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CRITICAL CARE AND TRAUMA

Effects of a Suction Laryngoscope in a Model with Simulated Severe Airway Hemorrhage

Thomas Mitterlechner, MD^*, Nicolas Nerbl^*, Holger Herff, MD^*, Peter Paal, MD^*, Martin Moritz, MD^*, Frank Kloss, MD, Karl H. Lindner, MD^*, and Volker Wenzel, MD, MSc^*

From the Departments of *Anesthesiology and Critical Care Medicine, and Cranio-Maxillofacial and Oral Surgery, Innsbruck Medical University, Innsbruck, Austria.

Address correspondence and reprint requests to Dr. Thomas Mitterlechner, Innsbruck Medical University, Department of Anesthesiology and Critical Care Medicine, Innsbruck, Austria. Address e-mail to Thomas.Mitterlechner{at}i-med.ac.at.

	Abstract

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In severe airway hemorrhage, simultaneous suction and laryngoscopy may render intubation difficult. We built a suction laryngoscope that consists of an adjustable stainless steel-guide tube fixed at the lingual surface of a standard Macintosh laryngoscope blade. Via this steel-guide tube, a large suction catheter can be inserted and positioned exactly to suction pharyngeal blood or vomitus, rendering simultaneous suctioning and laryngoscopy possible. In contrast to previous suction laryngoscopes, our suction catheter has a large lumen, which enables fast suctioning and exact placement by adjusting the steel-guide tube. To assess whether our suction laryngoscope could provide better intubation conditions in comparison to a standard Macintosh laryngoscope in a bleeding airway scenario, 44 medical students intubated a manikin with severe simulated airway hemorrhage using our suction laryngoscope and a standard Macintosh laryngoscope in random order. There was no significant difference in time needed for intubation when using the suction versus the Macintosh laryngoscope (mean ± sd: 43 ± 13 vs 52 ± 31 s; P = 0.07), but the number of esophageal intubations was significantly lower when using the suction laryngoscope [6 of 44 (13.6%) vs 19 of 44 (43.2%); P = 0.004]. In conclusion, when compared with a standard Macintosh laryngoscope, using a suction laryngoscope did not result in more rapid intubation, but significantly decreased the likelihood of esophageal intubations.

	Introduction

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In Fall 2005, a young man who was on his way home fell 10 m onto concrete. The arriving emergency medical service team found the patient in stable cardiocirculatory condition but with severe head trauma (Glasgow-Coma-Scale, 6), maxillofacial fractures, and a fractured femur. The patient was intubated and taken to the next county hospital; upon admission asystole developed. During advanced trauma life support, esophageal intubation was recognized and corrected. The patient was then transferred to a level one trauma center, where he died 2 days later of cerebral hypoxia.1

Intubating this patient was probably extremely difficult due to complex maxillofacial fractures with severe hemorrhage in the upper pharynx. Moreover, the laryngoscopist was inexperienced and initiated an intubation attempt that required skills and experience that he did not have. Thus, it may be prudent to provide built-in safety features for inexperienced laryngoscopists who have to manage blood or vomitus-filled airways to decrease the likelihood of fatal intubation complications.2

We have built a prototype suction laryngoscope, and compared it with a standard Macintosh laryngoscope in a mechanical model with continuing airway hemorrhage to simulate an extremely difficult intubation scenario. Our null hypothesis was that both devices would result in comparable results of the study's endpoints, duration to successful intubation, and number of esophageal intubations.

	METHODS

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This was a prospective, randomized, crossover, laboratory study using a newly developed Macintosh laryngoscope (size 3) (Fig. 1) with an incorporated suction feature versus a Macintosh laryngoscope (size 3) in a simulated bleeding airway scenario. Our suction laryngoscope consists of a stainless steel-guide tube that is fixed at the lingual surface of a standard Macintosh laryngoscope blade size three, which allows insertion of a large suction catheter (Rüsch, 20 French, Kernen, Germany). The suction catheter can be moved backward and forward through the stainless steel-guide tube. Fixed at one pivotal point at the laryngoscope, the stainless steel-guide tube can be turned around this point in the vertical line to optimize catheter placement. Positioning the laryngoscope to expose the vocal cords and simultaneous suction is performed with the left hand, rendering the right hand available to maneuver the suction tube and to intubate. The tip of the guide does not protrude from the blade in order to minimize risk of injuring pharyngeal mucosa, and laryngeal view is not obstructed. In a manikin (Laerdal, Stavanger, Norway), severe hemorrhage in the upper pharynx was simulated with black coffee running into the nasopharynx via tubes fixed in the nostrils with a standardized flow of 430 mL/min, maintained throughout laryngoscopy and intubation and thus obstructing the view of the glottis.

