We included 120 consecutive adult non-pregnant patients with American Society of Anaesthesiologist physical status classification I and with Mallampati classification I to IV requiring general anaesthesia and tracheal intubation for electives surgery. Because repeated laryngoscopies could increase intracranial and arterial blood pressure through sympathetic stimulation, we excluded patients with poor physical condition, hypertension, Ischemic heart disease, raised intracranial tension and respiratory distress. Also patients with loose molar teeth, intra-oral tumors, neck swelling and patients below 18 yrs and above 70 yrs were excluded from the study. A written informed consent for each patient was obtained

The study comprised four groups:

Group A It included [30] patients, who were intubated using the Macintosh Laryngoscope. Out of those, 15 were studied using Macintosh No.3 blade i.e. Group A1 and remaining 15 were studied using Macintosh No. 4 blade i.e. Group A2. Group B It included [30] patients, who were intubated using the McCoy's Laryngoscope. Out of those, 15 were studied using McCoy's No.3 blade i.e. Group B1 and remaining 15 were studied using McCoy's No. 4 blade i.e. Group B2. Group C It included [30] patients, who were intubated using the Balloon laryngoscope right balloon inflation followed by deflation and inflation of left balloon [R1L2]. Out of those, 15 were studied using Balloon laryngoscope No.3 blade i.e. Group C1 and remaining 15 were studied using Balloon laryngoscope No. 4 blade i.e. Group C2Group D It included [30] patients, who were intubated using the Balloon laryngoscope left balloon inflation followed by deflation and inflation of right balloon [L1R2]. Out of those, 15 were studied using Balloon laryngoscope No.3 blade i.e. Group D1 and remaining 15 were studied using Balloon laryngoscope No. 4 blade i.e. Group D2.

Selection of laryngoscope blade in each group was alternate.

During the study, each group patient underwent laryngoscopy in neutral position. Neutral position is given with the Rigid Cervical Collar. A black marker line was placed on right cheek of the patient with axis parallel to the occlusal surface of maxillary molars. In neutral position head extension angle [A1] and angle between the handle of blade and horizontal plane [A2] measured with the help of angle finder [goniometer] before and after manipulation (fig.2).

Laryngoscope Blade Levering Motion [LBLM] Angle calculated as angle [A1] ? [A2]. It is the angle formed between the occlusal surface axis of the maxillary molars or gums and a chord that is perpendicular to the axis of the handle and corresponds to the radian formed by the proximal one-third of the convex surface of the blade. This chord passes through the distal end point of the radian. Cormack Lehan grade of glottic visualization was compared before and after manipulation along with monitoring of pulse, blood pressure and saturation.

Manipulation was different in different groups. In group A it was optimal external laryngeal manipulation [OELM] done through the window created on the anterior surface of the cervical collar. In group B it was levering mechanism of the flexitip of McCoy's blade . In group C it was right balloon inflation by 3 cc of air with preattached syringe followed by deflation and inflation of left balloon by 3 cc of air with preattached syringe [R1L2]. In group D it was left balloon inflation by 3 cc of air with preattached syringe followed by deflation and inflation of right balloon by 3 cc of air with preattached syringe [L1R2].

A black marker line was placed on right cheek of the patient with axis parallel to the occlusal surface of maxillary molars. Anaesthesia was induced with intravenous propofol 2 mg/kg and Inj. Vecuronium. After preoxygenation with 100% oxygen for 3 minutes, rigid neck collar was applied. Patient was again ventilated for 1 min. Laryngoscopy was performed according to the group the patient belongs to.

In each group after introducing the blade at maximum glottic visualization head extension angle [A1] and angle between the handle of blade and horizontal plane [A2] was measured. Cormack lehan grading of glottic visualization was noted. After maneuvering as mentioned specifically for each group, Cormack lehan grading angle [A1] and [A2] was measured to at maximum glottic visualization .intubation was done if Cormack lehan grade is ? IIb. Procedure was carried out for 20 sec, if not completed patient was ventilated for 3 min.

If Cormack lehan grade would be ? IIIa, cervical collar would be removed Patient would be ventilated for 3 minutes. Laryngoscopy would be done with head extension, to achieve maximum glottic visualization. Cormack lehan grading, angle [A1] and [A2] would be measured with and without maneuvering. Intubation will be done if Cormack lehan grade is ? IIb. Assistant would be monitoring and measuring pulse blood pressure and saturation during laryngoscopy and maneuvering. The other assistant would be measuring both the angles A1 and A2.

