Eur Arch Otorhinolaryngol (2009) 266:1583–1588

DOI 10.1007/s00405-009-0974-z

LARYNGOLOGY

Curved rigid laryngoscope: missing link between direct suspension laryngoscopy and indirect techniques?

Gerhard Friedrich · Karl Kiesler · Markus Gugatschka

Received: 6 February 2009 / Accepted: 25 March 2009 / Published online: 7 April 2009© Springer-Verlag 2009

Abstract Microlaryngoscopy is the standard procedurefor endolaryngeal surgery. The advantages are a steadyoperating Weld, bimanual handling and stereoscopic view inhigh-resolution magniWcation. The major drawback is thatthe oropharyngeal structures have to be brought into anunnatural position by the straight rigid laryngoscope withconsiderable forces occurring. These forces can lead to tis-sue injuries or even make a microlaryngoscopic operationimpossible. To overcome these disadvantages, a few casestudies using curved rigid laryngoscopes are published.However, there is still a lack of information to what extentcurved rigid laryngoscopes could actually improve theendolaryngeal exposure with less forces occurring. It wasthe aim of this study to gain basic data on the forces that areneeded for endolaryngeal exposure with a prototype of acurved rigid laryngoscope and to compare the occurringforces with straight laryngoscopes. In 30 consecutivepatients scheduled for routine microlaryngoscopic proce-dures the curved laryngoscope was inserted and occurringforces were measured by a tension spring balance in fourdiVerent head positions. A standard straight laryngoscopewas inserted afterwards and measurements were takenagain. Our results showed that the occurring forces couldbe reduced signiWcantly in each head position when com-pared with a standard straight laryngoscope. Similarly, theanterior commissure could be exposed in a signiWcantly higherpercentage with the curved laryngoscope. In conclusion, we

could show that even with a moderate-curved rigid laryngo-scope a signiWcant reduction of the forces to the oro-pha-ryngeal tissues can be obtained and that endolaryngealexposure is possible in virtually all patients. Bimanual pre-cise operations should be possible in the common way likein standard microlaryngoscopy with the only diVerence ofnot using a microscope, but operating via a monitor. We donot think that traditional microlaryngoscopy with straightinstruments can or should be replaced by curved laryngo-scopes, but these techniques could bridge the gap to indi-rect techniques in particular in specialised institutionsdealing frequently with diYcult patients and situations.

Keywords Microlaryngoscopy · Curved laryngoscopes · Endolaryngeal exposure

Introduction

Indirect endolaryngeal surgery was performed as early as1859 [6], but remained anecdotal until the laryngeal mirrorwas introduced into medicine by Türck and Czermak [2,17, 20]. After that and especially after the introduction oftopical anaesthesia by Jelinek [4], transoral mirror-guidedindirect laryngeal surgery became standard for manydecades for minor and benign laryngeal lesions. Introduc-tion of microlaryngoscopy in the 1960s was a breakthroughin laryngology and enabled bimanual surgery under directmicroscopic vision and thus expending the Weld of endola-ryngeal surgery substantially [1, 3, 12–14, 16, 21]. With thedevelopment of chip-on-the-tip Xexible endoscopes thatprovide an excellent high-resolution picture these indirecttechniques experience a comeback as oYce-based proce-dures [15, 19, 22, 25]. Each technique has its special advan-tages and disadvantages and optimal therapy requires

G. Friedrich (&) · K. Kiesler · M. GugatschkaDepartment of Phoniatrics, Speech and Swallowing, ENT University Hospital, Medical University Graz, Auenbruggerplatz 26-28, 8036 Graz, Austriae-mail: gerhard.friedrich@klinikum-graz.at

M. Gugatschkae-mail: markus.gugatschka@klinikum-graz.at

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careful selection of the appropriate technique adapted to theindividual situation.

