A Comparative Study between Truview PCD Video Laryngoscope and Macintosh Laryngoscope with Respect to Intubation Quality and Hemodynamic Changes.

BACKGROUND AND AIMS: Video laryngoscopes resemble traditional laryngoscopes, but they have a video chip embedded in the tip of laryngoscope blade. This enables the operator to "look around the corners" which is not possible with conventional direct laryngoscopes. The present study was undertaken to compare Truview video laryngoscope and Macintosh laryngoscope for glottis visualization, ease of tracheal intubation, and associated hemodynamic response.
SETTING: The study was conducted in operation theater in a medical college. STUDY
DESIGN: It was a randomized prospective observational study.
MATERIALS AND METHODS: Sixty patients of American Society of Anesthesiologists Grade 1 and 2 of either sex aged 18-60 years who were scheduled to undergo elective surgery requiring general anesthesia with orotracheal intubation were selected. In patients of Group T (n = 30), intubation was done using Truview video laryngoscope, while in Group M (n = 30), intubation was done using Macintosh laryngoscope. Various airway and hemodynamic parameters were assessed and compared. STATISTICAL ANALYSIS: Statistical analysis was done using Chi-square test, paired and unpaired Student's t-test, and ANOVA test. P < 0.05 is considered statistically significant.
RESULTS: Distribution of modified Mallampati Class (MMPC), ease of laryngoscopic blade insertion, and size of cuffed endotracheal tube used were statistically comparable in both the groups. The time to intubation was more in Group T (37.16 ± 8.23 s) as compared to Group M (29.80 ± 6.75 s). There was a statistically significant better modified Cormack and Lehane (CL) grading view obtained in Group T as compared to Group M (P = 0.025). CL Grades 2 and 3 were not seen in any of either of the group. The mean intubation difficulty score (IDS) was significantly lower in Group T (0.3 ± 0.60) as compared to Group M (0.73 ± 0.86). In both the Groups T and M, the mean heart rate, systolic blood pressure (BP), and diastolic BP were significantly increased from baseline for up to 3 min after laryngoscopy, but they were comparable between the two groups all the time.
CONCLUSION: Truview propaganda cum distribution laryngoscope provides a better glottis view than the Macintosh laryngoscope. Although it requires a longer time to intubate using Truview, the overall IDS score was lower as compared to Macintosh laryngoscope. Hemodynamic changes remained similar in both the groups. Copyright:

INTRODUCTION

Airway management is the primary responsibility of the anesthesiologist i.e., secure, preserve, and protect the airway during induction, maintenance, and recovery from anesthesia. With conventional laryngoscopes such as Macintosh laryngoscope to be able to see the range of glottis opening, proper alignment of oral, pharyngeal, and tracheal axes is required. Majority of tracheal intubations are easy and effortless with this technique. However, in a small number of patients, this alignment of axes is difficult to achieve.

Direct laryngoscopy includes arterial hypertension and tachycardia secondary to proprioceptor stimulation of the supraglottic structures. As the use of Macintosh laryngoscope requires a considerable lifting force to have oral and pharyngeal axes in alignment, many adverse hemodynamic changes can occur. Complications arising from difficult or failed intubation remain a leading cause of anesthesia-related morbidity and mortality.[123]

Video laryngoscopes resemble traditional laryngoscopes, but they have a video chip embedded in the tip of laryngoscope blade.[4] This transmits magnified images to a display screen where they can then be viewed or recorded. Since the camera is positioned a few millimeters from the vocal cord, alignment of the oral, pharyngeal, and laryngeal axes for ling-of-sight is not essential. This enables the operator to “look around the corners” which is not possible with conventional direct laryngoscopes.

The Truphatek Truview PCD system (Truphatek International Ltd, Netanya, Israel) is a new laryngoscope blade system with an optical assembly that illuminates the larynx and with a unique blade that provides an optical view “around the corner.” The Truview PCD has a prism and lens system that provides a 46° angle of refraction, which enlarges the view field.[5] The Truview blade is based on a combination of an optical system with a specially profiled slim steel blade.[6]

Keeping the above things in mind, the present study was undertaken to compare Truview video laryngoscope and Macintosh laryngoscope for glottis visualization, ease of tracheal intubation, and associated hemodynamic response in patients undergoing elective surgery requiring general anesthesia and tracheal intubation.

