Background: The head-tilt/chin-lift (HT/CL) maneuver is simple and routinely used to open a closed upper airway.
Objectives: It has yet to be determined whether increasing the HT/CL angle further would be beneficial.
Methods: We enrolled 60 (30 males) 20-year-old conscious participants. Pre-HT/CL, post-HT/CL #1, and post-HT/CL #2 positions were defined as positions in which the angle between the ear-eye line and the horizontal line was 80°, 65°, and 50°, respectively. Peak exploratory flow rates (PEFRs) pre-HT/CL, post-HT/CL #1, and post-HT/CL #2 positions were recorded continuously at 1-minute intervals (one set). Five sets of measurements were performed (total, 15 measurements for each participant).
Results: We analysed 900 measurements (180 sets). The mean PEFRs pre-HT/CL, post-HT/CL #1, and post-HT/CL #2 positions were 348.4 ± 96.9, 366.4 ± 104.9, and 378.8 ± 111.2 L/min (percentage change compared to pre-HT/CL, 5.2% and 8.7%), respectively. Significant differences were observed among pre-HT/CL, post-HT/CL #1, and post-HT/CL #2 positions in all participants, as well as in subgroup classified according to sex, and medians of height, body weight, and body mass index.
Conclusion: Our findings suggest that a greater HT/CL angle would be beneficial, as the PEFR increased gradually. The decreasing manner in the PEFR increase with the HT/CL angle implies the existence of an angle threshold beyond which there were no further benefits in airflow, indicating a minimum in airway resistance. A HT/CL maneuver may be appropriate until locking the atlanto-occipital and cervical spine joints in extension occurs and the chest (sternal notch) begins to rise.