The advantages of direct microlaryngoscopy are a steadyoperating Weld, bimanual handling and stereoscopic view inhigh-resolution magniWcation. The major drawback is thatthe oropharyngeal structures have to be brought into anunnatural position by the straight rigid laryngoscope withconsiderable forces occurring [5, 7]. These forces can leadto tissue injuries or even make a microlaryngoscopic opera-tion impossible. In order to improve the technique of endo-laryngeal surgery, telescopic video microlaryngeal surgerywas developed [8–10, 24]. The use of rigid endoscopestogether with a video system has several advantages. Itallows the use of very slim rigid laryngoscopes and enablesan excellent overview over the whole endolaryngeal struc-tures due to the signiWcantly enhanced depth of Weld andgreater Weld of vision as compared to a microscope. DiVer-ent angled endoscopes (0°, 30°, 70°) together with curvedinstruments give access to regions of the endolarynx thatcannot be exposed directly. Comparison of this approachand standard microlaryngoscopic procedures showed spe-ciWc advantages and disadvantages for each of them [23].

When using endoscopes instead of a microscope astraight laryngoscope is not a precondition anymore. Arigid curved laryngoscope adapted to the anatomy of theoral cavity and the pharynx should allow an atraumaticinsertion in virtually all anatomical conWgurations with sig-niWcantly reduced forces. High-quality endoscopes in com-bination with high-resolution cameras and video monitorsand the use of curved instruments should enable a precisebimanual monitor-guided operation and may combineadvantages of both approaches.

There is a lack of information to what extent curvedrigid laryngoscopes could actually improve the endolaryn-geal exposure with less force. It was the aim of this study togain basic data on the forces that are needed for endolaryn-geal exposure with a prototype of a curved rigid laryngo-scope and to compare the occurring forces with straightlaryngoscopes.

Materials and methods

Curved laryngoscope

Together with the Storz Company a prototype of a curvedrigid laryngoscope was designed. A standard Kleinsasserlaryngoscope was bent at 20° as shown in Fig. 1. We tookcare that a small lumen remained visible under directvision, so that the laryngoscope can be inserted withoutendoscopic guidance (Fig. 2). Laterally, a metal tube wasplaced penetrating the laryngoscope that enables the intro-duction of a standard 30° nose endoscope (Storz

7230BWA) (Figs. 1, 2). Within this tube, the endoscopecan be moved forward and backward and rotated as well togive full overview over the regions of interest. A videocamera was attached to the endoscope and the endolaryn-geal picture displayed on a video monitor (Fig. 3).

Procedures and measurements

We have prospectively analysed 30 consecutive adultpatients scheduled for microlaryngoscopy at the PhoniatricsDepartment, Ear Nose and Throat University Hospital,Medical University Graz. Patients underwent a routinemicrolaryngoscopy due to the whole variety of micro-endo-laryngeal procedures including benign and malignantlesions. Descriptive data and laryngoscopes used are shownin detail in a previous paper [5]. All interventions weredone under general anaesthesia with endotracheal intuba-tion. The head of the patient was rested in the headrest afterHaslinger which allows a variable adjustment of thepatient’s head. The laryngoscope was hold in place with thelaryngoscope holder (Storz 8575 GK) in its modiWed

Fig. 1 Laryngoscope bent at 20°. A metal tube is placed laterally anda standard 30° nose endoscope is inserted penetrating the laryngoscope

Fig. 2 Curved laryngoscope in place. The endolarynx can be visual-ised by a small remaining lumen

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version with a bent arm. The laryngoscope holder wasrested on the chest support (Storz 8575L). With a tensionstring balance the force exerted on the chest support by thelaryngoscope holder was measured (Fig. 3) [5, 7]. Measure-ments were taken in four positions: neutral (head at thesame level at as the operating table), extension (head 8 cmbelow the table), moderate Xexion (head elevated 5 cm),maximum Xexion (head elevated 10 cm) (Figs. 3, 4). Weconsecutively calculated occurring forces on teeth/jaw andbase of tongue as described previously [5, 7].