MATERIALS AND METHODS

After the Institutional Ethics Committee's approval and written informed consent, this prospective randomized observational study was conducted on 60 patients of the American Society of Anesthesiologists Class I and II of either sex aged 18–60 years who were scheduled to undergo elective surgery requiring general anesthesia with orotracheal intubation. Patients having a high risk of pulmonary aspiration; anticipated difficult airway, head-and-neck pathologies; swelling and dressings on the face, neck, or restricted mouth opening (<2 cm); surgery of oral cavity, larynx, and pharynx; and increased intracranial tension were excluded from the study. All patients were made to understand the details of anesthetic procedure during preoperative visits.

Patients were randomly allotted to two groups of 30 patients each into Group T and M by computer-generated randomization list. Intubation was done using Truview video laryngoscope in Group T while in Group M (n = 30) intubation was done using Macintosh laryngoscope. Laryngoscopy and intubation were carried out by the same experienced anesthesiologist. In preanesthetic evaluation, demographic profiles including age, sex, weight, and height were recorded. Airway examination includes assessment of mouth opening, modified Mallampati Class (MMPC), dentition, and neck movements.

All patients were kept fasting for 8 h preoperatively. After arrival in the preanesthetic area, all patients were cannulated and 10 mg metoclopramide was given intravenously 1 hr. before anesthesia. After arrival in operation theater, monitoring equipments were attached to the patient including five-lead electrocardiogram, noninvasive blood pressure (BP), and pulse oximeter. End-Tidal Carbon Dioxide was kept in standby mode to be monitored after laryngoscopic orotacheal intubation had been done.

Premedication was done with glycopyrrolate 0.004 mg.kg−1 i.v. and midazolam 0.03 mg.kg−1 i.v. After premedication, patients were preoxygenated for 3 min. Anesthesia was induced with propofol 2–2.5 mg.kg−1 i.v. with dose titration to produce loss of verbal response and fentanyl 1–2 μg.kg−1 i.v. For muscle relaxation rocuronium 0.6 mg.kg−1 i.v. was given. Intermittent positive pressure ventilation was given for 3 min with 100% oxygen (O2).

In accordance with standard practice, after adequate depth of anesthesia and complete muscle relaxation has been achieved, laryngoscopy and intubation were carried out by the same anesthetist using Truview video laryngoscope and Macintosh laryngoscope according to the group they were allocated.

In Group M, the intubations were performed under the guidance of Macintosh laryngoscope without the use of stylet after attaining sniffing position using 8 cm high noncompressible head ring and extending the head. An oral cannula with O2 flow of 6–8 L.min−1 was placed during laryngoscopy and intubation. In Group T, intubations were performed using Truview video laryngoscope which was functionally pretested with all components mounted to the hilt of laryngoscope including an oxygen line delivering O2 at a rate of 6–8 L.min−1 and digital camera attached to the ocular piece. For better control of endotracheal tube (ETT) tip, the stylet was used in this group. Oxygen insufflation was used in both the groups by the use of oral cannula in Group M and through oxygen port of Truview laryngoscope in Group T to avoid fogging and apneic desaturation. Laryngoscopic view was assessed using the modified Cormack and Lehane (CL) class.[7] Intubation was carried out using cuffed ETT of appropriate size. Ease of intubation was assessed by Intubation Difficult Score.[8] Time just before laryngoscopy was recorded as time zero (T0). Time to intubation was measured from the time of introducing a laryngoscopic blade in the patient's mouth till the appearance of a square wave capnograph. A maximum of 1 min time was allowed for laryngoscopy. If intubation would not have achieved within 1 min or oxygen saturation (SpO2) falls below 92%, laryngoscopic blade is to be removed and mask ventilation is to be given for 30 s before a second attempt is to be allowed. A maximum of three attempts were planned. Intubation time in such a situation was planned to be sum of time taken in these steps. If a patient could not be intubated in the three attempts, the case would have been recorded as failure and airway to be managed according to the difficult airway protocol. However, all our patients were intubated on the first attempt. The placement of ETT was confirmed by auscultation of the chest and presence of a square wave capnograph. After endotracheal intubation, ventilation was controlled using O2 and sevoflurane 2%–2.5%. Anesthesia was maintained as per the requirement of surgery. After completion of the surgery, patients were reversed and extubated according to the standard practice and guidelines.

