A comparative study of effectiveness of video laryngoscopy and direct laryngoscopy in patients with at least three predictors of difficult intubation

 

 

Abstract               Background: Difficulty in achieving a patent airway depends mainly on anatomical factors which play a predominant role in deciding the degree of difficult airway. The identification of the patients with difficult airway is vital in the preoperative evaluation and planning anaesthesia management, so that endotracheal intubation and positive pressure ventilation can be achieved safely by alternative methods of tracheal intubation. Aim and objectives: To study and compare the effectiveness of video laryngoscopy and direct laryngoscopy in patients with at least three predictors of difficult intubation Materials and method: The present hospital based prospective randomized control study was conducted with 200 patients with atleast three predictors of difficult intubation. The patients were randomly divided into following groups of 100 patients each. Group D: Patients intubated with direct laryngoscope Group V: Patients intubated with video laryngoscope. Patients between the age group of 20-50years of age posted for various surgical procedures under general anaesthesia with ASA grade I or II and with atleast three 3 predictors of difficult intubation were included in the study.  Results: It was found that there was no statistically significant difference between the patients in both groups in terms of age, sex, BMI, ASA class, Mallampati classification III or IV , the mean interincisor gap , thyromental distance and the presence of buck teeth. In group D airway was secured in first attempt in 82% patients while it was 94% in group V.  Video laryngoscopy provided a significantly better view of the laryngeal structures than direct laryngoscopy as per Chi-Square test. The use of external laryngeal manipulation/facilitation with a bougie was significantly more in Group D as compared to Group V (37% vs. 24%). The mean laryngoscopy time was significantly higher in Group D as compared to Group V (42.33 ± 1.76 secs vs. 33.16 ± 2.08 secs).  In Group D, 25% patients had sore throat while 10% and 3% patients had Lip/gum/oral trauma and Oxygen desaturation <90% respectively. In Group V, 28% patients had sore throat while 6% and 4% patients had Lip/gum/oral trauma and Oxygen desaturation<90% respectively. Conclusion: Thus with reference to above mentioned results and discussion we conclude that Video laryngoscope eases tracheal intubations in patients with expected difficult intubations. The view of the laryngeal entrance is significantly improved, with a decreased number of optimizing manoeuvres and in less time. Overall, these improvements of the conditions for tracheal intubations result in a significantly higher success rate of trachael intubations.

Key Word: difficult intubation, video laryngoscopy, direct laryngoscopy

 

 

INTRODUCTION

Difficulty in achieving a patent airway depends mainly on anatomical factors which play a predominant role in deciding the degree of difficult airway. The identification of the patients with difficult airway is vital in the preoperative evaluation and planning anaesthesia management, so that endotracheal intubation and positive pressure ventilation can be achieved safely by alternative methods of tracheal intubation. Accurate preoperative prediction of potential difficulty with intubation can help reduce the incidence of catastrophic complication by allowing anaesthesia personnel to take additional precaution before beginning anaesthesia and establishing an artificial airway. In addition, more accurate prediction of difficulty with intubation might reduce the frequency of unnecessary maneuver. However it is still questioned whether true prediction is possible and which variable should be chosen for evaluation. Routinely Modified Mallampati Classification is the most commonly used method for assessment of airway. However it gives an idea about only the relative proportion of size of tongue and the oral cavity.¹ Direct laryngoscopy has been used for many years by otolaryngologists for diagnostic inspection, biopsy, and endoscopic microsurgery (e.g. Removal of a vocal cord polyp, injection of gelfoam or Teflon paste or for carbondioxide laser surgery of larynx (e.g. removal of papillomas, treatment of early malignancy).² However the stress of this procedure may lead to hemodynamic changes such as tachycardia and hypertension.³ These haemodynamic changes may have adverse effects on myocardial oxygen supply versus demand ratio and may result in higher incidences of perioperative ischemia.⁴ Transitory hypertension and tachycardia are of no consequence in healthy individuals, but either or both may be hazardous to the patients with hypertension, myocardial insufficiency or cerebrovascular disease.⁵ To minimize this risk due to difficult intubations, most of the national anaesthesia societies have developed guidelines for the management of expected and unexpected difficult intubations.^6-8 At the same time, ‘blind techniques’ via laryngeal airways and video-assisted devices for tracheal intubation have been developed to ease difficult intubations.^9-14 The development of video and optical laryngoscopy could be the most important change in this paradigm. Video laryngoscopes (VLs) are new intubation devices, which contain miniature video cameras, enabling the operator to visualize the glottis indirectly. In operating room studies, they have been shown to improve glottic exposure and the ease of intubation compared with direct laryngoscopes.^15,16,17 Their design is similar to conventional laryngoscopes, enabling clinicians familiar with direct laryngoscopy to use them successfully without the need for any extensive special training. Video laryngoscopy is becoming more accessible to emergency physicians (EPs), yet whether these performance characteristics translate to emergency patients remains unclear. In addition, video-assisted techniques offer the opportunity to improve the teaching of airway management. In general, these techniques offer the advantage of abandoning the need to align the optical axis in the pharynx and mouth to visualize the entrance of the larynx.¹⁸  Hence the present study was conducted at tertiary care centre to know the laryngeal view and intubation success rates using direct laryngoscopy or video laryngoscope in patients with predicted difficult airway.

