Anesth Analg 2005;100:284-288
© 2005 International Anesthesia Research Society
doi: 10.1213/01.ANE.0000139348.00435.33
GENERAL ARTICLES
Conventional Tracheal Tubes for Intubation Through the Intubating Laryngeal Mask Airway
Pankaj Kundra, MD, MAMS, FIMSA,
N. Sujata, MD, and
M. Ravishankar, DA, MD
Department of Anaesthesiology and Critical Care, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry, India
Address correspondence and reprint requests to Pankaj Kundra, MD, MAMS, FIMSA, D-II/21, JIPMER Campus, Pondicherry 605006, India. Address e-mail to pankajkundra{at}vsnl.net
 |
Abstract
|
|---|
The laryngeal mask airway (LMA)-FastrachTM silicone wire-reinforced tracheal tube (FTST) was specially designed for tracheal intubation through the intubating LMA (ILMA). However, conventional tracheal tubes have been successfully used to accomplish tracheal intubation. We designed this study to evaluate the success rate of blind tracheal intubation through the ILMA by using the FTST, the Rusch polyvinyl chloride tube (PVCT), and the Rusch latex armored tube (LAT). One-hundred-fifty healthy adults of ASA physical status I and II who were undergoing elective surgery under general anesthesia were randomly allocated into three groups. FTST (n = 50), prewarmed PVCT (n = 50), and LAT (n = 50) were used for tracheal intubation. Ease of tracheal intubation was assessed by the time taken, the number of attempts, and the number of maneuvers required for success. In addition, numbers of failed intubation attempts and times taken for ILMA removal were also recorded. After surgery, the incidence of trauma, sore throat, and hoarseness was noted. Significantly more frequent success in tracheal intubation was achieved with the PVCT and FTST (96%) compared with the LAT (82%) (P < 0.05). Tracheal intubation on the first attempt was similar with the PVCT and FTST (86%) and was significantly more frequent than with the LAT (52%) (P < 0.05). Esophageal placement was significantly more frequent with the LAT (29.7%) when compared with the PVCT and FTST (1.8% and 7.4%, respectively) (P < 0.05). The authors conclude that a prewarmed PVCT can be used as successfully as the FTST for blind tracheal intubation through the ILMA, whereas the LAT is associated with more frequent failure and esophageal intubation.
IMPLICATIONS: The laryngeal mask airway (LMA)-FastrachTM silicone wire-reinforced tracheal tube (FTST) was designed for tracheal intubation through the intubating LMA (ILMA). This study demonstrates that a prewarmed Rusch polyvinyl chloride tube can be used as successfully as an FTST for blind tracheal intubation through the ILMA, whereas the Rusch latex armored tube is associated with more frequent failure and esophageal intubation.
|
Introduction
|
|---|
The laryngeal mask airway (LMA)-FastrachTM silicone wire-reinforced tube (FTST) was designed for tracheal intubation through the intubating LMA (ILMA) (1). It is reusable and expensive. The design prevents it from retaining the curvature that it assumes by passage through the shaft of the ILMA. The polyvinyl chloride (PVC) tracheal tube is stiff and emerges from the ILMA with its distal end pointing too anteriorly to have a chance of entry into the glottis (1). However, despite the cited advantages of the FTST, both conventional PVC (2,3) and PVC-reinforced (4,5) tracheal tubes have been used successfully for blind tracheal intubation through the ILMA. The Rusch PVC tracheal tube (PVCT) and the Rusch latex armored tracheal tube (LAT), meant for single use, are much less expensive. They are disposable and readily available when required. This study was therefore designed to evaluate the ease of insertion and the success rate of tracheal intubation through the ILMA with the FTST, Rusch PVCT, and LAT.
|
Methods
|
|---|
This study was conducted in a selected population of 150 ASA status I and II adults of either sex scheduled for elective surgery. The institutional ethics committee approved the study. Written consent was obtained from all patients recruited for the study. Patients with potential or known airway problems with an interincisor gap >3 cm were recruited for the study where possible, whereas those with loose dentures, hypertrophied tonsils, and thyroid enlargement were excluded from the study. All patients were premedicated with oral diazepam 0.2 mg/kg, ranitidine 150 mg, and metoclopramide 10 mg the night before and on the morning of the surgery. In addition, IM meperidine 1 mg/kg was given half an hour before the surgery.