Parameters observed were:

Ease of laryngoscopic blade insertion – No difficulty, slight difficulty, and difficult

Laryngoscopic view as assessed by modified CL class:

Class I: visualization of entire vocal cords

Class II: visualization of posterior part of laryngeal aperture

II a: visualization of posterior parts of vocal cord and arytenoids cartilages

II b: visualization of only arytenoids cartilage.

Class III: visualization of epiglottis

III a: epiglottis can be lifted from posterior pharyngeal wall

III b: epiglottis cannot be lifted.

Class IV: no glottic structure seen.

Distribution of size of a cuffed endotracheal tube

Time to intubation was defined as the time of introducing laryngoscopic blade in the patient's mouth till the appearance of square wave capnograph

Correlation between MMPC and modified CL class

Correlation between modified CL class and time to intubation

Intubation Difficulty Score (IDS):

N1 – No of supplementary intubation attempts

N2 – No of supplementary operators

N3 – No of alternative intubation technique usedN4 – Glottis exposure as defined by Cormac and Lehane Grades minus one

N5 – Lifting force applied during laryngoscopy

N5 = 0 if little effort was used

N5 = 1 if subjectively increased lifting force was used for laryngoscopy

N6 – Necessity of applied external laryngeal pressure for optimized the glottic

exposure

N6 = 0 if no external laryngeal pressure applied

N6 = 1 if external laryngeal pressure is necessary

N7 – Positions of vocal cords at intubation

N7 = 0 if vocal cords are abducted/not visualized

N7 = 1 if vocal cords are adducted during laryngoscopy.

Comparision of parameters of IDS

Correlation between IDS and time to intubation

Heart rate (HR), Non Invasive Blood Pressure, and SpO2 were recorded at baseline before induction of anesthesia, time zero (T0) – just before laryngoscopy, and thereafter every 1 min after intubation till 5 min

Any injury to lips, teeth, or oral cavity or presence of blood on ETT

Postoperative complications, if any such as sore throat or hoarseness of voice, were recorded 1 h and 24 h after extubation.

Statistical analysis

Statistical analyses were performed using SPSS (version 23.0) for Windows gBM SPSS statistics for Windows, version 23.0. (Armonk, NY, gBM corp.). Sample size calculated from difference in the intubation difficult scale with 80% power of study at two-sided with a significance level of 5%.[8] Normality test was done using Shapiro–Wilk test. Continuous variables were presented as mean ± standard deviation. Categorical data were expressed as number and percentage. Statistical analysis was done using the Chi-square test, paired and unpaired Student's t-test, and ANOVA test. P < 0.05 was considered statistically significant.

RESULTS

All the 60 patients enrolled in the study were analyzed [Figure 1]. The demographic data were found to be similar in each group [Table 1]. Distribution of MMPC, ease of laryngoscopic blade insertion, and size of cuffed ETT used were statistically comparable in both the groups [Tables 2-4].

Figure 1

CONSORT flow

Table 1

Demographic data

Parameters	Group T	Group M	P
Age (years)	41.63±10.39	40.03±10.53	0.37
Weight (kg)	61.16±7.85	60.53±7.30	0.74
Height (cm)	162±6.54	161.86±4.80	0.78
Sex ratio (male:female)	19:11	17:13	0.59
Duration of surgery (min)	85.66±23.87	96±22.42	0.08

Table 2

Distribution of modified Mallampati Class

MMPC	Group T, n (%)	Group M, n (%)	P
MMPC 1	21 (70)	20 (67)	0.785
MMPC 2	9 (30)	10 (33)
Total	30 (100)	30 (100)

MMPC=Modified Mallampati Class

Table 4

Distribution of size of cuffed endotracheal tube used

Size of cuffed ETT used (mm)	Group-T	Group-M	P
Mean±SD	7.58±0.5	7.66±0.46	0.50

SD=Standard deviation, ETT=Endotracheal tube

Time to intubation was as the sum of time taken in each of three attempts. However in our study, all 60 patients were intubated on the first attempt. The mean time to intubation was 37.16 ± 8.23 s in Group T, while it was 29.80 ± 6.75 s in Group M. The difference between time to intubation was statistically highly significant between the two groups [P < 0.001, Table 5].