 

MATERIALS AND METHOD

The present hospital based prospective randomized control study was conducted with 200 patients with atleast three predictors of difficult intubation to compare the effectiveness of video laryngoscopy and direct laryngoscopy in obtaining a better laryngeal view and facilitating the ease of intubation. The patients were randomly divided into following groups of 100 patients each:

Group D: Patients intubated with direct laryngoscope

Group V: Patients intubated with video laryngoscope

Patients between the age group of 20-50years of age posted for various surgical procedures under general anaesthesia with ASA grade I or II and with atleast three 3 predictors of difficult intubation which include:

• Mallampati (Class3 and 4)
• Thyromental distance(<6.5cm)
• Head and neck mobility(restricted movements)
• Buck teeth
• Inter-incisor gap(<3cm)

                Patients fulfilling the above selection criteria were enrolled in the present study. Randomization was done in 1:1 ratio via specialized computer software. The patients remained blinded for their intubation technique. Both the study team and anesthesia team remained blinded until the patient enters the operating room at which time the randomization envelope were opened, One of investigators recorded all the relevant findings related to laryngoscopy and intubation. General anesthesia with controlled ventilation was induced. Intubation success was defined as confirmation of endotracheal tube placement by end tidal CO2 single blade insertion. Removal of laryngoscope from mouth constituted a failure. Failed attempts were managed by any other device for patient safety. Laryngoscopy time was defined as the time between blade insertion into the mouth and inflation of endotracheal tube cuff. Optimizing manoeuvres were the external manipulation of the larynx (BURP manoeuvre), use of a gum elastic bougie (Eschmann stylet), and changes in head positioning. A number of zero optimizing manoeuvres meant that the patient was intubated in neutral position without any manipulations. In cases where the anaesthesiologist could not intubate a patient despite all manoeuvres, the intubation attempt was declared as failed. During the tracheal intubation, standard monitoring, i.e. non-invasive arterial pressure measurement, heart rate, and arterial oxygen saturation (pulse oximeter), was performed and the results were recorded before induction of anaesthesia and at the end of the intubation.

RESULTS

Table 1: Distribution of patients according to ag

Group D had 27% patients in the age group of 20-30 years, 33% patients in the age group of 31-40 years and 40% patients in 41-50 years of age group. The mean age in Group D was 36.64 ± 8.32 years. While Group V had 28% patients in the age group of 20-30 years, 35% patients in the age group of 31-40 years and 37% patients in 41-50 years of age group. The mean age in Group D was 36.21 ± 8.67 years. The age of the patients between two groups were comparable and statistically not significant as per Student’s t-test (p>0.05). Group D had 63% male patients whereas Group V had 61% male patients. Group D had 86% patients in the normal range while 8% and 6% patients were overweight and obese respectively. While Group V had 83% patients in the normal range while 10% and 7% patients were overweight and obese respectively. The mean BMI of patients was 21.94 ± 3.30kg/m² in Group D and 22.68 ± 3.44kg/m² in Group V. The BMI of the patients between two groups were comparable and statistically not significant as per Student t-test (p>0.05). It was seen that in Group D and Group V majority patients were of ASA Class I grading (79% and 76% respectively). Group D had 86% patients with Mallampati Class III while Group V had 84% with Mallampati Class III.

