This study quantitated the force applied during tracheal intubation to determine (a) whether the force differed among novice and experienced intubators, and (b) whether the force required differed when intubating patients' tracheas versus intubating the trachea of a commonly used training mannequin. We studied 27 tracheal intubations performed by 17 experienced (greater than 100 prior intubations) and 10 novice (less than 10 prior intubations) intubators. Each intubation was performed with a No. 3 Macintosh blade instrumented with strain gauges to determine force applied in the sagittal plane. The mean force applied was 24.6 +/- 2.9 N (mean +/- SEM) and the maximum force applied by each intubator was 47.6 +/- 3.8 N. There was no difference between groups in the mean force applied (28.8 +/- 6.1 N for the novice group vs 22.3 +/- 2.7 N for the experienced group, P = 0.27) nor in the maximum force applied (55.1 +/- 6.5 N for the novice group vs 43.2 +/- 4.7 N for the experienced group, P = 0.08). The only difference was in the impulse (force x duration), which was more for the novice group largely because of the longer average duration of intubation (40 +/- 12 s vs 19 +/- 4 s, P = 0.06). Among experienced intubators, we found that applied force correlated with patient weight and Mallampati class. Intubation of the Laerdal Airway Management Trainer required mean forces comparable to those required in patients (26.6 +/- 2.5 N vs 22.3 +/- 2.9 N), although the maximum force applied during the intubation effort was greater (58.3 +/- 4.7 N vs 43.2 +/- 4.7 N, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)