Prior to the operation, the curved laryngoscope wasinserted and the measurements were taken in the four headpositions. After the removal of the curved laryngoscope, astandard straight laryngoscope was inserted and measure-ments were taken again in the four positions. The type oflaryngoscope was chosen according to the individualpatient and the surgical procedure planed.

It was the goal to expose the anterior commissure ineach position. If this was not possible manual externalcounterpressure was applied on the larynx. The force of thecounterpressure was subjectively rated as minimal, mediumor maximal. All measurements were taken by the Wrstauthor (G.F.). If exposure of the anterior commissure wasnot possible with maximum force and maximum counter-pressure it was rated “not possible”. SuYcient exposure for

the planned procedure could be achieved in all patients. Nocomplication occurred in any case. All patients gave a writ-ten informed consent and an approval by the local ethicscommittee was obtained.

Statistical analysis was performed using SPSS (Version12.0, SPSS Inc, Il, USA). Kolmogorov–Smirnov test wasused for the analysis of normal distribution and for thecomparison of normal variables we used �2 analysis;

Fig. 4 Positioning of the head using the adjustable Haslinger headrest in four positions

Fig. 3 Setting during laryngeal exposure with the curved laryngo-scope. The entire glottis is visualised on the screen using a 30° noseendoscope with a camera attached. The pressure exerted on the chestsupport is measured with a tension spring balance

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ANOVA with repeated measurements was performed inmetric variables.

Results

In general, it could be shown that the mean weight exertedon the chest support could be reduced signiWcantly in allpositions using the curved laryngoscopes when comparedwith a straight laryngoscope (P value always <0.001;Table 1, Fig. 5). In curved laryngoscopes signiWcant diVer-ences occurred between extension (mean 4.8 kg) and neu-tral position (mean 3.1 kg; P < 0.001). No signiWcantdiVerences occurred between neutral position, moderateand maximum Xexion. In contrast to straight laryngo-scopes, in the curved laryngoscopes lowest forces requiredoccurred at moderate Xexion and not at maximum Xexionposition (Fig. 5).

Likewise, the anterior commissure could be exposed in asigniWcantly higher percentage with the curved laryngo-scope: in either Xexion position no or only minimum exter-nal counterpressure was necessary to expose the anteriorcommissure in all patients (Fig. 6). In neutral position,medium to maximum external counterpressure was neces-sary to visualise the anterior commissure in three cases only(10%) compared with 13 (43%) cases with standard

laryngoscopes. In extension, position the anterior commis-sure could not be exposed in four cases (13%), comparedwith 12 cases (40%) in standard laryngoscopy.

Discussion

In 2002, Müller et al. [18] reported the successful use of acurved laryngoscope in a case of one patient whose endo-larynx could not be exposed with straight laryngoscopes.The curvature of this laryngoscope was not declared in thispaper, but might be around 50° according to the Wgure. AXexible endoscope was used to visualise the larynx.

Kim et al. [11] reported their experiences in sevenpatients with a curved rigid laryngoscope. This laryngo-scope had a curvature of 70° and the larynx was visualisedwith a Xexible Wberscope and a monitoring system. Withcurved forceps and a suction device, endolaryngeal surgery

Table 1 Mean values and standard deviation of forces measured

P values showing diVerences between the two laryngoscopes

Mean weight in kg (curved laryngoscope)

Mean weight in kg (straight laryngoscope)

P value

Extension 4.8 (§1.4) 6.4 (§1.1) <0.001

Neutral position 3.1 (§1.2) 5 (§1.5) <0.001

Moderate Xexion 2.7 (§1.3) 4.5 (§1.6) <0.001

Maximum Xexion 3 (§1.3) 4.2 (§1.7) <0.001

Fig. 5 Measured pressures at the four positions with curved andstraight laryngoscopes. P values showing diVerences between the twolaryngoscopes always <0.001

Fig. 6 Percentage of exposure of the anterior commissure in four diVerent positions. No or minimal, medium to maximum external counterpressure or, exposition not possible

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could be performed in all patients without complications.They concluded that the curved rigid laryngoscope with aWberoptic imaging system might provide a better laryngealvisualisation and less traumatic manipulation in patientswith diYcult laryngeal exposure.