Table 5

Time to intubation

Parameters	Group T	Group M	P
Mean time to intubation (s)	37.16±8.23	29.80±6.75	<0.001

Laryngoscopic view was assessed by modified CL class. Twenty-eight patients (93%) had CL Class I, while in Group M 20 patients (67%) had CL Class I. CL Class IIa was seen in two patients (7%) of Group T, while it was seen in six patients (20%) of Group M. CL Class IIb was not encountered in any of patients of Group T, while it was seen in four patients (13%) of Group M. There was a statistically significant difference between two groups in the CL view obtained (P = 0.025). CL Class II and III were not seen in any of patients of either of group [Table 6].

Table 6

Modified Cormack and Lehane grading

CL grade	Group-T, n (%)	Group-M, n (%)	P
1	28 (93)	20 (67)	0.025
2a	2 (7)	6 (20)
2b	0	4 (13)
Total	30 (100)	30 (100)

CL=Cormack and Lehane

Two groups were also evaluated comparing CL class for each MMPC.

In Group T, out of 30 patients, 21 patients had MMPC I and nine patients had MMPC II. Out of 21 patients with MMPC I, 20 patients had CL Class 1, while only one patient had CL Class IIa. Out of nine patients with MMPC II, eight patients had CL Class I, while only one patient had CL Class IIa. There was no correlation between MMPC and CL class in Group T (P = 0.522). In Group M out of 30 patients, 20 patients had MMPC I and 10 had MMPC II. Out of 20 patients with MMPC I, 14 patients had CL Class I, two patients had CL Class IIa, and four patients had CL Class IIb. Similarly out of 10 patients with MMPC II, six patients had CL Class I, four patients had CL Class IIa, while none of patients had CL Class IIb. There was no correlation between MMPC and CL class in Group M [P = 0.077, Table 7].

Table 7

Correlation between modified Mallampati Class and Cormack and Lehane grading

MMPC versus CL Grade	CL Grade 1, n (%)	CL Grade 2a, n (%)	CL Grade 2b, n (%)	P
Group-T
MMPC 1	20 (71)	1 (50)	0	0.522
MMPC 2	8 (29)	1 (50)	0
Group-M
MMPC 1	14 (70)	2 (33)	4 (100)	0.077
MMPC 2	6 (30)	4 (67)	0

MMPC=Modified Mallampati Class, CL=Cormack and Lehane

Two groups were evaluated comparing time to intubation for each CL class. In Group T, patients with CL Class I had mean time to intubation 36.39 ± 7.81 s, while patients with CL Class IIa had mean time to intubation 48 ± 2 s. There was a positive correlation between CL class and time to intubation (P = 0.029). In Group M, patients with CL Class I had mean time to intubation 26.3 ± 4.71 s, patients with CL Class IIa had mean time to intubation 36 ± 2.51 s, and patients with CL Class IIb had mean time to intubation 38 ± 4.91 s.

There was a positive correlation between CL grade and time to intubation [P < 0.001, Table 8].

Table 8

Correlation between Cormack and Lehane grade and time to intubation

CL grade versus time to intubation	Time to intubation, mean±SD	P
Group-T
CL Grade 1	36.39±7.81	0.029
CL Grade 2a	48±2
CL Grade 2b
Group-M
CL Grade 1	26.3±4.71	<0.001
CL Grade 2a	36±2.51
CL Grade 2b	38±4.91

CL=Cormack and Lehane, SD=Standard deviation

Ease of intubation was assessed in all the 60 patients by IDS. The mean IDS score in Group T was 0.3 ± 0.60, while mean IDS score in Group M was 0.73 ± 0.86. There was a statistically significant difference between the means of total IDS score of the two groups with P = 0.04 [Table 9].

Table 9

Intubation difficulty score

IDS	Group-T, n (%)	Group-M, n (%)
0	22 (80)	15 (53.33)
1	6 (13)	9 (30)
2	2 (7)	5 (13.33)
3	0	1 (3.33)
Total	30 (100)	30 (100)
Mean±SD	0.3±0.60	0.73±0.86
P	0.04

