徐振東 黨丹丹 徐江慧 焦 微 車薛華△

（1同濟(jì)大學(xué)附屬第一婦嬰保健院麻醉科 上海 200040；2復(fù)旦大學(xué)附屬華山醫(yī)院麻醉科 上海 200040）

Air way management and intubation in patients with li mited neck extension and mout h opening is challenging．These patients may have ankyl osing spondylitis，otor hinolaryngeal disease，cervical spine pat hol ogy or previous radiation t herapy in t he head and neck area． Awake fibreoptic intubation is the safest option f or them，but some patients ref use awake int ubation and many physicians have li mited skills wit h t he technique．Intubation with the GlideScope videolaryngoscope（GVL，Satur n Biomedical Systems Inc．，Bur naby，BC，Canada）has been proposed f or an alternate met hod．Prior st udies have demonstrated t hat the GVL reduces t he difficulty of or otracheal intubation （OI）in patients undergoing cervical spine i mmobilization when co mpared wit h the Macintosh lar yngoscope［1－2］．The GVL is also an effective device f or nasotracheal int ubation（NI）．It has been shown to be superior to direct laryngoscopy for NI［3－5］．Lai，et al［6］think that the tracheal intubation by the GVL would be easier by the nasal route than the oral route according their clinical experience．They pr ovided nasotracheal intubation with the GVL f or patients with ankyl osing spondylitis，and had a high success rate of intubation．

Like ankylosing spondylitis，rigid cervical collar i mmobilizes cer vical spine and reduces the mouth opening．Many studies apply cervical collar to si mulate a difficult air way to co mpare different int ubation devices［6－8］．However，less st udy has co mpared different int ubation r outes wit h the same laryngoscope in difficult air ways．We therefore wished to co mpare the oral r oute wit h t he nasal r oute when int ubation wit h GVL in patients wit h the si mulated difficult air ways by cervical collars．The GVL blade may infl uence t he place of endotracheal tube （ETT）from oral cavity．Nasotracheal intubation may have potential advantages over OI．Our hypot hesis is t hat nasal r oute wit h GVL i mpr oves t he ease of tracheal intubation compared with oral route．

Materials and Met hods

Subjects and patientsAfter obtaining instit utional et hics co mmittee appr oval and written infor med patient consent，60 patients with American Society of Anesthesiologists physical statusⅠ－Ⅱ，aged 18 years or older，were scheduled to under go elective supratentorial brain t u mor sur ger y at Huashan Hospital fro m Dec．，2011 to Jul．，2012，in a randomized，single－blind，controlled clinical trial．Patients were excluded if risk factors f or abnor mal coagulation，gastric aspiration，cervical spine pathology， mor bid obesity，hypertension，intracranial hypertension and／or anticipated difficult int ubation （Malla mpati classⅢ or Ⅳ，thyromental distance less than 6 c m，interincisor distance less than 3 c m） were occurred．

After f ull muscle relaxation was confir med with a nerve sti mulator，the pillow was removed and an appropriately sized，rigid Philadelphia collar was positioned around t he neck．Patients were rando mly assigned to OI group and NI gr oup wit h the GVL．Rando mization was based on computergenerated codes maintained in sequentially numbered opaque envelopes．

Intubation proceduresAll intubation procedures were completed by t wo experienced investigators（Xu ZD and Xu JH）who had perf or med each route of intubation with the GVL in more than 50 patients bef ore t he start of t his st udy．They did not collect the data．

The reinf orced treacheal tube （Safety－Flex with Mur phy Eye，Oral／Nasal，At hlone，Ireland）was used，size 6．5 mm f or nasal intubation and size 7．0 mm f or oral int ubation．An int ubating stylet adequately lubricated was inserted into the oral t ube．The distal end of a styletted oral t ube was bent anteriorly to an angle of 60°，which corresponded to t he specially designed GVL blade with a 60°cur vat ure．All t he tracheal t ubes were adequately l ubricated wit h sterile water－sol uble l ubricant bef ore use．The nasotracheal tubes were also war med．

In all t he gr oups，t he GVL blade was inserted into t he patient′s mouth al ong t he midline，gliding downwards on the surface of the tongue．The tip of t he GVL blade was placed int o the epiglottic vallecula and gently lifted to expose the glottis visualized on LCD．When the view of the glottis had been opti mized，a precur ved styletted oral tube was introduced along the right side of the GVL and advanced towar ds t he gl ottis in OI gr oup，or nasal tube （a stylet is not used）was inserted via the right nostril until t he t ube tip was guided towar ds the glottis in NI group．Finally，the respiratory circuit was connected and ventilation confir med by capnography．In each gr oup，tracheal int ubation was considered a fail ure if it coul d not be acco mplished wit hin 2 min or 2 attempts．If intubation failed，the Philadelphia collar was removed，facemask ventilation was provided and the trachea was subsequently intubated using a Macintosh laryngoscope．

