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Anesth Analg 2000;91:1513-1519
© 2000 International Anesthesia Research Society

GENERAL ARTICLES

Balloon Versus Conventional Laryngoscopy: A Comparison of Laryngoscopic Findings and Intubation Difficulty

Spyros D. Mentzelopoulos, MD, Constantina N. Romana, MD, Despina S. Corolanoglou, MD, Maria J. Tzoufi, MD, and Evangelia A. Karamichali, MD

Department of Anesthesiology, Evangelismos General Hospital, Athens, Greece

Address correspondence and reprint requests to Spyros D. Mentzelopoulos, MD, 2A Kypseli Str., 11362, Athens, Greece. Address e-mail to sdm{at}hol.gr


   Abstract
Top
 Abstract
Introduction
 Methods
 Results
 Discussion
 References
 
We compared laryngeal aperture (LA) exposure and endotracheal intubation difficulty scale (IDS) scores between balloon-assisted and conventional laryngoscopy. Thirty-two anesthetized and paralyzed elective surgery patients underwent laryngoscopy with a standard number 4 and a modified number 4 curved blade carrying a 6F Fogarty catheter. The balloon laryngoscopy technique included modified blade tip insertion into the vallecula, Fogarty catheter balloon inflation with 2 mL of air, and blade elevation until LA exposure maximization. On maximal LA exposure with both blades, the LA views were videotaped with a camcorder aligned to blade light source and the exposed LA areas measured electronically. The IDS scores were determined on passing the tip of an endotracheal tube through the vocal cords. The patient head position, the angle of laryngoscope handle elevation, and the time available for airway instrumentation were standardized. The data from 27 patients were analyzed. The exposed LA areas were significantly larger with balloon laryngoscopy than conventional (median, interquartile range: 0.94, 0.65–1.80 cm2 vs 0.52, 0.39–1.46 cm2 respectively) (P = 0.027), and the IDS scores lesser (median, interquartile range: 0, 0–1 vs 1, 0–2 respectively) (P = 0.012). We concluded that balloon laryngoscopy facilitates elective airway management.

Implications: The results of this study show that balloon-assisted laryngoscopy facilitates the airway management of elective surgery patients by providing greater laryngeal exposure than conventional laryngoscopy. Thus, the routine use of a curved blade carrying the inflatable balloon of a 6F Fogarty catheter on its distal end is recommended.


   Introduction
Top
 Abstract
 Introduction
Methods
 Results
 Discussion
 References
 
The laryngoscopic view grade (1) is a component of the endotracheal intubation difficulty scale (IDS) score (2). The visualization of only the posterior glottis or less is associated with intubation procedure prolongation (3), the need for external laryngeal manipulation (4), and the potential use of additional/alternative airway management equipment/techniques (5,6). Furthermore, the incidence of difficult tracheal intubation (5) is increased in patients with difficult direct laryngoscopy (5,7).

Laryngoscopy with a modified curved blade carrying either two 10 Foley catheters (8) or a 6F Fogarty catheter (9) (Fig. 1) facilitates tracheal intubation by improving the laryngoscopic view in patients with predicted difficult airway management and poor laryngeal visualization during conventional laryngoscopy (8,9). This new laryngoscopic technique, balloon laryngoscopy, uses combined balloon inflation and blade elevation to improve lifting of the epiglottis (8–12).



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  		Figure 1. One of the modified number 4 curved blades used in the present study. A 6F Fogarty catheter is attached on the midline of the blade concave surface. The Fogarty catheter balloon is inflated with 2 mL of air.

 
We tested the hypothesis that balloon laryngoscopy might result in improved laryngoscopic view and decreased IDS score relative to conventional laryngoscopy if used in routine clinical practice.


