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Overcoming Obstruction During Bronchoscope-Guided Intubation of the Trachea with the Double Setup Endotracheal Tube

1996; Lippincott Williams & Wilkins; Volume: 83; Issue: 1 Linguagem: Inglês

10.1097/00000539-199607000-00030

1526-7598

William H. Rosenblatt,

Foreign Body Medical Cases

The fiberoptic bronchoscope (FOB) has become prevalent for management of the patient with a difficult airway [1]. Although direct visualization with the FOB assures a path from the oral or nasal aperture to the trachea, obstruction of endotracheal tube (ETT) advancement into the larynx is a common problem [2-6]. Entrapment of the arytenoid cartilages, epiglottis, or other structures within the "cleft" created along the ETT bevel by the difference in the outer diameter of the FOB and the internal diameter of the ETT is responsible for this obstruction [5,6]. Not only does this situation leave the airway unprotected, but it may also result in injuries to the larynx and is often painful in the awake patient. Various maneuvers and tracheal tubes designed to overcome this obstruction have been described [3-6]. These techniques may be unsuccessful and/or significantly more costly than a simple, double tube technique described by Marsh [6]. The current double-blind, prospective study was designed to delineate the ease of FOB-assisted intubation with a double tube setup compared with a standard, preformed polyvinylchloride ETT. Methods With institutional Human Investigation Committee approval, 30 patients, aged 18 to 65 yr, scheduled to undergo elective surgical procedures under general anesthesia and neuromuscular block at Yale-New Haven Hospital were asked to participate. Patients were excluded if they had a history or physical examination consistent with possible difficult tracheal intubation or risk of aspiration of gastric contents or were ASA physical status III or greater. Age, height, weight, Malampatti classification of the oral cavity [7], incisor-to-incisor maximum distance (i.e., oral aperture), range of motion of the neck, condition of dentition, and thyroid cartilage-to-symphysis (i.e., thyromental) distance were recorded. After written, informed consent for study participation, the patient was assigned to either a true double setup (DS) or a mock double setup (mDS) ETT configuration group by use of a random number table. In both groups, the ETT configuration consisted of a 7.5-mm inner diameter (I.D.) preformed ETT (Kendal Company, Mansfield, MA), without a circuit adapter, cut to 23 cm in length and fitted internally with a silicone-lubricated 5.0-mm I.D., uncuffed ETT complete with a circuit adapter. The internal tube was cut to a length at which it either extended 1 cm beyond the distal tip of the outer tube (DS group) or terminated 3 cm proximal to the bevel of the outer tube (mDS group) when the two ETTs were fully engaged Figure 1.Figure 1: The double setup endotracheal tube (ETT) configuration as described by Marsh et al. [6]. A, True double setup: the internally fitted ETT extends beyond the bevel of the outer ETT; B, mock double setup: the internaly fitted ETT terminates within the outer ETT.Anesthesia was induced and maintained using techniques and anesthetic drugs at the discretion of the anesthesia personnel assigned to the care of the patient, who remained blinded to the ETT configuration group assignment. One investigator attended all trials for the purpose of preparing the appropriate ETT configuration. After adequate depth of anesthesia and neuromuscular block were achieved, a 90-mm or 100-mm Luomanen Trademark (Sparta, NJ) oral airway was placed in the oral cavity and the appropriate ETT configuration threaded onto the silicone-lubricated FOB by the investigator. The two ETTs of the double setup were partially disengaged so that the intubating anesthesiologist was unable to ascertain the eventual ETT configuration. The anesthesiologist performing the intubation advanced the FOB through the oral airway, pharynx, larynx, and trachea until the carina was visualized. The investigator then advanced the ETT configuration into the oral airway with the preformed concavity oriented anteriorly (to "12 o'clock"). Once the bevel and cuff of the outer ETT were within the oral airway, the two ETTs were fully engaged into their final ETT configuration. The entire ETT configuration was then advanced over the FOB until resistance was met or until a depth of 22 cm, as indicated on the outer ETT, was reached. If resistance was met, the protocol described by Brull et al. [5] was used to redirect the ETT configuration: the ETT configuration was withdrawn 2-3 cm from where resistance was met, rotated approximately 60 degrees counterclockwise (such that the concave curvature was pointing to "10 o'clock"), and then readvanced over the FOB. If during this second attempt an obstruction again prevented the ETT configuration advancement into the trachea, the tube was rotated 120 degrees clockwise (with the concave curvature pointing to "2 o'clock"). If a third attempt at intubation was unsuccessful, the ETT configuration and the FOB were removed from the patient and the above protocol was repeated using the other configuration (only the investigator was not blinded to the "cross-over" group assignment). Once unobstructed passage of the ETT was achieved (i.e., ETT configuration advanced without resistance to a depth of 22 cm), the tracheal cuff of the 7.5 mm ETT was inflated to approximately 20 mm Hg, the oral airway was removed, and the intubator