Ti me to int ubation （TTI）was defined as the ti me fr o m t he beginning of insertion of blade to the confir mation of int ubation by capnography［9］．If the first attempt was made，it was unsuccessf ul，and a second attempt was made，TTI incl uded t he entire ti me of t wo attempts when intubation succeeded．If intubation failed，TTI was not calculated in analysis．

MeasurementsMorphometric data，Mallampati score，mout h opening （inter－incisor distance），t hyro mental distance，and ster no mental distance（wit h head extended in upright position）were measured by an obser ver blinded to gr oup assign ment．The pri mary endpoint was TTI．The secondary endpoint was ease of intubation evaluated by intubation difficulty scale （IDS）scores．IDS score，developed by Adnet，et al［10］，is a quantitative scale of multiple indices of difficult int ubation t hat can co mpare more objectively the co mplexity of tracheal int ubations．IDS score is the su m of 7 variables［1，10］：N1，nu mber of int ubation attempts greater than 1；N2，nu mber of operators greater than 1；N3，number of alternative intubation techniques used；N4，glottic exposure（Cor mack and Lehane grade minus 1）；N5，lifting force required during laryngoscopy（0，nor mal；1，increased）；N6，necessity f or exter nal laryngeal pressure（0，not applied；1，applied）；N7，position of t he vocal cor ds at int ubation （0，abduction／not visualized；1，adduction）．

We also recor ded overall intubation success rate，nu mber of intubation attempts，frequency of esophageal intubation，hypoxia（Sp O2＜ 95%），mucosal trau ma （the observer suctioned the or opharynx using a suction cat heter after int ubation，and qualitatively graded the a mount of bl ood present in t he suction t ubing as none，trace，moderate，or copious．）．

Data analysisThe sample size was deter mined on a si milar study which compared nasotracheal intubation with orotracheal intubation using GVL f or nor mal air ways［11］．A significantly shorten TTI bet ween t wo gr oups was 11 s．The standar d deviation （SD）of TTI was esti mated fr o m t hree st udies investigating GVL assisted nasotracheal int ubation t hat demonstrated SDs of 13 s［3］，11．5 s［4］and 13 s［11］．So SD esti mate of 13 s for TTI was used with standard type I and typeⅡerror rates （α＝0．05，β＝0．20）．The calculated sample size was 23 per group．We rounded the nu mber t o 30 patients f or each gr oup．

Nonpara metric data （TTI and ease of int ubation） were co mpared wit h the Mann－Whit ney U－test．The incidence of int ubation co mplications，overall int ubation success rate，and sex distribution bet ween the groups were appropriately tested by Fisher′s exact orχ2tests．Para metric data were co mpared using unpaired St udent′s t－test．Statistical analysis was perf or med using SPSS 11．0．Data were presented as x—±s，and categorical data were presented as nu mber and frequency．Theαlevel f or all analyses was set as P＜0．05．

Results

Characteristicsand airway assessmentA total of 60 patients were entered into t he study．Thirty patients were rando ml y assigned to under go orotracheal intubation with GVL，whereas 30 under went nasotracheal intubation．One patient in NI group was withdrawn fro m analysis after rando mization due to t he resistance prevented easy passage of the t ube t hr ough t he right nostril．There were no significant differences in demographic or baseline air way para meters bet ween t he t wo gr oups（Tab 1）．

Tab 1 Morphometric and air way assessment data s，n （%）］

Tab 1 Morphometric and air way assessment data s，n （%）］

F：Data analyze by t－test；χ2：Data analyze byχ2 test；OI group：Orotracheal intubation group；NI group：Nasotracheal intubation group．

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Intubation dataThe total ti me f or tracheal int ubation was significantly shorter in NI gr oup．Nasotracheal intubation significantly reduced median IDS score co mpared wit h or otracheal intubation（Fig 1）．The first and second attempts at int ubation were si milar bet ween t he t wo gr oups．Tracheal intubation was successf ul in 26 of 30 patients in OI group，and in 28 of 29 patients in NI gr oup（P＝0．353）．These outco mes are detailed in Tab 2．