The patients were randomly allocated by the sealed-envelope technique to 1 of the 3 groups—FTST (n = 50), PVCT (n = 50), and LAT (n = 50)—to undergo blind tracheal intubation via ILMA. A Size 3 ILMA and a 7.0-mm tracheal tube was chosen for women and a Size 4 ILMA and a 7.5-mm tracheal tube for male patients. The PVCT was softened by prewarming at 40°C for 1 min. The PVCT was kept immersed in a sterile water bath heated to 40°C. Both the PVCT and the LAT were initially passed through the ILMA after lubrication, and the point at which their tip just lifted the epiglottis-elevating bar was marked on the tracheal tube by a transverse marker (15 cm). The PVCT was passed into the ILMA with its inherent curve facing forward. After the patient breathed oxygen, anesthesia was induced with a sleep dose of thiopentone and was maintained with 1% halothane in 100% oxygen. Vecuronium 0.1 mg/kg was used for muscle relaxation, and ventilation was performed for 3 min via a face mask. The ILMA was inserted by using a single-handed operator technique by one of the authors, and the cuff was inflated with air (Size 3, 20 mL; Size 4, 30 mL). After connecting the Bain’s circuit to the ILMA, appropriate placement and ventilation were determined by chest wall movement, auscultation of breath sounds, a square-wave capnograph trace, and no oropharyngeal leak with peak airway pressures 
20 cm H2O. If any one of the criteria for satisfactory ventilation was not met, the ILMA was manipulated in situ by using the first step of the Chandy maneuver (6); this consists of rotating the device in the sagittal plane until the least resistance to bag ventilation is achieved. Maintenance of anesthesia was continued with 1% halothane and 66% nitrous oxide in 33% oxygen. Mechanical ventilation through the ILMA was continued until the end-tidal carbon dioxide returned to baseline before blind intubation was attempted through the ILMA.
The group’s designated tracheal tube was inserted up to 15 cm. Intubation was considered successful if the tube passed beyond the 15-cm mark and there was a square-wave capnograph trace. Maneuvers tried for tracheal placement of the tube during an attempt were recorded on a three-point rank score: 0, tracheal tube slides in freely (without any maneuver); 1, twisting of the tracheal tube to align the bevel; 2, up-and-down movement of the tracheal tube. If the tracheal intubation was unsuccessful in the first attempt, a second attempt was made after repositioning the ILMA with the metal handle, by slightly lifting but not tilting the ILMA away from the posterior pharyngeal wall (second step of the Chandy maneuver) (6). Intubation failure was recorded if, despite two attempts, repeated tactile resistance was encountered or the tube passed beyond the 15-cm mark with no square-wave capnograph trace (esophageal intubation). A third attempt at intubation was allowed with the FTST in Groups PVCT and LAT after two failed attempts. When intubation was still unsuccessful or if the patient already belonged to Group FTST, the procedure was abandoned, and tracheal intubation was performed under direct laryngoscopy. Once the tracheal placement was accomplished, the ILMA was removed after the tracheal tube cuff was inflated and stabilized with the silicone pusher supplied with the FTST.
The ease of tracheal intubation was determined by the time taken to intubate the trachea (time from disconnection of the breathing circuit of the ILMA to confirmation of tracheal placement of the tracheal tube by auscultation and display of a square-wave capnograph trace), the number of attempts to achieve successful intubation, and the number of maneuvers required for success. In addition, numbers of failed attempts at intubation were also noted. Ease of ILMA removal after establishing tracheal intubation was noted by the time taken to remove the ILMA (time from insertion of pusher to reconnection of breathing circuit to the tracheal tube). Any critical incident during mask removal, such as accidental extubation or tube displacement, and the lowest oxygen saturation (SpO2) recorded during the procedure were also noted. The incidence of trauma, as evidenced by blood smeared on the tracheal tube after removal, was noted. Patients were visited after surgery to evaluate for hoarseness or sore throat.