   Methods
Top
 Abstract
 Introduction
 Methods
Results
 Discussion
 References
 
Ethics committee approval and informed, written patient consent were obtained. Thirty-two normotensive, ASA physical status I-II, elective surgery patients were enrolled. All participants had previous anesthesia records that confirmed the feasibility of mask ventilation and laryngeal visualization (arytenoids or more) with conventional laryngoscopy. Exclusion criteria were age >65 yr, morbid obesity, and a history of 1) any condition predisposing to either pulmonary aspiration or airway hyperreactivity, 2) head/cervical spine injury, 3) intraocular or pharyngolaryngeal pathology, and 4) anesthetic drug/adjunct-induced allergic reactions. Preoperatively, the simplified airway risk index score (13) was determined. Premedication was with oral lorazepam and intramuscular atropine.

The patients lay supine on the operating table that was kept parallel to the floor (11) with their heads elevated by pads placed below the occiput (14). Anesthesia was induced with fentanyl 4 µg/kg and thiopental 5 mg/kg. IV boluses of esmolol and lidocaine were added to blunt the reflex responses to airway instrumentation (15). Neuromuscular blockade was achieved with cisatracurium 0.2 mg/kg.

The manual patient ventilation was continued until the abolishment of the train-of-four response (ulnar nerve stimulation). Laryngoscopy was then performed with a modified number 4 curved blade carrying a 6F Fogarty catheter (Fig. 1) and a standard number 4 curved blade in random order. Just before each laryngoscopy, the patient’s head was placed in the standard intubating position (35° lower neck flexion and 15° plane-of-face extension relative to horizontal) (16) with the aid of an automatic angle finder.

In each patient, both laryngoscopies were performed by one of four experienced anesthesiologists. Balloon laryngoscopy technique (8–12) included modified blade tip insertion into the vallecula, Fogarty catheter balloon inflation with 2 mL of air (Fig. 1), and anterior blade-elevation until laryngeal exposure maximization. Each laryngoscopy lasted 60 s before attempting intubation. The laryngoscope handle-to-horizontal angle was kept at 25° with the angle finder’s aid and the light source-axis-to-horizontal angle at 35°. On laryngeal view optimization, the laryngoscopist’s hand grasping the laryngoscope handle was immobilized and the 25° handle-to-horizontal angle reconfirmed. External laryngeal manipulation (4) was used only when the posterior glottis or less was exposed solely with the blade elevation. In case of failure to expose the arytenoids, the study protocol was to be abandoned.

The "upper incisor-to-arytenoids" distance and the "upper incisor-to-blade light source" distance were measured with a gum elastic bougie, and their difference yielded the light source-to-laryngeal aperture (LA) distance. Subsequently, a Sony TRV 310 E camcorder (Sony, Tokyo, Japan) was brought to 2 cm behind the blade’s convex surface to capture the LA image. The 2-cm recording distance was selected to avoid capturing the Fogarty catheter image during balloon laryngoscopy (12). The camcorder’s zoom setting was standardized throughout the study. The angle finder was used to keep the camcorder roof’s longitudinal and corresponding transverse axes parallel to the laryngoscope’s light source-axis and horizontal plane, respectively.

The face-plane-to-horizontal angle was measured just before and immediately after the laryngeal view recordings and on the subsequent passage of an endotracheal tube (ETT) through the vocal cords, and any variation of >=5° from its initial value (15°) was considered a study protocol failure.

After the LA recordings, 30 s was allowed to confirm (visually or by end-tidal CO2 monitoring) (17) the passage of the tip of an ETT (Portex blue line, internal diameter of 8.5 and 7.5 mm for men and women, respectively) through the vocal cords. The first airway instrumentation procedure was concluded with ETT withdrawal. In between the instrumentation procedures, the manual patient ventilation was resumed (for 60 s), and thiopental (2.5 mg/kg) was readministered. The second airway instrumentation procedure was concluded with the ETT’s placement into the trachea.

The difficulty with laryngeal/tracheal intubation was graded with a slight modification of the original IDS (Table 1). The ideal intubation was defined as one performed without effort and external laryngeal manipulation, on the first attempt to pass the ETT through the vocal cords, without the use of an ETT guide, with full laryngeal visualization and the vocal cords abducted (2) (Table 1).


