Rescuer position for tracheal intubation on the ground
Introduction
For a rescuer attending an unconscious patient outside of the hospital setting, the ability to secure the airway rapidly may be the critical life-saving manoeuvre. Oral tracheal intubation is the most reliable means of establishing control of the airway. Intubation may be awkward when the patient is lying on the ground and the rescuer is forced to assume crouching or lying positions to obtain adequate visualisation of the larynx.
Several studies have endeavoured to determine the optimal rescuer position for intubating patients lying supine on the ground. Adnet et al. found the left lateral decubitus (LLD) position to afford better glottic exposure than the kneeling position in both manikins [2] and patients [3]. However, Koetter et al. [1] found that the time differences to intubation of a manikin in four positions (prone, sitting, kneeling and straddling) were clinically insignificant (<5 s). They found no significant differences between the positions with respect to subjective handling and complications. Birkinshaw et al. [4] found that none of 10 intubator positions studied on manikins were superior statistically with respect to speed or ease of intubation. This lack of significance may have been because a standard training manikin has an uncomplicated airway and experienced rescuers will have little trouble performing airway intubation in less than the AHA recommended time of 30 s [5] regardless of their position. However, it may take a rescuer considerably longer to intubate a real patient—especially one with non-optimal airway anatomy—from an awkward body position. In such real-life situations, the force that can be exerted to align and visualize the soft tissues may determine the quality of access to the airway [6], [7], [8], [9] and hence the chance of successful intubation.
Our aim was to study the effect of seven rescuer positions on the maximum force that the rescuer can apply in that position. We compared this to the force exerted by the rescuer to align the soft tissues of the pharynx for tracheal intubation. The ratio of these two forces was taken as an indication of the ‘reserve force’ available in case of difficulty in visualisation of the larynx.
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Subjects
Twelve male and eight female subjects with a variable amount of previous intubation experience volunteered for this study. The participants consisted of six respiratory therapists, one medical student, seven anaesthesia residents, three anaesthesia fellows and three staff anesthesiologists. Their mean age was 32±6 years (range 25–48 years), and their mean height was 171±7.3 cm (range 157–183 cm). Sixteen volunteers were right-handed and four were left-handed. Mean intubation experience was
Results
Values for Pi, Pmax and %max as well as results from all pair-wise comparisons are provided in Table 1. The pressure required to intubate was highest in the sitting position and this was significantly greater than all other positions except for LLD. The straddling and LLD positions afforded the greatest maximal pressure, and these pressures were significantly greater than RLD, kneeling and prone. The straddling position required only 68% of maximal pressure to intubate and this was
Discussion
The results of this study indicate that of the 7 positions, the straddling position provides the rescuer with the greatest reserve of force available to align the soft tissues with the laryngoscope during intubation. The straddling position has several major advantages over the other positions studied. First, the laryngoscope is held in the right hand (dominant for most people). Second, laryngoscopy is achieved through extension of the shoulder and flexion of the elbow, which uses powerful
Conclusion
We found that compared to the other positions studied, the straddling position allows the rescuer to apply greater force on the soft tissue to facilitate visualisation of the larynx. In addition, the straddling position has further advantages in that it (a) may provide better access to patients who are trapped in confined spaces and (b) would be less likely to expose the rescuer to hazardous material on the ground. We recommend that the straddling position become part of the standard training
Acknowledgements
The authors would like to acknowledge the staff members of the University Health Network's Respiratory Therapy and Anaesthesia departments for their participation and co-operation.
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