The data were collected and analyzed with SPSS Version 10 (SPSS Inc., Chicago, IL). Demographic data and the time taken for tracheal intubation and ILMA removal among groups were analyzed with one-way analysis of variance. Chi-square analysis was used for comparing nominal data. P < 0.05 was considered statistically significant.
|
Results
|
|---|
Placement of the ILMA was successful in all patients, and there were no immediate adverse events. The age, sex, weight, and ILMA sizes used were comparable in all groups. Blind tracheal intubation through the ILMA was successful in 144 (96%) of 150 patients with a maximum of 2 attempts, and more frequent success was demonstrated in Groups PVCT and FTST (96%; 95% confidence interval, 86–0.99) when compared with Group LAT (82%; 95% confidence interval, 68–91). Overall, 112 (74.6%) of 150 patients had successful tracheal intubation on the first attempt. Tracheal intubation was accomplished more frequently in Groups PVCT and FTST (86%) than in Group LAT (52%) (P < 0.05). The demographic data were comparable among the three groups (Table 1).
The tracheal tube slipped into the esophagus 28 times during the 199 attempts made for tracheal intubation through the ILMA. A significantly more frequent incidence of esophageal intubation was encountered with the LAT (29.7%) when compared with the PVCT and FTST (1.8% and 7.4%, respectively; P < 0.05). The FTST could be successfully passed in seven of nine patients when the LAT failed despite two attempts. In 6 of 150 patients in whom blind tracheal intubation was not possible, the tracheal tube was placed under direct laryngoscopy (Table 1). There was no significant difference among groups in the maneuvers applied to achieve successful tracheal placement of the tracheal tubes through the ILMA. The mean increase in end-tidal carbon dioxide and the lowest SpO2 value recorded were also found to be comparable among the three groups.
|
Discussion
|
|---|
The FTST designed for use with the ILMA and recommended by the manufacturer is a straight, soft wire-reinforced silicone tube with a full silicone distal inch terminating in a Tuohy-like tip (1). Investigators using silicone tubes for blind tracheal intubation through the ILMA have reported successful tracheal intubation ranging from 89% to 99.3% (5,7–9). A 99.3% success rate reported by Brain et al. (7) in a preliminary clinical trial remains the best. None of the subsequent studies could reproduce such a near-perfect success rate with silicone tracheal tubes. This study demonstrated a success rate of 96%.
Inappropriate positioning of the ILMA in relation to the glottis, as assessed by fiberoptic view, has been cited as the reason for an increase in the number of attempts and the incidence of failure to achieve tracheal intubation (10). In another study (3), the inability to obtain an optimal ILMA position in 54.5% of patients was the reason for repeated attempts. In our study, before tracheal intubation was attempted, the ILMA was manually aligned (Chandy maneuver) to achieve a good mask-larynx relationship. The efficacy of pulmonary ventilation was recognized subjectively through manual ventilation and objectively through the carbon dioxide exchange on the capnograph and the airway pressure read on the monitor. Apart from the ILMA alignment to the glottis, the principal factor that determines the direction of the tracheal tube toward the glottis or away from it is the angle at which it emerges from the distal aperture of the ILMA. On measuring the angle of emergence of the tracheal tubes in our study (Fig. 1), the FTST formed an angle of 35° to the plane of the ILMA, similar to that demonstrated by Brain et al. (1). Superimposing the angle of emergence of the PVCT (46°) onto that from the study by Brain et al. (1) (Fig. 2) reveals that the PVCT lies closer to the silicone tracheal tube than to the rest of the PVC tubes (Portex PVC, Mallinckrodt PVC, and reinforced and curved Euromedical PVC) and hence has a better chance for success.