Our device is diVerent from the aforementioned. Wedesigned a rigid laryngoscope with a moderate curvature of20°, thus enabling insertion of the laryngoscope withoutoptical help. This curvature furthermore allows using a cus-tom made 30° nose endoscope for visualisation. This pro-vides a much higher resolution when compared with aWberscope.

The major question is what the optimal design would bewith respect to manufacturing, instrument handling, visual-isation of the endolaryngeal structures and most of all thereduction of the forces exerted on the oropharyngeal tis-sues. Given the natural anatomy of the human vocal tract itis evident that a laryngoscope reXecting this anatomyshould be curved strongly. It is also evident that strongcurved laryngoscopes create more technical problems withrespect to visualisation, manufacturing and handling. Mod-erately curved laryngoscopes can be developed easily fromthe standard straight laryngoscopes. These can be used withcustom made instruments or slightly modiWed custom madeinstruments and are certainly easier to handle.

When using our laryngoscope with a moderate curvaturewe could show that a signiWcant reduction of the forcescompared with straight laryngoscopes can be achieved inall positions. Furthermore, positioning of the patient’s headwas not critical anymore as it is in the case of straight laryn-goscopes [5]. Either in neutral or in either Xexed position amean force of approximately 3 kg was exerted to the chestsupport. This is in the lowest percentile of patients operatedwith standard microlaryngoscopy as we could show in aformer study. Only in 13 patients out of 100, a force lowerthan 3 kg had to be applied using straight laryngoscopes,but without full exposure of the anterior commissure [7].

In all of our patients, we could expose the anterior com-missure in neutral or Xexed position with no or minimalexternal counter pressure. We can support the fact that dis-playing the endolarynx with an endoscope provides a sig-niWcantly enhanced overview over the endolaryngealstructures with an enhanced depth of Weld [8]. The possibil-ity of our prototype to move the endoscope for- and back-ward plus rotating enhances the visualisation of all regionsof the larynx and to focus the regions of interest.

Owing to the fact that this moderately bent laryngoscopehas a remaining Weld of vision the handling was very easyand by following the endotracheal tube, it could be insertedinto the endolarynx without any optical help (Fig. 2). Mod-erately bent instruments should be very similar to use asstraight instruments so there should be only a very limitedlearning curve.

The laryngoscope we designed is a prototype and is notfor use in clinical routine at this stage. At the moment, theposition of the camera attached to the endoscope is not opti-mal and interferes to a certain extend with the handling ofthe instruments. For the future chip-tip cameras linked to anendoscope could be the most promising development. Theusage of a standard 30° nose endoscope provides a cheapand high-quality solution for displaying the larynx.

In conclusion, we could show that even with moderate-curved rigid laryngoscopes a signiWcant reduction of thepressure to the oro-pharyngeal tissues can be obtained andthat endolaryngeal exposure is possible in virtually allpatients. Bimanual precise operations should be possible inthe common way like in standard microlaryngoscopy withthe only diVerence of not using a microscope, but operatingvia a monitor. At the moment, it is not clear whether whichcurvature would be the optimal with respect to the diVerentrequirements of such a device.

We do not think that traditional microlaryngoscopywith straight instruments can or should be replaced bycurved laryngoscopes but these techniques could bridgethe gap to indirect techniques in particular in specialisedinstitutions dealing frequently with diYcult patients andsituations.

ConXict of interest statement The authors declare that they have noconXict of interest.