SD=Standard deviation, IDS=Intubation difficulty score

Each patient in both the groups was assessed for ease of intubation with the following parameters of IDS: supplementary intubation attempts (N1), supplementary operators (N2), alternative intubation technique (N3), glottis exposure (N4), lifting force (N5), external laryngeal manipulation (N6), and vocal cord position (N7). Except IDS parameters such as N4, N5, and N6, the rest parameters were exactly the same in both the groups. IDS N4 (CL class minus one) Scored 0 in 28 patients and 1 in two patients of Group T, while it Scored 0 in 17 patients and 1 in 13 patients of Group M. It was statistically found to be significant (P = 0.001). IDS N5 Scored 0 in 26 patients and 1 in four patients of Group T, while it Scored 0 in 25 patients and 1 in five patients of Group M. It was not found to be statistically significant (P = 0.71) IDS N6 Scored 0 in 26 patients and 1 in four patients of both groups. Hence, no difference was found (P = 1). Hence, between Groups M and T, statistically significant difference was found with respect to glottic visualization (IDS-N4) but there was no statistically significant difference found with respect to lifting force (IDS-N5) and external laryngeal manipulation (IDS-N6) [Table 10].

Table 10

Parameters of intubation difficulty score

	IDS-N1		IDS-N2		IDS-N3		IDS-N4		IDS-N5		IDS-N6		IDS-N7
	T	M	T	M	T	M	T	M	T	M	T	M	T	M
0	30	30	30	30	30	30	28	17	26	25	26	26	30	30
1	0	0	0	0	0	0	2	13	4	5	4	4	0	0
Total	30	30	30	30	30	30	30	30	30	30	30	30	30	30
P							0.001		0.71		1

IDS=Intubation difficulty score

The correlation between IDS and time to intubation was also studied for both the groups.

In Group T for patients with IDS Score 0, 1, and 2, the mean time to intubation was 33.90 ± 6.75 s, 45.16 ± 3.28 s, and 49 ± 1 s, respectively. There was a positive correlation between IDS score and time to intubation in Group T (P = 0.0002). In Group M for patients with IDS Score 0, 1, 2, and 3, the mean time to intubation was 27 ± 4.55 s, 31 ± 7.29 s, 32.8 ± 6.53 s, and 46 s, respectively. There was a positive correlation between IDS score and time to intubation in Group M (P = 0.013). Hence in both the groups, it took a longer time to intubate patients with higher IDS score [Table 11].

Table 11

Correlation between intubation difficulty score and time to intubation

IDS versus time to intubation	Time to intubation (s), mean±SD	P
Group-T
IDS 0	33.90±6.91	0.0002
IDS 1	45.16±3.60
IDS 2	49±1
Group-M
IDS 0	27±4.55	0.013
IDS 1	31±7.29
IDS 2	32.8±6.53
IDS 3	46±0

IDS=Intubation difficulty score, SD=Standard deviation

In our study, HR, systolic BP (SBP) and diastolic BP (DBP) and arterial SpO2 were measured before induction of anesthesia (baseline), just before laryngoscopy (time 0), and every minute for 5 min after intubation. The HR changes were comparable between the groups all the time [Figure 2].

Figure 2

Trend of heart rate changes during laryngoscopy and intubation

In both the Groups T and M, the mean HR, mean SBP, and mean DBP at 1, 2, and 3 min after laryngoscopy significantly differed from their respective baseline values. However, they were comparable between the two groups at all the time [Figures 2-4].

Figure 4

Trend of diastolic blood pressure changes during laryngoscopy and intubation

Trend of systolic blood pressure changes during laryngoscopy and intubation

The arterial SpO2 within the group and in between the two groups was also comparable at all the time [Figure 5]. None of the patients had any injury to lips, teeth, or oral cavity or presence of blood on ETT or any postoperative complication such as sore throat or hoarseness of voice.

Figure 5

Trend of oxygen saturation changes during laryngoscopy and intubation

DISCUSSION

In our study, we assessed and compared Truview PCD using Macintosh laryngoscope for orotracheal intubation in adult population 18–60 years of age with regard to laryngoscopic view, ease of intubation, and hemodynamic changes. Truview laryngoscope provides a better glottis view but comparable amount of lifting force during laryngoscopy when compared with Macintosh laryngoscope in the adult population. The IDS was less with Truview group, but interestingly, time to intubation was more as compared to Macintosh group. There was no statistically significant difference in hemodynamic variables between the two groups.