View larger version (42K):
[in this window]
[in a new window]
|
Figure 1. Emergence angle formed by the tracheal tubes on exiting from the distal aperture of the intubating laryngeal mask airway (LMA). 1, Rusch polyvinyl chloride tracheal tube (PVCT; 7.0-mm internal diameter). 2, LMA-Fastrach silicone wire-reinforced tube (FTST; 7.0-mm internal diameter). 3, Rusch latex armored tracheal tube (LAT; 7.0-mm internal diameter).
|
|
View larger version (26K):
[in this window]
[in a new window]
|
Figure 2. Effect of tracheal tube curvature for different tubes at 25°C (•) and 37°C ( ) when passed through the intubating laryngeal mask airway tube. a = straight silicone tube, 8 mm; b = curved Euromedical polyvinyl chloride tube (PVC), 8 mm; c = Rusch red rubber, 8 mm; d = Portex PVC, 8 mm; e = Mallinkrodt PVC, 8 mm; f = Mallinkrodt PVC reinforced, 7 mm; g = Rusch PVC 7-mm prewarmed tube (40°C); h = Rusch PVC 7 mm at room temperature (27°C). Reproduced with permission from Oxford University Press (1).
|
|
Our study demonstrates an overall success rate with the PVCT that is similar to that with the FTST (96%); in addition, the first-attempt success rate was similar with both tracheal tubes (86%). Lu et al. (3) reported a 96.7% success rate (75% on the first attempt), with a Sheridan PVC tube, whereas Kapila et al. (10) achieved a 93% success rate (72% on the first attempt) with a Portex PVC tube. We attribute the better first-attempt success to the prewarming of the tube to 40°C. The conventional PVCT has not been recommended for use with the ILMA for numerous reasons. The PVC tube is unable to reverse its curvature from the plane of inlet to pass into the trachea because of the additional curvatures imposed on it by the metal shaft of the ILMA (1). As a result, the tip of the tube may push against the anterior portion of the glottis and vocal cords, which can cause trauma and an increased incidence of failed intubation. Despite these disadvantages, investigators continue to use the PVC tubes for blind tracheal intubation through the ILMA by using different techniques because it is inexpensive, disposable, and readily available. Joo and Rose (2) recommend backward insertion of the tracheal tubes into the ILMA such that the concave bend faces down. This technique allows the tube to follow a more anatomical direction compared with conventional insertion. More frequent sore throat (19.2%) and hoarseness (5%) were reported in patients who underwent conventional insertion (3). Softening of the PVC tube by prewarming and avoiding force during tracheal intubation are likely to decrease the incidence of trauma to the soft structures. However, it must be remembered that the softness of the PVC tube warmed to 40° is preserved only over a brief period of 40 seconds. Tracheal intubation in 86% of our subjects was accomplished within this time. The increased incidence of trauma and sore throat was observed in patients when repeated attempts were required and the time of insertion exceeded 40 seconds. All cases of sore throat resolved within a day, and no incidence of hoarseness was recorded in any of the groups.
The Parker Flex-Tip PVC tube may be a suitable alternative to the beveled-tip PVC tube to overcome the problem of the distal tip impinging the anterior of the glottis. The centered, tapered, and flexible distal tip helps it to gently flex when hitting resistance and slide past the anatomical structures of the airway, thereby minimizing intubation trauma (11).
Our success rate with the LAT was significantly less (82%) when compared with the PVCT and FTST. The LAT is extremely soft and wire-reinforced to its bevel, unlike the FTST, which has a full silicone distal inch. The pressure exerted by the epiglottis-elevating bar on the distal end of the LAT directs it more posteriorly, and it emerges at an angle of 30° from the distal aperture of the ILMA. Consequently, when mild force is applied on encountering resistance during tracheal intubation, it tends to buckle and bulges upward with the tip pointing downward, without the change in the angle of emergence (Fig. 3). Thus, a downward and posterior orientation of the tracheal tube is attained, making it more vulnerable to slip into the esophagus. This is reflected by significantly more esophageal intubations encountered with the LAT (29.7%) when compared with the FTST and PVCT (7.4% and 1.8%, respectively). The FTST is firm enough to be directed anteriorly toward the glottis with a change in its angle of emergence when it strikes anywhere posterior to the glottis.