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  		Table 1. The Modified Endotracheal Intubation Difficulty Scale (IDS) Used in the Present Study
 
The patient data were to be discarded if the preset time limits of a laryngoscopic or an intubation procedure were exceeded, and if IDS-grading discrepancies between the laryngoscopist and the two independent observers (Table 1) were confirmed.

The recordings were displayed on a personal computer screen and the laryngoscopic images grabbed, saved, and encoded in Photoshop 5.0 (Adobe Systems Inc., San Jose, CA); identical codes were assigned to the corresponding light source-to-LA distances, and a random number was assigned each time to the laryngoscopic technique. Image resolution was always kept at 72 pixels/inch. The visible LA areas were defined as the areas encircled by the epiglottis base, the vocal cords, and the arytenoids. The LA-area borders were drawn on each laryngoscopic image (Fig. 2).



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  		Figure 2. Determination of the exposed portion of the laryngeal aperture. The area of the exposed laryngeal aperture portion was encircled by dark lines drawn on the base of the epiglottis (E), the vocal cords (VC), and the arytenoids (AR).

 
Each laryngoscopic procedure was simulated by corresponding the LA to a 1 cm2 square (drawn on millimeter paper) and by aligning the camcorder and a laryngoscope with a number 4 Macintosh blade relative to each other and positioning them as described above; the light source-to-square distance was adjusted to the corresponding light source-to-LA distance and the square’s image was captured. The height and width of this reference image were then adjusted so that the square’s surface area was 1.0000 cm2 when measured with Autocad 2000 (Autodesk Inc., San Rafael, CA). Subsequently, identical adjustments were performed on the corresponding laryngoscopic image, and the encircled LA area was measured with Autocad 2000.

Before the clinical study, this distance was determined with a gum elastic bougie 10 times repeatedly during test laryngoscopies performed (as described above) in a manikin. During each laryngoscopy, the maximal within-measurement variability was <=0.2 cm.

The determinations of the LA-area borders, image size adjustments, and LA-area measurements were performed consecutively and separately by two investigators who were blinded to the laryngoscopic technique. All codes were broken after measurements’ completion, and the means of the LA-area values determined by the two observers were used in the statistical analysis.

The IDS scores and LA-area values determined during balloon and conventional laryngoscopy were compared with the Mann-Whitney exact U-test (2,7) (SPSS Version 8.0; SPSS, Chicago, IL). Significance was accepted at P < 0.05.


   Results
Top
 Abstract
 Introduction
 Methods
 Results
Discussion
 References
 
The data from 27 patients were analyzed. The cause of data rejection was the failure to standardize the head posture. Table 2 displays demographic and preoperative airway evaluation data. There were no study protocol-related adverse hemodynamic effects or clinically notable upper airway trauma; furthermore, postoperative throat discomfort was never reported. Oxygen saturation was maintained >95%, and laryngeal intubation was achieved within 30 s in all cases.


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  		Table 2. Patient Demographic (1–6) and Preoperative Airway Assessment Data (7–13), and Simplified Airway Risk Index Scores (14)
 
The light source-to-LA distances were similar in each patient with both blades (maximal difference = 0.4 cm). The applied computer methodology allowed consistent LA-area-determination within 0.01 cm2. Balloon laryngoscopy resulted in significantly greater LA exposure (P = 0.027) and lesser IDS scores (P = 0.012). Fig. 3 displays the patient-by-patient LA-area values and IDS scores, respectively. The median LA areas were 0.94 cm2 (25th–75th percentile = 0.65–1.80 cm2) and 0.52 cm2 (25th–75th percentile = 0.39–1.46 cm2) and the median IDS scores were 0 (25th–75th percentile = 0–1) and 1 (25th–75th percentile = 0–2) with balloon and conventional laryngoscopy, respectively. The best laryngoscopic view grade was <=II and included the posterior portion of the vocal cords or more in all cases. Excessive lifting force was never used. The conventional/balloon laryngoscopy ratios of supplementary attempts at intubation, necessary additional equipment, best laryngoscopic view grade II, and necessary external laryngeal manipulation (see also Table 1) were 12/4, 7/3, 4/1, and 12/6, respectively. Finally, the conventional/balloon laryngoscopy ratio of "ideal" intubations (IDS score = 0) was 10/19 (Patients 3, 5, 6, 8, 10–12, 14, 20, 23 and Patients 1–3, 5–12, 14, 19–24, 27 in Fig. 3B, respectively).