 

Table 2: Comparison of Pre-operative Characteristics between Groups

The mean interincisor gap of patients in Group D and Group V was comparable (3.62±0.88cm vs. 3.75±0.89cm) and the thyromental distance in patients in Group D and Group V was also comparable (6.79±0.66cm vs. 7.05±0.86cm). In Group D 20% patients and Group V 22% patients were found to have buck teeth. The presence of buck teeth was comparable between the groups by the Fischer's test and was not statistically significant (p>0.05).

Table 3: Comparison of efficacy in both groups

It was observed that in group D airway was secured in first attempt in 82% patients while it was 94%in group V and the difference observed was statistically significant.                In Group D,Cormack-Lehane laryngeal view was graded I and II in 69% and 24% patients respectively. In Group V, Cormack-Lehane laryngeal view was graded I and II in 48% and 32% patients respectively. Video laryngoscopy provided a significantly better view of the laryngeal structures than direct laryngoscopy as per Chi-Square test (p<0.05). The use of external laryngeal manipulation/facilitation with a bougie was significantly more in Group D as compared to Group V (37% vs. 24%) and the difference between the groups was also statistically significant as per Fisher test (p<0.05). The mean laryngoscopy time was significantly higher in Group D as compared to Group V (42.33 ± 1.76 secs vs. 33.16 ± 2.08 secs). There was statistically significant difference between the two groups as per Student t-test (p<0.05).

Table 4: Comparison of Adverse Events between Groups

In Group D, 25% patients had sore throat while 10% and 3% patients had Lip/gum/oral trauma and Oxygen desaturation <90% respectively. In Group V, 28% patients had sore throat while 6% and 4% patients had Lip/gum/oral trauma and Oxygen desaturation<90% respectively. There was no significant difference between the groups as per Chi-Square test (p>0.05).