View larger version (133K):
[in this window]
[in a new window]
|
Figure 3. Orientation of the tracheal tube tips as force is applied proximally and the tip encounters resistance during tracheal intubation. 1 = the tip of the laryngeal mask airway-Fastrach silicone wire-reinforced tube is directed upward with a change in angle of emergence; 2 = the tip of the Rusch latex armored tracheal tube gets directed downward, tending to buckle and bulge upward without a change in the angle of emergence.
|
|
A drawback of our study is the lack of blinding, because it was impractical to conceal the tubes during insertion through the ILMA. A good mask-larynx relationship was ascertained clinically rather than with a fiberoptic view, because its availability was not always guaranteed.
We conclude that a less expensive and more readily available prewarmed Rusch PVCT can be used as successfully as the FTST for blind tracheal intubation through the ILMA, but the LAT is associated with more frequent failure and esophageal intubation.
|
References
|
|---|
- Brain AIJ, Verghese C, Addy EV, et al. The intubating laryngeal mask. I. Development of a new device for intubation of the trachea. Br J Anaesth 1997; 79: 699–703.[Abstract/Free Full Text]
- Joo HS, Rose KD. The intubating laryngeal mask airway with and without fiberoptic guidance. Anesth Analg 1999; 88: 662–6.[Abstract/Free Full Text]
- Lu PP, Yang CH, Ho ACY, et al. The intubating LMA: a comparison of insertion techniques with conventional tracheal tubes. Can J Anaesth 2000; 47: 849–53.[Abstract/Free Full Text]
- Asai T, Shingu K. Tracheal intubation through the intubating laryngeal mask in patients with unstable necks. Acta Anaesthesiol Scand 2001; 45: 818–22.[ISI][Medline]
- Pandit JJ, MacLachlan K, Dravid RM, et al. Comparison of times to achieve tracheal intubation with three techniques using the laryngeal or the intubating laryngeal mask airway. Anaesthesia 2002; 57: 128–32.[ISI][Medline]
- Ferson DZ, Rosenblatt WH, Johansen MJ, et al. Use of the intubating LMA-FastrachTM in 254 patients with difficult-to-manage airways. Anesthesiology 2001; 95: 1175–81.[ISI][Medline]
- Brain AIJ, Verghese C, Addy AV, et al. The intubating laryngeal mask airway. II. A preliminary clinical report of a new means of intubating the trachea. Br J Anaesth 1997; 79: 704–9.[Abstract/Free Full Text]
- Avidan MS, Harvey A, Chitkara N, et al. The intubating laryngeal mask airway compared with direct laryngoscopy. Br J Anaesth 1999; 83: 615–7.[Abstract/Free Full Text]
- Kihara S, Watanabe S, Taguchi N, et al. A comparison of blind and lightwand-guided tracheal intubation through the intubating laryngeal mask. Anaesthesia 2000; 55: 427–31.[ISI][Medline]
- Kapila A, Addy EV, Verghese C, et al. The intubating laryngeal mask airway: an initial assessment and performance. Br J Anaesth 1997; 79: 710–3.[Abstract/Free Full Text]
- Kristensen MS. The Parker Flex-Tip tube versus a standard tube for fiberoptic orotracheal intubation. Anesthesiology 2003; 98: 354–8.[ISI][Medline]
Accepted for publication June 28, 2004.
This article has been cited by other articles:
|
|
|
|
 
T. Zhu
Conventional Endotracheal Tubes for Intubation Through the Intubating Laryngeal Mask Airway
Anesth. Analg.,
January 1, 2007;
104(1):
213 - 213.
[Full Text]
[PDF]
|
|
|
|
|
|
|
P. Kundra
Conventional Endotracheal Tubes for Intubation Through the Intubating Laryngeal Mask Airway
Anesth. Analg.,
January 1, 2007;
104(1):
213 - 214.
[Full Text]
[PDF]
|
|
|
|
|
|
|
H. Joo and V. Naik
Conventional Tracheal Tubes for Intubation through the Intubating Laryngeal Mask Airway
Anesth. Analg.,
October 1, 2005;
101(4):
1245 - 1245.
[Full Text]
[PDF]
|
|
|
|
|
|
|
ILMA Intubation with a Conventional Tracheal Tube
Journal Watch Emergency Medicine,
March 2, 2005;
2005(302):
8 - 8.
[Full Text]
|
|
|
Top
Abstract
Introduction