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  		Figure 3. Patient-by-patient values of the surface area of the exposed laryngeal aperture (A), and the intubation difficulty scale (IDS) score (B). SA = supplementary attempt at intubation; G = endotracheal tube guide; CLII = Cormack and Lehane laryngoscopic view Grade II; ELM = external laryngeal manipulation. In Fig. 3B, the IDS score bars represent the sums of the IDS component scores (see also Table 1); the abbreviations added above each IDS score bar provide a precise description of how the trachea of the corresponding patient was intubated when the corresponding laryngoscopic technique was used. Apart from patient 17, in whom two SAs at intubation were needed with the Macintosh blade, all the IDS component scores (when present) add one point to the total IDS score. The absence of an IDS score bar (with one or both laryngoscope blades) indicates ideal intubation (IDS score = 0) as defined in Methods.

 

   Discussion
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
References
 
We demonstrated that balloon laryngoscopy results in improved laryngeal view and reduced tracheal intubation difficulty when compared with the conventional laryngoscopic technique. Balloon laryngoscopy provides two sequential laryngoscopic maneuvers with additive effects on LA exposure (Fig. 4). When the modified blade tip reaches the hyoepiglottic membrane, the still-deflated balloon is positioned below the tongue base and the hyoid body. The inflation of the balloon causes anterior hyoid/tongue base elevation, stretching of the hyoepiglottic membrane (and ligament) (18), and epiglottis lifting (Fig. 4) that is subsequently augmented by the anterior blade elevation.



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  		Figure 4. Representation of laryngoscopic conditions in patients with unfavorable upper airway contour for the establishment of effective contact for epiglottis lifting between the distal concave surface of a Macintosh laryngoscope blade and the hyoid bone. LB = laryngoscope blade; B = balloon; E = epiglottis; G = glottis; ET = tip of epiglottis; H = body of the hyoid; HM = hyoepiglottic membrane. I, conventional laryngoscopy; the arrows point toward the direction of blade elevation; however, the desired epiglottis lifting is not achieved. II, balloon laryngoscopy; the arrows point toward the direction of displacement of the anatomic components of the larynx; the bold dashed line indicates the upward motion of the epiglottis. Note that with balloon laryngoscopy, the inflated Fogarty catheter balloon fills the gap between the blade and the hyoid and initiates the epiglottis lifting by effectively stretching the hyoepiglottic membrane and ligament; a subsequent blade elevation results in augmented epiglottis lifting and improved laryngeal visualization. Reproduced in part with permission from Ellis H, Feldman S, eds. Anatomy for Anaesthetists. 7th ed. Oxford: Blackwell Science Ltd, 1997.

 
During conventional laryngoscopy, effective hyoepiglottic membrane/ligament stretching can occur only if adequate contact is established between the distal blade-concave surface and the hyoid/tongue base. However, such contact is not always established because of anterior upper airway contour variability (19) (Fig. 4). A restricted LA exposure (3) and difficulties with tracheal intubation may then ensue. In such cases, an inflated balloon can fill the gap between the distal blade-concave surface and the hyoid/tongue base (Fig. 4) and improve LA visualization.