DISCUSSION

The present hospital based prospective single blind randomized control study was conducted with 200 patients with atleast three predictors of difficult intubation to compare the effectiveness of  video laryngoscopy and direct laryngoscopy in obtaining a better laryngeal view and facilitating the ease of intubation. The patients were randomly divided into following groups of 100 patients each; Group D: Patients intubated with direct laryngoscope and Group V: Patients intubated with video laryngoscope. It was observed that in Group D had 27% patients were in the age group of 20- 30 years, 33% patients in the age group of 31-40 years and 40% patients in 41-50 years of age group.  In Group V 28% patients were in the age group of 20-30 years, 35% patients in the age group of 31-40 years and 37% patients in 41-50 years of age group. The mean age in Group D was 36.64±8.32 years while the mean age in Group D was 36.21 ± 8.67 years and the age of the patients between two groups were comparable and statistically not significant as per Student’s t-test (p>0.05). In Group D had 63% male patients and Group V had 61% male patients. thus both the groups were comparable with respect to age and sex. Similar findings were also reported by Rao KV et al¹⁹. In the present study, Group D had 86% patients in the normal range of BMI while in Group V had 83% patients were in the normal range. The mean BMI of patients was 21.94 ± 3.30kg/m2 in Group D and 22.68 ± 3.44kg/m2 in Group V. The BMI of the patients between two groups were comparable and statistically not significant (p>0.05).                It was observed that majority of the patients of Group D (79%) and Group V (76%) were of ASA Class I grade. The ASA Grading of the patients between two groups were comparable and statistically not significant as per Chi-Square test (p>0.05).     It was observed in the present study that Group D had 1% and 2% patients with Mallampati Class I and II classification respectively and 86% and 11% patients with Mallampati Class III and IV classification respectively. Group V had 2% patients each with Mallampati Class I and II classification respectively and 84% and 12% patients with Mallampati Class III and IV classification respectively. The Mallampati classification of patients between two groups were comparable and statistically not significant as per Chi-Square test (p>0.05). This is comparable to the study of Jungbauer A et al²⁰.  It was observed in the present study that the mean interincisor gap of patients in Group D and Group V was comparable (3.62±0.88cm vs. 3.75±0.89cm) and the thyromental distance in patients in Group D and Group V was also comparable (6.79±0.66cm vs. 7.05±0.86cm). This was in concordant to the studies of Rao KV et al¹⁹ and Jafra A et al²¹. It was observed in our study that 20% patients in Group D and 22% patients in Group V had buck teeth. Similar findings were also reported by Salama A K et al²². It was observed in the present study that the number of attempts to insert the device  was statistically significant as there were 18% cases of two attempts in Group D and only 6% cases of two attempts in Group V (p<0.05). This is consistent with the study of Rao KV et al¹⁹.In our study, the mean laryngoscopy time was significantly higher in Group D as compared to Group V (42.33 ± 1.76 secs vs. 33.16 ± 2.08 secs). There was statistically significant difference between the two groups (p<0.05). Jungbauer A et al²⁰ study evaluating the conditions and success rate of tracheal intubation using direct laryngoscopy or video laryngoscopy reported time for tracheal intubation was significantly shorter for video laryngoscopy compared with direct laryngoscopy with a standard Macintosh blade. Similar observations were noted in the studies of Rao KV et al¹⁹ and Jafra A et al²¹. In Group D of our study, Cormack-Lehane laryngeal view was Grade III and Grade IV in 6% and 1% patient respectively. In Group V, Cormack-Lehane laryngeal view was graded III and Grade IV in 18% and 2% patients respectively. Thus Video laryngoscopy provided a significantly better view of the laryngeal structures than direct laryngoscopy (p<0.05). Glottis view was assessed using modified Cormack-lehane grading during initial laryngoscopy and intubation. The results of present study showed a significant improvement in laryngoscopy views in GVL group when compared between two groups and in intragroup comparison between scores of initial and final laryngoscopy hence strengthening the role of video laryngoscopes in difficult airway scenarios. Jungbauer A et al²⁰ observed similar observation in their study.        In the present study, the use of external laryngeal manipulation/facilitation with a bougie was significantly (p<0.05) more in Group D as compared to Group V (37% vs. 24%).. This is in concordance to the studies of Jungbauer A et al²⁰, Rao KV et al¹⁹ and Jafra A et al²¹. It was observed that in Group D, 25% patients had sore throat while 10% and 3% patients had Lip/gum/oral trauma and Oxygen desaturation<90% respectively. 2% patients had dental trauma. In Group V, 28 (28%) patients had sore throat while 6% and 4% patients had Lip/gum/oral trauma and Oxygen desaturation<90% respectively. 1% patient had dental trauma. But the difference was not statistically significant. Jafra A et al²¹ reported in Group G (GlideScope video laryngoscope), three patients and in Group M (Macintosh laryngoscope), two patients had minor lip and tongue bleed and only one patient in group G had sore throat, which was found to be statistically not significant. Depending on the management, tracheal intubation in patients with difficult airways can lead to airway trauma or even a life-threatening disaster^6,23. Therefore, on the one hand, difficult airway management guidelines have been developed and, on the other hand, video-assisted devices have been developed to ease tracheal intubation⁷. The rationale behind the development of these devices is to abandon the need for the alignment of the optical axis to receive a direct view of the glottis¹⁸. In a multi-centre trial enrolling 867 patients, Kaplan MB et al¹² found a significantly improved view using the Stortz video laryngoscope view on the monitor compared with the direct ‘naked’ view by the same laryngoscope. The author found that the video laryngoscopy can be used safely and this technique seems to provide better intubation conditions.

 

CONCLUSION

Thus with reference to above mentioned results and discussion we conclude that Video laryngoscope eases tracheal intubations in patients with expected difficult intubations. The view of the laryngeal entrance is significantly improved, with a decreased number of optimizing manoeuvres and in less time. Overall, these improvements of the conditions for tracheal intubations result in a significantly higher success rate of trachael intubations.

 

REFERENCES