Airtraq laryngoscope in aobese patient. J Med Assoc Thai. 2008 2008; 91: 564-567.

9.Dhonneur G, Ndoko S, Amathieu R, Housseini LE, Poncelet C, Tual L: Tracheal intubation using the Airtraq in morbidly obese patients undergoing emergency cesarean delivery. Anesthesiology 2007; 106: 629-630.

10.Marrel J, Blanc C, Frascarolo P, Magnusson L: Videolaryngoscopy improves intubation condition in morbidly obese patients. Eur J Anaesthesiol 2007; 24: 1045-1049.

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Address:

*Tomasz Gaszynski
Katedra Anestezjologii iTerapii UM wLodzi
ul. Kopcinskiego 22, 90-153 Lódz
e-mail: tomaszyn@poczta.onet.pl

Received: 17.12.2008
Accepted: 07.04.2009