or investigator placed a gloved hand in the patient's mouth to ensure that the ETT configuration was not arched in the oropharynx. The FOB and 5.0-mm ETT were then removed from the 7.5-mm ETT, while tracheal and ETT structures were visualized through the FOB. The 7.5-mm ETT was then fitted with a circuit adapter and the anesthesia circuit attached. Endotracheal intubation was again confirmed using auscultation and measurement of end-tidal CO (2). If unobstructed passage of the ETT was never achieved with either the initial or cross-over ETT configuration, the anesthesia team was allowed to choose their method of intubation as well as ETT type. In each case, the ease of ETT advancement over the FOB was graded using the system described by Brull et al. [5]: Grade I if advancement of the ETT over the FOB was accomplished on the first attempt; Grade II if two or three attempts were required; and Grade III if ETT tube passage was unsuccessful after three attempts. The difference in the incidence of easy (Grade I) or obstructed (Grades II and III) ETT passage between the two groups as well as demographic data were compared with Mann-Whitney U-test analysis. Results Fifteen patients were enrolled in each study group. The groups did not differ significantly in age, height, weight, Malampatti class, gross range of motion of the neck, oral aperture, and thyromental distance. The DS configuration was significantly easier to pass into the larynx and trachea than the mDS configuration (P < 0.01) Table 1. In three patients, the mDS would not pass into the larynx and trachea after three attempts. After cross-over into the DS group, these three intubations were achieved on the first attempt (12 o'clock position).Table 1: Comparison of Ease of Intubation with True Double, Mock Double, and Spiral-Wound Endotracheal Tubes (ETTs)Discussion This study demonstrates that the DS ETT configuration described by Marsh [6] improves the ease of FOB-aided intubation compared with the standard preformed ETT. Comparison of the current trials with the summarized, raw data provided by Brull et al. [5] demonstrated no difference in the ease of passage between the DS configuration and the spiral-wound ETT. In addition, there was no difference between their control group data (standard preformed ETT) and the current mDS group data. Direct comparison of these studies is limited by the use of different size ETTs (Brull et al. used 8.5-mm I.D. ETTs in males and 8.0-mm I.D. ETTs in females) and by the fact that only the current study was double blind. Although of similar efficacy as the spiral-wound ETT in overcoming obstruction to ETT passage, the DS configuration does offer additional advantages: 1) The cost of the spiral-wound ETT at our institution is $22.53, whereas the cost of the DS using standard preformed tubes is $3.06. 2) Use of the spiral-wound ETT may preclude the use of oral airways that are circumferentialy solid (e.g., the Williams airway), because the circuit adapter is not removable. This is undesirable if the oral airway must be removed (e.g., for rigid laryngoscopic examination or esophagoscopy) or for prolonged intubation. 3) Several case reports have described obstruction of spiral wound or armored ETTs caused by patient biting, due to kinking of the wire reinforcement [8,9]. A potential drawback of the DS configuration was illustrated by the inability to adequately secure the airway in one patient with either the mDS (no passage after three attempts) or the true DS (passage into the trachea on first attempt). This patient, who was 113 kg and 175 cm in height, was felt by the anesthesia care team to require an ETT longer than the 23-cm length used in the current study for the airway to be securely controlled (i.e., to have adequate extraoral length to allow fixation with the ETT bevel at the level of the mid trachea). The usual distance from the teeth to the mid trachea is 17.8-19.6 cm in the adult but may be as long as 24.5 cm [10]. Unfortunately, the length of the available 5.0-mm uncuffed ETTs required that the outer, 7.5-mm ETT be shortened and used initially without its circuit adapter. This precludes the use of this configuration in patients who may require longer tubes, including those in whom nasotracheal intubation is desirable. In addition, replacement of the circuit adapter may be difficult in the critical airway situation. This latter obstacle can be overcome with the use of a 5.0 nasal Rae Registered Trademark tube (Malinckrodt, St. Louis, MO), which is distributed by the manufacturer cut to 26 cm in length and may be used within a 7.5-mm ETT cut to 21 cm with the circuit adapter attached. This configuration is easier to secure to the anesthesia circuit in a critical situation. Of interest, during the FOB examination of one patient, a polyp was noted on the larynx 1 cm proximal to the vocal cords. The study and the scheduled surgery were completed, and the patient was referred to outpatient-otolaryngology consultation. In summary, we have shown in a double-blind, prospective manner that the DS setup described by Marsh [6] is a useful and low-cost aid in the FOB-aided intubation of the trachea. Use of this configuration should provide improved ease of intubation and patient comfort and safety during this critical anesthetic procedure. The author wishes to thank Sorin J. Brull, MD; Lori Abrahamiam, MD; and the Anesthesiology Technicians at Yale-New Haven Hospital for aid in data collection. Drs. Brull et al. [5] are thanked for their permission to reprint the data used in the table.