AUTHORS:  R. V. Prasad, M.D., S. Dogra, FFARCSI, and B. Johnson, M.S. II

AFFILIATION:  Dept. of Anesth., Univ. of N. Carolina School of Medicine, Chapel Hill, NC  27599-7010

INTRODUCTION: All anesthesiologists must be prepared for the difficult or failed intubation.  Information about previous difficulty in intubating any given patient can help with this preparation.  However, we believe there is presently no good way of communicating the degree of difficulty.  We therefore developed a scale that describes the level of difficulty of intubation, and compared it to other methods currently in use.

METHODS:  We prospectively collected data on airway management in a random selection of 203 adult patients undergoing general anesthesia in a university hospital setting.  The intubation attempts were assigned a Level of Difficulty of Intubation (LDI), as follows:
LDI 1: Straightforward.  No modifications to usual technique required.
LDI 2: Need to apply laryngeal or cricoid pressure, adjust patient position, or reintroduce blade.
LDI 3: Change of blade, change of operator, or elective fiber optic intubation.
LDI 4: Non-elective fiber optic intubation, emergent LMA, retrograde wire, crico-thyroidotomy, tracheotomy, or failed intubation.
We also recorded the Mallampati classification, MP Class 1-4, and grade of view on laryngoscopy, Grades 1-4 (1).  We compared each to the LDI scale.

RESULTS: We were unable to determine the  MP class on 15 patients, and grade of view on 4 patients. The data obtained is presented below, as number (percent) of patients.

                      Mallampati Class                            Grade of View

LDI	1	2	3	4		1	2	3	4
1	40 (20)	29 (14)	6 (3)	0 (0)		63 (31)	20 (10)	0 (0)	0 (0)
2	35 (17)	31 (15)	12 (6)	2 (1)		58 (28)	24 (12)	2 (1)	0 (0)
3	9 (4)	17 (8)	4 (2)	1 (0)		11 (5)	13 (6)	5 (2)	0 (0)
4	0 (0)	1 (0)	2 (1)	0 (0)		0 (0)	1 (0)	1 (0)	1 (0)

The Pearson Product Moment Correlation Coefficient (r-value) for Mallampati Class vs. LDI and for Grade of View vs. LDI was 0.242 (p<0.01) and 0.327 (p<0.01), respectively.

DISCUSSION:  Knowledge of previous difficulty in intubating a patient can help anesthesiologists prepare to intubate that patient again.  Until now, however, there has been no simple, accurate way of describing and classifying, and therefore easily communicating, the difficulty of an intubation.  The scale described above is simple, descriptive, and informative.  It concisely conveys information about the actual process of intubation for any given patient.  Our data show that neither the Mallampati classification, nor the grade of view on laryngoscopy correlate well with the actual Level of Difficulty of Intubation.  Neither adequately describes the many, often difficult, steps needed to intubate a patient.  Use of the LDI scale may improve patient safety by clearly conveying useful information to future anesthesiologists.

REFERENCES: (1) Cormack RS. Lehane J. “Difficult tracheal intubation in obstetrics.” Anaesthesia. 39(11):1105-11, 1984 Nov.