References

1. Albrecht R (1954) Über den Wert kolposkopischerUntersuchungsmethoden bei Leukoplakien und Carcinomen desMundes und des Kehlkopfes. Arch Ohren Nasen Kehlkopfheilkd165:459–463

2. Czermak J (1858) Über den Kehlkopfspiegel. Wiener Medizini-sche Wochenschrift 8:196–198

3. Jako GJ (1970) Laryngoscope for microscopic observation surgeryand photography. Arch Otolaryngol 91:196–199

4. Jelinek E (1884) Das Cocain als Anästheticum und Analgeticumfür den Pharynx und Larynx. Wiener Medizinische Wochenschrift34:1334–1337, 1364–1367

5. Friedrich G, Gugatschka M (2009) InXuence of head positioningon the forces occurring during microlaryngoscopy. Eur ArchOtorhinolaryngol 2009 (in press)

6. Green H (1859) Morbid growths within the larynx. GP Putnam,New York

7. Gugatschka M, Gerstenberger C, Friedrich G (2008) Analysis offorces applied during microlaryngoscopy: a descriptive study. EurArch Otorhinolaryngol 265(9):1083–1087

8. Kantor E, Berci G, Parlow E, Paz-Partlow M (1991) A completelynew approach to microlaryngeal surgery. Laryngoscope 101:676–679

9. Kantor EA, Berci G, Partlow E, Paz-Partlow M (1991) Ancillaryinstruments for the video microlaryngoscope. Ann Otol RhinolLaryngol 100:317–319

10. Kawaida M, Fukuda H, Kohno N (2001) Video-assisted rigidendoscopic laryngosurgery: application to cases with diYcult la-ryngeal exposure. J Voice 15(2):305–312

123

1588 Eur Arch Otorhinolaryngol (2009) 266:1583–1588

11. Kim JK, Jeong HS, HyN Kwon (2007) A new curved rigid laryn-goscope to overcome the diYcult laryngeal exposure (DLE) inendolaryngeal surgery. Eur Arch Otorhinolaryngol 254:901–905

12. Kleinsasser O (1964) Mikrochirurgie im Kehlkopf. Arch Ohren-heilkd 183:428–433

13. Kleinsasser O (1968) Mikrolaryngoscopy and endolaryngealmicrosurgery. Saunders, Philadelphia

14. Kleinsasser O (1968) Mikrolaryngoskopie und endolaryngealeMikrochirurgie. 1. AuX. Schattauer, Stuttgart, New York

15. Koufman JA (2007) Introduction to oYce-based surgery in laryn-gology. Curr Opin Otolaryngol Head Neck Surg 15(6):383–386

16. Leden HV (1988) Microlaryngoscopy: a historical vignette. JVoice 1(4):341–346

17. Lesky E (1976) The Vienna medical school of the 19th century.The Johns Hopkins University Press, Baltimore

18. Müller A, Verges L, Schleier P, Wohlfarth M, Gottschall R (2002)The incidence of microlaryngoscopy associated complications.HNO 50(12):1057–1061 (in German)

19. Simpson CB, Amin MR (2004) OYce-based procedures for thevoice. 83 (7 Suppl 2):6–9

20. Skopec, Majer EH (1998) History of oto-rhino-laryngology inAustria, Christian Brandstätter Wien, München, 1998

21. Strong MS (1970) Microscopic laryngoscopy: a review and ap-praisal. Laryngoscope 91:324–326

22. Woo P (2006) OYce-based laryngeal procedures. OtolaryngolClin North Am 39(1):111–133

23. Yanagisawa E, Horowitz JB, Yanagisawa K, Mambrino LJ (1992)Comparison of new telescopic video microlaryngoscopic and stan-dard microlaryngoscopic techniques. Ann Otol Rhinol Laryngol101(1):51–60

24. Yeh AR, Huang HM, Chen YL (1999) Telescopic video microla-ryngeal surgery 108:165–168

25. Zeitels SM, Burns JA (2007) OYce-based laryngeal laser surgerywith local anesthesia. Curr Opin Otolaryngol Head Neck Surg15(3):141–147

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