video laryngoscopes ( vl ) which work on the principles of indirect laryngoscopy have become popular in clinical practice .
they provide a significantly better view of the larynx , which may be useful in difficult tracheal intubation scenarios . the key novel feature of these 
indirect laryngoscopes is that they facilitate visualisation of the vocal cords without the need to align the oropharyngeal and tracheal axes .
kaplan and berci introduced c - mac vl ( karl storz , tuttligen , germany ) in 2003 .
it has been found to improve cormack - lehane ( c - l ) grading by 2 to 1 grade and possibly aid easier intubation .
it provides both a direct laryngoscopic view and a small digital camera view that is displayed on the video screen , in contrast to many previous vls .
recognition of the anatomical structures and anomalies is easier , and manipulation of airway devices is facilitated .
nasotracheal intubation ( nti ) is often required for head and neck surgeries like tonsillectomies .
direct laryngoscopy with the macintosh blade , with the use of magill 's forceps to direct endotracheal tube ( ett ) into glottic opening , is time - consuming and may lead to trauma to surrounding structures and damage ett cuff .
hence , this study was conducted to assess the intubating conditions , using the conventional macintosh laryngoscope and the storz c - mac vl during nti in paediatric patients posted for tonsillectomy surgeries .
this prospective randomised study was conducted after obtaining approval from the institutional review board ( iec no .
patients of either sex , aged between 8 and 18 years , belonging to american society of anesthesiologists physical status i , ii and mallampati grade i , ii were included and study was conducted between january 2013 and june 2014 . parents who refused to give consent , patients with significant systemic disease and patients having contraindications for nti were excluded from the study .
the procedure was explained to the patients and written informed consent from parent / guardian was obtained .
patients in group 1 underwent conventional laryngoscopy using macintosh direct laryngoscope and group 2 underwent videolaryngoscopy using c - mac vl for nasal intubation .
the sample size was estimated based on a pilot study carried out in 10 patients where it was found that mean intubation times for the macintosh group , and the c - mac group were 55 s and 45 s respectively with standard deviation ( sd ) of 5 s. based on these figures and using alpha error = 0.05 and 0.85 power of the study , we got the required sample size of 25 each . hence , we recruited 30 into each group by increasing the sample size by 5 .
the investigator who performed the intubation in this study had previously performed about 100 nti using c - mac vl .
after connecting the routine pre - induction monitors , baseline values of systolic blood pressure ( sbp ) , diastolic blood pressure ( dbp ) , mean blood pressure ( mbp ) , heart rate ( hr ) and oxygen saturation ( spo2 ) were recorded .
all patients were pre - medicated with injection glycopyrrolate 10 g / kg , injection fentanyl 2 g / kg and injection midazolam 10 g / kg intravenous ( iv ) .
anaesthesia was induced with injection propofol 2 mg / kg iv and neuromuscular blockade achieved with injection vecuronium 0.1 mg / kg .
patients were ventilated with oxygen , nitrous oxide ( 33:67 ratio ) and end - tidal concentration of isoflurane 0.81.2 as observed on the gas monitor for initial 4 min , followed by ventilation with 100% oxygen for 1 min before intubation .
preservative free injection lignocaine 1.5 mg / kg iv was administered 90 s before intubation .
five minutes after giving injection vecuronium , ensuring adequate muscle relaxation , lubricated appropriate sized nasotracheal ett was inserted through the most patent nostril until its tip lay in the oropharynx .
laryngoscopy was then performed using either macintosh laryngoscope ( blade size 2 or 3 ) or storz c - mac vl ( macintosh blade size 2 or 3 ) as per the group and a view of laryngeal opening was obtained .
initially , attempt was made to pass the ett through the vocal cords without the aid of manoeuvres ( m0 ) .
if difficulty was encountered , additional external manipulations ( m1 ) such as head flexion , rotation of tube and backwards , upwards , rightwards pressure ( burp ) were used . in case of failure to intubate using above manoeuvres , cuff of the ett
was inflated with approximately 10 ml of air and the ett brought into view ( m2 ) ( as per study done by baddoo hk et al . ) .
once the tip of ett was in the glottic opening , cuff was deflated ; the ett was then advanced into the trachea and then cuff was reinflated .
if this technique failed then , cuff was deflated , and magill 's forceps alone ( m4 ) or in combination with burp ( m5 ) was used to position and guide the tube .
