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sophagienne]
From the Department of Anesthesiology, Kansai Medical University, Osaka, Japan.
Dr. Takashi Asai, Department of Anesthesiology, Kansai Medical University, 10-15 Fumizono-cho, Moriguchi City, Osaka, 570-8507, Japan. Phone: 0081-6-6992-1001; Fax: 0081-6-6991-1301; E-mail: asait{at}takii.kmu.ac.jp
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Abstract |
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Clinical features: A 43-yr-old man with osteogenic sarcoma of the mandible underwent mandibulectomy, radical neck dissection, reconstruction of the mandible and radiation therapy. He was scheduled for revision surgery to the mandible. He had a limited mouth opening and neck movement after operation and radiation. After the cuffed oropharyngeal airway (COPATM) was inserted, anesthesia was induced with sevoflurane, and fibreoptic nasotracheal intubation attempted, but it was impossible to insert the fibrescope into the trachea because of a deformed larynx. While equipment for tracheostomy was prepared, one last attempt was made to insert the tube blindly into the trachea. The capnograph showed apparently normal carbon dioxide waveforms, and the reservoir bag inflated and deflated regularly. However, immediately after inflation of the cuff of the tracheal tube the reservoir bag movement stopped and CO2 waveforms disappeared. Fibreoptic bronchoscopy showed that the tube was in fact in the esophagus. It was then noticed that the patient was still breathing spontaneously through the cuffed airway. The patient was awoken and tracheostomy performed. It was considered that egress of the expired gas was partially prevented by the cuffed airway, pooled in the oral cavity, aspirated down the esophagus during inspiration (likely to be due to negative intrathoracic pressure) and pushed out through the tube during expiration; inflation of the cuff prevented the gas entering the esophagus.
Conclusion: Under such exceptional circumstances, apparently normal carbon dioxide waveforms were observed despite esophageal intubation in a spontaneously breathing patient.
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Case report |
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Preoperatively, the patient was conscious and was able to eat. The artificial mandibular plate limited mouth opening to 2 cm. The view of the oropharynx was limited, and only the base of the uvula could be seen. Neck movement was markedly restricted because of operation and radiation. Tracheal intubation was predicted to be difficult because of the limited head and neck movement and mouth opening. Manual ventilation through a facemask was also predicted to be difficult, since a facemask would not fit over the mandibular defect. We planned to intubate the trachea nasally using a fibreoptic bronchoscope while the patient was breathing spontaneously under general anesthesia. We considered that the awake insertion of a cuffed oropharyngeal airway (COPATM) (Mallinckrodt, Athlone, Ireland) was indicated, since oxygen and inhalational anesthetics can be delivered during attempts at fibrescope-aided nasotracheal intubation (Figure 1
).8,9
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About ten minutes later, when the airway reflexes were judged to have been sufficiently suppressed, a fibrescope was passed through a reinforced tracheal tube (internal diameter (ID): 7.0 mm) and the combination was inserted through a nostril into the oropharynx. The distal end of the cuffed airway was positioned about 2 cm cranial to the vocal cords. However, the device was not elevating the epiglottis, which was lying on the posterior pharyngeal wall, rendering it difficult to pass the fibrescope beyond the epiglottis. After considerable difficulty, it became possible to locate the glottis. Both the epiglottis and arytenoid cartilages were enlarged, and the latter were displaced inwardly toward the glottis, narrowing the supra-glottic region. The hypopharynx and esophagus remained open and the esophageal lumen widened during inspiration and narrowed during expiration. Because of the narrowed glottis, both the fibrescope and the tube were removed and the 7.0–mm ID tube was replaced by a 6.0–mm ID tube reinforced tube. Several attempts at advancing the fibrescope into the trachea failed, as the tip of the fibrescope always slipped into the esophagus.