The above theoretical considerations are supported by our previous experience (8,9) and by the present results that show a median increase of 41% (range -25%–325%) in the exposed LA area with balloon laryngoscopy. In patients in whom almost the entire LA was visible with conventional laryngoscopy, the laryngoscopic findings, exposed LA-area values, and IDS scores were similar with both blades (Fig. 5, A and B). However, balloon laryngoscopy consistently resulted in improved LA visualization and decreased IDS scores in patients with Grade II views during conventional laryngoscopy (Fig. 5, C and D). Furthermore, in eight patients with Grade I views with both blades, both the exposed LA-area values and IDS scores were improved with balloon laryngoscopy.



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  		Figure 5. Laryngoscopic findings during conventional (A, C) and balloon (B, D) laryngoscopy. A, B: in this patient (Patient 5 in Fig. 3), a Grade I laryngoscopic view and an intubation difficulty scale (IDS) score of 0 were provided by both blades, and the areas of the exposed portions of the laryngeal aperture (LA) were 1.34 cm2 and 1.86 cm2 with the conventional and the modified blade respectively. C, D: in this patient (Patient 19 in Fig. 3), the laryngoscopic view grades, IDS scores and exposed LA-area values with the conventional and the modified blade were II and I, 4 and 0, and 0.20 cm2 and 0.85 cm2 respectively. D: the artifacts displayed below the blade’s light source are because of reflections of light on patient secretions.

 
It could be argued that the further stretching caused by the inflated balloon might cause soft tissue damage (e.g., ruptures of the upper airway mucosa) in the vallecula epiglottica. However, the modified blade tip was never stained with blood immediately after withdrawal. With balloon laryngoscopy, the actual lifting pressure is exerted by the smooth upper surface of a compressible balloon and not by the rigid metallic surface and/or tip of a Macintosh blade (10). Also, the overall number of supplementary attempts at intubation and consequently the number of possible ETT tip impacts on the arytenoids that (if sufficiently forceful) may traumatize the cricoarytenoid joints (20) was three times larger with conventional laryngoscopy.

The standard intubating position was chosen as a simple and reproducible geometrical standard that is easily applicable in research work (16). The 25° angle of handle elevation was chosen to both minimize the potential leverage forces exerted by the blade on the upper teeth (16) and maximize LA exposure.

We measured the cross-sectional area of the visible part of the gap between the vocal cords and the arytenoids. This gap is what we are actually looking for during direct laryngoscopy to intubate the trachea. The absence of Grade III laryngoscopic views despite the participation of six patients with a simplified airway risk index score of >=3 should be because of the reliability of the laryngoscopic inclusion criterion.

The IDS score was adjusted to the study conditions by replacing the alternative technique component (2) by the ETT guide component, and by excluding the supplementary operator component (2), because laryngoscopic view may vary between laryngoscopists (21). The absence of intubations with major difficulty (IDS scores >5) (2) and the relatively low proportion of ideal intubations with conventional laryngoscopy (38% vs 53%) (2) should be a result of the laryngoscopic inclusion criterion and the limited number of the study participants, respectively. However, the proportion of ideal intubations with balloon laryngoscopy was nearly double (70%), clearly showing its increased effectiveness.

In conclusion, we recommend the routine use of the Fogarty catheter blade in the airway management of elective surgery patients because it is a simple, effective, and easy-to-use modification of the standard curved blade that improves laryngeal visualization and facilitates endotracheal intubation.


   Acknowledgments
 
The authors thank Mr. N. Nikolaides and Dr. P. Giannakopoulos for their technical advise and support, and Drs. E. Papageorgiou and S. Zakynthinos for their helpful suggestions on the revision of the original manuscript.


   References
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 

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  10. Mentzelopoulos SD, Ballas CJ, inventors. International Application No. PCT/GR97/00038 published under the Patent Cooperation Treaty. Laryngoscope with a flexible blade, inflatable balloons, two thin double lumen tubes, and one thin single lumen tube. International Patent Document No. WO 98/19589. May 14, 1998.
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Accepted for publication August 2, 2000.




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Lippincott, Williams & Wilkins Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins and Stanford University Libraries' HighWire Press®. Copyright 2000 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999 HighWire Press