In each group the number of attempts required for intubation and laryngoscopy and post procedure complications were noted.

The laryngeal view of glottic visualization with direct laryngoscopy was classified according to Modified Cormack and Lehane as follows: Grade – I, full view of glottis; Grade – IIa, More than 50% of glottis is visible; the anterior commissure of glottis is not visible. Grade – IIb, Less than 50% of glottis is visible; the posterior commissure of glottis and arytenoid are visible. Grade – IIIa, Only the arytenoid cartilages and the epiglottis are visible, Grade – IIIb, only the epiglottis are visible, Grade – IV, Only the retropharyngeal wall is visible.

Figure 1

Figure 1: Balloon laryngoscope blade, Rigid cervical neck collar and Goniometer

Figure 2

Figure 2 : Measurement of the angle between the handle of blade and horizontal plane [A2]

Figure 3

Figure 3: Balloon Laryngoscopy

All data are expressed as mean (SD). Demographic parameters and airway parameters compared by ANOVA application and Pearson chi. Square test. The effect of each laryngoscopic approach on the grade of laryngeal view before and after maneuvering was compared using Pearson's chi. square test. Approach related hemodynamic changes were compared by ANOVA application, while complications were compared using Pearson's chi. Square test.

Differences between groups were considered significant at P < 0.05

In group A , of 2 patients who had Cormack lehan grade I before manipulation ,both remained cormack lehan grade I after manipulation.

2 patients who had Cormack lehan grade IIa before manipulation, 1 improved to grade I and 1 remained grade IIa.

Of 21 patients who had Cormack lehan grade IIb before manipulation, 4 improved to grade I, 12 improved to grade IIa and 5 remained grade IIb

Of 5 patients who had Cormack lehan grade IIIa before manipulation, 3 improved to grade IIa and 2 improved to grade IIb

In group B, of 8 patients who had Cormack lehan grade I before manipulation, all remained Cormack lehan grade I after manipulation.

13 patients who had Cormack lehan grade IIa before manipulation, 10 improved to grade I and 3 remained grade IIa.

Of 9 patients who had Cormack lehan grade IIb before manipulation, 2 improved to grade I and 7 improved to grade IIa.

In group C, of 6 patients who had Cormack lehan grade IIa before manipulation, 3 improved to grade I and 3 remained grade IIa.

Of 19 patients who had Cormack lehan grade IIb before manipulation, 1 improved to grade I, 9 improved to grade IIa and 9 remained grade IIb

Of 5 patients who had Cormack lehan grade IIIa before manipulation,2 improved to grade IIa and 3 improved to grade IIb

In group D of 9 patients who had Cormack lehan grade IIa before manipulation, 2 improved to grade I and 7 remained grade IIa.

Of 15 patients who had Cormack lehan grade IIb before manipulation, 1 improved to grade I, 9 improved to grade IIa and 5 remained grade IIb

Of 6 patients who had Cormack lehan grade IIIa before manipulation,1 improved to grade IIa and 3 improved to grade Iib(Table 2, Graph 1).

Figure 5

Table 2: Distribution Of Change In Cormack Lehane Grades In Different Laryngoscopy Approaches

Figure 6

Graph 1

The mean head extension angle in group A was 20.6 ± 2.67degrees. In group B it was 20.53 ± 2.7 degrees. In group C it was 20.53 ± 2.77 degrees and in group D it was 20.73 ± 2.58 degrees

The mean laryngoscope blade levering motion [LBLM] angle in group A was 11.83 ± 2.15 degrees. In group B it was 11.43 ± 2.41 degrees. In group C it was 11.06 ± 1.85 degrees and in group D it was 11.16 ± 1.39 degrees.

The pressure response was significant in all approaches of laryngoscopy. There was significant change in pulse rate, and systolic blood pressure in McCoy's laryngoscopy group as compared to other groups

There were significant blood pressure changes between the Macintosh blade with OELM and the Flexitip blade with lever activation.

Balloon laryngoscopy had minimal pulse rate and blood pressure changes as compared to others.

In group A , 4 patients had lip injury and 4 had sore throat while 22 patients were free of complications. In group B, 4 patients had lip injury and 3 had sore throat while 23 patients were free of complications. In group C, 7 patients had lip injury and 4 had sore throat while 19 patients were free of complications. In group D, 4 patients had lip injury and 4 had sore throat while 22 patients were free of complications (Graph 2).

Figure 7

Graph 2