It was decided to perform a tracheostomy after awakening the patient. Yet, before removal of the tracheal tube from the nose, one last attempt was made to insert the tube blindly into the trachea. The tube was inserted about 25 cm, the breathing system was detached from the cuffed airway and attached to the tracheal tube while the cuffed airway was left in place. Surprisingly, the capnograph showed apparently normal carbon dioxide waveforms: the concentration increased and decreased regularly, synchronized with inspirations and expirations; the peak concentration ranged 38–40 mmHg with the minimum concentration of 0–3 mmHg. The reservoir bag (connected to the tracheal tube via a breathing system) also inflated and deflated regularly, although bag movement was slight. The chest expanded adequately and auscultation of the chest indicated good air entry. During this period lasting several minutes, peak carbon dioxide concentration remained constant.
Since capnography indicated a successful tracheal intubation, the cuff of the tracheal tube was inflated. Immediately after, movement of the reservoir bag stopped and there was no longer any increase in carbon dioxide concentration. Deflation of the tracheal tube cuff produced waveforms, but this time the peak concentration was much lower (less than 10 mmHg). Fibreoptic bronchoscopy showed that the tube was, in fact, inserted deeply into the esophagus. It was then noticed that the patient was still breathing spontaneously through the cuffed airway. Throughout the procedure, hemoglobin oxygen saturation remained greater than 98%. The patient was allowed to awaken and tracheostomy performed. The operation proceeded uneventfully thereafter.
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Discussion |
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The exact mechanisms to explain the apparently normal capnogram despite accidental esophageal intubation are not clear, but likely explanations are as follows. First, the esophagus was anatomically distorted, and remained patent, possibly because of the scarring from the previous surgery and radiotherapy. Normally the esophagus has no intrinsic structure to maintain its patency, so that when a negative pressure is applied it easily collapses and no or little gas is aspirated. This principle is utilized by an esophageal detector device, which has been shown to be reliable in detecting esophageal intubation in paralyzed patients.13,14 Our patient was breathing spontaneously and the esophagus remained open; the lumen widened during inspiration and narrowed during expiration.
Second, expiration of gas was probably hampered by the cuffed oropharyngeal airway and the presence of a tracheal tube in the nose. The cuffed airway can be used to allow oxygenation during attempts at nasotracheal intubation and while confirming the position of the tracheal tube, since the distal end of the cuffed airway is usually positioned just above the tip of the epiglottis and the device occupies the oral cavity.15 We used this technique in our patient who was breathing only through the narrow orifice of the cuffed airway and the nose during attempts at fibreoptic intubation. In addition, a tracheal tube and a fibrescope were obstructing one nasal passage. Therefore, it is possible that expired gas was pooled in the oral cavity and travelled down into the esophagus during inspiration (Figure 2). Carbon dioxide waveforms disappeared after inflation of the endotracheal tube cuff and waveforms reappeared (although with lower peak concentrations) after deflation of the cuff. These suggest that the expired gas entered the esophagus during inspiration (likely due to negative intrathoracic pressure), and forced gas out through the tube during expiration; inflation of the cuff prevented gas entering the esophagus.
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Our report indicates that, under exceptional circumstances, when a patient is breathing spontaneously, apparently normal carbon dioxide waveforms, in addition to reservoir bag and chest movement, can be observed and clear lung sounds heard despite accidental esophageal intubation.
Revision received August 1, 2001. Accepted for publication February 15, 2001.
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2
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3
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5
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14
Salem MR, Wafai Y, Baraka A, Taimorrazy B, Joseph NJ, Nimmagadda U. Use of the self-inflating bulb for detecting esophageal intubation after "esophageal ventilation". Anesth Analg 1993; 77: 1227–31.
15
Greenberg RS, Kay NH. Cuffed oropharyngeal airway (COPA) as an adjunct to fibreoptic tracheal intubation. Br J Anaesth 1999; 82: 395–8.
16 Robinson JS. Respiratory recording from the oesophagus. Br Med J 1974; 4: 225.
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