the manuoevres were followed in the sequence described in table 1 . if there was failure to intubate with all the above - said manoeuvres , oral intubation was performed .
correct placement of ett was confirmed by auscultation over the chest for bilateral equal air entry and using capnograph .
sequence of additional manoeuvres used in the study during this procedure , hr , sbp , dbp , mbp and spo2 were recorded every minute for the initial 5 min after induction of anaesthesia , and thereafter at 5 min intervals for next 15 min .
if a decrease in saturation to 90% or lower was observed during nasal intubation then oral intubation was performed .
parameters noted during the study were : c - l grading , time required for intubation , intubation without any manoeuvre ( m0 ) , need for the manoeuvres , type of manoeuvre ( m1m5 ) used , haemodynamic changes , lowest recorded spo2 during or immediately after intubation attempt and occurrence of any other complications .
duration of nti was defined as the time taken from the insertion of the ett through the nostril , till passage of tube through vocal cords by visual confirmation by the intubating anaesthesiologist .
duration of nti more than 120 s , fall in spo2 below 90% during the procedure were considered as failed nti .
data collected were coded , tabulated , and then analysed using statistical package for the social sciences ( spss 20 , ibm , armonk , ny , united states of america ) computer package .
mann - whitney u - test was used for analysing age , sex , c - l grading and for comparing the duration of intubation between both groups .
independent - t - test was used to compare haemodynamics with respect to hr , sbp , dbp , mbp in both groups . a difference with the adjusted p
demographic profiles were evenly distributed between both groups . in group 1 , 86.7% of patients and in group 2 , 96.6% had c - l grading of 1 and remaining patients had c - l grading of 2 , which was not statistically significant ( p = 0.35 ) .
duration of intubation was significantly shorter in group 2 compared to group 1 patients . in group 1 , 36.6% of patients and in group 2 , 93.3% of patients were intubated within 2 min which was statistically significant p = 0.001 [ figure 1 ] . comparison of intubation time between the groups in group 1 , 3.3% of patients and in group 2 , 23.3% of patients were intubated successfully without the application of manoeuvres ( m0 ) .
application of optimisation manoeuvres ( m1m5 ) was needed more in group 1 compared to group 2 ( c - mac ) ( 97% vs. 77% ) and was statistically significant p = 0.001 [ figure 2 ] . in group 1 , 30% of patients and in group 2 , 53.3% patients needed additional external manipulation ( m1 ) .
only 6.7% patients of either the groups were intubated using cuff inflation technique alone ( m2 ) . combined use of cuff inflation with external laryngeal manipulation ( m3 ) was not useful in both groups .
use of magill 's forceps alone ( m4 ) and m4 with external manipulation ( m5 ) were required more in group 1 compared to group 2 ( m4 - 37% vs. 13% ) ( m5 - 23% vs. 3% ) .
( m3 = combined use of cuff inflation with external laryngeal manipulation was not useful in both the groups ) after induction , haemodynamic parameters ( hr , sbp , dbp and mbp ) decreased in both groups when compared to pre - induction values . at the 1 min after intubation ,
the values increased in both groups , but there were no intergroup differences and both the parameters returned to baseline after 5 min after nti [ table 2 ] .
no complications ( drop in spo2 , dental trauma , etc ) were observed during the procedure in both groups .
c - mac vl allows adequate glottic view , without the need for aligning oropharyngeal and laryngeal axes .
we found no significant difference in airway assessment using c - l grading in both groups .
this can be explained by the fact that both groups of patients were of similar demography and patients with airway difficulties were excluded from the study .
duration of nti was significantly decreased in group 2 in comparison with group 1 patients .
c - mac vl has slim blade profile and edges are inclined , thus reducing the potential contact area of the blade with the upper incisors .
it magnifies airway view and allows supporting staff to optimise their assistance such as applying adequate external manipulation as necessary .
the anterior angulation of the blade and placement of the video camera allow the operator to see structures that would be difficult or even impossible to see under direct vision .
the majority of patients in group 1 required different manoeuvres as per study protocol . external laryngeal manipulation ( m1 )
this can be explained by the fact that there was requirement of more hand - eye coordination while viewing the glottis on vl monitor and intubating the patient even with experienced anaesthesiologists .
