Influence of head positioning on the forces occurring during microlaryngoscopy.

Considerable forces are exerted on oropharyngeal tissues during microlaryngoscopic procedures. Although it is generally accepted that positioning of the patient's head influences the quantity of these forces and the easiness of the exposure of the anterior glottis, there is a lack of systematic studies on this topic. The aim of our study was to measure the forces occurring during microlaryngoscopy in different positions. This should result in a recommendation for a "low-pressure" position which minimises the risk of postoperative complications due to tissue trauma. Thirty consecutive patients planned for microlaryngoscopy underwent study procedures. During general anaesthesia, measurements were taken using a tension spring balance in neutral position, during extension of the cervical spine, as well as under moderate and maximum flexion. Elevation of the patient's head thus flexing the cervical spine reduced the occurring forces significantly. Maximum elevation allowed a full exposure of the anterior commissure in all cases, whereas exposure of the anterior commissure was not possible even with maximum external counterpressure in almost 40% of cases with maximum extended cervical spine. The largest differences were observed between extension, neutral and flexion position, whereas the differences between moderate and maximum flexion were not significant. Elevation of the patient's head with consecutive flexion of the cervical spine allows for better exposure in microlaryngoscopy and reduces significantly the pressure exerted on the oropharyngeal tissues thus minimising the risk of tissue injury. A slight modification of standard instruments can be necessary when using this "low-pressure" position.