View larger version (45K): [in this window] [in a new window]   Figure 1. The suction laryngoscope. A 20-French suction catheter is inserted through an adjustable stainless steel-guide tube.

The IRB approved the study; 44 third-year medical students undergoing an emergency medicine class, including theoretical explanations and five manikin intubations using the Macintosh laryngoscope, volunteered for the study, and signed written informed consent. After handling of both devices was demonstrated to the students, they were asked to intubate the manikin with a 7.5 mm internal diameter cuffed tracheal tube with the suction laryngoscope and its integrated suction catheter, or with a standard Macintosh laryngoscope and a separate suction catheter of the same size and same model (Rüsch, 20 French, Kernen) in random order. In both groups, suction catheters were connected to a vacuum source with a standardized vacuum of 0.8 bar, which is the maximal vacuum reached with the commonly used suction device in our emergency medical service system.

The time from touching the laryngoscope until placement of the tracheal tube was measured with a stopwatch. Placement of the tracheal tube was controlled by the investigators by checking lung ventilation via the tube with a bag-valve device. The number of successful versus unsuccessful intubation attempts was recorded. In our model, we assessed the time needed to suction 250 mL, which is required to obtain a free view of the manikin's glottis, using our 20 French suction catheter and compared it with suction catheters used in previous studies.

All data are given as mean ± sd. Statistical analysis was performed using SPSS 12.0 statistical package (SPSS, Chicago, IL); duration of intubation attempts was analyzed using Student's t-test, intubation success was analyzed using Fisher's exact test. P < 0.05 was considered significant.

	RESULTS

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There was no significant difference in time needed for intubation when using the suction laryngoscope versus the Macintosh laryngoscope (43 ± 13 vs 52 ± 31 s; P = 0.07). The number of esophageal intubations was significantly lower when using the suction versus the Macintosh laryngoscope [6/44 (13.6%) vs 19/44 (43.2%); P = 0.004].

Using a 7.5-French suction catheter requires 37 s to suction 250 mL, using a 10-French catheter requires about 18 s, and using a 18-French catheter requires 8 s, whereas our device (20 French suction catheter) only needs about 6 s to suction 250 mL in our model with a standardized vacuum of 0.8 bar.

	DISCUSSION

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Several attempts to develop a suction laryngoscope have been made to improve intubation conditions in very difficult airways with severe oropharyngeal bleeding, when simultaneous suctioning and laryngoscopy is necessary.3–11 Problems surfaced quickly regarding thin and stiff suction tubes, which resulted in insufficient suction rates and complicated exact positioning of the suction tube, and fixed catheters are difficult to clean. For example, Khan8 attached a 7.5-French suction catheter to the laryngoscope blade only, which would require 37 s to suction 250 mL in our model. In Vavilala and Bramhall's laryngoscope, a 10-French catheter can be inserted,9 which requires about 18 s to suction 250 mL; further, Hempel used a 18-French catheter3 requiring 8 s for 250 mL, whereas our device only needs about 6 s for 250 mL. Because of the large lumen of our suction catheter, rapid removal of vomitus and blood clots is possible as well. Furthermore, the possibility of simple and rapid positioning of our suction catheter facilitates individual adjustment to each situation or anatomy. Since our suction tube guide is made of stainless steel with a large lumen, it allows easy and rapid cleaning.

Although the suction laryngoscope provided no significant time advantage to allow a more rapid intubation attempt, correct endotracheal intubations were more likely when using the suction laryngoscope over the standard Macintosh laryngoscope. Although our volunteers managed reasonably well performing simultaneous suctioning and laryngoscopy with the Macintosh laryngoscope and a separate suction catheter, performing the next step of manually changing from the suction catheter to the endotracheal tube was the key point of losing control over the situation. At this point, concentrating on grabbing the endotracheal tube distracted from maintaining optimal laryngoscopy especially with continuing simulated bleeding, thus increasing the probability of esophageal intubation. This may be an important observation when discussing how to optimize intubation training. Since intubation training for emergency medical service personnel is mainly performed in fasted patients undergoing scheduled surgical procedures in operating rooms, it may be insufficient to prepare for extremely difficult airway management scenarios.