Our study results revealed that both the groups were comparable with respect to demographic variables. All the patients had normal mouth opening, dentition, and neck movements. MMPC was comparable between the groups (P = 0.785). It is expected that a better laryngoscopic view will be associated with easier intubation. However, ease of intubation depends on many factors also. Hence along with CL class for laryngoscopic view assessment, time to intubation and IDS were measured in all the patients. The glottis view was assessed using the modified CL class.[7]

In our study, it took a significantly longer time to intubate with Truview when compared to Macintosh laryngoscope (P < 0.001). The mean time to intubation in Group M was 29.8 ± 6.75 s, however, in Group T, it was 37.16 ± 8.23 s. In spite of achieving the operator's criteria, an overall lesser experience of using Truview as compared to Macintosh laryngoscope may have contributed to the longer duration of intubation time. In addition, the indirect view of larynx, requiring hand–eye coordination for intubation could have increased intubation time with Truview. Barak et al. defined time to intubation was as the time from laryngoscope blade insertion in the mouth to inflation of cuff of ETT.[9] They found that in adult patients, the mean time to intubation was significantly longer with Truview EVO2 laryngoscope 33 ± 12 s as compared to Macintosh 24 ± 13 s (P < 0.001).

Li et al. also proposed that the mean time to intubate adult patients using the Truview EVO2 laryngoscope was significantly longer (51 s) as compared to Macintosh laryngoscope (34 s).[10] Time to intubation in their study was defined as the time recorded from laryngoscope blade insertion in the mouth to detection of end-tidal CO2. Saxena et al. in a cross-over study on 140 patients found that the mean time to intubation was significantly longer in the Truview group (34.15 ± 1.19 s) as compared to the Macintosh group (22.42 ± 12.68 s).[11] In their study, time to intubation was recorded from removal of mask to the earliest detection of end-tidal CO2.

Malik et al. also concluded in their study that the duration of tracheal intubation was significantly shorter with Macintosh as compared to video laryngoscopes.[12] Duration of intubation in their study was defined as the time taken from insertion of the blade between teeth until the ETT was placed through the vocal cords, as evidence by visual confirmation by the anesthetist. They also experienced considerable difficulties advancing the tube toward the view of digital camera and this difficulty was the principal reason for increased duration of tracheal intubation in these patients as described by them.

Our study revealed a better glottis view with the Truview laryngoscope as compared to the Macintosh laryngoscope. Majority of patients in Group T, i.e., 28 patients (93%) had CL Class I as compared to only 20 patients (67%) in Group M. CL Class IIa was seen in two patients (7%) in Group T and six patients (20%) in Group M. Interestingly, CL Class IIb was not encountered in any of the patients in Group T, however, four patients (13%) in Group M had CL Class IIb. This difference was statistically significant (P = 0.025). We believe that the better glottis view obtained with Truview as compared to the Macintosh laryngoscope in our study is due to specialized optical system present in the Truview blade, which enables us to “look around the corners” without requiring the alignment of oral, pharyngeal, and laryngeal axes.

Our results are consistent with those of Barak et al., Li et al., and Inel et al.[91013] They also found a better glottis view with the Truview blade than with Macintosh. Inal et al. who also found a better glottis view with the Truview EVO2 blade than Miller blade (P = 0.034) in the pediatric population (2–8 years) attributed this improved view with Truview EVO2 to the prismatic effect of its lens system.[13] Barak et al. found that CL grade was significantly better in the Truview group than the Macintosh group. All the above-mentioned studies concluded that Truview EVO2 provides a better glottis view when compared with Macintosh laryngoscope in adult patients.[9]

In our study, there was no intubation failure. An intubation score of >3 was not observed in any patient. Group T had significantly lower mean IDS (0.3 ± 0.60) as compared to Group M (0.73 ± 0.86). Furthermore, IDS = 0, relating to easy intubation, was observed in 22 (80%) of patients in Group T, while only 15 (53%) patients had IDS = 0 in Group M. Similarly, IDS = 1 and 2 were observed in 6 (13%) patients and 2 (7%) patients, respectively, in Group T, whereas IDS = 1 and 2 were observed in 9 (30%) patients and 5 (13%) patients, respectively, in Group M. Only one patient in Group M had worst IDS score of 3. On further analysis of IDS score, we found that this difference in IDS between the two groups was attributed to mainly two parameters out of the total seven, i.e. N4 and N5 which are CL class and lifting force, respectively. Four patients in Group-T and five patients in Group-M required subjectively increased lifting force (IDS-N5) during laryngoscopy. No statistically significant difference was observed in IDS-N5 score (P = 0.71). There was statistically significant difference between Group T and Group M with regards to glottis visualization but lifting force required seemed to be comparable in both groups.

