A randomised controlled study comparing the efficacy of  video - laryngoscope  versus  direct laryngoscope with Macintosh blade in patients undergoing general anesthesia

Endotracheal intubation is an important skill of an anesthetist for securing the airway. It is a lifesaving procedure both in the ICU and operation theater. With the advancement in surgical procedures, there is an increasing incidence of patients presenting with more number of co-morbidities who are posted for surgery. This includes an increasing number of patients with difficult airway. The incidence of difficult laryngoscopy and intubation in Indian population is around 9.7% and 4.5% respectively ¹.

The ASA defines difficult airway as a clinical situation in which a conventionally trained anesthesiologist experiences difficulty with facemask ventilation of the airway, difficulty with tracheal intubation or both². Anesthesiologists have been constantly making efforts to develop skills and tools to manage difficult airway.

Video laryngoscopes are emerging as an important tool for the management of difficult airway. The ASA (American Society of Anesthesiology) suggests video laryngoscopy as an initial approach in case of a predicted difficult airway and as an alternative approach during the second attempt at intubation in an unanticipated difficult airway². They can be used in cases with decreased mouth opening^{3, 4} and restricted cervical spine movements^5,6. These are unique advantages of video laryngoscopes over conventional laryngoscopy. 

The demographics of the patients coming to our institution will benefit from this tool. We have patients being admitted under head & neck onco-surgery who have oral malignancies and decreased mouth opening. There are also a considerable number of road traffic accident patients with cervical spine injuries.

Hence, proficiency of use of video laryngoscopes in patients with a normal airway can help us put it use in the emergency situations⁷, where it can be life- saving.

a.  Design: A randomized controlled trial.

 b.  Total number of study subjects: The sample size is based on time to intubation, as reported in a similar study by Reena et al ¹⁰.The sample includes patients in the age group of 18 – 50 years. The study reported an average variance estimate of 12.5² seconds, with a 90% power and an error of 1%. To detect a difference of 28% in time for intubation, an estimated sample size will be 35 per group. Expecting a non - compliance, the final sample size is 35 + 5, which is equal to 40 in each group. The sample size was calculated using OpenEpi version 3.01

c.   Mode of selection:

After approval from the central ethical committee, an informed written consent will be obtained from all patients before including them in the study. The subjects for the 2 groups will be chosen using block randomization technique, with a block size of 4.  

Anesthetists who have a minimum experience of 100 intubations with Macintosh blade and 30 intubations with  video laryngoscope will perform the laryngoscopy. 

Group L: Patients will undergo a direct laryngoscopy with Macintosh Laryngoscope. The Cormack – Lehane Grading and POGO scoring in sniffing position will be assessed. This will befollowed by stylet- assisted endotracheal intubation.

Group K: Patients will undergo video laryngoscopy ( by Anesthetics India Private Ltd.) with Videolaryngoscope. Endotracheal intubation assisted by a stylet will be done after assessing the Cormack – Lehane Grading and POGO scoring in sniffing position.

The primary outcome measures will be assessment of grade of glottic view and time to intubation. 

c.   Inclusion Criteria: 

1.      Adults aged between 18 to 50 years, 

2.      ASA grade I and II planned for General Anesthesia

d.  Exclusion Criteria:

1.      Patient refusal

2.      Patients with modified Mallampatti scoring of Grade 3 and 4

3.      Patients with restricted neck mobility

4.      Patients with decreased inter- incisor gap (18 mm-30 mm) 

Data will be entered into Microsoft excel data sheet and will be analyzed using SPSS 22 version software. Categorical data will be represented in the form of Frequencies and proportions. Continuous data will be represented as mean and standard deviation. Chi-square will be the test of significance. Independent t test will be the test of significance to identify the mean difference between two groups. P value <0.05 will be considered as statistically significant