In patients undergoing emergent intubation in operating rooms, even careful administration of 100% oxygen over 4 min improved Pao₂ only by about 37 mm Hg,12 whereas the identical maneuver in scheduled cardiac surgery patients with severe underlying pathophysiology resulted in Pao₂ increases of about 325 mm Hg.12 When performing an emergent intubation in the field in hypoxic and hypercapnic patients, oxygen administration success may be even less frequent due to continuing blood loss, trauma-related increased oxygen consumption, and hypoventilation. Some authors argue that intubation in the field is not only a waste of valuable time, but also threatens the patient's life with hypoxic episodes13 that may produce subsequent ischemia-mediated catastrophic intracranial pressure increases, or simply rapid death due to unrecognized esophageal intubation. Thus, the more severely a patient is injured, the more important a rapid and initially successful intubation attempt may become. However, because of the shortage of experienced laryngoscopists, emergency medical care is not available 24 h a day, 7 days a week, countrywide.

For example, one German study revealed that intubation attempts in the field may be performed only about 5–10 times per year per physician in physician-manned emergency medical services,14 suggesting that maintaining clinical skills to manage an extremely difficult airway is impossible when nonanesthesia or nonintensive care unit personnel works in the emergency medical services. Thus, esophageal intubation still occurs frequently in the emergency medical services, independently of whether they are physician- or paramedic based.15–20 However, the suction laryngoscope will never be able to compensate for insufficient airway management, but it might be a helpful device in bleeding airway scenarios.

Some limitations need to be noted. First, we used a mechanical model, which cannot represent a real patient, especially not with a facial trauma. Although our students were distressed by the high coffee flow and being clocked with a stopwatch, it cannot be compared with a true clinical situation. On the other hand, we wanted to perform the first step of evaluating the suction laryngoscope in a mechanical model in order to prevent harm to patients. After proving the value of the suction laryngoscope, the next step will be to use this device in patients. In this special case of massive airway bleeding, it is hardly possible to perform a study in a real-life clinical scenario.

Second, our medical students simulate inexperienced rescuers, but do not professionally respond with an emergency medical service to field emergencies. As a consequence of the participant's lack of intubation practice, even in the suction laryngoscope group the number of esophageal intubations was too high. Especially in cases of airway bleeding, the rescuer's competence in difficult airway management is more important than the use of upgraded airway devices. Thus, a study with experienced emergency doctors will have to follow. Third, using our device has potential risks. The more power the vacuum source produces, the higher the risk of mucosal damage by mucosal elevation and invagination into the catheter-tip's hole or even resulting pulmonary damage. However, this risk depends on the vacuum source and is the same when using a Macintosh laryngoscope and a separate suction tube. In massive airway bleeding, suction is necessary to enable intubation. Although the stainless steel-guide tube does not protrude from the blade to decrease the risk of mucosal lesions, it could still happen accidentally. The suction catheter itself is flexible and will not cause damage. Moreover, our bleeding rate may have been too rapid to exactly represent bleeding stemming from maxillofacial blood vessels, but may have been similar to massive regurgitation of stomach contents. Also, our simulated blood was coffee, since multiple intubation attempts with real blood would have produced changing intubation conditions over time due to coagulation and drying effects.

In conclusion, when compared with a standard Macintosh laryngoscope, using a suction laryngoscope did not result in more rapid intubation, but significantly decreased the likelihood of esophageal intubations.

	ACKNOWLEDGMENTS

 
We are indebted to Fritz Zschiegner for technical advice.

	Footnotes

 
Accepted for publication January 31, 2008.

Supported, in part, by the Austrian National Bank Science Foundation grant 11448, Vienna, Austria.

No author has any conflict of interest in regard of devices or methods described in this article.

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a colleague Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Mitterlechner, T. Articles by Wenzel, V. Search for Related Content PubMed PubMed Citation Articles by Mitterlechner, T. Articles by Wenzel, V. Related Collections Critical Care Economics and Health Care Research Equipment