a previous study showed that cuff inflation technique ( m2 ) helps to lift ett from the posterior pharyngeal wall , thus helping to bring it into view and also directs it towards the glottis .
this technique of cuff inflation has been described for blind nasal intubation in spontaneously breathing patients .
however , the technique was found to be less useful for successful intubation in this study .
combined use of cuff inflation with external laryngeal manipulation ( m3 ) was not useful in this study .
direct laryngoscopy requires elevation of the laryngoscope blade , moves the larynx upwards and elevates the glottis .
thus , lengthens the distance between the glottic orifice and the posterior pharyngeal wall and also makes the nasally introduced tube slide upwards and then downwards in sequence .
thus , it often requires the use of magill 's forceps to align this ett tip with the glottic inlet and its use may sometimes lead to trauma to surrounding structures , damage to ett cuff .
magill 's forceps alone ( m4 ) and m4 with additional external manipulation ( m5 ) were needed more in group 1 as compared to group 2 .
similar studies conducted by kaki et al . and hirabayashi and seo concluded that vls needed lesser use of magill 's forceps for nti .
c - mac vl helped the supporting staff to assist intubation , using less invasive manoeuvres and thus may prevent trauma to oral cavity , damage to ett cuff .
it was also observed that there was a positive correlation between the number of manoeuvres used and the intubation time required in both groups .
patients in group 1 required longer time ( 2 min ) to intubate than group 2 ( 1.5 min ) when the use of additional manoeuvres of the highest level ( m5 ) was required . for good glottic view
, videolaryngoscopy requires the application of lesser force as compared to direct laryngoscopy to the base of the tongue .
therefore , videolaryngoscopy is less likely to stimulate pressor - response and induce local tissue injury .
in contrast , both groups in our study had similar intubation responses which returned to baseline after 5 min .
the difference between both groups preoperatively , before induction and after intubation was statistically insignificant .
further studies are required to know its utility in paediatric patients with difficult airways as well as in adult patients posted for nasal tracheal intubation .
limitation of this study was that anaesthesiologist could not be blinded to the type of device being used for nti .
the study was limited to only sixty patients considering intubation time as the primary outcome parameter .
larger number of enrolled cases are required to assess other parameters of the nasotracheal intubating conditions .
storz c - mac vl provided better glottis visualisation as compared to conventional macintosh direct laryngoscope .
lesser time was required for intubation and there was lesser need for magill 's forceps during nti .
however , requirement of additional external manipulations ( m1 ) was more with the c - mac vl group .
thus , c - mac vl improves the nasotracheal intubating conditions and can be superior alternative to macintosh laryngoscope in clinical practice in paediatric patients .
 background and aims : c - mac video laryngoscope ( vl ) with macintosh blade has been found to improve cormack - lehane ( c - l ) laryngoscopic view as well as intubating conditions for orotracheal intubation . 
 however , studies done on the performance of c - mac vl for nasotracheal intubation ( nti ) are very few in number . hence , we compared laryngoscopy and intubating conditions between macintosh direct laryngoscope and c - mac vl for nti.methods:sixty american society of anesthesiologists physical status i , ii patients , aged 818 years , posted for tonsillectomy surgeries under general anaesthesia with nti were randomised , into two groups . 
 patients in group 1 were intubated using macintosh direct laryngoscope and group 2 with c - mac vl . 
 c - l grading , time required for intubation , need for additional manoeuvres and haemodynamic changes during and after intubation were compared between the groups.results:c-l grade 1 views were obtained in 26 and 29 patients in group 1 and group 2 , respectively ( 86.7% vs. 96.7% ) . 
 remaining patients were having c - l grade 2 ( 13.3% vs. 3.3% ) . 
 duration of intubation was less than a minute in group 2 ( 93.3% ) . 
 need for additional manoeuvres ( m1m5 ) were more in group 1 ( 97% vs. 77% ) . 
 m1 ( external manipulation ) was needed more in group 2 compared to group 1 ( 53.3% vs. 30% ) . 
 magill 's forceps alone ( m4 ) and m4 with additional external manipulation ( m5 ) were needed more in group 1 compared to group 2 ( 60% vs. 16%).conclusion : the overall performance of c - mac vl was better when compared to conventional direct macintosh laryngoscope during nti in terms of glottis visualisation , intubation time and need for additional manoeuvres . 