Failed intubationFour patients in OI gr oup failed to be intubated within 2 min or 2 attempts because t he distortion of t he stylet angulation in mouth made the tip of the ETT fail to advance into gl ottis．After t he Philadel phia collar was removed，the trachea was successf ully intubated using a Macintosh lar yngoscope．Int ubation failed in one patient in NI group，f or the tip of the ETT was i mpeded in anterior co mmissure，and coul d not be f urther advanced into glottis．After we removed the anterior portion of t he collar and flexed t he patient′s head，the tube was s moothly introduced into gl ottis．

Intubation complicationsThe incidence of moderate bleeding in OI gr oup was higher t han that in NI group （7%vs．28%，P＝0．042）．Other co mplications such as esophageal intubation or hypoxia（Sp O2＜95%）were not observed．

Fig 1 Intubation IDS distributions in the OI group and NI group

Tab 2 Data for Intubationin tested groups

Discussion

We f ound t hat a shorter ti me was required f or nasotracheal intubation compared with orotracheal int ubation using GVL．Nasotracheal int ubation was also f ound to be easier f or t he anest hesiol ogist．The nu mber of second intubation attempts and overall intubation success rates were si milar in the t wo groups．

In our st udy，t he measurement of TTI was started as insertion of blade and stopped when end tidal CO2was obser ved on t he anesthesia monitor．TTI mainly depended on insertion into the pharynx and pass t hr ough t he epiglottis of t he ETT．The precur ved ETT initially intr oduced into t he mout h probably had so me difficulties due to the li mited mouth opening as s mall as 2 c m．The stylet angulation of the malleable stylet was frequently lost during introduction of the ETT contacting wit h t he teet h，which can distort t he stylet．This defor med angulation and li mited oral cavity may make ETT more difficult to advance down the trachea．In addition，it was necessar y f or an assistant to wit hdraw t he stylet as t he operator advanced ETT to facilitate insertion．Removing the stylet also increased the delay．For t he nasotracheal int ubation，li mited mout h had little eff ect on it，and the tube was war med and lubricated，so most of the intubation were smooth．The GVL was not necessary to align the tracheal，phar yngeal，and oral axes in contrast to DL and less distorted the superaglottic anato my［12］． Reduced air way distortion could potentially create a more direct r oute fr o m the nasophar ynx to t he trachea，necessitating less ETT manipulation and a shorter TTI，consequently．Magill forceps and stylet were not used in NI group，which can f urther decrease TTI．

Xue，et al［11］co mpared the perfor mances of the GVL in oral and nasal int ubations in patients without cervical spine i mmobilization．They also f ound t hat t he total incidence of difficulties encountered during the intubation was higher in OI gr oup t han in NI gr oup （29%vs．6%，P＜0．05）．They concluded that the nasal tube passing t hrough t he nasal cavity tends to be more aligned with the laryngeal and tracheal axes than the oral t ube intr oduced t hr ough t he mout h，because t here is no shar p turn bet ween the posterior nasal apert ure and t he glottis．This makes advancement of the nasal tube downwards into the trachea easier．Our st udy confir med t heir findings，and demonstrated that nasotracheal intubation reduced IDS score when co mpared wit h or otracheal intubation．

No patients in t wo gr oups experienced esophageal intubation．The design and f unctionality of t he Glidescope provide a nearl y co mplete view of the larynx，which allows the clinician to observe and correct advancement of t he t ube int o the trachea fro m outside larynx．The serious bleeding seemed more co mmon in NI group．

The current study had a nu mber of li mitations．First，success rate is pr obabl y t he best way to assess the usef ulness of an intubation technique．But TTI was chosen as t he pri mar y outcome in this study because it represents an objective gl obal assess ment of all of the f actors necessary to intubate the trachea，incl uding device insertion，glottic exposure，advancement of the ETT and device removal．In addition，TTI can be easil y measured wit h a clear end－point by a blinded observer［5］．Some studies also chose TTI as the pri mary outco me［5，8－9］． Thir d，t he intubating investigator had more experience with orotracheal int ubation t han nasotracheal int ubation using the GVL．Yet，this seemed to have little influence in t he study，since int ubation ti me was nonet heless significantly faster with nasotracheal intubation．

Despite statisticall y significant of t he TTI obser ved bet ween t he t wo gr oups，the difference is small （11 s）．The clinical significance of the difference might not be i mportant．Since nasal bleeding is more evident and problematic f or nasotracheal int ubation．

In conclusion，when compared with orotracheal intubation，nasotracheal int ubation wit h t he GVL results in a faster，easier intubation of patients who require cer vical spine i mmobilization wit h cer vical collar．Nonetheless，both routes are comparable in success rate of tracheal intubation，and nasotracheal intubation is associated with a clinically significant bleeding．Nasotracheal intubation will not likely be preferred in this setting．

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