Saxena et al. also observed a low mean IDS score in the Truview group (0.32 ± 0.716) as compared to the Macintosh group (0.68 ± 1.032).[11] However, they did not elaborate that which parameters of IDS were attributing to the lower IDS score with Truview laryngoscope. Inal et al. in their study in pediatric population found no significant difference in IDS when Truview blade was compared to the Miller blade.[13] Probably, this difference in the finding was due to Miller blade used in their study and Macintosh in our study. Kaur et al. have found that intubation was easy in Tuview group (87.50%) as compared to Macintosh group (65%).[14]

Barak et al.[9] did a study in which he actually measured the lifting force in kg using a Digital Force Gauge (Mark-10, Corporation; Hicksville, NY, USA) handle connected to the evaluated blade and proposed that significantly higher force was required to intubate with Macintosh laryngoscope than with Truview EVO2 laryngoscope (P < 0.00). On subjective assessment, they observed that difficulty in intubation was significantly more with Truview as compared to Macintosh (P = 0.00) and this difficulty was attributed to the “hand eye coordination” technique of intubation under the indirect vision and relatively less experience with the Truview.

In our study, we did not find any statistically significant difference in lifting force required for intubation may be due to relatively small size of the study population or absence of any device to actually measure the lifting force required. Another reason may be relatively less time required for intubation in Group M which has given an impression of easy intubation creating a sense of less lifting force required.

The mean HR, SBP, and DBP were found to increase from 0 to 3 min after intubation in both the groups. There was no significant stress response to laryngoscopy with Truview EVO2 laryngoscope when compared to Macintosh even though it took a significantly longer time to intubate. The probable reason for prolonged laryngoscopy not leading to significant stress response could be the lesser lifting force required for intubation with Truview EVO2 laryngoscope as found in other studies like Barak et al.[9]

Our findings are consistent with Singh et al. and Kurnaz et al. study in the geriatric population (P > 0.05) who also found hemodynamic parameters to be comparable with Truview and Macintosh laryngoscope.[1516] Our findings are in contrast to those of Bag et al. who found statistically significant less hemodynamic response in Truview laryngoscope when compared to Macintosh laryngoscope.[17] In another interesting study by Inal et al. in pediatric population who found a significant rise in HR when using Truview EVO2 which they attributed to the prolonged laryngoscopy; however, there was no rise in mean arterial pressure.[13] The concurrent media access control (C-MAC) has a higher hemodynamic response to intubation compared to McCoy laryngoscope, while no statistically significant differences were seen between Macintosh and C-MAC laryngoscopes.[18]

In our study, the difference between mean SpO2 from time 0 to 1, 2, 3, 4, and 5 min was not statistically significant in both the groups. Both the groups were comparable in terms of SpO2 all the time. The mean SpO2 was always maintained above 99% in both the groups, which could be attributed to the continuous oxygen insufflation during laryngoscopy and intubation in both the groups.

We strongly believe that time to intubation can be shortened by practice and regular use of Truview laryngoscope. There were few limitations of our study. First, the less experience with Truview laryngoscope may have added to the mean time of intubation as compared to Macintosh laryngoscope which is the one of the most common laryngoscope used on day-to-day basis. Second, more larger sample size and quantitative method to measure lifting force required during laryngoscopy and intubation could have produced different or new results. Third, the study was not blinded as blinding the laryngoscopist was not practically possible.

CONCLUSION

We conclude that the Truview PCD laryngoscope provides a better glottis view than the Macintosh laryngoscope. Although it requires a longer time to intubate using Truview, the overall IDS score was lower as compared to Macintosh laryngoscope. Hemodynamic changes remained similar in both the groups. Truview should be considered a useful alternative to the Macintosh laryngoscope and should be introduced in day-to-day practice for more expertise for orotracheal intubation in the adult population.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

Table 3

Distribution of ease of laryngoscope blade insertion

Ease of blade insertion	Group-T, n (%)	Group-M, n (%)	P
No difficulty	30 (100)	28 (93)	0.15
Slight difficulty	0	2 (7)
Difficult	0	0
Total	30 (100)	30 (100)